12DW7 reverb (new 5E5 build)

[StevieRayVehkakoski]

I'm starting a new build, this one's going to be pretty much a Fender 5E5 Pro but I'm adding reverb and tweaking this and that.

Attached is the schematic, I've good a few questions:

1. The 12DW7 reverb; the 12AU7 side is the driver but what load would it like to see and what should the bias be? I've got about 300V on OT which is a 3w Hammond single-end with plenty of impedances to choose from

2. The reverb insertion, I've put it right after the first triode in order not to overdrive the reverb drivet. In my previous builds I've put it closer to the PI and I've had issues that the reverb is weak with low volume and with higher volumes it gets unclear and mushy probably because the driver is overdriving badly. With this set-up and with pretty low-output pickups will I be overdriving the reverb driver?

3. Is my grid-stopper on the PI in the right place?

[Fresh_Start]

I can't help you much in terms of the tap to use on your "reverb" transformer.  Assuming you're using using a 4AB3C1B tank, it has a nominal input impedance of 8 ohms:
http://www.accutronicsreverb.com/
(sorry I pull out a direct link to the Type 4 tanks)

As PRR frequently reminds me, reverb is an effect anyway - not a precise circuit to say the least.  Impedance varies all over the place depending upon frequency.  Be ready to experiment.  At least you've got a variety of taps

You don't want to insert the reverb that way.  The 1 meg (with 47pf in parallel) reverb mixing resistor will screw up both the tone control and the volume pot - it creates voltage dividers and changes the drop-off frequencies.  Actually, that's the whole idea with Fender's 3.3 meg mixing resistor - it knocks the dry signal way down relative to the wet (reverb) signal by creating a voltage divider with the 470K resistor and 100K Reverb pot.

You can either put the reverb insertion/return point before your 3rd driver (PI driver that is), or use what Doug Hoffman calls the Western Electric approach (see Library).

For testing purposes, I'd build the amp without the reverb, diddle with values and get the "right" level for your dry signal, then add the reverb.  Where you have the two 470K resistors before the 3rd driver, figure out what signal level works by experimenting with the ratio between those two.  Then use the same ratio for the mixing resistor and the 470K plus Reverb pot.

Oh, and a Dwell pot in place of the 500K resistor before the reverb driver would give you the flexibility to tailor the Reverb input to your volume.

Last but not least, Merlin will have to tell you where he thinks that grid stopper ought to go.
http://www.freewebs.com/valvewizard/cathodyne.html

Hope that helps,

Chip

[StevieRayVehkakoski]

1. I just checked the valve wizard site and found a 12AU7 reverb driver on their site, although that was parallelled and the tank was cap-driven. Anyway, taking one triode instead of 2 I would guess 20k load and 1.5k cathode resistor should be about right.

2. About the reverb: I agree there's plenty of stuff before the second triode and I might as well move the volume and tone controls after the second triode. The first gain stage with the reverb and the mixer would be sort of standalone unit that only mixes the reverb to the signal. The signal level should be cut back to about the same level as I would get straight from the guitar but I guess that should be pretty easy with a signal voltage divider. The reason I would like to have the reverb inserted as early as possible is that I tried the Fender standalone unit in front of one of my amps and it made the one-tube reverb on the amp sound really anemic. I've got a feeling that's because the reverb driver on the stand-alone unit doesn't overdrive as badly as the half 12AX7 on the amp so that allows way more dynamics but also because the reverb is inserted in the signal before the real amp-magic happens.

3. The Merlin site only showed an example of a DC-connected cathodyne with the grid-stopper but I guess my schem is allright the way it is.

EDIT: Revised schematic added, what do you think?

[Fresh_Start]

1. If two 12AT7s in parallel want to see 8K (roughly), then 16K ought to be a reasonable starting point for one 12AU7.  Or 20K...

2. Move the tone & volume controls and you don't have anything like a 5E5.  Please look at Doug's Western Electric reverb approach:  http://www.el34world.com/charts/reverbmod.htm  (It was hard to find, except I knew exactly what I was looking for.)

3. AC or DC, the Young brothers rock no matter what

Cheers,

Chip

[StevieRayVehkakoski]

I've got a feeling this discussion isn't really going anywhere..

