Transformerless Reverb

[gary sanders]

I found a few discussions elsewhere talking about this.Using a small power tube to push the springs instead of a preamp with a transformer.For example,the Ampeg Gemini II used a 6CG7 driver and a few other old designs by other manufacturers.Anyone did this before in a build?

[oldhousescott]

I "borrowed" the design that Carvin uses in their Vintage series of amps for a D-style amp conversion. I bought an Accutronics/Belton tank with the high input impedance, and used a single 12DW7 -- the 12AU7 side for the drive and the 12AX7 side for the makeup. Worked well enough, not surf quality, but it adds enough depth as needed.

[gary sanders]

The tank I have just happens to be an accutronics out of a carvin.I dont care for the surf type I just like for it to ad a little to the clean tone and in a lead now and then.(Im a Carvin fan,own 6 Carvin guitars ) Will give that a try!Thanks for the advice

[TUBEDUDE]

Greetings Gary,
What are your concerns with transformers for reverb. I have several myself, but have found that using a push/pull tranny has solved those issues and has given me the most dynamic 3D reverb I could have imagined. Are you thinking of a full bore power tube like a 6BQ5, or something like an ECC99?

[passfan]

Without having a chance yet to study this enough to determine if it will do what I think it can, the front end of this circuit could possibly allow the implementation of not only transformerless reverb but tubeless as well. All you may need is a tank and a few passive devices. If you look at the input to this circuit you see that this accepts a speaker output, sends it through a tank and back into the preamp of the amp. Why couldn't this speaker out come from the amp being fed by the tank part of the circuit

http://ampgarage.com/forum/files/valco_510_121_157.pdf

[gary sanders]

I have considered a 6BQ5 or even a 6DN7 dissimilar triode.half is 1.5 watt and other is rated ten.(Thats a comparison to the 12DW7 on the Carvin circuit.)I have a few different power tubes I could use to make this work,even a 6K6 like in the fender reverb units.

[TUBEDUDE]

+1 on Carvin. I have 4 Carvin amps, a VTX-100, loud and heavy but toneless ,X-60B, small and powerful, and a modified VT-50, which I love. For bass, my Carvin BX500 does it all. My main bass is a modified LB-76F, sweet thunder! When I'm not using the BX500, I play through the VT-50 and it handles the bass admirably. The open back 4 10 cab is amazing! It goes to low C# before dropping volume slightly.

[pula58]

Greetings Gary,
What are your concerns with transformers for reverb. I have several myself, but have found that using a push/pull tranny has solved those issues and has given me the most dynamic 3D reverb I could have imagined. Are you thinking of a full bore power tube like a 6BQ5, or something like an ECC99?

tell me please about the push-pull reverb drive. What tranny did you use?

Thanks!

P.

[TUBEDUDE]

I used a hammond 125. It was what I had on hand but is serious overkill. The 124 series is plenty of iron for this. In fact, using the push pull topology, the magnetizing currents negate each other so you avoid flux saturation of the core, so less iron is required. I drove it shunted with a 33K 2W resistor from plate to plate on a 12AT7. Use a small cap on grid 1 so you amplify only the higher freqs and select a common cathode resistor to set bias, just like a baby cathode biased output stage.
I keep the verb signal seperate by taking the output of the recovery amp and injecting it on Grid 2 of a LTPI. I think this improves the fidelity of the overall signal as the reverb isn't being fed thru further stages with the dry signal. But I digress, the Hammond 124 will do.

[pula58]

I used a hammond 125. It was what I had on hand but is serious overkill. The 124 series is plenty of iron for this. In fact, using the push pull topology, the magnetizing currents negate each other so you avoid flux saturation of the core, so less iron is required. I drove it shunted with a 33K 2W resistor from plate to plate on a 12AT7. Use a small cap on grid 1 so you amplify only the higher freqs and select a common cathode resistor to set bias, just like a baby cathode biased output stage.
I keep the verb signal seperate by taking the output of the recovery amp and injecting it on Grid 2 of a LTPI. I think this improves the fidelity of the overall signal as the reverb isn't being fed thru further stages with the dry signal. But I digress, the Hammond 124 will do.

Hm..it sounds like you have a long tailed pair circuit, like a Standard Phase inverter, to drive the primary of the reverb tranny.

[TUBEDUDE]

It's like a LTPI, except it's a short tail. The 1 meg grid resistors go to ground with the cathode resistor, no extra tail resistor between that junction and ground.