Sourcing the correct Iron for clone AC 15 and Discussion of build

[Ed_Chambley]

The 1959 VOX ac15 Choke is 10H, 150ma, 250DCR,
Classictone, 10H, 100ma, 270DCR
Close Enough?

Output
Primary, 8 ohms at 15 watts, Secondary, 8 and 15 taps only.
Who has the closest Reproduction.  Opinion and experience.  Also anyone ever used something like an old Baldwin 8k pull?  Very beefy Transformer and I am not sure if a lot of the overdriven tone comes from the OT being saturated.
Classictone spec sheet specs the primary at 6K, which is either a typo or wrong.  No response in trying to contact them.

Basically I am trying to find the closest and learn a little of how the Output Transformer influences the AC15.  I am planning a head version since it will have the EF86 and I will be using a Marshall style layout with tubes up head.  Since it is documented that JMI had problems with their OT's during the early years and struggled with reliability, the trail gets foggy as to who's OT they continued using once the problem was resolved.

May not be an issue as I am not sure the influence the OT has on the tone.  Some amps, a lot like the princeton, others, not so much loke a Black Face Bassman.

What I have noticed, or seems to be true is the lower the wattage the amp the greater the OT's influence.  Don't know for sure, but it seems that way.  Maybe someone could shed some light.

[sluckey]

Classictone has a full set of iron. So does Hammond. Both are about the same price. MM probably has a much more expensive set of iron.

I was wondering about the 6K spec on the Classictone also. I converted a Hammond AO-39 to an AC-15 lite (ef86 preamp). Sounds decent but no "WOW" factor. There's a guy , lego4040, over at BYOC that's currently building a 1960 AC-15 using my single board Marshall style layout. He may have some ideas about iron. If I ever build another amp it will probably be the AC-15. The Vibrato/Tremolo is really my attraction to this amp.

[Ed_Chambley]

Classictone has a full set of iron. So does Hammond. Both are about the same price. MM probably has a much more expensive set of iron.

I was wondering about the 6K spec on the Classictone also. I converted a Hammond AO-39 to an AC-15 lite (ef86 preamp). Sounds decent but no "WOW" factor. There's a guy , lego4040, over at BYOC that's currently building a 1960 AC-15 using my single board Marshall style layout. He may have some ideas about iron. If I ever build another amp it will probably be the AC-15. The Vibrato/Tremolo is really my attraction to this amp.

Thanks, I will go over and see what he uses.  I had a real ac15 so I know what they are and respond like.  I too am using your layout/schematic.  I built one using some iron similar the 18 watt iron and it was not even close.  I had amperex EL84 and all mullard pre's and a Celestion blue.  I changed it to an 18 watt standard with tremolo and sold it.

I do think the choke and OT have a lot to do with the character and I cannot see why the layout should be a factor.  Maybe Mercury OT only.  Thanks for the lead, I will definitely wait to see how his turns out.

I know you dig a nice tremolo.  I have a another friend who is the same way.  If you unblock me from PM's I promise not to bombard you with build questions any more. :icon_biggrin

[sluckey]

I too am using your layout/schematic.

Be sure to use the current version on my website.

[lego4040]

 Seems lots of people have questions when it comes to transformers. I just started a thread over at BYOC on the ins and outs of transformers. I was looking at classictone options and they weren't on spec. I have to look at heyboers. Look at the thread I got going in BYOC and you'll see the Hammond recommendations. http://byocelectronics.com/board/viewtopic.php?f=9&t=48438

[sluckey]

Hey lego4040, people here at Hoffman's would love to follow your build. Lot's of friendly, helpful, knowledgeable people here. Would you consider starting a thread?

[HotBluePlates]

...  I had a real ac15 so I know what they are and respond like.  ...

...  I am planning a head version since it will have the EF86 ...

When I got to your 2nd post, I did a thread double-take. Once you mentioned the EF86, I understood the earlier comment.

When I lived outside Nashville, most vintage shops had all the Fender stuff, and they might get a Marshall once in a while. But there was one place 30 minutes outside town that carried ALL the Brit amps. I recall them having a couple 60's AC-30's on-hand, and a couple AC-15's (but with 2x12 so it looked at first like there were 4 AC-30's). One had the EF86, the other didn't. The EF86 channel seemed to win hands-down when I played through it.

Anyway, I'd love to know what you come up with in the end.

...  I built one using some iron similar the 18 watt iron and it was not even close.  ...

What was wrong with the sound? It's hard to know how something should change without knowing how it's falling short.

...  Since it is documented that JMI had problems with their OT's during the early years and struggled with reliability, the trail gets foggy as to who's OT they continued using once the problem was resolved. ...

From reading The Vox Story, the picture I got was that JMI didn't build its amps. Dick Denney designed them, and Tom Jennings outsourced production. Further, he used several different contracted manufacturers, and this is given as the reason you could find one of 4 or 5 different brands of transformers in your 60's Vox, and yet all could be original. I don't see this as a slight on Jennings, as he was a music store owner and was looking for the most expedient way to ramp up production and move product.