1. Done, I'll try 20k for plate and 1.5k for cathode and see how it biases with this setup

2. If you look carefully at my revised schematic you'll see that it's 98% 5E5 from the second triode on all the way to the poweramp. It's missing one cathode cap and it's got NFB loop but that's it. As I said I would like to add the reverb to the signal before the real amp-part starts so the idea is to amplify the signal first some, then mix the reverb and then cut it back to the original level before going in to the 5E5-part. Plus the way it's on the Western Electric approach the reverb takes 3 whole triodes and I've only got 2 to play with.

3. If I put my grid-stopper the way it is shown on Merlin's site then I'm cutting my signal in half and losing gain? If I put it the way it's on my schem then it only restricts the grid current, right?

[tubenit]

I've got a feeling this discussion isn't really going anywhere..

My best guess is that you will be very disappointed with the approach you are taking.

Fresh Start is giving you some excellent feedback and information.  The 3.3M resistor will dramatically alter your tone in a way that I think you may not like.

Fresh Start also recommended Hoffman's "add reverb to a western circuit". That is advice worth considering. I have used it before and it does work just fine.

Following Fresh Start's lead in that direction, I am posting a schematic for you to consider. I don't have time to alter the 5E3 fully to a 5E5 this morning so I am posting the SCH file for you to do that for yourself if you want.

This is as close as I can envision trying to preserve the 5E5 tone. Yes, I realize the tone stack is a quasi 5E3 design but it does work and I use it on the OD sections of my amps as a tone control.  You may need to change the .1 cap to a .047 or a .02 also.

EDIT:  V1-2 & 7 are tied together
With respect, Tubenit

[tubenit]

Since my personal preference is to have more mids instead of just treble reverbed, I am posting this version (still using Hoffman's topology) also for your consideration.

With respect, Tubenit

[StevieRayVehkakoski]

Thanks guys, I know you 2 are way more experienced than I am in these things but still I'm not really convinced why this 3.3M mixer resistor would kill my tone as that's the way it's done in all blackface Fenders and I don't hear much complaints about their sound. I'm only doing the mixing between triodes 1&2 whereas Fender does it between 2&3 and they knock down the signal by a huge amount with the mid-dip tone-stack so I guess the signal levels in my idea are pretty much the same as in Fender apporach?

Anyway, I'll leave plenty of room and holes on the board to experiment. I'll try it first my way and report back if it sounded good or not.

[tubenit]

that's the way it's done in all blackface Fenders

VS.

I'm only doing the mixing between triodes 1&2 whereas Fender does it between 2&3

so I guess the signal levels in my idea are pretty much the same as in Fender apporach?

Not sure why you think that since you're not doing the same way as it's done in all blackface Fenders.  Plus your amp is a 5E5.  Topology is signficantly different then the blackface Fenders.


Well, you seem set in trying it that way. Please let us know how you like it & whether you think it sounds anything like a 5E5. Good luck with it.

With respect, Tubenit

[StevieRayVehkakoski]

I got the chassis ready yesterday and some of the bits in but wiring a Hammond 1645 output got me jammed so I'll continue tonight.

Like I said, this really isn't going anywhere but I just can't help fighting back since I don't see the theory behind these arguments. There are 1000 ways to put reverb in a guitaramp and they all work, they just have their own sound. The Hoffman approach is pretty close to what Gibson used in some of their amps in early 60's and also pretty close to what I'm trying, tubenits one-tube reverb is pretty much the Fender black-face reverb with lower loss and weaker driver, Ampeg has cool reverb circuits, Magnatone has unique circuits, Traynor had some etc. What I'm trying to achieve with this thing is the sound I get from guitar -> Standalone reverb (Fender 6G15 or such) - Tweed amp turned up. The reverb is done before the amp-magic adds the overdrive in the signal.

Like this:

And please don't get me wrong, I'm not trying to disrespect anybody here. I'm an engineer by trade and I want to know how and why things do what they do, it's not enough for me if somebody says that don't do it, it won't work without explaining why it won't work. In my day-job I see lots and lots of things that are done like they are done just because that's the way somebody else did it.

And that's how I see the situation right now, I've come up with an idea and you say that it won't work but don't say why it wouldn't work?

[tubenit]

The amp may have the exact tone you're looking for and be a wonderful amp for you. I hope you'll build it and report back how it sounds and whether it retained the 5E5 tone. I admire that you're thinking outside the box and hope it works out well for you.

