Adding 1-tube reverb

[sluckey]

Clearly, I'm missing a critical piece in this puzzle.

Maybe you're just overthinking this. A tube plate is usually a high impedance (Z) device. The reverb tank input is whatever you specify it to be. If you want a low Z tank, then a transformer is the best choice of matching the high Z tube plate to the low Z tank. If you want a high Z tank, then a capacitor is the best choice for matching the high Z tube plate to the high Z tank.

Your example circuits A, B, and D are all CAPACITOR coupled drivers and require a high input impedance tank. Don't be confused by circuit A. Circuit A is NOT a transformer coupled driver. Someone is just using the primary of a transformer as a choke inductor for the plate load of the driver tube. A 14Hy choke could be used just as well. Hammond AO-43 is an example of a choke plate loaded driver that is CAPACITOR coupled to the tank.

Your example circuits C, E, F, and G are all TRANSFORMER coupled drivers and will use a low input impedance tank. When using a transformer, the transformer is used to match the input of the tank to the plate of the tube. A small output transformer used to couple a speaker to a tube circuit is cheap and plentiful, so most transformer coupled tanks will have a low Z input, typically about 8Ω. However, 600Ω transformers are used in communications circuits. You could use one of these transformers to couple to a 600Ω tank input. (A 600Ω transformer is not a common component that you would find stocked at most guitar amp supply houses.

So, in summary, for tube circuits, "usually" if you see a transformer coupled reverb driver, the tank input will be 8Ω. A cap coupled reverb driver will connect to a high Z tank input. And all tanks will have a high Z output.

The attached file is all the info you will likely need to be able to chose a tank...

[jbefumo]

Got it, and thanks again!


Since I have a few old USA-built tanks on hand, I'm leaning toward the transformer approach on this one -- will tinker with the alternative down the road.


I'm gravitating toward the 'F' circuit in my illustration mainly because the specified transformer (Hammond 1750B), with its 5K:8-Ohm windings most closely jives with what I think I understand about power tubes and their required loads. (Will probably use the Edcor trans mentioned in my previous post.)


The recovery side I'm pretty comfortable with. 


My plan for the reverb return is to follow the topology used in the Matchless Chieftain -- feeding it to the second input on the phase inverter.  My thought is to avoid sending the reverb through the overdrive circuit when it is engaged.  Other than that, I'm pretty much going to follow the Tweed OD circuit ... except that the output will be a pair of KT88s -- simply because I have the tubes and associated iron out of an old Sundown amp.  Am also using a Hiwatt tone stack for the main circuit, and a 6G4A bass-treble control for the overdrive. May also experiment with the NFB approach used in the old HiWatts.


Thanks again for all the valuable help.


Joe

Clearly, I'm missing a critical piece in this puzzle.

Maybe you're just overthinking this. A tube plate is usually a high impedance (Z) device. The reverb tank input is whatever you specify it to be. If you want a low Z tank, then a transformer is the best choice of matching the high Z tube plate to the low Z tank. If you want a high Z tank, then a capacitor is the best choice for matching the high Z tube plate to the high Z tank.

Your example circuits A, B, and D are all CAPACITOR coupled drivers and require a high input impedance tank. Don't be confused by circuit A. Circuit A is NOT a transformer coupled driver. Someone is just using the primary of a transformer as a choke inductor for the plate load of the driver tube. A 14Hy choke could be used just as well. Hammond AO-43 is an example of a choke plate loaded driver that is CAPACITOR coupled to the tank.

Your example circuits C, E, F, and G are all TRANSFORMER coupled drivers and will use a low input impedance tank. When using a transformer, the transformer is used to match the input of the tank to the plate of the tube. A small output transformer used to couple a speaker to a tube circuit is cheap and plentiful, so most transformer coupled tanks will have a low Z input, typically about 8Ω. However, 600Ω transformers are used in communications circuits. You could use one of these transformers to couple to a 600Ω tank input. (A 600Ω transformer is not a common component that you would find stocked at most guitar amp supply houses.

So, in summary, for tube circuits, "usually" if you see a transformer coupled reverb driver, the tank input will be 8Ω. A cap coupled reverb driver will connect to a high Z tank input. And all tanks will have a high Z output.

The attached file is all the info you will likely need to be able to chose a tank...

[Willabe]

I don't think you want to use a 10w single ended (SE) output transformer (OT) for a tube reverb.

It's way over kill and that OT is big (taking up chassis space) and heavy compared to a standard Fender reverb(~3w, SE) OT.