The Mercury Magnetics article makes it sound like transformer companies were directly bidding to Vox for sales, but The Vox Story again makes it sound like the contracted manufacturers were the ones making bids on per-unit price of completed amp chassis, and so would likely be the ones to swap individual component manufacturers (like choosing the cheapo benad that met all of Vox's specs, to deliver a lower per-unit cost and secure more orders).

It is interesting to me that the 1960 AC-15 "Bass" schematic indicates an 8kΩ OT, while the clone OTs that provide impedances specs cite 6kΩ more or less. Of course, there's no OT info on the 1959 AC-15 schematic. Or on the other AC-15 models.

[Ed_Chambley]

What was wrong with the sound? It's hard to know how something should change without knowing how it's falling short.

The amp sounded fine, but where it fell short was looseness.  These amps have a unique way of being very greasy, but still hold together when played hard.  It felt like I was playing a 18 watt anyway.  The true 18 watt marshall.

I concur with you and the Vox story and the builders of the amps.  I had a AC15 and the OT was really large for a 15 watt amp.  It had bell ends, whereas the choke did not.  It was the EF86, single Celestion Blue 12.  The amp feels very open and distorts the same way.  Dare I say it, but a little to the hifi side.

When you dig your fingers in you could get a SERIOUS bite.  Very touch, but not in trainwreck way.  You played one so you know when they are opened up they are not extremely loud.  They speak of chine all the time, but that is not the deal.  All amps will chime and sound bell like if you want them to, well most will.

I modified a layout I had when I saw Sluckey's and used Iron Alden at Heybour said was like the Vox.  It looked like the OT Doug sells.  Now I am not dissing the iron as the amp sounded good.  More like a DR Z.  Sorry to the DR Z fans, but not my thing.

So difficult to describe tone and Jim will get me, but with any of my Telecasters I could not get a bad sound whether hitting hard chords with a wonderful distortion or simply softer and harder finger.  Basically I could play anything on it.  It is the biggest regret I have ever made selling it, but I was very young and could not afford to keep paying to have it fixed.

I did not ever consider reverb either as it seemed to do that as well.  Maybe just euphoric recall, but the sound is like John Jorgenson.  Ever heard of him and listened to his tone?

I know you have.

Most of the time he is using an old Vox or there is one near him.

[SleepLess]

Hi Ed!
Well if you manage to source the closest transformers possible for an old AC-15 build, I'll be joining you in that build. I've been wanting a close-to-the-original AC-15 replica for a long time! 

[Backwoods Joe]

Ed I've built several AC-15 clones and after trying 4 different brands of OT's, I'd have to recommend the MM... hands down. I know they are high but the magic is THERE! Like you said to begin with, it seems like in smaller amps especially cathode bias, a lot of the tone is in the OT.

[HotBluePlates]

Well, there are a number of forum members who have already bought enough quantity of MM transformers to qualify for the discount. I'd probably suggest putting the word out for assistance with placing an order.

I need another amp like I need another hole in the head, but I might be willing to join in on a group buy for some AC15 transformers. It's just one of those amps that sounds like nothing else, so it might be a worthwhile build. Go nice with the guitar I need to buy (mentioned on the guitar board). 

I dunno if it's worth calling MM to find out if their '59 OT is based on the RadioSpares version, or which they recommend...

[Ed_Chambley]

Not really concerned with the cost of MM.  Thanks for the recommendation as that is what I was wanting.  Not that I am rich, but where can you buy a 1960 Vox AC-15?  Like was said, there is nothing really the same.  I know I have everything but choke and OT, so no big price.  I have been reading about the caps a tad and it seems like some feel the darker caps work best like mallorys or Sozo in the signal path.

Looks like lots of turrets so Doug's will work best.  I will be revising the chassis to 19 x 8 x 2.  I like it roomy.  I am really just in the thinking stages, but if we can get an order together for the MM OT and Choke, I am in.  I am not even going to skimp here unless I can find the same value.

This is the last amp I am going to build for a long time.

[drew]

What about the West Labs transformers that were supposedly made for Matchless?  http://westlabs.com/Trannys.HTML#15watt

[HotBluePlates]

I never really liked any of Matchless' EL84 amps, though I haven't played a DC-30... I'm not sure if those will be a plus or minus for the project.

[Ed_Chambley]

Ed I've built several AC-15 clones and after trying 4 different brands of OT's, I'd have to recommend the MM... hands down. I know they are high but the magic is THERE! Like you said to begin with, it seems like in smaller amps especially cathode bias, a lot of the tone is in the OT.

Backwoods, thanks for joining the party.

Have you owned or had access to the early 60, EF86 Vox AC15?  Is your recommendation of MM based on getting the tonal quality of these amps or is it based on the outcome of builds and finding what your preference is?

In other words, were you attempting to clone?

