Vox AC15 Tweed Deluxe hybrid w/ reverb schematic

[Opry Audio]

Hi Everyone,

I'm close to finishing the first draft of a schematic for a build I'm planning. The first few stages are almost exactly a hoffman ac30 with a matchless style input stage included. I could use some feedback on the potential of a circuit like this being good, what I could change to make it better and power supply considerations. I'm going to put a cut control in there too!

I lifted the power supply from Geezer's Tubemeister because the PT voltages on the secondary line up exactly with one I have on hand that I plan to use. The OT I plan on using is a classictone 8K. I'm sure I made a mistake or two, I appreciate all of your help in advance! So.. how does it look?

[Opry Audio]

Also, apologies for the clear inconsistencies in the schematic, still kinda new to expressSCH and was working with some custom components I couldn’t modify. Shouldn’t be hard to figure what that is though! Thanks for looking

[kagliostro]

Calling it VOX AC15 seems a bit risky to me, the differences are too strong, don't you think ?

Hybrid amp will be a better designation to me

Franco

[Opry Audio]

Calling it VOX AC15 seems a bit risky to me, the differences are too strong, don't you think ?

Hybrid amp will be a better designation to me

Franco

That’s true! The tonestack is the only real voxy thing about it, but I’ve seen many people suggest using the cascode input stage as an alternative to an EF86 input stage. Maybe I’ll end up doing a partially bypassed input stage top boost style, I just wanted to be wary of there being too much high end

[tubenit]

I really like your design!  I think that's gonna be a great amp.  Only thing I might change is the post phase invertor coupling caps from .1 to .047.

With respect, Tubenit

[Opry Audio]

I really like your design!  I think that's gonna be a great amp.  Only thing I might change is the post phase invertor coupling caps from .1 to .047.

With respect, Tubenit

Thank you tubenit 

Can you elaborate why? I know it would be filtering higher frequencies into the output stage. Think it might be too dark?

[shooter]

Think it might be too dark

having 2 25uf caps bypassing the preamp tubes tends to muddy n darken
have a handful on hand between 2uf - 15uf once it makes guitar sounds

[Opry Audio]

Think it might be too dark

having 2 25uf caps bypassing the preamp tubes tends to muddy n darken
have a handful on hand between 2uf - 15uf once it makes guitar sounds

Might be a good excuse to build a substitution box 

[Opry Audio]

I would definitely like to put out there that I would like some input on the B+ rail. The transformer I’m using has a 660v secondary at 120ma. Will the power supply that I’ve provided suffice? Will voltages drop to something each stage likes as specified on the schematic?

[shooter]

Will voltages drop

you gotta do the math and experiment

estimate ~ current draw for both PA tubes based on ohms law
with max I and the schematic "guess" at the A tap calculate R with ohms law INCLUDING Watts.
buy steal or make a test R (dummyload)
connect it from A tap to ground n monitor VDC at A tap
do it quick in case you messed up your decimals 

[Opry Audio]

Will voltages drop

you gotta do the math and experiment

estimate ~ current draw for both PA tubes based on ohms law
with max I and the schematic "guess" at the A tap calculate R with ohms law INCLUDING Watts.
buy steal or make a test R (dummyload)
connect it from A tap to ground n monitor VDC at A tap
do it quick in case you messed up your decimals 

Cool, I will go with what I have and see what the results are. I think a better question is what voltages I should be shooting for on each stage to get the most out of the design that I’ve laid out. I know that’s a bit subjective, and for the reverb stage the correct voltages are well documented in fender schematics. Mostly asking about the input stage, CF, cathodyne PI. The A and B voltages should be fine based on the transformer that I’m using.

350vDC for voltage E seems ideal for example. Maybe I’m overthinking it and I should just build the thing, but I have historically wasted many hours not thinking ahead 

[JB]

Don't know what rectifier you're using but 50u//50u = 100uF may be too much for it.
If you don't want to mock up loads to determine your power supply then Duncan's PSU designer is what you need:
http://www.duncanamps.com/psud2/

[tubenit]

Don't know what rectifier you're using but 50u//50u = 100uF may be too much for it.

Yeah, that could be a concern.