FWIW,  I genuinely would prefer that you are right (& I am mistaken) and this works out for you and is a great build for you.  My comments in previous posts were strictly an aim to help you achieve the 5E5 tone with great reverb that I was understanding that you were wanting. If this works out for you, I'll cheer along with you with your success.

with respect, Tubenit

[Fresh_Start]

And please don't get me wrong, I'm not trying to disrespect anybody here. I'm an engineer by trade and I want to know how and why things do what they do, it's not enough for me if somebody says that don't do it, it won't work without explaining why it won't work. In my day-job I see lots and lots of things that are done like they are done just because that's the way somebody else did it.

tubenit and I both tried to make constructive suggestions.  We both tried to explain WHY we were making those suggestions.  Tubenit even took the time to draw up a schematic using Hoffman's "add reverb" approach which should do almost exactly what you asked for in terms of "standalone reverb" in front of the 5E5 circuit.  This "should" is based on our experience (tubenit has much more than I do) tweaking circuits and building amps, not because "that's the way somebody else did it".  If you looked at tubenit's posting history, you would see that he hardly qualifies as a follow-the-leader kind of contributor here.  Actually, he and Geezer have put together more original circuits and shared them with the rest of us on this forum than virtually anyone else.  

Please note that neither of us has ever seen that particular circuit before - it was an attempt to take concepts from other circuits and put them together to reach the design goals YOU specified.  

If that "isn't getting anywhere" it's not our fault.

[moonbird]

Hi Tubenit --

Great suggestions as always. I am in the process of building a VERY orthodox 5E3 and then a modified (dare saw improved??) version. For my orthodox - I am using a fiberboard and the original layout and tone circuit etc. For the modded one, I am basing it on the Hoffman topology. I'm afraid I know nada about the 5E5 , but could the approach you kindly offered be applied to the 5E3? I am presuming the added tube is a 12dw7 right? Is there a better tube for this?? thx again for all you do!!

[tubenit]

Moonbird,

The schematics that I posted of the Hoffman "add reverb to western circuit" were actually 5E3 not 5E5 schematics.

I have not built a 5E3 reverb. I have built a Plexi 25w amp with Hoffman's reverb and it worked fine. I don't see why what I posted wouldn't work but again it's a DRAFT idea.

I don't know if the 12DW7 is best or not, but all you have to do is plug in another 12A_7 tube and compare it.

Best regards, Jeff

[StevieRayVehkakoski]

tubenit and Fresh_Start, I honestly don't know what I did to upset you but let's try to get this thread back on track. I know I'm stubborn and I guess I chose the wrong words.

About the Hoffman approach: I don't really get the idea that the signal to reverb driver needs to be amplified by a separate triode instead of taking the signal from the "main signal". Attached is the schematics, the first one is per the Hoffman approach and the second is more like the Fender blackface approach. The way I see it, the signal that the reverb driver gets is the same in both cases and also the signal coming back to the 250k mixer pot is the same? Only on the Fender case the first triode sees the plate impedance as a bit smaller (the 1M to the ground on the driver grid.)

[DummyLoad]

signal to reverb - me thinks both plans are not good - the "mainline" is especially bad plan.

you have a 250K pot in a simple feedback loop. with respect to dry signal, is signal from reverb recovery NFB? or is it positive FB? - with reverb signal delay very likely a mix of both. positive feedback is likely to cause reverb system to oscillate.
 
..and why fender stuck a 3M3 resistor at the signal split, not a pot, THEN fed both recovery and dry signals to a summing amp AFTER running weakened dry signal through another gain stage.

no disrespect intended but there is no point in bantering back and forth. just try it; you're an engineer, you'll figure out why some topologies don't work so well and some do work with varying degrees of success.

respectfully,

--DL

[octal]

I agree that the "mainline" plan has some potential issues. I'm guessing that you're looking at the fender stand alone reverb and trying to 'value engineer' a way of mixing the dry & wet signals in a similar manner.  In the Fender reverb unit, the cathode follower section helps isolate the wet & dry signals- there's no way the wet signal can be "forced" back through the grid of the cathode follower to the input of the reverb causing an unwanted feedback loop.

I think your original schematic with the 3.3meg resistor will probably work, and it might not alter tone as much as folks think. You can adjust the value of the cap bypassing the resistor to achieve flat frequency response. (The function of the cap is to compensate for the treble rolloff caused by the combo of the 3.3meg resistor and the 'Steve' Miller capacitance of the following triode stage.) Also, you probably don't need a resistor as large as 3.3Meg to achieve enough reverb. 