[Ed_Chambley]

Here is what is supposed to be a clone of an AC15
http://www.jmiamplification.com/combos/jmi-15

They are going to great extremes to clone, but I have a 68 Vox Cambridge Reveb with a 10" bulldog that sounds closer IMO.  Just a quick look at the Transformers on the new JMI website and you will see the difference if you are familiar with them.  I have no idea what they have used and I am also aware that you may not be able to recreate exactly, but I know the knowledge around here can do better.

Here it is from youtube, but it is recorded.  Pay attention to the opening licks right at the first.  Now either he did not compensate for humbucker but still there is way to much speaker flab.  The solo notes are extremely flat sounding and opposes what I meant about hi-fi sounding.  There is no bloom that I can hear.  This is what I found and is why I converted to a Marshall circuit.  It sounds nothing like a Vox to me and neither do some of the other youtube reviews.

Let me know what you think.

https://www.youtube.com/watch?v=lU3NX4yGK6s

[SleepLess]

Let me know what you think.

https://www.youtube.com/watch?v=lU3NX4yGK6s

It sounds like shit...

[Ed_Chambley]

Let me know what you think.

https://www.youtube.com/watch?v=lU3NX4yGK6s

It sounds like shit...

That is what I am saying.  When I built one it did not sound that bad.  It actually sounded good, just not like a real Vox.  There is another where a guy is playing a Telecaster, but he doesn't crank it.  It could be simply the guy does not know how to dial in Humbuckers, but it still shouldn't be all flabby.

I feel like the Iron, as usual, is most of the tone.  I have always been able to tweak Mercury iorn and get something nice and Heyboer makes great Marshall OT's.  I actually prefer Heyboer's Drake to an original Drake 50 watt I have.  What I am saying is they both make good iron, but all around Mercury has the edge.

I have been looking at some Marstran as I have some of them and where Heyboer is more in your face, the Marstran's I have (I hate to use this word) are more transparent.  What I mean as they don't rock as hard, but individual notes can still be easily heard.  This is what I think of when I think of Vox and the old one I had did this with an SG I had at the time.

I wish I had the Hammond 1650F on the shelf that Sluckey spec'd on the schematic.  I have never been disappointed with Hammond stuff.  It may be a little wait and see as lego4040 is working on his right now.

You would think that if the new JMI went to all the trouble to clone as close as they have, they would have gotten an original set of Iron and cloned that too.  I am still researching.

[sluckey]

I wish I had the Hammond 1650F on the shelf that Sluckey spec'd on the schematic.  I have never been disappointed with Hammond stuff.

Hey guys, I spec'd that OT because I've had good results with it in a couple EL84 builds. The specs look great, but you can't hear specs. I don't know if it will capture that "Vox AC-15" sound. I don't even know what that sound is because I've never heard one (other than YouTube).

The original OT on my EF86 AC-15 lite conversion (from AO-39) sounds good to me, but it sure ain't got no "WOW" factor. My main attraction to the AC-15 is the Vib/Trem circuit. I really want that sound. It may be no better than my Revibe sound, but I want to know.

I hope you guys with ears and experience can come up with a good OT recommendation. I'm following closely.

[SleepLess]

Hi.
I know this is not about transformers, but in case you guys need the proper dimensions and cut outs for te eAC15 chassis + a nice faceplate idea, there you go:

http://members.ziggo.nl/jheijer/Chassis.htm

I wish I could source everything for a true AC15 replica. I'd love to build it!

[Ed_Chambley]

Hi.
I know this is not about transformers, but in case you guys need the proper dimensions and cut outs for te eAC15 chassis + a nice faceplate idea, there you go:

http://members.ziggo.nl/jheijer/Chassis.htm

I wish I could source everything for a true AC15 replica. I'd love to build it!

Look at this link,
http://forums.vintageamps.com/viewtopic.php?f=2&t=74424&sid=34cca521ae77ff96d7021bc262ee2cfc

They have sourced the chassis.  You can get a replica cab from North Coast music.  It can be done.

I am still reading, but have came to understand Mercury Magnetics has the most accurate Output Transformer in an 8K, but I also found Vox used a 6k3 during the same time which is messing with me a touch.  I have yet to find out which was used first, but assuming Mercury's is 8k, I would thing this is the correct, but may explain why Classictone is using 6K Primaries.

I have also read where the Mercury Power Transformer's voltage is higher to the point where it may be too much.  Anyway, I see no good reason to buy a Mercury PT when a one of nice quality can be had for much less. 

I plan to build a head using a layout Sluckey has drawn.  It is not conventional to Vox and lends itself more to Marshall style.  I have a couple of the hammond 270 series PT's and from memory I believe the 270FX.  Hell with memory:
270FX   
138VA
   
115VAC
   
60HZ
   
550V C.T. @ 173ma.
   
5V @ 3A
   
6.3V C.T. @ 5A

Should be very close.
I am checking on the original choke compared to what is available.  AS soon as I run it down I will be ordering the Output Transformer and Choke.

