Planning a stereo tube guitar amp

[Ed_Chambley]

The noticable difference in the th AC15 and A30 is the AC30 to me would be a better all around amp.  I use a Prinston reverb and a AC15 for gigs and I can stay clean in a smaller place, but I have had to turn down the AC15 and use the line out in a bit larger place.  The big draw to this idea for me is I have always prefered Parallel Push Pull.  But like a Super Lead Marshall, if you lose one tube it is obivous.  If you lost 1 of 8 El84 I don't think it would shut down the gig.  Plus, they are cheap too and running more of the politely IMO is better than toasting them with the higher voltages in other deaigns.  Should get you in the neighborhood of 60 very clean per


After I wrote the comment, which I did mean, I began looking for one of those Transformers since a UL 135 watt would "should" reproduce lows well.  I know my Push Pull kt120 with the Triode Dynaco replacement transformer will cleanly pass 75hz at 80 watts and that my freind is reallly good for tubes.  So I added a Bass cabinet to use with it as well.  My it does sound great.


really it is just an 8 tube amp with a preamp tube.  It is not THAT rediculous.  Just look at the tube lineup in the Brown Twin.  I did breadboard a SE, 4 El84 and started one in Dougs stock chassis, but got sidetracked on repairs.  The reason I did this is the larger Vox wattage amps do not use El84's and sound quite different, but will play louder and cleaner.


Back to the El84 idea.  Sure I made a joke on punching the chassis, but it really would not be difficult.  BTW, I am sorry my old southern joke was missed.  I have 2 of them I say often.  One is "Sure I can do___________ (fill in the blank with a project), I can put windshiled wipres on a Jackrabbit's A$$.  It is just a way of saying yes, I can do it, no problem.  With people who understand and share the sense of humor, it is just a coy way of saying the same thing.


And the other which is a funny.  If someone is complaining, but nothing serious, like they got cut off in traffic or something like this, around here you might here "Do you think it would help if I pissed on a spark plug."

[Toxophilite]

Revisting this as the idea solidifies more.
Partly inspired by checking out an ampeg super echo twin. Neat amp! and supposedly only 48lbs


I'm not at all looking for endless clean headroom
I'm looking for enough, JUST enough. in a compact stereo package that doesn't weigh a tonne
My vibrolux reverb 2 x 10 build weighs in at 37 lbs! 
For this amp I'm aiming at under 50lbs


With my lighter jazzier,latin pop combo (which is louder than a jazz combo but quieter than a full on rock band)
I can achieve this with a pair of my homebuilt deluxes not quite at full clean volume (Vol around 4 on the main amp) I'm only using two for the stereo echo. I'm pretty sure one could do it.


With my rock/pop trio(with a louder drummer and bassist) I can achieve this with my vibrolux reverb build running around 4.
 
I was aiming at building an amp for the quieter band to start so I maybe need 18-20 watts a side tops
Especially as there will be 'two' amps


As far as El84s go. They were one idea. the other was 7189s which are capable of 20 watts in pushpull.
 The modern Russian equivalent the Ep14-Ev (Eb, Er depending on how you read Cyrillic)/El84M seems like it can handle higher voltages and might be worth a try.
Regardless I have enough older 7189s to give the idea a shot


I was thinking smaller bottle tubes= a smaller footprint on the chassis


I will probably be building using a AO-29 donor chassis and PT


I guess my next design hurdle will be layout.
I have a long narrow chassis. I've seen a few variations.


1- power amp in separate chassis bottom of the amp
2- everything in a line(ala fender amps except stereo) pre  pre PI and PA , PI and PI  power supply
3 or like the super echo which I think is particular to using two separate power supplies(CRAZY!)
 PS PA and PI pre    pre, PI and PA  PS


I was going to try for option 2
Any big problems with this provided I lay things out well and use shielded Coax for my audio signal runs from each pre to each PI ?


I was also looking at the Ampeg reverb and trem circuits. I like what I've heard of them, I like how they each use one preamp stage and low component count(except for the trem)and I like how they're each on different channels.
 This would save me two preamp tube (less power drain and space) while still achieving the effects I like


Any reason why I can't use this in a AB763 stereo setup?

[sluckey]

I think that stereo Ampeg is a very good choice.

[Toxophilite]

I think that stereo Ampeg is a very good choice.

Hi Steve


Are you actually commenting that you think that I should go for the ampeg super echo twin amp that I have in another thread?
Or are you obliquely commenting on my convoluted build plans?


Other than the a Jazz chorus and various hifi conversions it would be my only other brand/ type of amplifier.

[sluckey]

Are you actually commenting that you think that I should go for the ampeg super echo twin amp that I have in another thread?

Yes. I've owned a Gemini II from that era and am familiar with the warm clean tone of those amps. I think you should at least go see how the amp sounds. I don't think you'll be disappointed.

[Toxophilite]

Oh man!
I really really really wish I could go see how the amp sounds...except it's a 9 hour drive NORTH at the worst time of year to do so!! I did make an offer on it though, and as it's within Canada shipping isn't too crazy. It would cost more to drive there and back than it would to ship it!!

[Rp3703]

Not sure where you're at on this project but I'm trying to do something similar only I am trying to repurpose a Marshall 9000 dual 50 watt tube power amp. You can pick one up for around $400 which is less than parts to build it would cost. I'm planning to pair a stereo Plexi preamp with it but want to run everything in the pre off the 9000 so I won't need a PSU in the preamp. Once it's finished, I plan to stick a Mimiq pedal infant of it. Even if it doesn't work live, it should cut recording time in half.

http://el34world.com/Forum/index.php?topic=23047.msg247113#msg247113

[Toxophilite]

Cool!
I'm not alone! 