[ac427v]

"Steelwitch Amps" Now that's a great name!
I had some random thoughts on your design. Haven't learned the math for power supply design. It seems easier to just try resistor values and experiment. In a similar amp I used a 6.2k/3 watt resistor between points A and B. That dropped 48 volts. I think that is an essential part of the tweed deluxe sound. I would expect your design to have about the same voltage drop. 10 watt resistors are hard to place on a circuit board so I avoid them unless truly needed. Fender used a 2 watt in this location on their Tweed Deluxe RI. Doug Hoffman sells nice 3 watt that I use to ensure cool running.I like using a cap can for the first filter but I connect one section (50uf on your case) to B+ and the second section to the screen supply B. Ground the - terminal to the R/Y center tap and connect to the chassis in a location separated from the other cap grounds to minimize noise.The reverb on this plan does not have a mix stage. The 3meg resistor will direct almost all of the signal to the reverb driver and almost none to the phase inverter. Tubenit gets around this problem by using a long-tail pair PI for gain and drastically reducing the size of the 3meg resistor to something like 150k. If you go that route, you may still find that you need every speck of signal available to achieve low hum drive for the reverb tube. Could use a 1meg resistor instead of a dwell pot. Try the dual dwell/mix pot on another build. That is a cool idea!
You are great about posting on how your builds go. Input from others and your updates are always interesting.

[Opry Audio]

Don't know what rectifier you're using but 50u//50u = 100uF may be too much for it.
If you don't want to mock up loads to determine your power supply then Duncan's PSU designer is what you need:
http://www.duncanamps.com/psud2/

Ah that’s totally true. 100uf would be too much for basically any rectifier tube. My 5v winding runs at 3A so I have a bit of a range to play with. Thank you for linking this Duncan power supply designer. I didn’t know this existed and it’s exactly what I need

[Greg]

Nice work! That 5k power resistor will drop more than 1 volt (likely 25 volts) and this might be a good thing for the screens at higher voltages. But it's true that you are missing a recovery stage in the preamp (also to introduce feedback if desired). You could drop the parallel input stage and reconfigure to have a recovery stage added. If the 6V6's plate voltages are 425 v. high, you might choose a pair of 6V6S from JJ. Going from 0.1 to .047 is fine (15Hz high pass) but your first coupling cap is only 500 pf and it will cut some bass starting at 318Hz for the rest of the circuit. To be consistent with the high pass frequency through the amp (let's say 15Hz), you might choose 0.01 µf as the first coupling cap and second (assuming a recov. stage with 1 meg input resistance not in your schematic) and use the 500pf as the input cap of your cathodyne inverter and both 0.047 at the PI's output. But all the values could be trimmed by ear of course!

[Greg]

That missing recovery stage that I was talking about could be (also) the opportunity to add a master volume after it, right before the phase splitter side. This will give more utility to the 1 meg dwell reverb control and roll it back since high settings on the first volume control might slam the springs which will get you a kick-in-the-pan- for-every-note kind of sound. Which could be also desirable. Climate change type of wave. Extreme surf.

[Opry Audio]

In a similar amp I used a 6.2k/3 watt resistor between points A and B. That dropped 48 volts. I think that is an essential part of the tweed deluxe sound. I would expect your design to have about the same voltage drop. 10 watt resistors are hard to place on a circuit board so I avoid them unless truly needed. Fender used a 2 watt in this location on their Tweed Deluxe RI.

Thank you for that take! I will try a 6.2k and see what the results are, I may end up seeing what gets me the most unique sound ultimately without giving up making the screens happy. I'm updating the current schematic with my results from the duncan psu calculator now :) I am so stoked something like it exists. I have a pretty nice ground scheme going based on Merlin's grounding chapter. I'm doing this amp constructed on terminal strips (sort of half in the style of a traditional circuit board with PTP elements when it's convenient, so component size isn't too much of an issue for me. You'll see when I post the layout.

The reverb on this plan does not have a mix stage. The 3meg resistor will direct almost all of the signal to the reverb driver and almost none to the phase inverter. Tubenit gets around this problem by using a long-tail pair PI for gain and drastically reducing the size of the 3meg resistor to something like 150k. If you go that route, you may still find that you need every speck of signal available to achieve low hum drive for the reverb tube. Could use a 1meg resistor instead of a dwell pot. Try the dual dwell/mix pot on another build. That is a cool idea!
You are great about posting on how your builds go. Input from others and your updates are always interesting.