Anyone know how many need to be ordered from Mercury to get a decent discount?

[Ed_Chambley]

Hi.
I know this is not about transformers, but in case you guys need the proper dimensions and cut outs for te eAC15 chassis + a nice faceplate idea, there you go:

http://members.ziggo.nl/jheijer/Chassis.htm

I wish I could source everything for a true AC15 replica. I'd love to build it!

Sleepless, Provide anything you find.  I would appreciate it.

[Ed_Chambley]

Cannot find an exact value Choke.
The 1959 VOX ac15 Choke is 10H, 150ma, 250DCR,

Classictone, 10H, 100ma, 270DCR
Close Enough?

My weakest understanding is screen chokes, but I have experimented with changing then on amps and it is not just grab this one.  For instance, I have a 40H, 50ma, 330DCR and replaced A Mojo777 expecting the amp to tighten up a tad.  I was surprised to notice a big difference.  It actually sounded more compressed and had a noticeable cleaning up in overall tone.  This example may be extreme and I am not certain if it is the Organ influence in Old Vox amps, but the chokes are physically much larger.

I think the choke plays a large part, but I may be way off base here since I really do not understand much about what the Henry measurement is in application.  I get the additional ripple reduction which could be very important to the Vox tone.  I thinking it is, but cannot prove it.

I am asking to shed some light here because after reading old threads and internet articles, the test I did worked much different that expected.  I also know this is different than inductor input, or at least I think it is.

[terminalgs]

RE: Chokes.   When you swapped chokes, how did your screen voltages change?  I suppose that's the change that effected tone?   

The schematic for a "AC/15 Amplifier No.2" 4-12-69 shows a 8HY 120ma choke. FWIW..,   Also, if you are looking at AC15 schematics, don't overlook the late 1990's AC15TB and AC15TBX.  This is a highly regarded AC15 and has a couple feature worth noting:

* the top-boost circuit.   oddly enough the GA77 is the subject of another current thread elsewhere on the forum.  (from what I've read), the GA77 was the amp that Denney got the TB circuit from.  Even if you are planning for a EF86 in one channel, I'd consider the a TB circuit for the other channel. 

* the AC15TBX uses a 5Y3 instead of a EZ81.   more reliable rectifier tube plus spares you from having to worry about the EZ81 failures and their reputation of shorting plate-to-cathode and heater when they fail. 

* no choke.

I get to play all the matchless' amps.  Atlanta Discount Music is a dealer and each new one that comes in I give it a run through.

Ed_Chambley:  I used to go to ADM all the time when I lived over there,  late 80s, mostly early 90's.  I used to love that place.   mid-town music was my favorite for lusting after old vintage amps.

[SoundmasterG]

I used Heyboer for a Vox AC100 build for the choke and OT and I couldn't be happier. They did a really nice job and the amp sounds great. I am sure they must have the specs to make an accurate AC15 clone and still be cheaper than MM. MM makes nice stuff but they cost too much, and they aren't perfect. I used one of their replacements for a Magnatone 260 for a customer and while it sounds good, the original one sounded better before it blew up. just sayin.....

Greg

[Ed_Chambley]

RE: Chokes.   When you swapped chokes, how did your screen voltages change?  I suppose that's the change that effected tone?  

The schematic for a "AC/15 Amplifier No.2" 4-12-69 shows a 8HY 120ma choke. FWIW..,   Also, if you are looking at AC15 schematics, don't overlook the late 1990's AC15TB and AC15TBX.  This is a highly regarded AC15 and has a couple feature worth noting:

* the top-boost circuit.   oddly enough the GA77 is the subject of another current thread elsewhere on the forum.  (from what I've read), the GA77 was the amp that Denney got the TB circuit from.  Even if you are planning for a EF86 in one channel, I'd consider the a TB circuit for the other channel.  

* the AC15TBX uses a 5Y3 instead of a EZ81.   more reliable rectifier tube plus spares you from having to worry about the EZ81 failures and their reputation of shorting plate-to-cathode and heater when they fail.  

* no choke.

I get to play all the matchless' amps.  Atlanta Discount Music is a dealer and each new one that comes in I give it a run through.

Ed_Chambley:  I used to go to ADM all the time when I lived over there,  late 80s, mostly early 90's.  I used to love that place.   mid-town music was my favorite for lusting after old vintage amps.

Sure, the screen voltage changed because of the DC Resistance of the Choke, but I am sure the ability of the choke to reduce ripple has an impact, maybe a larger one.

I am building a 1960 version.  I have taken a run at building this before with the attitude this change may be better, like a different rectifier and whatever choke I had at hand,  I explained earlier in the thread what the result was.

Ther is no midtown music anymore.  Not like you remember.

[Ed_Chambley]

I used Heyboer for a Vox AC100 build for the choke and OT and I couldn't be happier. They did a really nice job and the amp sounds great. I am sure they must have the specs to make an accurate AC15 clone and still be cheaper than MM. MM makes nice stuff but they cost too much, and they aren't perfect. I used one of their replacements for a Magnatone 260 for a customer and while it sounds good, the original one sounded better before it blew up. just sayin.....

