Tweed Bassman / Deluxe w/ reverb. any opinion?

[tubeswell]

Hi Tubenit

Have you tried the 5F6A variant? I am curious about how the tone of the dry signal would be affected with that 100k resistor between RV and RV2. I am also wondering about the signal level you would get in the 5F6A with only having one reverb recovery straight in front of the LTP. (Also I guess that with having a 1/2 12AX7 reverb driver, you wouldn't get much current going into the pan.)

(Still no reason why it couldn't work with two tubes as well I guess, one initial (say 1/2 12AX7) gain stage, followed by a parallel triode (say 12AT7) driver, and then a single (other 1/2 of 12AX7) recovery stage).

[Tubenit]

one tube reverb

Not sure I understand your question? I have tried it in numerous amps successfully. Two of my current amps have this same setup now going into a LTPI. It works fine. I have used it in a Marshall Plexi 50 type amp.
I do not anticipate ever using a Fender reverb in one of my personal amps. I will continue to use this one tube version. I like it alot.

I have owned and played Fenders and honestly prefer this reverb as it verbs more mids which is what I like. For example, I played the Princeton Reverb I owned with the reverb around 2.5-3 and play my current amps around 3 on reverb also. The PR was unuseable for what I want above 5. This amp would be have waaayy too much reverb closer to 6-7.

A Fender 3.3M resistor is going to attentuate the signal more than a 100k resistor. I am somewhat guessing what you're really asking?

I'm not trying to talk you into using it. Feel free to use what you want. If you want a surf tone, this isn't the reverb to use. If you want to hear a soundbit of it. Click here and listen at about 2 minutes into Rainy Day blues to the lead. You can hear it on Cruisin on Home song also.

http://www.soundclick.com/bands/defa...&content=music

With respect, Tubenit

[txstrat]

The sound clips are great.
Have you tried your verb circuit with no dwell pot and a 1M resistor instead? (just like the fender verb). If not, do you have a standard setting of the dwell pot, to get an idea for the values of two resistors instead.
I'm asking cause I'd like to try your sort of verb in one of my amps but haven't got the space for another pot (dwell) on the faceplate.

thanks

Matt

[Tubenit]

dwell pot vs. 1M

Yes, I have used a 1M resistor and it does just fine. However, I put a 1M pot on the back of the chassis instead. See picture with dwell pot near V1 tube and reverb trannie.

http://s28.photobucket.com/albums/c2...srearpanel.jpg


Ironically, when I occasionally post about this reverb circuit, invariably I get some challenges or questions about whether there will be enough reverb. However, my experience is that I had to find ways to lessen the reverb rather than increase it ........... and that is why I used the 1M dwell pot. I dial it usually to about 7. One the Little Wing Reverb amp (6BM8 tube) it was dialed to about 5.

I also changed (from the original D'Lite design) the reverb pot from 2.2M to 1M and used a lesser value cathode cap to reduce the reverb to a more subtle level.

I'd try a 1M resistor there first. You could "tack in" a 1M pot temporarily and measure what sounds best to you and use the closest value resistor.

With respect, Tubenit

[tubeswell]

V2 layout

Here is the layout incorporating the suggestions by MWJB and a couple of other minor refinements resulting in shortened wires, as well as a 500mA Slo-Blo fuse between the reservoir cap and the standby switch (to provide some protection for the OT). (I may very likely put the filter caps in a doghouse on the back of the chassis, but I have shown them still on the main board, as this would be simpler if I could fit it in when I have finalised a scale layout/design)

The darker green wires are where I think shielded cable would be merited. If there are any suggested additions, please feel free to let me know.

Having got this far I was wondering whether I would actually need 2 reverb recovery gain stages before the direct-coupled pair going into the tone stack.

I have already included a 470k/470k voltage divider between these two recovery stages (thinking some attentuation was in order).

However I guess I could also drop one of the bypass caps; would it be better to drop the second one (I had both of them at 220uF), and instead just have (say) a 4k7 cathode resistor on the second stage?

Or alternatively would it possibly be worth turning that second recovery stage into a CF (i.e. making the reverb recovery a direct-coupled pair - so that the 250kN mixing resistor is blending two low impedances for better impedance bridging into the DC pair before the tone stack)? Would that improve fidelity from the reverb circuit?