I'm going to put some more consideration into the reverb circuit. I'll post more about it in another post or reply. Thanks for readinng my threads, I mostly come here for help and I'm extremely grateful.. even when sluckey rips me to shreds and makes me think about my life choices  ;)

[Opry Audio]

Nice work! That 5k power resistor will drop more than 1 volt (likely 25 volts) and this might be a good thing for the screens at higher voltages. But it's true that you are missing a recovery stage in the preamp (also to introduce feedback if desired). You could drop the parallel input stage and reconfigure to have a recovery stage added.

Ahhhh I would love to keep this parallel input stage but you're right, I need to give up a triode somewhere for the recovery stage. I can't believe I didn't even consider that. Is it going to completely kill the quality of this reverb design to run the driver from one triode only? I know I would be giving up less by changing the input stage, but I would also consider doing something based on tubenits one tube reverb in some way. I'm not looking for extreme surfiness specifically. This is kind of a crazy idea but are there alternatives a full triode recovery stage? tap it off from somewhere else?

If the 6V6's plate voltages are 425 v. high, you might choose a pair of 6V6S from JJ. Going from 0.1 to .047 is fine (15Hz high pass) but your first coupling cap is only 500 pf and it will cut some bass starting at 318Hz for the rest of the circuit. To be consistent with the high pass frequency through the amp (let's say 15Hz), you might choose 0.01 µf as the first coupling cap and second (assuming a recov. stage with 1 meg input resistance not in your schematic) and use the 500pf as the input cap of your cathodyne inverter and both 0.047 at the PI's output. But all the values could be trimmed by ear of course!

I will give this a try too. (I'll put ranges of C values instead of specific values in my revised schematic). I put in a 500pf just because I really like how it sounded in the hoffman ac30 build I did. There is a bit of low end lacking but it ended up being the right thing in the context of that design. I could see it being somewhat too high of a high pass on something like this but that's what tweaking is for! I do like the .047 coupling cap into the PI output tweak that was suggested. I'm going to give that a try as well.

[Opry Audio]

That missing recovery stage that I was talking about could be (also) the opportunity to add a master volume after it, right before the phase splitter side. This will give more utility to the 1 meg dwell reverb control and roll it back since high settings on the first volume control might slam the springs which will get you a kick-in-the-pan- for-every-note kind of sound. Which could be also desirable. Climate change type of wave. Extreme surf.

I'm not sure I understand the correlation between a master volume control and the dwell control for the reverb  could you explain what potental problems I'd have? Plenty of amps cronch and have well balanced reverb with no MV

[Greg]

Of course, keep your parallel input and you could make a parallel reverb recovery stage also like your input stage. Or you could also use a single tube to drive the reverb tank AND the return using a single 12DW7. 12DW7  is half-12au7 and half-12ax7. Keeping the circuit the same exept a bias resistor of 1k for the ½  12au7 driver section with the same 22k transformer, 300 V B+ not like 425 or someting.

Forget the master volume story if you don't want one really... I don't like them either. All is ok for the Dwell pot, absolutely nothing wrong with it. I was basically babbling about the dwell meg pot being more effective to tame the drive, not to augment it like its implementation in the Fender stand alone reverb unit. In the case of your amp, you set the dwell at maximum when using low amplifier volume and you set the mixer control instead. As you get near max on the amplifier's volume, the preamp send a very strong dry signal to the driver tube which might distort or overcrash the reverb. A condition that doesn't  usually occur in the fender stand alone unit because the drive signal is independent on volume, and unless you run it with 20% higher B+ or insert an EL34 in it, the pan won't usually sound overdriven.

So, basically what I was saying is, in your amp, at high volume (or high gain with a master), reverb distortion is going to be cleaned-up by the dwell control and could be very utile in that matter and less so, if the amp is played always clean as fender intended (and that's probably why it was omitted on the onboard reverb amps where your reverb circuit was derived from.

[Opry Audio]

Of course, keep your parallel input and you could make a parallel reverb recovery stage also like your input stage. Or you could also use a single tube to drive the reverb tank AND the return using a single 12DW7. 12DW7  is half-12au7 and half-12ax7. Keeping the circuit the same exept a bias resistor of 1k for the ½  12au7 driver section with the same 22k transformer, 300 V B+ not like 425 or someting.