Greg

I agree with you about Heyboer except for this build.  You see, I already tried it using Iron suggested by Heyboer I mentioned earlier in the thread.  If I were building a AC100 your comments would have excellent merit.

That is what I am looking for.  People who have built the 1959 Vox ac15.

I have done a lot of research and what I am asking about is chokes.

Yes, there has to be a choke on this build and it specs at
The 1959 VOX ac15 Choke is 10H, 150ma, 250DCR,

The classictone replacement specs are:
Classictone, 10H, 100ma, 270DCR

I do not know enough about the specs of a choke to know if these would preform the same, but I do know they are not the same.  I understand the DCR and ma are different and most of the time people would say it doesn't matter, so would I if I hadn't already built the thing with this attitude.

Is the classictone a good choice for a replacement?  If so, why is that since they are different.  I do not know enough about chokes, but I am reading about them.  Come to find out after reading post of many that have gone before they have given up on replicating this AC15 and the tone it produces.  Others have even found if the same tremolo is not present the amp the amp is much different.

I appreciate all input as it makes me look and study more. Research to find if others have tried it and how it worked.  Using a different choke has not worked well in every case I have read about, I just do not know if the specs are close enough between the original and the Classictone to use the classictone.

[sluckey]

Yes, there has to be a choke on this build and it specs at
The 1959 VOX ac15 Choke is 10H, 150ma, 250DCR,

Where did you get those specs? The two original looking schematics I have simply say 10-20H.

The classictone replacement specs are:
Classictone, 10H, 100ma, 270DCR

Based on your specs above, the classictone is an excellent replacement. So is the Hammond 159P.


Here's a practical explanation of the specs you're likely to see for a choke used in a power supply...

1.  H is Henry is inductance. Inductance is the property of a component that opposes any change in current thru that component. Inductance will smooth the current flow in a similar manner as a capacitor will smooth the voltage. A bigger H value (inductance) will have a larger current smoothing effect.

2. Current rating. This is the current rating that the inductance rating is based on. The inductance is not a fixed number. It varies with the current flowing thru the choke. Less current means less inductance. More current means more inductance up to a point. The current flowing thru the choke coil creates a magnetic field (strength depends on the amount of current) that produces a voltage of such polarity as to oppose current flow thru the coil. It's called CEMF (look it up). When increasing the current you will reach a point where increasing the current even more no longer increases the strength of the magnetic field, so the inductance no longer increases. This is called core saturation and sets the upper limit on inductance for a particular choke. What does this all mean? Well for your classictone example it means that if you have 100ma flowing thru the choke it's inductance will be 10H. If you only have 75ma the inductance will be less, just take a WAG and say 7.5H. If the current is 125ma the inductance may increase to 12.5H (another WAG).

3.  DCR, or direct current resistance, is the actual measured resistance of the wire used to wind the choke coil. A perfect choke would have zero DCR, but that's only possible on paper. This resistance will cause a voltage drop across the choke IAW Ohm's law. A larger DCR will cause a larger voltage drop. This causes the choke to heat up due to the I²R power loss.

Using a choke together with capacitors will create a smoother/stiffer B+ as compared to caps and resistors. It will definitely have an effect on the sound and feel of an amp.

When choosing a choke you need to consider the three specs above. Bigger H means smoother B+. Chose the current rating based on the anticipated B+ current requirements and the H will be what you expect. You would typically want a lower value DCR unless you're trying to copy some existing choke.

Notice that the AC-15 circuit feeds B+ to the output tube plates as well as screens and everything else so the classictone 100ma choke is a good match. So is the Hammond. But the Hammond has a lower DCR than the classictone and in my mind that means the Hammond is a better choke when considering electrical properties. I think it would take a very educated ear to tell the difference in the sound of these two chokes.

[Ed_Chambley]

Yes, there has to be a choke on this build and it specs at
The 1959 VOX ac15 Choke is 10H, 150ma, 250DCR,

Where did you get those specs? The two original looking schematics I have simply say 10-20H.

Thanks for the explanation as I have been reading the inductance changes with current.  I have a general understanding as I have built a L-C, or if you will, inductor input amps.  I like the way voltage is dropped to a .88-.9 factor.  Initially, I made some mistakes with current and burned a couple.  Kept on reading and began to understand the saturation, but there are many other things to consider.  That is when I started just following proven schematics like in Hammond Organs, but have not given up on understanding from a design point as the amps I have built are sparkling clean, but cost a tad more to build.  I still use a screen choke as well.

The original specs come from a guy I found who sells original Use Vox Iron and seems to know a lot about it.  Right now his site is down due to a family illness and I have not heard back from him as to what it is.

