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previous: SteveR Hi,I was just readi... -- 9/9/1999 10:23 PM

Re: fold back reverbs

9/10/1999 7:34 PM
Mike D.	Re: fold back reverbs I have added this feature to a couple of old Harmony guitar amps. If you only need a moderate amount of reverb, the concept works ok. If you try to make the reverb too strong, you will get a high-pitched feedback. You will need to experiment with the voltage divider on the output stage to provide the correct "dwell" to the tank, you will also need to futz with the gain of the recovery stage. I believe the Champ 12 incorporates a trim-pot to adjust the recovery gain. As an alternative, I have used a Jfet/Mosfet cascode driving a standard reverb transformer along with a jfet/mosfet cascode recovery stage with excellent results. I have used both the fender reverb transformer and an output transformer scavenged from an old tube radio. They both worked fine, and were capable of Dick Dale reverb. There is information on Steve Ahola's page regarding the use of Fets in tube circuits. I am the one who wrote this doc. Use a long tank if you can, but the world will not stop turning if you use a short tank. regards, Mike Donovan

9/10/1999 7:34 PM

Mike D.

Re: fold back reverbs

I have added this feature to a couple of old Harmony guitar amps. If you only need a moderate amount of reverb, the concept works ok. If you try to make the reverb too strong, you will get a high-pitched feedback. You will need to experiment with the voltage divider on the output stage to provide the correct "dwell" to the tank, you will also need to futz with the gain of the recovery stage. I believe the Champ 12 incorporates a trim-pot to adjust the recovery gain.

As an alternative, I have used a Jfet/Mosfet cascode driving a standard reverb transformer along with a jfet/mosfet cascode recovery stage with excellent results.

I have used both the fender reverb transformer and an output transformer scavenged from an old tube radio. They both worked fine, and were capable of Dick Dale reverb.

There is information on Steve Ahola's page regarding the use of Fets in tube circuits. I am the one who wrote this doc.

Use a long tank if you can, but the world will not stop turning if you use a short tank.

regards,

Mike Donovan

Replies:

Farrow I worked on a Bassman that a guy ha... -- 9/10/1999 9:38 PM