Good luck, have fun experimenting.

Nathan
 

[StevieRayVehkakoski]

I agree that the "mainline" approach has the potential to oscillate at some frequencies as the reverb signal is fed back so close to the input of the driver. So that's probably the reason why it on the Hoffman approach it's separated completely. I would use the Hoffman approach in the amp but I've got a feeling that I would be lacking in gain as I would have only on triode amplifying the main signal going into 5e5 or 5e5-a like PI + poweramp. I guess with 5E5 (cathode on the triode before cathodyne + no NFB) I would have enough gain but with 5E5-A not really enough.

On the Fender blackface reverb I believe the signal is cut down by the 3300/570 ratio just because the dry signal on that point of the amp is so strong that the reverb signal (amplified by only one triode) is too weak that it would be lost in the mix without the voltage divider. In this case if I put the reverb after the first triode I wouldn't need that big voltage divider. Actually the only thing I'm worried about is that the background noise could be a trouble in this approach.

I guess this is enough theory, I'll got some experimenting to do.

[StevieRayVehkakoski]

I got this thing running and after a few tweaks it's great!

Attached is the final schematic, I guess the only thing I'm going to change is the reverb-pot, I'm going to change it to 250k linear pot.

I'll try to record some sound samples later this week, I really do like the 12DW7 reverb. I'll also open the thing up once again to get all the voltages, I've got quite low voltages all the way but it sound good so I'll leave it be.

[sluckey]

Probably just a drawing glitch.... The triode grid that's connected to the wiper of the tone pot needs a resistor to ground to work properly. Volume pot needs a ground too.

[tubenit]

Congrats!  Glad you got it sounding like you wanted & that it was successful for you!

Will look forward to hearing the sound clips.  I'm curious how much it retained the 5E5 tone that you were wanting?

With respect, Tubenit

[ThermionicEngine]

Interesting thread.  I always run 12AT7 in parallel to drive my reverb tank, if I am not using a 6V6 or EL84.  Depending on the circuit, I could easily use it as a 3-3.5 Watt driver.  But, I have never tried to reverberate a 5E5 circuit either...  I am inclined to agree with FreshStart and Tubenit's take on the project.  I am refreshed from this topic- now I have to return a G 30 that someone thought was a GA 30.  I can't find a schematic with cap and resistor values included.  Anyone got one of those?  I shoulda returned it to the store, but part of me says I should fix it anyway...
Allbest, Larry

[StevieRayVehkakoski]

Here's the corrected schem.

[StevieRayVehkakoski]

Here's the "final" version of the amp. I really didn't like the 5AR4 rectifier as it was too stiff to my ears so I changed to a Sovtek 5V4 which is now perfect. I also changed the first filter-cap to 22uF as 32 might have been too much for the 5V4. I also did some experiments with cathode caps and to my ears it sounded best without them. If you put cathode cap on the first triode it hits the reverb driver too hard. When I tried the cathode caps on both second and third triode it had more "cut" and generally really good sound but it had too little head-room and way too much gain. With cathode cap on either on second or on third triode it just didn't sound right to me, don't really know why bit just was kinda loose and messy.

The reverb is the best I've heard in guitar amp, it's really airy and dynamic and it can go from slight echo to Dick Dale and beyond. I would record some sound samples but my 1-year old son has ear infection so I guess I shouldn't crank this thing up right now  

[tubenit]

THANK you for sharing your schematic and innovative approach!  I am glad you are pleased with the amp and have the reverb tone you are looking for.  Nice to see you think out of the box and have success!

I hope you will post sound clips when you can.

Can you address the issue of whether it has a 5E5 sound but with reverb ........ OR does it sound like a great amp with good tone but different then a 5E5?  I am very curious about that answer?

With respect, Tubenit

[StevieRayVehkakoski]

I really can't say if this sounds like a 5E5 or not because I've never tried a real 5E5. However I really can't see why this wouldn't sound like a 5E5 as all the parts that overdrive are pretty much the same in this amp compared to a real 5E5. I actually put back a 4.7uF cap on the cathode on the last triode before the PI and I think it sounds better with the cap in there.

I'll try to get some samples recorded next week, I can't get real hi-fi recordings as I've got a small Yamaha Pocketrak to use but it's good enough to demonstrate the sound of this thing.

[tubenit]

yeah, please post the soundclips.  I'd love to hear them. I like seeing innovative approaches that are successful.