I'm still in the planning stage. I have most of the parts assembled. going to pick up a PT friday. I have a couple of those Hammond Ao-43 OTs they should do the trick
I'm going for lower wattage(18-20 watts aside) and easy portability in a combo format

[Toxophilite]

I was initially planning to do my amp 18-20 watts a side with those Hammond AO-43 type OTs and maybe a single power supply in the form of one of the bigger ones from an AO-29


Looking at the super echo twin got me thinking,
Was there a good reason Ampeg used two PTs ?
Was it it overbuilding in the interest of uber clean reliable power for both amps? Was it laziness of design?
Was it visual symmetry??


Anywho as a result I was thinking maybe a similar layout but with AO-44 type PTs?


THose AO-44 Pts look like good ones but not huge


I was also thinking of powering 7189s in this amp


But has anyone tried 6V6s with a Hammond organ AO-44 type transformers?

[Toxophilite]

Okay I was asking about 2 small PTs or one big one
While wondering why ampeg used two PTs on the super echo twin
I was wondering if there was a useful rational other than because they did sort of thing


I think if I was to use the sort of trem and reverb circuit/configuration ampeg has in the super echo twin I could get down to a 4 tube power supply section, 2 pIs and 4 tube preamp and 'effects'


10  tube amp seems pretty good for a stereo build

[PRR]

It's two medium amps to make one big amp.

If they expected to make a million, they woulda designed one big PT, be a buck+ cheaper than two.

But they were making a million (well, thousands) medium amps, they had all these parts on the shelf, the stereo amp might be (was?) a bust on the market. Best to start with the parts on hand; worst-case, you strip each unsold Stereo and make two single amps.

Your economics and logistics may be different. The 80W-100W Fender/Marshall PTs are now real commodities, and could serve a 2x40W amp.

[Toxophilite]

Ah expediency
I figured it might be something like that
So no real advantage
Speaking of expediency as I'm building a stereo 20 watt aside amp ,I might try a PT and chassiss from a Hammond AO-29.
 I have one on hand and as the footprint is large the space can accommodate a bigger PT  if need be
Thanks

[Toxophilite]

Well now I've buried my Ampeg thread, but learned a lot in the process
I'm getting back to this build
I have 2 stripped AO-29 chassis, one with the uber PT which will be my starting point. I had considered pop riveting a few more inches from the one AO-29 chassis onto the other but I'm going to see if I can manage without doing  that first


I also have 2 OTs . The same sort used in the AO-43 and the AO-63(reverb amp). these work for a deluxe so they should be good enough for my initial experiment. I have a 10 henry choke which is likely overkill but it's here,available and FREE.


My question is regarding layout. I believe I asked this earlier but didn't get an answer.
Is there any problem with laying this thing out in a linear fashion, like a fender, except with the power amp and PI sections side by side, then the effects and then the preamps?
like this:


PA PI  PA PI Treme  reverb  preamp  preamp


That makes sense to me,grouping the similar components together. It will also make the B+ and filter cap nodes easier to manage etc

[Toxophilite]

Sometimes having these forum conversations with myself can really make things clear.....


Maybe some pictures will help!



Here's a few orientations of OTs and layouts


-First with 6V6s (this is assuming I'd go with the amp Super echo twin Ot drive reverb and their 1/2 preamp tube bias vary trem) 20 - 22 watts aside
(oops I just realized I have one too  many tubes in the 6V6 layouts..ah well more room is better!)


-OTs different


- with 7189s. this allows me to squeeze in an extra preamp tube in case I want to go with a fender AB763 style reverb or what have you 18-20 watts a side.

[silverfox]

Sounds like your on track. As far as orientations go, you will want to power the amp up and check for noise levels before you finalize the location of the transformers. Unfortunately, at that point there may not be sufficient room to move the OT to where it may need to be. Plan accordingly.

Keep in mind, noise can also be conducted through the chassis itself to the OT.

silverfox.

[Toxophilite]

Thanks. Other than the 2nd OT that would be pretty well the exact sort of placement I've used successfully with my deluxe and vibrolux builds all based on the same or similar Hammond Chassis.


Out of curiousity If I copied the Ampeg PA and PI as well as the effects but put a two gain stage 12AX7 AB763 pre in front of it. Is there anything I can do to tweak the PI and PA to get a little more power out of it?

[silverfox]

I got quite a benefit in asking for help with the signal matching and debug of my power amp after completing it. Here is the link to that episode: http://el34world.com/Forum/index.php?topic=19662.msg204695;topicseen#msg204695

regards,

silverfox.

[Toxophilite]

  Cool! That's what this thread is about, I've built a few amps from scratch successfully before using the help of the nice people here.
On this amp, at this stage it's mostly the planning and layout stages I'm looking for counsel on.
Who knows I might just have to do it....


https://www.youtube.com/watch?v=V-6X7VR9Abo

[Toxophilite]

I've assembled al the bits and pieces and I have a few questions


From measuring my vibrolux reverb with bias vary trem in an AO-43 chassis and tagging on another power amp, phase Inverter, bias supply and preamp my measurements say I need about 18" of boards. I'm reusing old hammond cone boards like I have successfully in most of my builds.


The hammond AO-29 chassiss has an interior length of jusT 19". I might still extend it or make my own.


- If I don't I was wondering if there is any problem with have the first filter caps and bias supplies on a short board mounted OVER the power transformer?
The chassis is deep enough to accommodate this. (see picture)


In the interest of space and maybe a tube or so less
I was thinking of a  one tube reverb as suggested by tubenit here:
http://el34world.com/Forum/index.php?topic=7957.0


-Any problems with this with a 7189/El84 based AB8763 style amp ?


-and possibly(though it isn't necessary, I just kind of liked it) the half tube tremelo used in the ampeg super echo twin I have.


Same question as above except about the tremelo