18Watt.com

So, throughout my career as an engineer, I have found that in many cases there is more than one way to design something and still have it be a good functional product. As I have researched tube amp schematics, I find that most all of them are derived from someone else (probably Fender). Similar but with minor changes. Many times when I design something, I take (steal ) parts from other designs.I'm doing this with my current build. It is a cross between a 18watter (Ceriatone TBM) front end, with low gain ch, and high gain ch. with a 6G3 power section, and I am adding a spring reverb circuit from a Blues Jr.
my question to the more experienced here: As you can see from my schematic, I have a low gain section and a high gain section that meet up at the PI. It is this point I want to inject the reverb, so that I have it for both channels. Trial and error is probably how I will go about testing this design, but wanted to get opinions here. Do you see any issues with how I have integrated the R19, R20 and combining with R21, to feed into V3A?
thanks in advance

Not sure how much it will help you, but the schematic below shows my DIY Marshall(ish) 36W. Based on circuit impedances and signal levels, I decided to drive the reverb signal into one of the stages preceding the tone stack. You might want to model your design in LTSPICE before proceeding.

Jack

Jack.. take a look at the Tone King imperial MK2 schematic. There is a difference in input values for the reverb that blocks some signal in high gain mode.
Might be inspiring.
If you would replace the mixing resistors with a dpdt switch, or even better a relays circuit, you could turn it into a giggable channel switching amp

thanks Bieworm. But I think your idea would only allow reverb on one channel. But I want it available on both. My concern with how I have it designed is that I would not have an equal amount of signal going to reverb from both channels. I may have to play with the values of R 19, 20, 21, so the signal level going into V3 is equivalent.
Unfortunately I do not have access to LTspice

thanks

Davidscott wrote: ↑

Sat 10/07/23 11:50 am

Unfortunately I do not have access to LTspice

https://www.analog.com/en/design-center ... lator.html

https://learn.sparkfun.com/tutorials/ge ... tspice/all

Davidscott wrote: ↑

Sat 10/07/23 11:50 am

thanks Bieworm. But I think your idea would only allow reverb on one channel. But I want it available on both. My concern with how I have it designed is that I would not have an equal amount of signal going to reverb from both channels. I may have to play with the values of R 19, 20, 21, so the signal level going into V3 is equivalent.
Unfortunately I do not have access to LTspice

thanks

You misread the schematic. It clearly is on both channels. I have built this amp several times in a seriously tweaked form.

"So, throughout my career as an engineer, I have found that in many cases there is more than one way to design something and still have it be a good functional product."
Reminds me of a saying an old tradesman used to say to me as an apprentice
" There are more ways of killing a cat than shoving butter up its arse with a hot hat pin"
Thought I would share

Bieworm wrote: ↑

Sat 10/07/23 2:08 pm

Davidscott wrote: ↑

Sat 10/07/23 11:50 am

thanks Bieworm. But I think your idea would only allow reverb on one channel. But I want it available on both. My concern with how I have it designed is that I would not have an equal amount of signal going to reverb from both channels. I may have to play with the values of R 19, 20, 21, so the signal level going into V3 is equivalent.
Unfortunately I do not have access to LTspice

thanks

You misread the schematic. It clearly is on both channels. I have built this amp several times in a seriously tweaked form.

Are you referring to my schematic? Yes I have two channels and reverb injected. But the schematic you attached did not look like it had 2 channels. anyway, I don't seem to be getting any help on this one. guess its trial and error time...

JMPGuitars wrote: ↑

Sat 10/07/23 12:05 pm

Davidscott wrote: ↑

Sat 10/07/23 11:50 am

Unfortunately I do not have access to LTspice

https://www.analog.com/en/design-center ... lator.html

https://learn.sparkfun.com/tutorials/ge ... tspice/all

thanks I will check this out! seems like the last time i tried analog devices spice it cost me... and i didn't think they would have valve models available!

AussieTim wrote: ↑

Sun 10/08/23 8:01 am

"So, throughout my career as an engineer, I have found that in many cases there is more than one way to design something and still have it be a good functional product."
Reminds me of a saying an old tradesman used to say to me as an apprentice
" There are more ways of killing a cat than shoving butter up its arse with a hot hat pin"
Thought I would share

Yeah the other quote is "more ways to skin a cat and still get it to howl", but I was trying to keep it a serious thread...

Why write things like not getting any help? That’s exactly what I was trying to do. You don’t have to be an engineer to see on the Tone King schematic that the reverb circuit takes off between each coupling cap and the mixer resistors and gets back into the track after the mixing resistors. The relays switch puts one channel to ground to let the other channel in the signal path. What I was trying to point out is that with the application of a series R/C you can determine the amount of signal getting to the reverb driver tube. THAT will give you the opportunity to tweak the signal strength of the reverb for each channel separately.
Honestly, I don’t see how this would not help you figure out an easy way to tame the reverb on the higher gain setting without dialing the knob.
Here is a clip of an amp I built using that structure. Tell me if there is no reverb on both channels. The red led will show the switchting and the overdrive will prove there are two channels.
https://youtu.be/VKUAzA2PB-g?feature=shared

Bieworm wrote: ↑

Mon 10/09/23 12:26 am

Why write things like not getting any help? That’s exactly what I was trying to do. You don’t have to be an engineer to see on the Tone King schematic that the reverb circuit takes off between each coupling cap and the mixer resistors and gets back into the track after the mixing resistors. The relays switch puts one channel to ground to let the other channel in the signal path. What I was trying to point out is that with the application of a series R/C you can determine the amount of signal getting to the reverb driver tube. THAT will give you the opportunity to tweak the signal strength of the reverb for each channel separately.
Honestly, I don’t see how this would not help you figure out an easy way to tame the reverb on the higher gain setting without dialing the knob.
Here is a clip of an amp I built using that structure. Tell me if there is no reverb on both channels. The red led will show the switchting and the overdrive will prove there are two channels.
https://youtu.be/VKUAzA2PB-g?feature=shared

Thank you for your clarification. I apologize for stating not getting any help. Its not exactly what I was meaning. I was thinking of another way of doing this, and was mental blocked on your concept. Meaning, your design was not going to help me. Not that YOU were not helpful! I downloaded your schematic and took a more in depth look at it. Online it is sideways and difficult to follow, I lost continuity pretty quick. I see your point, and perhaps I can integrate this concept into my design.

Don’t worry about that. Written words are not always read the way they should