Please recommend single tube reverb circuit.

[psychepool]

I made Dumble reverb layouted by Normster.

DCFB5828-954A-4D7B-83C7-7D71FDAE180E.jpeg

It works fine but the amount of reverb is not enough for me.

Can you recommand another circuit that has single tube?
I use Hammond 1750A and 8AB3C1B

I am interested in Rockerverb and Mesa Lonestar circuits. Will they work well?

-Rockerverb-

4A04B3BB-CB06-4A21-8947-48F1602DB033.jpeg

-Mesa Lonestar-

B22E900E-C0C9-4341-815C-F13EDB31F16F.jpeg

Please recommend other circuits to apply to my Dumble.

[10thTx]

You may find some information on this thread that may be of use such as the 6BM8 reverb design?

http://el34world.com/Forum/index.php?topic=7957.0

With respect, 10thtx

[psychepool]

You may find some information on this thread that may be of use such as the 6BM8 reverb design?

http://el34world.com/Forum/index.php?topic=7957.0

With respect, 10thtx

Thanks! The circuit you show me is almost the same with my circuit.
Here’s my schematic.

28866D53-84E2-4E40-93F6-47BC98FD4E89.jpeg

What’s the key difference between two?
The cathode resistor value? B+ resistor on reverb transformer? Input capacitor value?
First of all, I want to lower the value of the cathode resistor on reverb send because the DR has 2.2K on Parallel Reverb send.
What is your opinion?

[tubeswell]

I had a Morgan SW22R on the bench a while back and reverse engineered out a schematic and took some gutshot pics.

Big-sounding amp (for a p-p 6V6). Try a 12AT7 in the LTP slot for extra razzle-dazzle. The reverb is nice sounding for a 1-tube 12AX7 jobbie. For more 'splash', I'd be inclined to try a 12DW7 tube with the 'AU' triode as the driver, but subbing in a beefier cathode resistor at say 4k7 to 5k6

[psychepool]

I had a Morgan SW22R on the bench a while back and reverse engineered out a schematic and took some gutshot pics.

Big-sounding amp (for a p-p 6V6). Try a 12AT7 in the LTP slot for extra razzle-dazzle. The reverb is nice sounding for a 1-tube 12AX7 jobbie. For more 'splash', I'd be inclined to try a 12DW7 tube with the 'AU' triode as the driver, but subbing in a beefier cathode resistor at say 4k7 to 5k6

Thanks for your good recommendation!
This amp looks like a Dumble ODS with no OD stage. (with reverb)

It also very close with my amp's reverb circuit.
B+ resistor of reverb transformer and cathode resistor value of the reverb send stage seems the key.
I decided to change them. Thanks again!

I have one question about the circuit.
Except for the Blackface reverb circuit, most of the tube-driven reverb circuits have a "mix" type reverb knob.
It receives the signal with potentiometer 2 pin, outputs it to pin 3, and sends pin 1 to ground.
But this circuit has "volume" type reverb knob as it is used in the Blackface.
It receives a signal with pin 3, sends it to pin 2, and sends pin 1 to the ground.

What is the difference between these two types of reverb knobs? Is there a difference in the amount of reverberation?

[tictac]

My Magnatone Panoramic has the typical Fender BF / SF reverb circuit but uses one preamp tube for the reverb drive & recovery instead of two. The other difference is they flip the 220k / 470k reverb mix circuit. I.E. the 470k is grounded and the 220k connects the reverb control with the grid of the dry/wet mix....

They use a 12AX7 but I like a 12AT7, it's a bit smoother sounding to my ears...

TT

[turbo5speed]

I've been searching for a really long time but no one seems to say either the reference of the reverb tank or the transformer in this schematic. As you know, reverb tanks have different specs and there are lots of different ones. I know that the transformer is some fender type but what is the specific reference? Anyone want to shed some light on this subject? Thank you!

[pompeiisneaks]

Yes, you pick the transformer for the reverb pan. Basically the transformer is designed for an output of a 12A*7 type tube, maybe in the 10k ish range, and outputs either 4 or 8 ohms or whatnot. Then you couple that with a tank of the same ohms and you're in business. Most common fender amp reverb transformers and pans work perfectly here because they're set to work together, so long as you use the same part numbers from the same amp.

Example, the typical one I've used has part number: 022921 which is a 14.5k input and 4 ohm output, Pair that with a 2 spring reverb like: 4AB3C1B and you have a perfect pair.

~Phil

[turbo5speed]

Yes, you pick the transformer for the reverb pan. Basically the transformer is designed for an output of a 12A*7 type tube, maybe in the 10k ish range, and outputs either 4 or 8 ohms or whatnot. Then you couple that with a tank of the same ohms and you're in business. Most common fender amp reverb transformers and pans work perfectly here because they're set to work together, so long as you use the same part numbers from the same amp.

Example, the typical one I've used has part number: 022921 which is a 14.5k input and 4 ohm output, Pair that with a 2 spring reverb like: 4AB3C1B and you have a perfect pair.