That sounds like an interesting idea, but I haven't seen any fender derived reverb circuits run with a 12au7.. not to say a 12DW7 wouldn't work. *after doing some research i learned there is.. sorry! But I'm also trying to consider the ability to get replacement tubes for my amp very easily, and I'm not sure what the quality of currently produced 12DW7's are like. BUT what interests me even more is using a parallel reverb recovery. It seems like something that can be done with a 12ax7, no? I would rather make a common tube work. I assume you mean to drive the tank with a single triode and a parallel recovery into the phase inverter. I have a feeling like maybe the recovery would still be weak without a separately biased and powered triode gain stage. I haven't built an amp with reverb yet though so I'm not sure if anyone's gotten good results from a circuit design like that but if you have please chime in!

So, basically what I was saying is, in your amp, at high volume (or high gain with a master), reverb distortion is going to be cleaned-up by the dwell control and could be very utile in that matter and less so, if the amp is played always clean as fender intended (and that's probably why it was omitted on the onboard reverb amps where your reverb circuit was derived from.

Ah I understand now, makes sense. It also begs the question if overdriving the tank at a certain point could be a cool sounding effect. It's kind of here or there though. Some solid state reverb units that I love sound really good when the tank is overdriven, and turning the reverb mix down brings a little bit of cronch through to dry signal. being said, good clean and good cronch and touch sensitivity and good, versatile reverb is my goal for this amp

[Opry Audio]

Here's a revised schematic with a single triode input stage instead. The reason for the parallel input stage is because it brought down the noise level in my V1 stage in my ac30 build and added some really nice even order harmonics. It sounded way beefier and wanted to do it again. But it would be fine without it if the reverb recovery stage is worth it. I'll wait to hear some input about the parallel reverb recovery vs. separate recovery stage. This type of thing could work too. Thanks yall!

[Greg]

Now I don't understand when you say parallel reverb recovery vs. separate recovery stage. You got four socket holes right? If you want to keep the parallel input stage and the CF buffer, you have to make concessions in the reverb drive. Fender choose to bias a paralleled 12AT7 at 9 volt to drive the tank with very high plate voltage. Gibson uses half a 12AU7 at 9 volts for the same duty with 250 v. The transformer 22k primary is the right load for the 12au7. So voilà you got one tube reverb with good drive. It will work. I know it is not how fender did it, but I'm sure you will have plenty of reverb. JJ makes a current production 12DW7 called ECC832. This isn't a rare tube anymore. However, if you don't insist on the paralleled input stage and you prefer the fender reverb design, you can do your second version.

[Opry Audio]

Now I don't understand when you say parallel reverb recovery vs. separate recovery stage. You got four socket holes right? If you want to keep the parallel input stage and the CF buffer, you have to make concessions in the reverb drive. Fender choose to bias a paralleled 12AT7 at 9 volt to drive the tank with very high plate voltage. Gibson uses half a 12AU7 at 9 volts for the same duty with 250 v. The transformer 22k primary is the right load for the 12au7. So voilà you got one tube reverb with good drive. It will work. I know it is not how fender did it, but I'm sure you will have plenty of reverb. JJ makes a current production 12DW7 called ECC832. This isn't a rare tube anymore. However, if you don't insist on the paralleled input stage and you prefer the fender reverb design, you can do your second version.

I think you’re right about it being a middle ground. I hadn’t checked out Gibson reverb circuits like you mentioned, but I think this could be good. I will post a 3rd revision with all of these changes included to the thread. Thanks for your suggestions Greg! I wouldn’t have thought about that solution on my own and I appreciate your knowledge. Would the bias for the driver need to change to accommodate a 12au7 triode?

[Opry Audio]

The transformer 22k primary is the right load for the 12au7. So voilà you got one tube reverb with good drive.[\quote]

Just something of note: maybe my original schematic specified or insinuated the primary impedance is 22k for the reverb transformer, but it’s 25k. Not sure if that’s a small or huge difference in terms of what it will need to drive it, or if this great solution is still possible. I will get a 22k if not and reuse the current one for another build. 