[txstrat]

After I've heard what a two triode reverb can do I think you could even leave out two triodes.
The one right after the dwell pot and the second recovery stage after the 470K/470K voltage divider. That would leave you with more space on the board and one less tube to feed.
You might have to lower the 12AT7s cathode resistor value to 1.5K or 1K to push the signal a little more and raise the value of the coupling cap before the 12AT7s grid. That would make out a standard Fender reverb section INCLUDING a dwell, tone and a mix pot. Since that is a proved circuit you could also lower the value of the bypass cap of the remaining recovery stage, unless you're willfully looking for something different.
For the dry signal there is still the triode under the mix pot.
It might be a technical challenge to accomplish the board the way you've drawn it, though.

[tubeswell]

V11 Schematic

This schematic incorporates what I was alluding to earlier w.r.t. a DC pair recovering the reverb pan. I merely copied the Tone stack DC pair set-up, but if necessary (for extra gain) I could put a bypass cap on the DC pair's driver cathode. I have also lost one of the extra 10uF pre-amp filter caps and 10k dropping resistor (figuring that I only need 1 cap per 2 pre-amp tubes - if I am wrong about this somebody please sing out. I could always up these to 22uF caps). All up I am thinking this should make for a bit less clutter on the main board. I guess the reverb will sound nice as well. (I just realised I made a mistake with the coupling cap following the CF in the recovery stage - it should probably be .1uF) Layout to follow

[tubeswell]

5F6A T & R Ver 11 layout

Here's the layout for the last schematic. The extra space saved on the board in this version has enabled me to get the circuit parts (by and large) adjacent to the relevant tubes.

Since it also shortens the wires to the pots, I swapped the position of the mid and bass pots around, (and as an afterthought) I could also swap the presence with the trem pots.

I have corrected mistakes in the power rail wiring as well. (But as a further afterthought I could also probably swap the position of the middle 10uF filter and 10k dropping resistor to be between the circuit for the reverb recovery and circuit for the tone stack driver (if I need better alignment of the circuitry with the tube sockets). But it also seems to me that the way it is shown now offers some space/separation between the tone stack circuitry and the tremolo oscillator circuitry (if unwanted coupling could be an issue?)

On the face of it if I move the filter caps to a doghouse on the back of the chassis, I'll have more than enough room inside, but I'll do a hand drawn scale pic of the board inside the chassis to juggle things around and see if I actually have enough room for keeping the filter caps inside.

(Hi txstrat - I don't want to go with dropping one of the pre-amp tubes from the reverb circuit just yet. All the BF circuits have a stage before the paralleled 12AT7 as well as two stages after the pan before the PI. I know that this design I am beavering away on has more than two stages between the reverb and the PI, but the tone stack is being driven by the last DC pair (my aim is still to keep the tweed bassman feel), and I am thinking that when in 'dry' mix mode, it'll sound quite like a 5F6A, and when in wet mix it'll sound quite full like a BF reverb. So that's what I'm aiming at and why I don't want to drop any stages at this point.)

[Tubenit]

adding reverb & tremolo

Obviously, it's a different type of amp. However, take a look at how I have the reverb done on this Carolina Blues Rocket amp. I have the dwell at 7 and reverb pot at 3 the majority of the time and have all the reverb I need.

The reverb system your using is somewhat more complicated.

With respect, Tubenit

[Tubenit]

Bassman w/reverb & tremolo

I think you should build the amp that you want, so this may not be an idea you wish to consider.

With respect, Tubenit

[txstrat]

TW
Now I get it. That way the additional stages make sense.
The BF sound (reverb or not) is dominated by the scooped mids and I believe that's what your amp will be missing, although it will be full sounding.
One thing still, in a conventional BF amp the 4th triode after the reverb recovery is a mixing stage to amplify the mixed signals.
I don't know if it's necessary to add it before the mix pot in your circuit. Might be a matter of try and error.
I also agree with Tubenit and his uncomplicated design of the reverb. It's basically what your goal is, just to tinker around and try something new (and learn that way - that's what I do) or find the simplest circuit to reach your tonal aim (that's what I like).

[tubeswell]

Hi tubenit

It interesting to see how that reverb in the CBR is before the PI (but after the tone stack). I have a PV C30 in my amp cupboard and altho' it has an op-amp driven reverb circuit and and SS FX loop, they are in a similar position in the signal path to your Caroline Blues rocket, and the reverb on the C30 sounds okay.