Also if you use that OT with a small power pentode, 6GW8 or 6BM8, depending on how you set it up/bias it, you may get to much signal output from it and fry the verb tanks input coil.     

[sluckey]

I'd stick with a transformer driven reverb circuit just because I'm more familiar with those. The only cap driven circuits I've ever had were Ampeg Gemini II and Magnatone 10A. Both of those sound great too.

12DW7 twin triode makes a good one tube reverb. Use the lo gain triode for the driver and the hi gain triode for the recovery. 

I think a 6BM8 --> 1750C --> 8Ω tank is a good combo. I'm using a 6V6 --> Champ OT --> 9AB3C1B (8Ω tank) in my Revibe. The cathode resistor will control the amount of drive to the tank.

[jbefumo]

That was precisely my conclusion -- will mess with other stuff later ... in my copious spare time 

I'd stick with a transformer driven reverb circuit just because I'm more familiar with those. The only cap driven circuits I've ever had were Ampeg Gemini II and Magnatone 10A. Both of those sound great too.

12DW7 twin triode makes a good one tube reverb. Use the lo gain triode for the driver and the hi gain triode for the recovery. 

I think a 6BM8 --> 1750C --> 8Ω tank is a good combo. I'm using a 6V6 --> Champ OT --> 9AB3C1B (8Ω tank) in my Revibe. The cathode resistor will control the amount of drive to the tank.

[jbefumo]

I see, and yes, I will hunt up an appropriate reverb transformer (hadn't even considered chassis space -- which I generally come to regret late in the build process).  Did figure the biasing would control the power, regardless of the capacity of the transformer.  All this stuff works WAY better than 'Luminicity' in staving off Alzheimer's ;^)

I don't think you want to use a 10w single ended (SE) output transformer (OT) for a tube reverb.

It's way over kill and that OT is big (taking up chassis space) and heavy compared to a standard Fender reverb(~3w, SE) OT.

Also if you use that OT with a small power pentode, 6GW8 or 6BM8, depending on how you set it up/bias it, you may get to much signal output from it and fry the verb tanks input coil.     

[2deaf]

6BM8 Datasheet specifies a load resistance (pentode section) of 5600R

5600 ohms is just an example that RCA used to show what happens under those conditions.  Svetlana gives you an example with a 7000 ohm load and Sluckey gave you a scenario with a 17,500 ohm load.  The standard Fender transformer used in amplifiers is around 25,000 ohms.  You don't need to use a 5K primary, nor do you want to.

The primary impedance puts an upper limit on how much power you can deliver to the tank.  Reducing the primary impedance raises the upper limit, but you have to feed it more current to achieve this limit.  It comes down to how hard you want to drive the tank and how many milliamps you're willing to spend. 

There is only so much you're going to get out of a tank no matter what you put in.  Putting more power into the tank after reaching this maximum is a waste and possibly even dangerous for the input coil.  A 25K primary with a tube that can handle sufficient current is plenty for a guitar amp.  A 15K primary with an appropriate tube will make sure that the tank is max'ed out long before the driver would clip.  A 5K primary is just totally unnecessary.   

[jbefumo]

Understood -- and thanks again!


Joe

6BM8 Datasheet specifies a load resistance (pentode section) of 5600R

5600 ohms is just an example that RCA used to show what happens under those conditions.  Svetlana gives you an example with a 7000 ohm load and Sluckey gave you a scenario with a 17,500 ohm load.  The standard Fender transformer used in amplifiers is around 25,000 ohms.  You don't need to use a 5K primary, nor do you want to.

The primary impedance puts an upper limit on how much power you can deliver to the tank.  Reducing the primary impedance raises the upper limit, but you have to feed it more current to achieve this limit.  It comes down to how hard you want to drive the tank and how many milliamps you're willing to spend. 

There is only so much you're going to get out of a tank no matter what you put in.  Putting more power into the tank after reaching this maximum is a waste and possibly even dangerous for the input coil.  A 25K primary with a tube that can handle sufficient current is plenty for a guitar amp.  A 15K primary with an appropriate tube will make sure that the tank is max'ed out long before the driver would clip.  A 5K primary is just totally unnecessary.

[2deaf]

I've seen the 6GH8A triode/pentode tube pop-up here and on other forums using the pentode as a reverb driver.  This tube is cheap and seems to be readily available.  Both sections are rated at 2.5W, but the pentode is capable of way more gain than the triode.  Since both sections have the same limit when it comes to driving a transformer, I would rather have the high gain one be the recovery.  I don't know if there is a microphonic problem with the pentode at higher volumes, but at bedroom levels this setup is Surf City.   

