Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jerry garrcia on June 09, 2024, 04:11:38 am
-
I have a friend whom I built a 5B2 for studio work. Now he asked me if it was possible to do one with a spring reverb. A stupid idea or not? To keep parts cost as low as possible (do have 250V secondary PT with 4A 6.3V tap, suitable OT’s for a build and some chassis from old radios including speakers).
1) If not a totally stupid idea where would be the best place to insert it?
2) to keep parts costs down what about this Ampeg gemini reverb but with 6SN7 instead of the 6CG7) circuit since its without a transformer? https://el34world.com/charts/Schematics/files/Ampeg/Ampeg_g15_gemini_ii.pdf Only heard good things about it an have some 6SN7’s. In the reverb circuit included it runs just after the tone stack.
3) if it’s not a crazy idea to add the Ampeg reverb in a 5B2 should I add a 6SQ7 or 6SF5 as a recovery before the second half of the 6SL7? Would like a dwell pot if possible.
Just a nice, simple, nice sounding 5B2 but with a spring reverb for home and studio use.
Any ideas?
-
This is not a direct answer to your question but still may prove useful to your thinking?
Champ (&5F2 Princeton) w/reverb variations (el34world.com) (https://el34world.com/Forum/index.php?topic=630.0)
With respect, Tubenit
-
This is not a direct answer to your question but still may prove useful to your thinking?
Champ (&5F2 Princeton) w/reverb variations (el34world.com) (https://el34world.com/Forum/index.php?topic=630.0)
With respect, Tubenit
Thanks for your answer and will dig in to it. I thought I searched the forum thoroughly but missed this.
Obsessed with octals and the concept of a transformer less reverb really would be a nice touch. Especially since it will be a scrap build. But it might be useful to find out where the best insert location would be.
As I contemplate I realized that I wouldn’t need a dwell pot. If the reverb level pot, after the recovery stage, could be a switched pot (have a few 500K lin with a switch) it would be neat to be able to turn the reverb on or off there.
-
Maybe this current thread (https://el34world.com/Forum/index.php?topic=31634.0) might be helpful..?
I added reverb to BF Champ circuit but used a 3rd triode for mixing wet & dry. With your circuit you might have to add a resistor between the 1st & 2nd stages as an insertion point.
Seems like there are some schematics on this forum with something along those lines.
I would keep the dwell if it were me.
-
Maybe this current thread (https://el34world.com/Forum/index.php?topic=31634.0) might be helpful..?
I added reverb to BF Champ circuit but used a 3rd triode for mixing wet & dry. With your circuit you might have to add a resistor between the 1st & 2nd stages as an insertion point.
Seems like there are some schematics on this forum with something along those lines.
I would keep the dwell if it were me.
Will read up on that as well. With the Ampeg transformer less reverb I can’t really find the suitable place to fit the dwell. Have some more reading to do tonight I suppose.
-
Looked through some saved SE + reverb schematics.
One of them in particular, came from THIS THREAD (https://el34world.com/Forum/index.php?topic=25039.0), (2Deaf, post #16) & might also be of interest as the reverb signal is pulled earlier in the signal path than the typical Fender circuit. Might give you some options with your insertion point.
Lots of other designs there to check out as well.
-
This is how I would add a Dwell pot...
-
Looked through some saved SE + reverb schematics.
One of them in particular, came from THIS THREAD (https://el34world.com/Forum/index.php?topic=25039.0), (2Deaf, post #16) & might also be of interest as the reverb signal is pulled earlier in the signal path than the typical Fender circuit. Might give you some options with your insertion point.
Interesting insertion point🙂. But that thread also reminded me of Uncle Dough’s current GA-1RVT build series. The reverb pot with the switch might come in handy since I have a 500K with a switch in my gutted audio stash. Well now just find the insertion point for the dwell since it’s not like a 6G15. And much more. I can fit four tubes in the planned chassis so with SS rectifier a 6SL7, 6SN7, 6SQ7 and a 6V6 will fit. More reading.
Thanks for all inputs.
-
Well now just find the insertion point for the dwell since it’s not like a 6G15.
Dwell is used to control the amount of signal sent to the input of the reverb tank. It doesn't matter if the tank input is cap coupled or transformer coupled. I showed you the ideal place to put a dwell pot in the Gemini II reverb circuit.
-
Well now just find the insertion point for the dwell since it’s not like a 6G15.
Dwell is used to control the amount of signal sent to the input of the reverb tank. It doesn't matter if the tank input is cap coupled or transformer coupled. I showed you the ideal place to put a dwell pot in the Gemini II reverb circuit.
:worthy1:
In your opinion where would you insert it ( reverb circuit)? The original version is after the tone stack and if possible it would be nice to be able to totally bypass it. And have you tried the circuit? I’ve only heard it in high gain amps. Not in this vintage tweed one.
-
I bought a Gemini II brand new in 1968. Nobody has ever tried to put this reverb circuit in a simple 5B2 amp. Only one or two places to insert. Just experiment.
-
Whichever way you approach it, the critical part is being able to get a workable balance between wet and dry signals going back into the main signal (remembering that the reverb recovery stage input signal - from a spring pan’s output transducer - is much weaker than most guitar pickups, and so you’ll likely need some sort of dry signal attenuation and/or additional wet signal boost - or gain stage - so that the wet isn’t drowned out by the dry (ironic as that metaphor may seem).