[Greg]

No the bias would stay the same around -9 v. But to accomplish this with the 12au7 side of the 12dw7, you need to use a 1k cathode bias resistor. No problem with 25k! I had 22k in mind...maybe I confused it with a common resistor value? It's my pleasure to help you out but it's not easy online and english is not my first language! Also, there are others with more knowledge and sometimes, this make me feel kind of «unauthorized». Let's just say that I was able to help you out on this one, keeping the circuit the way you intend it to be.     

[Opry Audio]

No the bias would stay the same around -9 v. But to accomplish this with the 12au7 side of the 12dw7, you need to use a 1k cathode bias resistor. No problem with 25k! I had 22k in mind...maybe I confused it with a common resistor value? It's my pleasure to help you out but it's not easy online and english is not my first language! Also, there are others with more knowledge and sometimes, this make me feel kind of «unauthorized». Let's just say that I was able to help you out on this one, keeping the circuit the way you intend it to be.     

Got all these changes down. Here's another revision with some target voltages. I might make some other PSU considerations to get them but I think they should work. Will post a layout soon! There is a typo in the revision schematic: the input stage should be supplied by voltage D and not E

[Opry Audio]

The last thought I have on this for the night is that maybe I'm using too many stages for node D. Not sure if parallel input stages count as 1 triode in terms of the supply. I feel like it should be ok, I've seen vox schematics that kind of do this. I wonder if the triode after the reverb mix could benefit from its own node, or if any other stages will interact in a bad way causing feedback / unwanted stuff

[PRR]

> one tube reverb with good drive. It will work.

[Opry Audio]

> one tube reverb with good drive. It will work.

Dot removed :) I need to make a jumper symbol in expressSCH

[Greg]

Here's an approximation of the current flowing through all nodes with voltage drop using your specific voltages and updated resistors. You need to add an extra RC filter section for the reverb transformer because 400 v. is too much... 300 v. should do it. 20ma total is an approximation of the whole preamp including the screen grids at idle. It could be less than 20ma. Between 15 and 20ma. I doubt it could be more than 20ma.

[Greg]

Ok I might have overdone it for tonight ha ha... But I just saw your 330vac at 120ma and you aren't going to get 425VDC with a 5Y3 rectifier. More in the vicinity of 350 v. or a bit less, which is nice... On the other hand, you might get near 425 volts with a 5AR4. The 350 v. prototype might give a sweeter sound (I think) when cathode biased and the bias resistor could be made lower like 270 ohms keeping the B+ resistor chain the same. Of course tweaks could be made, like lowering the screens for more 6V6 gain while giving up a bit on power... Unbypassing the cathode of the recovery stage before the split-load inverter instead of NF loop... Stuff like that. This is fun stuff and if you are using terminal strip construction, you might be pleased to change or add components.

Good night and good luck!

[tubenit]

You could free up a triode by using a mosfet CF.  That could allow an active FX & reverb …. OR an LTPI …...OR a paralleled send for your reverb.

See the first post here for schematic, layout and photo:  http://el34world.com/Forum/index.php?topic=21873.0

Would you be willing to post the SCH version of your schematic, please?

I have done the 12DW7 "one tube reverb" approach and it works quite well.

With respect, Tubenit

[shooter]

maybe I'm using too many stages for node D.

the basic "rule" no more than 2 gain stages.  The reason is PFB sneaking back through the PS

[Opry Audio]

Ok I might have overdone it for tonight ha ha... But I just saw your 330vac at 120ma and you aren't going to get 425VDC with a 5Y3 rectifier. More in the vicinity of 350 v. or a bit less, which is nice... On the other hand, you might get near 425 volts with a 5AR4. The 350 v. prototype might give a sweeter sound (I think) when cathode biased and the bias resistor could be made lower like 270 ohms keeping the B+ resistor chain the same. Of course tweaks could be made, like lowering the screens for more 6V6 gain while giving up a bit on power... Unbypassing the cathode of the recovery stage before the split-load inverter instead of NF loop... Stuff like that. This is fun stuff and if you are using terminal strip construction, you might be pleased to change or add components.

Good night and good luck!

Greg, this is a really great revision to the psu. It’s true the voltages will be lower when loaded down, but I think all of this is in the range it needs!

[Opry Audio]

maybe I'm using too many stages for node D.

the basic "rule" no more than 2 gain stages.  The reason is PFB sneaking back through the PS

I should be good then assuming a CF stage is being counted as one gain stage?