[jbefumo]

I could easily be mistaken, but my impression was that the driver side is not looking to produce gain, so much as driving current.  This would seem to correspond to Fender's use of parallel 12AT7s (or a 6V6, for the stand-alone unit) on the drive side, and a single 12AX7 for the recovery.  That also seems to be the way all of the relevant schematics I've seen have been configured.  Being basically lazy, I used my usual approach: built a simulation of a standard (BF Super Reverb) circuit, then modeled my pentode-triode circuit against that until I came up with a similar curve, but with a bit more 'oomph' out the back end.  Of course, the final arbiter will be how it sounds -- hope to hear that soon!  (Only reason I'm taking this approach is to save the necessity of using an extra triode in the driver, though a 12DW7 was also a possibility.  (Here again, the '12AU7' side [higher current capability] seems to be typically used to drive the transformer, while the '12AX7' side is used for recovery.)  Of course, one could probably use a pair of pentodes, but that seems like driving thumbtacks with a sledge hammer ....

I've seen the 6GH8A triode/pentode tube pop-up here and on other forums using the pentode as a reverb driver.  This tube is cheap and seems to be readily available.  Both sections are rated at 2.5W, but the pentode is capable of way more gain than the triode.  Since both sections have the same limit when it comes to driving a transformer, I would rather have the high gain one be the recovery.  I don't know if there is a microphonic problem with the pentode at higher volumes, but at bedroom levels this setup is Surf City.

[jbefumo]

I would, however, like to ask another question on this topic:  I was considering taking the reverb drive signal from the second preamp stage, after the volume control, but returning it to the second input of the phase inverter, ala' the Matchless Chieftain.  My intent is that a) only the clean signal will appear in the reverb, and b) when I kick in the overdrive channel (this is being integrated into a Tweed OD Spcl circuit), the reverb will be relatively less prominent, which is what I generally want.  Anyone foresee any problems with this? (Other than interference with the usual placement of the NFB/Presence control -- I will probably try bringing that back to the upper end of the phase inverter, the way the old HiWatts did ...

[2deaf]

I could easily be mistaken, but my impression was that the driver side is not looking to produce gain, so much as driving current.  This would seem to correspond to Fender's use of parallel 12AT7s (or a 6V6, for the stand-alone unit) on the drive side, and a single 12AX7 for the recovery.  That also seems to be the way . . .

Quoted me, so I guess this is in response to my 6GH8 driver/recovery.

I didn't mean to suggest that the 6GH8 setup would be something for you - - I had reverted to the original subject of the thread having thought that the 6BM8 discussion had ended.

That 6BM8 can do just about double of anything a 6GH8 can do and, as such, can drive a reverb considerably harder while staying well within the limiting values.

[jbefumo]

My mistake -- thought you were suggesting using the triode side for the driver and the pentode side for recovery ...

I could easily be mistaken, but my impression was that the driver side is not looking to produce gain, so much as driving current.  This would seem to correspond to Fender's use of parallel 12AT7s (or a 6V6, for the stand-alone unit) on the drive side, and a single 12AX7 for the recovery.  That also seems to be the way . . .

Quoted me, so I guess this is in response to my 6GH8 driver/recovery.

I didn't mean to suggest that the 6GH8 setup would be something for you - - I had reverted to the original subject of the thread having thought that the 6BM8 discussion had ended.

That 6BM8 can do just about double of anything a 6GH8 can do and, as such, can drive a reverb considerably harder while staying well within the limiting values.

[tdvt]

Doing the layout for a DeArmond R5T which is very similar to a Princeton 5E2. This one has trem & I am thinking I would like to make accommodations to add the 1-tube reverb while I'm at it.

So a few questions;

I have looked at many threads which confirm my thought of adding it at the second-stage grid, which is fed directly from the volume wiper. I have inserted a 100K between the two & have also added coupling cap on the reverb send, though I'm not sure that is necessary, it is in some drawings & not in others. Any other considerations in this area?

Second, I will have to add a 4th B+ node, it looks like they are typically added using a 1K resistor from B+3. What is the preferred voltage differential for the reverb tube plates?

Third, I am thinking about deleting the dwell control, so do I replace the pot with a 1M resistor to ground?

Last, at this point, is regarding grounding. As a signal circuit the reverb should get grounded with the pre-amp & the trem, as a power circuit get grounded with the B+?