Here is the link:
http://livinginthepast-audioweb.co.uk/index.php?p=xfrmrclassic

He is in england and has been very helpful in hashing out this stuff as he has the original iron for sale, but honest enough to say if I am planning to play the amp a lot it would be best to use Mercury.  I mentioned the New JMI Amplification was using Mercury and I dod not like the amps at all.

He is the one who told me the voltage was too high in the Mercury PT and the choke was inconsistent with the original.  The result was a less brown sounding amp with the EF86 getting very harsh.  I have not heard back from him since the message of the illness.  Basically he told me the Mercury OT will work even though he had an original for sale.  He was also kind enough to give me these specs for the choke.

He explained to me why my first attempt did not sound right without me even asking.  He did tell me that everything in that amp is important to be the way it is.  I really don't think I can duplicate a 1960 Vox Ac15, but I do think I can get close.

edit... untangled quote. sluckey

[sluckey]

Ed, I've seen you refer to the 1959 AC-15 and also the 1960 AC-15. They are not the same. My circuit is based on the 1960 version.

[Ed_Chambley]

Ed, I've seen you refer to the 1959 AC-15 and also the 1960 AC-15. They are not the same. My circuit is based on the 1960 version.

I know.  It is a mistake I have been correct on before already.  Thanks for bringing it to my attention.  I sometimes do not type everything correctly, but it is the attached I am working with.  I have been sending this with my questions to Vox enthusiasts, parts and cabinet folks.  I have found many more as I get referred to others.  This is a lot smaller group of people and much harder to find information.  NEW PDF POSTED

I will tell you this.  Even the hardcore Vox folks are interested in this layout.

While I am here, I am planning a 19 x 8 x 2 Chassis.  It looks like I can get the Filter Caps inside on a cap board.  Any reason not to?

I should have started the thread with this PDF attached, but once I get all the information together, I will start a new thread on parts sourcing and building.

Sluckey, you know I am going to make a mess of the build.  The trem circuit is way cool and I am wanting to isolate it to use in another future build, but one screw up at a time

I am looking forward to building this and I have never researched one as much, but I have played the Handwired Vox AC15 (China) and the JMI.  The JMI is the same circuit, but what I have been told he has the wrong choke and to high voltage.  These thing are really important from what I have been told.  I cannot find a youtube video of a 60 Vox, 1 x 12" celestion.  I found one of a 2 x 12 which jarred my memory.

I firmly believe watching lego4040 and with the help from this forum we can get a really nice AC15 in a marshall headbox.

[SleepLess]

The JMI is the same circuit, but what I have been told he has the wrong choke and to high voltage.  These thing are really important from what I have been told. 

Well, there's one for sale not too far away from where I live but it's more than 2K$... It's a bit too much for a mod platform! lol...

I firmly believe watching lego4040 and with the help from this forum we can get a really nice AC15 in a marshall headbox.

So do I, we'll make it!

[sluckey]

but it is the attached I am working with.

Ed, that's and old version. There are a couple very minor error. Please delete that version and get the latest version on my website.

THX... Steve

[Ed_Chambley]

Sluckey,
Here is the new PDF from your website.  I removed the wrong one.

Thanks

[Ed_Chambley]

While I am waiting for an editable layout, a couple of things have come to mind reading Lego4040 progress over at BYOC.  The switches.  I have found some rotary that will accommodate a knob, the nicest one being at Mouser.  Also a 3 position switch.

I also found the original, but are expensive and limited. Sluckey made a suggestion on the BYOC thread I think I would prefer since I'm not doing an authentic style chassis and using a single plane.

Please let me know if I have this correct as I am getting together a parts order.  

Use to mini toggles SPST and a 3Mra pot like on a Fender Tremolo.  This would be a mini toggle for Tremolo/Vibrato and and another for the Brillance and the 3Mra pot to replace the 3 selectable resistance switch.

If all is correct and will work, please confirm.  My only question is why Vox would have used 3 dedicated resistors instead of the pot?

I am planning 19 x 8 x 2 chassis and began a rough layout on the chassis and it looks like it would be nice to put it into the 1 x 12 British/Buesbreaker cab Mojo has.  The Fawn replica North Coast Music has is $500, but Mojo offers many different coverings they just do not have the Vox grill cloth.

I am simply doing a Small Box Marshall head.

Tubes: any reason to find a NOS rectifier, or current production up to the task?  Never used current production rectifier tube as NOS are fairly cheap except for a few.

The EL84, I have read the best are European, Amperex and Mullard topping the list.  As so far as new production, JJ's seem to win the crown, but DR Z and Matchless both use Electro-Harmonix.

 

[terminalgs]

for a cabinet, you might consider buying a Vox V112TV fawn extension cab for $170 new. you'd need to make the cut out for the control panel (which can be done in a way to not cut the tolex so it can be folded over).   I don't know what the materials are and whether or not the cabinet sounds good, or if the included celestion sounds good or not.

The Vox AC15/VR is showing up used now and again for less than $300,  but thata the later black cab style.

[sluckey]

Here is the new PDF from your website.  I removed the wrong one.