~Phil

Thank you very much Phil, this will help me a lot!

Cheers.

[tubeswell]

I've been searching for a really long time but no one seems to say either the reference of the reverb tank or the transformer in this schematic. As you know, reverb tanks have different specs and there are lots of different ones. I know that the transformer is some fender type but what is the specific reference? Anyone want to shed some light on this subject? Thank you!

Depends on the driver tube and how much current to need to drive the pan's input transducer. A tube-and-transformer driver will generally deliver higher current than a purely tube-driven pan (but you can do the latter, and a number of guys around here have over the years).

In terms of a transformer option, you want a tranny that reflects a load back to the tube that the tube is comfortable 'seeing' under normal conditions (so that it runs within normal operating parameters). An equivalent load to a resistive load is a useful staring point. For a 12AX7 triode, this can be anywhere between 47k and 220k, with 100k being the norm. Because a transformer isn't a resistive load, you need to bias the tube so that it doesn't run over it's spec'd Pmax. The problem with using a 12AX7 as a driver is that these have a highish internal plate resistance, so won't be able to suck much current through this tube under normal operating parameters. You will get some reverb, but it won't be as luscious as other types of tubes could provide. All this goes to say, that its best to pick a driver tube that has a lower plate resistance and can push more current, like an out tetrode, pentode or if a preamp tube, a 12AT7 or 12AU7. (Fender uses AT7 drivers in its classic reverb amp circuits. 12AU7 is a commonly used output tube in little 1W amps). If you want a 1-tube reverb, you could use a 12DW7, which has an AU7 triode in one half (which could be the driver) and an AX7 triode in the other half (for the recovery stage).

If using the AU7 as a driver with a 400V supply, it will happily tolerate any reflected load between about 15k (which would deliver heaps of current) to 47k (low current). Most Fender reverb driver transformers are wound to reflect around 18k to 25k with an 8R pan input transducer, so these are good to use with a single 12AU7 driver stage. You want to bias a 12AU7 driver between about -8V to -10V to be sort of in the middle of the load line. Start out with 1k8 to 2k2 cathode resistance and see where that lands with plate idle voltage and cathode current. In a 12DW7 envelope, a AU7 triode Pmax is 3.3W.

[Stevem]

I can look thru my old info if you like as I recall I had a circuit that uses a triple triode / compaction 12 pin type.

[turbo5speed]

Most Fender reverb driver transformers are wound to reflect around 18k to 25k

According to the ECL86 datasheet, the anode load resistor of the pentode stage, in class A, should be arround 7k to 10k. I've got 2 NOS Philips ECL86 lying around that should not be used with this transformer correct?

I have seen reverb schematics with this tube but never quite liked them for some strange reason

[pompeiisneaks]

Most Fender reverb driver transformers are wound to reflect around 18k to 25k

According to the ECL86 datasheet, the anode load resistor of the pentode stage, in class A, should be arround 7k to 10k. I've got 2 NOS Philips ECL86 lying around that should not be used with this transformer correct?

I have seen reverb schematics with this tube but never quite liked them for some strange reason

The tube will match the reflected load of the transformer, but it may not operate well in that range, and may have a severely shorter lifespan. You'd need to see if there's data in the datasheet about ranges allowed etc. Otherwise, no it's better to find a transformer that goes from the 7-10k range in and outputs either the 4 or 8 ohm range that the more common reverb pans come in.

I'm not 100% sure this is the 'right' one, but this hammond seems to fit the bill for that tube with 8 ohm primary with 8k secondary, so you'd need to ensure it has the current capacity as well, etc:

https://www.mouser.com/ProductDetail/Ha ... zpGznKU%3d

again, if you really wanted to use that specific tube. 12A*7s are so easy and cheap, they're common. seems someone earlier was talking about which work best and why, I can't remember exactly, I'll probably scroll back and re-read it again myself to make sure I remember it


~Phil

[tubeswell]

Most Fender reverb driver transformers are wound to reflect around 18k to 25k

According to the ECL86 datasheet, the anode load resistor of the pentode stage, in class A, should be arround 7k to 10k. I've got 2 NOS Philips ECL86 lying around that should not be used with this transformer correct?

A reverb tranny out of a Fender (stand alone) reverb tank should be close enough to okay for an ECL86 driver.

[pompeiisneaks]

Most Fender reverb driver transformers are wound to reflect around 18k to 25k

According to the ECL86 datasheet, the anode load resistor of the pentode stage, in class A, should be arround 7k to 10k. I've got 2 NOS Philips ECL86 lying around that should not be used with this transformer correct?

A reverb tranny out of a Fender (stand alone) reverb tank should be close enough to okay for an ECL86 driver.

So then even though the ecl86 wants 7 to 10k and the usual fenders are 15 to 20k, that shouldn't be enough of an impedance mismatch to push the ECL86 too much? How do you know what that threshold is?