Thanks,

TD

[dchang0]

That 6BM8 can do just about double of anything a 6GH8 can do and, as such, can drive a reverb considerably harder while staying well within the limiting values.

I can confirm this firsthand. I'm the author of two of the 6BM8-based schematics that tubenit posted (the 5F1 Champ with Eric Barbour-inspired one-tube 6BM8 reverb, third schematic in Reply #26 in this thread and the third schematic in Reply #2).

That 5F1 w/ 6BM8 reverb schematic in Reply #26 is a bit old--it is version 1.0j, and the final one is at 1.0l (see attachment). The design does work and has worked well for five years now. It is meant to be a clean/dry reverb and was designed around the 500pF capacitor's trebly tone. To warm it up considerably, change that 500pF to a 0.001uF--BUT, read further before doing so.

---

I decided to sign up and post here specifically to confirm that the 6BM8 is more than powerful enough to overdrive an 8F-series (high impedance) reverb tank via direct capacitor-coupling when using the pentode side in pentode-strapped-as-a-triode mode for the reverb driver and the triode side as the reverb recovery. So powerful that when I replace the 500pF cap with a 0.001uF cap--with a 470K resistor right behind it (see schematic version 1.0l) instead of the 220K (in 1.0j)--it introduces a overdrive/distortion that's scary enough that I wonder if I'll break the reverb tank's input coil. You can hear the tank vibrating and the springs rattling.

Easy fix when swapping the 500pF with the 0.001uF is to keep the 220K resistor as it originally was in version 1.0j. Another possible fix that I haven't tried is to replace the 0.470uF coupling cap with a smaller and less-expensive 0.022uF cap. Both of these component choices should reduce the signal/bandwidth being shoved into the reverb tank if you choose to go with a warmer tone.

Anyway, the 6BM8 is a good choice for a one-tube reverb. It can be arranged to send more than enough current into the reverb tank with plenty of room for tweaking and tone-shaping.

[Willabe]

Welcome dchang0!   

Thanks for posting that information. We hope we continue to see you posting in this forum. 

[tdvt]

I can confirm this firsthand. I'm the author of two of the 6BM8-based schematics that tubenit posted (the 5F1 Champ with Eric Barbour-inspired one-tube 6BM8 reverb, third schematic in Reply #26 in this thread and the third schematic in Reply #2).

Thanks for taking the time to post this.

The additional drive looks good & plus no transformer...(?)

[dchang0]

Thanks for taking the time to post this.

The additional drive looks good & plus no transformer...(?)

Thanks for the warm welcome, everyone!

Yes, the circuit was specifically designed not to use a transformer because the tight quarters inside and under a 5F1 chassis would not allow the attachment of a reverb transformer.

Also, Eric Barbour's original 6BM8 reverb driver example featured a transformer, so I figured that people interested in that approach could simply follow his schematic (see attachment) with some adjustments (he doesn't show a reverb recovery circuit, so you would have to take the triode side of the 6BM8 and move it over to the recovery side).

I ended up mostly ignoring Barbour's schematic because the transformer is so integral to its design and designed my 6BM8 driver by drawing new load lines and picking one that produced more current to drive the tank through the coupling cap.

[jbefumo]

Huh -- I just threw something very similar, together on a hunk of 2X4, just to see if a one-tube amp would be feasible, and was really impressed by result.  Those 6BM8s open many possibilities - push-pull power amp + LTP in a pair of bottles, gain stage plus cathodyne PI, two preamp gain stages plus two pentodes in SW Parallel .... I've really looked no further than just the gain factor, but that suggests that the triode section of the 6BM8 is similar to a 5751 (or a 6SL7GT), which is just fine by me, and pentode section is similar to an EL82 -- haven't checked that.  Just seems like a multiplicity of ways to do the Fender Tweed Champ size/power thing with alternative approaches.

Thanks for taking the time to post this.

The additional drive looks good & plus no transformer...(?)

Thanks for the warm welcome, everyone!

Yes, the circuit was specifically designed not to use a transformer because the tight quarters inside and under a 5F1 chassis would not allow the attachment of a reverb transformer.

Also, Eric Barbour's original 6BM8 reverb driver example featured a transformer, so I figured that people interested in that approach could simply follow his schematic (see attachment) with some adjustments (he doesn't show a reverb recovery circuit, so you would have to take the triode side of the 6BM8 and move it over to the recovery side).

I ended up mostly ignoring Barbour's schematic because the transformer is so integral to its design and designed my 6BM8 driver by drawing new load lines and picking one that produced more current to drive the tank through the coupling cap.