You may want to just post a link to that PDF. That way the latest version will always be available. Right now I'm considering a change to a 20" chassis. Eliminate the cap board. Use a F&T 2X16µF can. Make the main board longer to accommodate the remaining three filter caps or just tack them along side the board Hoffman style.

... and a 3Mra pot like on a Fender Tremolo.

You'll want to put a 100K resistor in series with that pot. Otherwise turning the speed to max will kill the oscillator. I'll probably do the same if I ever build this.

Tubes: any reason to find a NOS rectifier, or current production up to the task?

I've had good luck with old and new EZ81s. On a related note, the reason I prefer the Hammond 270FX is because you can use a 5Y3 or GZ34 or EZ81, in case you may want to juggle B+ values.

[Ed_Chambley]

Here is the new PDF from your website.  I removed the wrong one.

You may want to just post a link to that PDF. That way the latest version will always be available. Right now I'm considering a change to a 20" chassis. Eliminate the cap board. Use a F&T 2X16µF can. Make the main board longer to accommodate the remaining three filter caps or just tack them along side the board Hoffman style.

... and a 3Mra pot like on a Fender Tremolo.

You'll want to put a 100K resistor in series with that pot. Otherwise turning the speed to max will kill the oscillator. I'll probably do the same if I ever build this.

Tubes: any reason to find a NOS rectifier, or current production up to the task?

I've had good luck with old and new EZ81s. On a related note, the reason I prefer the Hammond 270FX is because you can use a 5Y3 or GZ34 or EZ81, in case you may want to juggle B+ values.

I have a Hammond 270FX, that is why I am using it.  

Good point about the 5v tap and the options.

When are you going to redraw for a 20"?  I was planning something similar and I love the cap can idea for the 16uf's.  If you are doing it for a 20, I am sure it will fit a 19 that I have.

If you are going to do this, I would like to wait since it would take me a week to revise all those things in visio.  There will need to be a new drill template with wiring scheme and I don't think I want to attempt that.  I am out of board material and was needing to put together a small order to get drilling and staking.

If you plan to do it soon, please let me know!!!

I was just going to make a filter cap board and move the pre amp filters close since I am working in an 8" deep chassis.  It will work as is, but I would have one fairly long B+ run on the 33uf, but it would work fine.  Shorter is better.

When you speak of creating a link to the file are you speaking of uploading and provide a server link like you do?  That way the forum does not get trashed with obsolete files?  I believe that is what you mean.  I will look into it as it makes good sense if the file is not editable, however I do like all the .sch files that have been revised and the old ones still hanging around.

[sluckey]

I don't know when I'll revise the drawing. Springtime is a busy time for me so it will probably be a while. Could even be next winter! So, if you're in a hurry, better do it yourself.      However, the drawing you have right now is very doable and the cap board under a doghouse on the outside of the chassis will look fine.

[Ed_Chambley]

I don't know when I'll revise the drawing. Springtime is a busy time for me so it will probably be a while. Could even be next winter! So, if you're in a hurry, better do it yourself.      However, the drawing you have right now is very doable and the cap board under a doghouse on the outside of the chassis will look fine.

Sure, I will redraw that drill layout.

I have some very old fenders and the doghouse worked just fine and still humming after 50 years.  It is not a bad idea.  I will drill the board and see where I am and how it is going to fit the chassis.  It looks as the B+ connections are all fairly close together.  I have been looking at the thing so much, I can remember a lot of it and see it when I close my eyes.

I don't mind the drawing and layout, but this tremolo is sort complex.  The EF86 channel is simple.  Thanks for what you have shared.  I ain't mess with it except for chassis dimensions.

[Willabe]

I drew out a couple of different layouts this last winter for the Gibson/Vox vibrato/trem.

They are not tested or finalized but they might help you.

Where there's a - t - in an eyelet it's really a turret the rest are eyelets, but if you go with all turrets it wont matter.

I don't remember why I put a 0.0047 cap in series with the 2nd tubes plate R? It is wrong but you can fix that.  


                 Brad    

[Ed_Chambley]

I drew out a couple of different layouts this last winter for the Gibson/Vox vibrato/trem.

They are not tested or finalized but they might help you.

Where there's a - t - in an eyelet it's really a turret the rest are eyelets, but if you go with all turrets it wont matter.

I don't remember why I put a 0.0047 cap in series with the 2nd tubes plate R? It is wrong but you can fix that.   


                 Brad    

Thanks, I have been wanting a Gibson Tremolo layout.  I like them a lot.

[Willabe]

Yes but will they work?    

Have to wait for Sluckey and/or HBP and Tubeswell to say yea or nay.

Vox copied the Gibson vibrato/trem. They are very close to being the same thing, with the output summing/filtering as the main difference.

Took me a long time to work those out. The sch is free and I'm greatfull to have it but it is NOT very modify friendly.  

A lot of how and why I design my layouts is to end up with any B+ PSU +/- wires very close together so I can keep the circuit B+ loop short and so I can have twisted pairs of wires going to the next B+ filter cap node.  