[Opry Audio]

You could free up a triode by using a mosfet CF.  That could allow an active FX & reverb …. OR an LTPI …...OR a paralleled send for your reverb.

See the first post here for schematic, layout and photo:  http://el34world.com/Forum/index.php?topic=21873.0

Would you be willing to post the SCH version of your schematic, please?

I have done the 12DW7 "one tube reverb" approach and it works quite well.

With respect, Tubenit

This is a very cool design! I would love to try this in another build with more features. Maybe if this one turns out good I'll do a version with an effects loop. Have you tried these mosfets on their own? or are the best results in conjunction with a tube stage? I'm going to check out that thread a little later today. I haven't really made a leap into building anything solid state, but would love to know more to solve problems like this and for things I want to offer as a feature like channel switching. I know there are many proven and good circuits for that here already.

 Here is the SCH file for your editing and free knowledge pleasure.

Good to hear others have had good luck with the 12DW7 driver and recovery. I can't wait to give it a try. I will be posting a layout soon in this post as a .diy and pdf file. I have to work the extra node into what I already have going on

[tubenit]

The only time I've ever used mosfets in an amp is as a CF. IMO, using it in this position does NOT introduce any solid state "tone" & the tube tone is still preserved.  If it sounds just as good as a tube triode in the CF position, I'd rather use the tube triode in another way.

http://www.geofex.com/Article_Folders/mosfet_folly/mosfetfolly.htm

Thanks for sharing the SCH schematic.

With respect, Tubenit

[Opry Audio]

The only time I've ever used mosfets in an amp is as a CF. IMO, using it in this position does NOT introduce any solid state "tone" & the tube tone is still preserved.  If it sounds just as good as a tube triode in the CF position, I'd rather use the tube triode in another way.

http://www.geofex.com/Article_Folders/mosfet_folly/mosfetfolly.htm

Thanks for sharing the SCH schematic.

With respect, Tubenit

No problem, tubenit.

Just a few more thoughts. —

Regarding the reverb dwell control, someone mentioned to me that it would benefit from a resistor of 20% or lower between the pot and ground (200k for example) to fully bypass the dwell control when the reverb is switched off. Could be a potential source of noise. Can anyone verify? It wouldn’t be a difficult tweak to make at all, just wondering if it could benefit.

As I’m thinking more about what I want in this amp as a final product, I’m very interested in VVR power scaling. I have room for it in the chassis where the bias board would usually be mounted and would require no more drilling, and could use the chassis as a heat sink for the mosfet. I found a thread where you posted a PTP power scaling design and I think it could work in this amp! Can you verify this? What considerations would I need to make / potential obstacles.

The last consideration I’m having is adding a passive effects loop. You mentioned using a mosfet in the CF to free up a triode for an effects loop buffer, which is a possibility, but is a GOOD passive effects loop design possible for this amp? What would the drawbacks be? Thanks yall

[Greg]

I don't quite understand the resistor trick, but I would just dime the depth control and since the input of the reverb recovery stage will be grounded by the footswitch, this should take care of everything.

It looks like builders assume the C.F and the gain stage preceding it has to be in the same tube envelope... Maybe because it was presented as such in manuals. They could be an envelope a part. Say you don't like 12DW7. V1 can be stage one and two with a 12AX7... V2 could be the cathode follower and reverb driver using a 12AU7, a common tube... V3 could be reverb recovery and recovery gain stage... V4 could be the phase splitter and... a tremolo oscillator? Gibson for cathode bias or Fender for fixed bias, they all use half a 12AX7 with a great trem. Tremoluxes, vibroluxes, Falcon, GA-18T etc... Anyways if someone hates tremolo, this might be a good reason not to put tremolo.

I find that a hot biased first stage 12ax7, let's say 1.5k cathode and 270k plate will reduce the fidelity a bit like the effect of the miller capacitance in a paralleled tube... It does give a good fat compressed tone. Sounds «almost» like a paralleled triode!

[Opry Audio]

I toiled away at this layout and came up with something like this. What do you think? Would I be better off going with a turret board? I really love the idea of doing PTP amps, but I could be off the mark with this. Looking forward to hearing your input! It'll look better in 3 dimensions (hopefully). Thank you

[shooter]

My next build will be PTP.  Consider "studying" this turret layout with a terminal strip eye.  The BIG advantage no "fly" parts.  That said, my layout flys parts in a "spoke" array, sorta  .