[tubenit]

jbefumo shared this on this thread

http://el34world.com/Forum/index.php?board=13.0

With respect, Tubenit

[jbefumo]

KNEW it looked familiar      encroaching dementia?

jbefumo shared this on this thread

http://el34world.com/Forum/index.php?board=13.0

With respect, Tubenit

[MartinB]

I've just successfully incorporated the 1-tube reverb (as per tubenit's schematic in the first post) in a 50 watt plexi build, and so far I'm impressed with it.  I made a little strip of eyelet board next to the tube socket, so that the rest of the amp layout was unchanged from a stock plexi layout. 
It took a little tweaking to get the supply voltage right - at first I connected the reverb transformer to the phase inverter point in the power supply and the plate voltage was too high for my JJ ECC83.  Moving it down one node solved that problem.  It has less depth available than a blackface fender style reverb, but on those I typically run the reverb knob at no more than 2 on the dial and turning the 1-tube reverb to 7 or 8 gets me to a similar place.  It seems a good match for this style of amp - nobody plays surf with a plexi, but it's great for adding a nice wash of 'verb to bluesy leads. 

[Stevewdewitt]

I would like to add a 1-tube reverb to a Ted Weber amp that I built. It is the smokin joe II amp. Attached is the schematic. I have plenty of room in my chassis and enough power for at least one more 12ax7. I really don't know where to add the reverb circuit but I think it has to be after the Tone and/or Volume. The preamp stage uses an SRPP design. I have never built an amp with this type of tone control before. I really like the sound and simplicity of this amp. It is small, light weight and puts out about 15 watts. Plenty loud enough when mic'd. I have marked up two potential spots in the circuit where I could insert the reverb. Have a look, let me know if it is possible with this amp.

Thanks very much,
Steve

[tubenit]

The one on the right between the volume and LTPI.   I'd use a 150k mixing resistor.  Look at the 5879 blues amp GIF attached to the first post of this thread on the first page.

With respect, Tubenit

[Stevewdewitt]

After a week in Mex, I got the 1-tube reverb installed in the Weber Smoking Joe II using the Blues Amp circuit. Thanks tubenit! I left out the the dwell pot and used a 1M resistor instead. I used a 3 spring 9xxx reverb tank.

Sounds perfect. Exactly what I was hoping for.

Steve

[mbrooks0711]

Hello all,

I'm looking to build my first amp, a Matchless Lightning clone. I'll be using a layout and schematic from the good folks at Trinity amps, but I would like to add reverb to it.

Could someone help me with where the insertion point should be? I believe  that it should go after the Tone-stack & before PI tube OR if it should go after the Master Volume?Full disclaimer I am at the beginning of this hobby/addiction and as far as amp expertise and knowledge, I am like a Kindergartener who knows their letters but can't actually read yet. I can look at a schematic and identify just about everything on it, but I'm not understanding everything at 100% right now. I appreciate any help you could provide.

[tubenit]

I am wondering about that schematic that you posted being correct?  It might be but I've never seen a resistor in that one spot before?

Here is how I would do it.

With respect, Tubenit

[sluckey]

I am wondering about that schematic that you posted being correct?

It's correct. The preamp is pretty hot in the lightning. That 220K and 100K make a voltage divider to knock the signal down quite a bit before it hits the PI.

[mbrooks0711]

I am wondering about that schematic that you posted being correct?  It might be but I've never seen a resistor in that one spot before?

Here is how I would do it.

With respect, Tubenit

Thanks so much Tubenit. I'm new to the forum so I don't see a like/give kudos/thanks button, but I found this to show my appreciation 

I know most people are adding these reverbs into the circuit as a separate board to the main board, but would there be any reason to not include it on the main if I plan on having Hoffman make the board anyway?

[sluckey]

but would there be any reason to not include it on the main if I plan on having Hoffman make the board anyway?

That's how I'd do it.

[tubenit]

I agree with Sluckey & would put it on the main board.

Tubenit

[mbrooks0711]

Tubenit, in the schematic you provided are the two 1M resistors the Potentiometers for the reverb controls? If so, are their lugs 1-2-3 from north-middle-south?

 Also, what are "E" and "B"?

Assuming that the 1M resistors are the pots, I've done a mock layout. I know the spacing, etc. is wrong, but I've never tried to translate a schematic to a layout before. Could those more knowledgable than me check this layout against the schematic Tubenit provided?