The 22uF filter caps I was going to change to only a 10uF or 8uF.

The drawings are to scale including parts.

           Brad      

Edit; Now I remember the B+ for the 2nd tube is really the circuit output mix? I think I lifted it from Merlin's build where he got ride of some extra parts that Vox added? Something like that.  
 

[TNblueshawk]

Subscribed.

[sluckey]

Ed, this is a quick screenshot of the revised board. The length will be 13.75". By using the F&T dual 16/16 can the filter cap board goes away completely. It will all easily fit in a 20" chassis. Might even fit a 17.5" chassis if you don't put the cap can in line with the tube sockets.

I still have to verify the new board layout. Then I can update the drill guide. I'm gonna keep the other version on my website and I'll just call this the long board version.

If you have any comments or suggestions, or spot any errors, spit'em out before I get too deep in this.

[lego4040]

  Thank god I havent started the soldering yet. I promise I will post pics of my AC15 build so far tonight, maybe sooner. I will go over and see what changes I need to possibly make, Thanks for the update sluckey. I am getting the Hammonds because I swapped great hockey ticket seats to my friend who owns a hardware store(I love the Barder system) I will buy Different ones tho, Everyone is all over the MM but Triode had the DYnaco that I thought would work. That revision will not work for me on my board, I would have to start over, no bueno.

[Ed_Chambley]

Ed, this is a quick screenshot of the revised board. The length will be 13.75". By using the F&T dual 16/16 can the filter cap board goes away completely. It will all easily fit in a 20" chassis. Might even fit a 17.5" chassis if you don't put the cap can in line with the tube sockets.

I still have to verify the new board layout. Then I can update the drill guide. I'm gonna keep the other version on my website and I'll just call this the long board version.

If you have any comments or suggestions, or spot any errors, spit'em out before I get too deep in this.

My god is it winter already?

This is a real winner I think.  I usually fold up 19 x 8 x 2 chassis and corner weld them.  I can usually get anything I want in them.  This will fit nicely and still give me plenty of room to make the lead dress purty.  I am going to attempt to build this one where it looks like a real amp builder did it.

I looked at it and it looks like what I was thinking.  Everything seems like it is in the right place.  I printed it and am going to check it against the schemo.  We all cam make mistakes, but I would bet it is right on.  

I just placed an order for some board material and many other small items.  I went with the exact Filter caps you have drawn, imagine that. A 30uf F&T.  I have a dual cap can already.

I am trying to come up with cool design for the faceplate now.  As fate would have it, I am getting a tad sidetracked since I have a job and we are getting busy.

Anyway, if you get a drill guide for the long version I would really be grateful.  You know me, I would just fit it in and that is want I was planning, but allowing for the caps is really cool of you to do.

I am not concerned with my Visio skills, it is the drill guide and underboard wiring I am scared to draw as I know it would be wrong.

[sluckey]

I am not concerned with my Visio skills, it is the drill guide and underboard wiring I am scared to draw as I know it would be wrong.

The drill guide is a lot easier than you might think. All I do is copy the loaded board to a new page. Then I just delete all the components. All that's left is the board, turrets, jumpers, and other holes. Then I do a little cleanup with colors etc. Wala! A drill guide. Only takes about 15 minutes for a complex board like this.

The hard part is re-verifying the layout is correct. I slid some stuff around when I stretched the board and sandwiched the other caps and resistors in place. It's always a good idea to recheck the whole thing and make sure it still agrees with the schematic.

[Ed_Chambley]

I am not concerned with my Visio skills, it is the drill guide and underboard wiring I am scared to draw as I know it would be wrong.

The drill guide is a lot easier than you might think. All I do is copy the loaded board to a new page. Then I just delete all the components. All that's left is the board, turrets, jumpers, and other holes. Then I do a little cleanup with colors etc. Wala! A drill guide. Only takes about 15 minutes for a complex board like this.

The hard part is re-verifying the layout is correct. I slid some stuff around when I stretched the board and sandwiched the other caps and resistors in place. It's always a good idea to recheck the whole thing and make sure it still agrees with the schematic.

Thanks for the tip on the drill guide.  Did not think of doing that, but it is way better as it insures proper placement.

As you can see, I an typing before I think.  I am getting excited.  How weird.

[dbishopbliss]

Ed, this is a quick screenshot of the revised board. The length will be 13.75". By using the F&T dual 16/16 can the filter cap board goes away completely. It will all easily fit in a 20" chassis. Might even fit a 17.5" chassis if you don't put the cap can in line with the tube sockets.

I still have to verify the new board layout. Then I can update the drill guide. I'm gonna keep the other version on my website and I'll just call this the long board version.

If you have any comments or suggestions, or spot any errors, spit'em out before I get too deep in this.

Will you be posting the longboard layout on your site?  I have a friend that is GAS-ing for an AC15.  I think it will be next on the list after I finish up my bandmaster and 1 Watt.