different ways to tame/reduce reverb on a Twin Rveveb AB763

[mguitarworks]

hi, what are the best ways to tame/reduce the reverb on a TR, i have tried 12AU7 in the return a love it ,only problem its also 2nd gain stage so ive lost volume and punch.currently running a DW7 there, not too bad. but i would like to run a 12AY7 in there for the 2nd gain stage and a 12AU7 for the reverb return, that would be ideal. my TR is a clone with no normal channel and vibrato has been removed so i have free socket. can i split the return in 2 and take the 2nd gain stage to the free socket and leave the return reverb where it is?

any other ideas? swapping the 2.2k resistor in the driver for a 1k? but i dont want to cook the at7..how much of an reduction would this give?

many thanks Mark

[sluckey]

Turning the reverb knob down is not enough?   

Using separate tubes for recovery and gain stages is an option. But before doing that consider replacing the 1meg grid return resistor for the 12AT7 driver with a 1meg audio taper pot. This becomes a dwell control. Also consider replacing the 100K linear reverb pot with a 100K audio taper pot for finer reverb control at low reverb settings.

Tubenit has a neat one tube reverb circuit based on the AB763 circuit. He uses a 1/2 of a 12AX7 for the driver and the other half as the recovery. Plenty of usable verb without being in surf city.

[LooseChange]

Try replacing the 12AT7 with a 12AU7.

[Fresh_Start]

I like the Dwell control idea.  Works in a Princeton Reverb build that I put an overly excitable 3-spring tank into.  Audio taper Reverb pot works too.

You could remove the cathode bypass cap on V3, the 12AT7 driving the reverb transformer.

Or you can experiment with a 2.2meg or even 1.5meg resistor in place of the 3.3meg paralleled with a 10pf cap.  That boosts the dry signal relative to the reverb signal.  Actually the opposite of what you asked for but might be fun...

Cheers,

Chip

[stratele52]

Try to reduce the 1 M resistor at the 12AT7 pin 2. But sometimes "to much" reverb is a defective bypass caps on 12AT7 pin 3-8 and 1/2 7025 pin 3 on the schematic.

[mguitarworks]

hi guys, i have tried a 12AU7 AND 12AY7.what i want is to change the balance of dry to wet...increase the dry reduce the wet so its less overpowering. I think when that get balanced to what i like, the control pot sweep /sensitivity will sort itself out..what about replacing the 2.2k cathode resistor with a 1.5k or the 3.3mohm mixer resistor with a 3.0 or 2.5? anyone ever tried this?

cheers Mark

[mguitarworks]

sorry fresh start just re read your post...also,which pin on a 9 pin preamp tube is the one you measure plate voltage on?

[Fresh_Start]

http://www.mif.pg.gda.pl/homepages/frank/vs.html

12A_7: pins 1 & 6 are plates, 2 & 7 are grids, 3 & 8 are cathodes

Cheers,

Chip

[HotBluePlates]

You can also reduce the value of the 3.3M resistor that splits the reverb signal down to the 1M resistor on the reverb driver.

A smaller value there increases the dry signal strength as it reduces the reverb signal strength. You'll have to taste-test to find a value that suits you.

[phsyconoodler]

Sluckey said:"Also consider replacing the 100K linear reverb pot with a 100K audio taper pot for finer reverb control at low reverb settings."

   This works by far the best because it doesn't alter the circuit and interrupt the bias of the driver and recovery tubes.I've tried dwell controls but they don't really do much on a stock tank.They work best on the three spring tanks.

[mguitarworks]

Thanks guys..ive also split the cathode resistor on the reverb return and gave them each one 1.5k with 25uf bypass cap. noticeable difference for the better much more responsive. i want to split the reverb driver cathode too, it has a 2.2k shared res with bypass cap. what would be the value of two single ones?..... 3.9k with 25uf bypass cap?

also changing the 1M grid resistor that drives the reverb driver tube was someones suggestion...do i need a higher or lower value to reduce the intensity of the reverb?


thanks

[Fresh_Start]

Mike - I would experiment with the value of the mixing resistor (3.3 meg stock) before changing the grid return resistor for the reverb driver stage. Try 2.2 meg or 1.5 meg.  A lower value raises the level of the dry signal.

Also, there's no point in splitting the cathode resistor of the reverb driver because those two triodes are operating in parallel.  Frankly, there shouldn't have been much difference splitting the cathode resistors for the reverb return and the stage it shares an 820 ohm cathode resistor with.  My first guess would be that you had a bad cathode bypass cap on one or both of those triodes.

Cheers,

Chip

[mguitarworks]

hi chip...there was nothing wrong with caps all brand new sprauges..its made a big difference thats for sure..i have since heard a few people recomend it.fender only shared cathode resistore as a cost cutting and space saving measure.

side question..has any lowered the value of the negative feedback resistor on a twin to 47ohm?..

 did srv vibroverbs run 47 with the 2 ohm output tap?
cheers