But I built a 6G15 standalone reverb last year, and it sounds awesome with my home-made tweed style amps, and I really love the range of deep deep reverb sounds it is capable of, as well as the not-so deep sounds. But it has an idiosyncracy in that so far it works better with one of my amps than with the others as far as ground loop hum is concerned. On one of my amps (a 5G9 clone) it works almost flawlessly (which I attribute to a flukeley equivalent chassis potential). Of course this combination has me in rapture every time I play it, and I cart these two amps everywhere I jam.

But lo and behold, before I get to spend more time ironing out this problem (which i will probably come back to again in the future), I have (like Toad of Toad Hall) succumbed to the next fetish, which is to build a tweed bassmanish style amp. However I didn't want to risk building a further amp to find out that it doesn't match the chassis potential of the existing reverb unit. What's more, I really love the bias-vary trem on the 5G9 (so you get an idea of how sad I am). Well seeing as how I am hanging out to have a go at a tweed bassman style amp somewhat along the lines of a Marshall blues-breaker but with bias vary trem and deep deep reverb...

I thought that if I could build a tweed bassmanish thing with reverb that has similar characteristics to my standalone reverb (albeit that I realise that the tank won't be driven by a pentode), whereupon I could keep the basic 5F6A topology as much as practicable when the signal was 'dry' and the trem was off, I would not have to worry about ground loop hum interfering with my enjoyment of surf reverb/cajun swamp blues nirvana.

That is why I have gone down this path. I understand that you are trying to steer me towards a simpler solution with good intentions, and I appreciate your wisdom. However I have become rather sadly fixated on my goal. Maybe it is futile, but I have an itch to attempt it, and now I have amassed a heap of parts again ready to go. Seeing as how I am tragically addicted to building and then playing my valve amps, I may well be beyond a rationally objective state. I do want spend a bit of time enjoying contemplating the design aspects, because experience has taught me that forward planning in this regard makes for a higher quality result (as well as enhancing the adrenaline rush of the whole trip). However seeing as how I am venturing a little bit into unknown territory with this particular project, I realise I am at risk of procrastinating a bit, but I do really appreciate everyone's comments, yours included.

Now where have I got myself to?

(Edit it was such a long rambling post that you managed to post another post in between)

[tubeswell]

Wow! That looks good - thanks for that suggestion. I will spend some time contemplating that

Do you have a layout for that circuit by any chance?

Are those trem values something you have tested? (They look like modifications of the vibroverb trem - I see it doesn't have the .02uF between the plate and the cathode of the LFO stage, and some of the cap values are a bit different). What does the .047 to ground do on the depth pot wiper? (take out some of the whumpiness?)

[txstrat]

Hi tubenit

I am tragically addicted to building and then playing my valve amps, I may well be beyond a rationally objective state. I do want spend a bit of time enjoying contemplating the design aspects, because experience has taught me that forward planning in this regard makes for a higher quality result (as well as enhancing the adrenaline rush of the whole trip).

I agree. The fun is a mighty part in this (building AND playing).
That way I rebuilt my last output several times. While it started with a barely modified Deluxe Reverb II circiut it's ended so far with a double channel amp of a mix between a brown vibrolux and a brown deluxe. Although I'm very satisfied with the result I'm still thinking about altering it a little (tremolo comes to mind). Most of the threads I started in recent times were related to this amp.
Keep on soldering...

[tubeswell]

TW
Now I get it. That way the additional stages make sense.
The BF sound (reverb or not) is dominated by the scooped mids and I believe that's what your amp will be missing, although it will be full sounding.

Yep full sounding, like a 60's Pete Green type of sound, or semi-pink floyd, I guess, if one was to put a handle on it, but something that also sounds good doing Otis Rush (All Your Lovin'), and yet Blues-Breaker era Clapton as well, or just plain old surf music, or cajun swamp music like CCR. (Yikes!) I have a couple of new 25W Greenbacks sittin' in the cupboard ready for it.

One thing still, in a conventional BF amp the 4th triode after the reverb recovery is a mixing stage to amplify the mixed signals.
I don't know if it's necessary to add it before the mix pot in your circuit. Might be a matter of try and error.

Yep I realised that, so I get the reverb mix inserted before the bassman DC pair driving the tone stack, which in turn goes straight into the LTP. That way I figured the tone stack's DC pair would be doing the job of the BF mixing gain stage, but in a tweed bassmanish sort of way.