[tubenit]

The 1M "resistors" are indeed 1MA potentiometers.

I don't know what 1,2 & 3 is?  You'll have to figure out that one on your own or get help. I don't number the lugs.

E and B are nodes on the B+ rail.  I simply cut and pasted from a schematic I had to illustrate the insertion points.

With respect, Tubenit

[mbrooks0711]

Perfect, that's what I was thinking. I just meant pot lug numbers. I've only seen them numbered before, but the way you have it they are implied and clear. Thanks again.

[sluckey]

You need to move the ground wires to the left lug on those pots in your layout.

[mbrooks0711]

You need to move the ground wires to the left lug on those pots in your layout.

Ok, thanks. I have to triple check things when orientations change and I didn't there. We're there any other errors?

[sluckey]

Yes, there are several other errors. Put the schematic and the layout side by side and it should be easy to sort them.

[mbrooks0711]

Well, that's embarrassing. I'll give it another go then.

[sluckey]

That's how we learn. Post your revised layout and I'll have another look. And I'll be more specific next time. Wanted you to try to sort it first.

[mbrooks0711]

Sluckey, here is my second attempt. Did I at least move from an F to a C-?

[sluckey]

If I was grading you I'd give you a B on this drawing. The only thing that I see that's wrong is the 220K and 500pf on the return jack. Look at the schematic again. You'll see it immediately.

[mbrooks0711]

Yeah, they are parallel to ground? Should I just ground them to the closest star ground or run them back onto the board to be grounded?

Also, any tips about ways to improve the layout would be helpful. Like I said this is my first schematic to layout attempt, so I understand it may be functionally right, but not logically correct. I've really searched for a good tutorial on this, and found some, but nothing that has just clicked with me yet.

[sluckey]

Fender didn't use that 500pf. They only used the 220K and it was mounted directly on the return jack.

Hanging out on this forum (and others), looking at what others have done, designing your own layouts based on the schematics, etc. will go a long way toward making good logical board layouts. You'll get better as you go. I feel that my stuff has progressed a lot since my first layouts. Oh, and making mistakes is a good teacher too! 

[rlh5599]

So, with your help, I got my Epiphone Pacemaker running.  While I was going through all my parts, I realized I have everything to install one of these 1 tube 'verbs in my AO43 Hoffman Stout TMB, (except a tank, not sure which one to get)
I have an extra open noval socket in the chassis, plenty of room at that end of the chassis to use the circuit in tubenit's first post, and plenty of heater current.
I am just circuit challenged.  I've been through all the posts, all the layouts and schematics, and I can't figger out where to insert the circuit in the the tmb circuit.
Attached is the layout and schematic, although the schematic doesn't include the MV parts.
Any help would be appreciated..

[sluckey]

I'd do it like this...

Refer to the schematic... Remove R12. Disconnect C5 from C8 and install a 100K resistor between C5 and C8. Connect Tubnit's reverb circuit input to the junction of C5 and the 100K. Connect the reverb output to the junction of the 100K and C8.

Or refer to the layout... Replace R12 (470K) with a 100K. Remove the short ground buss jumper from the bottom of R12. Remove the short jumper between the bottom of C5 and C8. Install a jumper between the bottom of C8 and the bottom of R12 (now a 100K). Bottom of C5 connects to reverb input. Bottom of C8 connects to reverb output.

[rlh5599]

I'd do it like this...

Refer to the schematic... Remove R12. Disconnect C5 from C8 and install a 100K resistor between C5 and C8. Connect Tubnit's reverb circuit input to the junction of C5 and the 100K. Connect the reverb output to the junction of the 100K and C8.

Or refer to the layout... Replace R12 (470K) with a 100K. Remove the short ground buss jumper from the bottom of R12. Remove the short jumper between the bottom of C5 and C8. Install a jumper between the bottom of C8 and the bottom of R12 (now a 100K). Bottom of C5 connects to reverb input. Bottom of C8 connects to reverb output.

Is that C5 and C8, or C5 and C6??  Thanks!! actually where I thought it should go, (more or less)  use an 8 ohm tank, correct?

[sluckey]

C8 should be C6. Sorry, bad eyes.

[rlh5599]

C8 should be C6. Sorry, bad eyes.

No worries, that's what I thought.  Thanks again!

[goldstache]

How do you think the originally posted 1 tube circuit would work with an EF86?


EF86>LTP>EL84PP

[jayallen]

I would like to add this to a peavey windsor. I was wondering where I would add the in and out signal for the one tube reverb. Thanks