[Opry Audio]

My next build will be PTP.  Consider "studying" this turret layout with a terminal strip eye.  The BIG advantage no "fly" parts.  That said, my layout flys parts in a "spoke" array, sorta  .

what do you mean by spoke? this is a great layout. whats the advantage to no flying?

[shooter]

Pg 1 reply #45 has a pic, I like to color 

http://el34world.com/Forum/index.php?topic=25104.0

Downsides;
lead length/stress
parts in close proximity have a tendency to talk about each other 
aesthetics, mine is a "play" on the old way, that WORKED, pretty sure rev 1 will have issues 

[Greg]

The way your chassis was pre-punched calls for some kind of circuit board à la fender, I mean from a point to point perspective, it looks like your chassis is backwards (see example). By backwards, I mean the control pots could be on the tube socket side of the chassis when doing point to point. This way, you have (say) a cap going from a socket to a pot without any wire. You eliminate two solder joints. Of course you can do it like your drawing but I don't think there is any real benefit signal wise. Since your chassis is punched for a circuit board, I would use a circuit board or two parallel turret/terminal strips in the middle. Also, it will be easier to change parts.

Regards,
JP

[Greg]

I wanted to correct myself in saying that you have one connection less compared to the fender board style. (I included examples below, using one part for simplicity, your style is #3).

I'd say, do it your way. Ptp is not always used to save connections and electronically wise, if the solder joints are sound, there is no problem at all if general layout conventions are respected. I guess output grid wires could be shorter if they didn't have to run to the front cut control. I'm wondering why the cut control since you have already a tone stack. I thought the treble cut was to accomodate the channel that didn't have tone controls in AC10, 15, 30 etc... I'm not good at inspecting layouts but it looks ok. Someone who are better at it might chime in.

[66Strat]

Stand-off tube sockets might be a good option for PTP wiring.

https://www.ebay.com/itm/Lot-Of-4-NOS-VECTOR-8N9T-9-pin-miniature-STANDOFF-VACUUM-TUBE-SOCKET-12ax7-EL84/163927120099?epid=17024894052&hash=item262ad158e3:g:J5EAAOSwHbldvKhT

https://www.ebay.com/itm/Lot-Of-4-NOS-VECTOR-8O9T-8-pin-octal-STANDOFF-TUBE-SOCKET-6L6-6V6-Amp-Guitar/163927172287?hash=item262ad224bf:g:8SgAAOSwHVhdvLl6

[Opry Audio]

I wanted to correct myself in saying that you have one connection less compared to the fender board style. (I included examples below, using one part for simplicity, your style is #3).

I'd say, do it your way. Ptp is not always used to save connections and electronically wise, if the solder joints are sound, there is no problem at all if general layout conventions are respected. I guess output grid wires could be shorter if they didn't have to run to the front cut control. I'm wondering why the cut control since you have already a tone stack. I thought the treble cut was to accomodate the channel that didn't have tone controls in AC10, 15, 30 etc... I'm not good at inspecting layouts but it looks ok. Someone who are better at it might chime in.

Your point is heard! I think you’re all correct in saying that this chassis was made for a board, and I may rework the layout in favor of a board *type* of layout. At least for the excuse of building something into this chassis and to see how this design sounds. I have been thinking a lot about the great layouts y’all have been sharing! I think I want to experiment with moving the the preamp tubes up towards the controls for true PTP

As far as the cut control goes, it’s always situated in line with the grid leaks to the output stage, so it affects both top boost and normal channels

[Greg]

I didn't see a normal channel but maybe you decided to include one. I built both type of circuit layouts (PTP and circuit boards) and I can't tell which is better in a guitar amp. But it can be fun to experiment with both types and I encourage you to do so. A circuit board is easier to work on, and you see them in miltary equipement as far back as in the '30's and even the first gibson amplifiers (although I never had an opportunity to work on such vintage equipement, but saw pictures). A point to point could be neat but a bit of a PITA to work on later as you might have guessed.

Those vector sockets are cool, but expensive when they pop-out somewhere on the web... They were making great sockets back then. I believe there was a use for them in high freq radios where mounting parts vertically could prevent oscillations... In guitar amp the usual input low pass filter (usually a 68k in series with the input grid can prevent this, I believe.