Typically, when I have changed the cathode cap values or eliminated them, it had pretty dramatic changes in the tone and feel of an amp.   

Having said that, your amp may sound absolutely spectacular whether it retained or lessened the 5E5 tone. Who knows it might sound "better" than a 5E5?

With respect, Tubenit

[StevieRayVehkakoski]

Here are some soundclips, quite lo-fi but that's the best I can do.

Here's clean with the reverb almost maxed:
http://soundclick.com/share.cfm?id=10450869

Here's the same song that I found on youtube played through a 5E5-A:
http://soundclick.com/share.cfm?id=10450870

Edit: here's the comparison:

Here's just something to demonstrate the overdriven sound:
http://soundclick.com/share.cfm?id=10450868

I really wish I could get the real sound of this amp on tape as these samples are kinda muffled and raspy but I just don't have the equipment..

[tubenit]

VERY nice playing!   

The reverb sounds reasonably strong especially on that first clip.

I appreciate your sharing the sound clips. Thank you for doing so.

With respect, Tubenit

[Willabe]

Oh yeah! Very nice. A blues man. Love it. I played a little while for Johnny Little John and Son Seals here in Chgo. Both gone now.

What speaker are you using?


            Brad            

[Fresh_Start]

Great work!  Both on getting the amp to sound the way you like it and the very nice playing.

Please note the second quotation in my signature...

Respectfully,

Chip

[StevieRayVehkakoski]

Thanks guys!

The samples are played with a Baja Tele and the speaker is an old Jensen EM1500 which I guess is pretty much a C15N.

[StevieRayVehkakoski]

I've got a question I've been wondering for a few nights now: The tone control on this amp works just like you would expect it to do but for some reason it feels like some portion of the really highest treble gets through. The tone darkens as you roll the pot and everything seems ok but there's just something really high up there that doesn't feel like it's supposed to be there. I don't really know how to describe it better but the neck pickup on a Tele or a Strat sounds just a bit like the neck and middle pickups together on a Strat? You know the sound, it kind of scoops the middle from the sound but leaves the lows and highs alone, only in this case the dip feels to be higher in the range.

I tried to roll off some of the highest highs by putting a cap between the cathodyne outputs but at least I can't hear it making any difference. Any ideas what to try or what could be the source of this glassiness on the sound? I already tried to take off the 150p bright cap on the volume-pot and that didn't completely do the trick plus it made the amp too dark for P-90:s and anything other than Strats. Ideas? Bigger grid stoppers on the 5881, small cap to the ground from the cathodyne grid?

[tubenit]

It seems like the reverb works well for you, but the amp doesn't quite have the tone you want?

I will offer food for thought.  I think the high end "hash" that you're hearing is a design flaw.  

IF you look carefully at "Hoffman's add reverb to western circuit", you will see he uses fairly low cathode caps on the reverb.  There is a reason for that.  Having built an amp with Hoffman's reverb, I would say there is comparable reverb available to the sound clips you posted.

My experiencing eliminating cathode caps on pream triode leaves the tone somewhat harsh, thin and fizzy sounding, IMO. I hear the high end hash/fizziness when I have attempted that.

So if you're still wanting to use the design of reverb insertion where you have it, I would consider experimenting with these ideas:

1) lower the cathode cap values on the reverb tube

2) add cathode caps of low value such as 2.2uf to 4.7uf on the preamp tube

3) if need be, put a 500p - .001 cap across the plate resistor on the 3rd gain
    stage

Just food for thought.

With respect, Tubenit

[StevieRayVehkakoski]

Thanks for the help tubenit! This really is a great dirty amp with P-90s and other fat and middy pickups but with Strats and Teles the "shimmer" is a bit too much.

The reverb is good as it is, I guess I'll check if I've got enough 4.7uF caps to try on the reverb but the "hash" is there with the reverb on or off so most likely you've got a point on the cathode caps on the preamp. I already tried putting cathode caps on each of them and the sound was good but there was way too much gain and no headroom.

I'll try first what happens with the cap on the plate resistor, I guess you mean the same thing as in 6G3 normal channel first triode:
http://www.davidsonamp.com/sf/images/deluxe6g3.gif

If that doesn't help I'm going to have to try 250k volume pot and tweak the 470k/220k voltage divider where the tone-pot is right now located.

[tubenit]

I already tried putting cathode caps on each of them and the sound was good but there was way too much gain and no headroom.

