onboard reverb pro 5E5-A

[sloblues]

was considering trying out a "fold-back" reverb circuit on my brown pro. KOC in TUT1 talks about this briefly, and I have an unused 1/2 12AX7 available for recovery. Has anyone done this or have knowledege about a circuit such as this? It seems the basics are to properly pad a tap from the output jack, drive the tank with this signal, use the 1/2 12AX7 for recovery amp, then feed this wet signal back in ....somewhere ?
any ideas would be much appreciated.

[sloblues]

make that 6G5-A not 5E5

I meant pro model 6G5-A, not 5E5-A

[52 Bill]

It seems the basics are to properly pad a tap from the output jack, drive the tank with this signal, use the 1/2 12AX7 for recovery amp, then feed this wet signal back in ....somewhere ?

The only problem I've noticed with amps that use this style of circuit, is that the drive to the reverb tank is based on how loud the amp is playing. When changing from a rhythm volume level to a solo volume level, the reverb drive level changes.

If I remember correctly, some Magnatones used this idea. Check out schematic heaven and see if there are any circuits for you to review there.

[tubeswell]

FWIW I found out (courtesy of Bruce) recently that the Champ 12 also does this, albeit that it uses a transistor and 1 tube triode for the recovery. "Doesn't have" a 'reverb tranny' either. No idea what it sounds like, but the concept of a 'transformerless' reverb driven from the output tranny is an interesting variant.

http://www.ampwares.com/ffg/schem/champ_12_schem.gif

[52 Bill]

...the concept of a 'transformerless' reverb driven from the output tranny is an interesting variant.

Actually, if I remember correctly, this was one of the ways that the original tanks were designed to be used.

The original circuits that I remember seeing were meant to be "Add-ons" to home and car sound systems. Rather than tear into the circuitry, you would take the signal from the speaker output feed it to the reverb springs and then either send the return signal back into a second input of the original amp, or into an second amplifier with a separate speaker.

When I was in high school, a friend's dad had a Lincoln that had a Gibbs reverb system on the radio. Everytime the car bounced, like over railroad tracks, there was the splashy sound of the springs, and we would both yell "Wipe Out!" and start drumming on the dashboard.

[sloblues]

speaker load verb'

thanks '52 I did consider that output level would directly affect the drive to the tank in a scheme such as this. but I nearly always set my amp to the same level and control overall 'loudness' with my guitar volume .. trickier is getting the right amount of signal to the tank. At '7' (my volume setting) my Pro puts out 17.4VAC into an 8 ohm load or about 37watts .... the Accutronics website recommends the current into the tank I have (type 4) should be 28ma .....
after I get the input drive right, where would be a good place to return this wet signal into the amp? At the .001 cap into the PI? On the cathode of the PI like where the NFB goes? Seems like phasing might be an issue also?
thanks for the info to date !!

[Bruce / Mission Amps]

FWIW I found out (courtesy of Bruce) recently that the Champ 12 also does this, albeit that it uses a transistor and 1 tube triode for the recovery. "Doesn't have" a 'reverb tranny' either. No idea what it sounds like, but the concept of a 'transformerless' reverb driven from the output tranny is an interesting variant.

http://www.ampwares.com/ffg/schem/champ_12_schem.gif

Isn't it interesting that the Champ 12 amp uses the voltage from the power tube's cathode biasing resistor to run FET tank recovery amp?
Then it takes that FET amplified signal and shoves it into the 12AX7 triode and the output of that goes right back to the grid of the power tube!
This reverb actually works OK and yes it is crashy if you dime the amp with the reverb up high (and can actually break into an oscillation if too hot) and the reverb is a little weaker sounding then the dry signal if your play quiet.
It's still very clever.

[TD_Madden]

Actually, if I remember correctly, this was one of the ways that the original tanks were designed to be used.

The original circuits that I remember seeing were meant to be "Add-ons" to home and car sound systems. Rather than tear into the circuitry, you would take the signal from the speaker output feed it to the reverb springs and then either send the return signal back into a second input of the original amp, or into an second amplifier with a separate speaker.

When I was in high school, a friend's dad had a Lincoln that had a Gibbs reverb system on the radio. Everytime the car bounced, like over railroad tracks, there was the splashy sound of the springs, and we would both yell "Wipe Out!" and start drumming on the dashboard.

Wow, I had forgotten about my high-school girlfriend's car.....a Lincoln with reverb on the radio and an electric rear-window that rolled down!

[Bruce / Mission Amps]

Wow, I had forgotten about my high-school girlfriend's car.....a Lincoln with reverb on the radio and an electric rear-window that rolled down!

Mercury Monterey....
http://web.ics.purdue.edu/~stanchfi/mycarback.jpg