Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Leevi on March 28, 2011, 03:26:45 pm

Title: Reverb question
Post by: Leevi on March 28, 2011, 03:26:45 pm
Do you think a spring reverb could work if it is placed just before the PI i.e.
after the tone stack?
/Leevi
Title: Re: Reverb question
Post by: tubeswell on March 28, 2011, 07:41:31 pm
Do you think a spring reverb could work if it is placed just before the PI i.e.
after the tone stack?
/Leevi

All depends on the gain structure of the amp in question and the relative level of attenuation of the dry signal compared to the wet signal you are getting from the recovery side. This is why BF amps typically have the dry signal more heavily attenuated than the wet signal from the recovery stage (i.e. because there is only 1 recovery stage driven from a comparatively weak pan output transducer, and it has to blend back in with a dry signal that has been through 2 pre-amp (dry) stages.)
Title: Re: Reverb question
Post by: Leevi on March 28, 2011, 11:31:47 pm
I'll have one double triode reserved for the amplification of the dry signal.
I think that's enough especially if if I use serial coupling?
/Leevi
Title: Re: Reverb question
Post by: tubeswell on March 29, 2011, 01:34:28 am
Have a look at how they do the recovery in the Allen Old Flame. They attenuate the dry side more and then have another triode stage that both dry and wet go into to boost the overall mixed signal back up to where it drives the PI nicely. Some peeps call this 'brute force'. I just think its a smart approach.
Title: Re: Reverb question
Post by: sluckey on March 29, 2011, 06:50:02 am
Quote
Do you think a spring reverb could work if it is placed just before the PI i.e. after the tone stack?
Yes. You may like the Matchless approach... The reverb driver input is picked up just prior to the LTP PI input and the recovery amp connects to the other PI input.

http://www.el34world.com/charts/Schematics/files/matchless/matchless_chieftan.pdf

Title: Re: Reverb question
Post by: Leevi on March 29, 2011, 10:54:18 am
sluckey,
Yes, I know that since I have built a Chieftain w. reverb some years ago. I was thinking
more a preamp like in VOX AC30 and the placement of the reverb after its tone stack. A good idea
might be to connect the delayed signal to the second input of the PI like Matchless did in the Chieftain.
/Leevi
Title: Re: Reverb question
Post by: tubeswell on March 29, 2011, 01:37:28 pm
Remember that the chieftain utilise a parallel stage for the reverb recovery as well, and this drives the LTP nicely because of the extra gain and lowish output impedance. If you are trying to do that with a single triode recovery stage, you may not get a very strong wet signal in the mix.