I quit using 22uf and larger caps on preamp cathodes years ago. I find them waaayyy  too muddy sounding for me.  I typically use 2.2uf - 5uf caps. Occasionally will use a 1uf.

So if the cathode caps you tried were 22uf or larger and they had too much gain and too little headroom, that would make sense to me.

I attached an example of two ways of trying to use "smoothing" caps on a preamp triode.

IF you still can't get it to sound "right", then please consider trying a lower value
cathode resistor and a lower value cathode cap on the reverb send and recovery.  Such as instead of  1.5k/22uf ,  use a 820 ohm and 2.2uf.  You will find still getting good gain in the reverb but perhaps without as much harshness in the overall amp tone. There is a reason Hoffman used a 820ohm/.68uf and still has good reverb.


with respect, Tubenit

[StevieRayVehkakoski]

I did a bunch of experiments with cathode caps, cathode resistors and plate resistors. I actually put a 250k pot to ground before the last triode (the one before the cathodyne) and noticed that I get fatter and overall better sound when this voltage divider was 470k to 47k so it knocks down the signal to 1/10. Then I noticed that my tone-pot didn't do anything anymore when there was only 47k to ground at that point. I moved the tone-pot to where the volume-pot is and now it's just like a Princeton 5F2-A volume/tone-combination except that I've got 150p bright-cap instead of 500p. This actually cured the hi-treble shimmer 100% that was annoying me.

Then I started experimenting with the second triode that's between the input and the one before cathodyne. I've never really tried how different combinations affect the sound but man, what a difference these make. I really didn't notice much difference in the clean sounds except that some combinations were darker and some where brighter but the overdrive and the "just on the edge of overdrive" sound really changed a lot.

So the original combination was 100k/1k5 without cathode cap into 100k/1k5 with 4u7 cap. This had really good clean sounds and the transition from clean to overdrive is really good. It's got punch and clarity all the way to light overdrive but with higher gain settings (I'm talking about classic rock'n'roll tone here, think black crowes etc.) the sound got kinda farty and fuzzy.

Then I added a 4u7 cathode cap to the first triode. That added compression to the sound and the thing lost lots of the punch it had and it got way looser. Also the sound got brighter and I'd say the overdrive sound got a lot better but the edge-of-overdrive wasn't so graceful and I felt it had some unpleasant dirt to it.

So, I took away the cap and changed the cathode resistor from 1k5 to 820R. The sound got a bit brighter but also warmer and more "tweedy" bluesy but again the overdriven sounds were too farty and blatty.

So, in goes a 2k7 cathode resistor. This darkened the sound but also I think it added headroom? The distortion got more into Fender blackface territory but I still wasn't quite happy with it, it was maybe a bit fizzy?

I had to stop here as I run out of time but I guess the perfect sound is there, I'll just have to find it..

Has anybody got any good suggestions what to try for the plate/cathode resistors? I'll draw the revised schematic tonight but basically it's like this right now: input - 12ax7triode - reverb mixer-volume/tone-pot - 12ax7triode - 470k/47kdivider - 12ax7triode - cathodyne -5881 push-pull. I'm now messing with the 2 last triodes. I see 120k/1k8 and 150k/2k2 pretty often on overdriven amps, how would you compare this to the usual Fender 100k/1k5? Or what would be the effect of bigger plate resistor to the overdrive, say 120k/1k5 or 150k/1k5? I've got to confirm the voltages but from the memory I've got 275V on the triode before PI and 235V on the middle triode.

And I guess I'm looking for a warm bluesy fat tone with a nice edge to the break-up.

[tubenit]

I'm going to suggest trying something that would be VERY easy to do.  Try jumpering across the reverb insertion point and then play the amp.

How does it sound without the reverb insertion point?  If it sounds good, then perhaps the reverb insertion point is problematic with the overdriven tone?

With respect, Tubenit

[StevieRayVehkakoski]

I can try that but I really don't see the point as I've got reverb turned to zero anyway when doing the tests. At least I see the reverb mixer as a simple voltage divider that doesn't effect the overdrive anyway as the overdrive in this amp happens after the volume-pot. I believe that the first thing to overdrive in this amp is the triode before cathodyne, then there are the triode after volume-pot, the cathodyne and power-amp but I can't say in what order they overdrive. At least changing the values of the triode after volume-pot seems to affect the overdrive at higher gain levels.