Adding 1-tube reverb

[tubenit]

I've had quite a few forum guys post or PM me about the "one tube reverb".  First off, it's NOT my design. I "stole" it from the D'Lite builders who were using it.  I have used other methods for adding reverb that also worked including Hoffman's "add reverb to Western Circuit".  But this one has worked the best for me.

It has worked on every single amp I've tried it on without a problem. I have it on the 3 amps I currently own and play. No oscillation issues at all.

This uses the "Fender" type replacement reverb transformer and tank that Hoffman sells. Same one you'd use for a Princeton Reverb.

I have owned a Princeton Reverb and played numerous AB763 Fenders. Comparing this to those, I like it better because:
1) it uses just one tube, 2) it verbs more mids (for a fuller tone to my ears) and 3) I don't do "surf" stuff even though I like that sound.   I honestly prefer the tone of this reverb more than the Fender but again that's just my preference.

With my PR, I used the reverb on around 2.5-3        With the one tube reverb, I use it on about 3 or maybe 4-5 on a slow blues tune. Originally, the design had a 2.2M reverb pot but I changed that to 1M to reduce the reverb, I also added a dwell pot to reduce the reverb.   I typically have the reverb pot at 3 and dwel pot at 5-7 & that gets me the reverb fullness and tone that I want. It has waaaayyy more reverb than I'll ever use.

If you want to see examples in a circuit. Look at the Blues Amp, 56T reverb or my 5879 Carolina Blues Special ......OR
the Carolina Blues Special that was made for my friend Gene. They are all in the SCH library. It has worked on an 18watt type design (reported to me), and I have had success using this reverb with concertina phase invertor, & long tailed phase invertor type amps.
 
With respect, Tubenit

[Heinz]

I have used this type of reverb in one of my builds. I got a 4F... reverb tank for free and was looking for a way to drive it with a tube.
These tanks have an input impedance of around 1500 ohms and are usually used with solid state drivers.

The driver circuit is basically just a 'normal' grounded cathode stage but with a beefy tube and a pretty high idle current (and therefore low output impedance) which is needed to drive the tank. The tank is coupled via a coupling cap to prevent DC current from flowing through the driver coil. The main advantage is the absence of a reverb transformer. The disadvantages are higher power consumption, more heat and the need for a bigger tube.

Initially I copied the Traynor circuit but made some changes that improved its performance. Traynor uses a power pentode in triode mode and a high power resistor in the driver stage. This worked for me to some extent but didn't give enough reverb depth. Using the pentode as a pentode improved this somewhat but the most significant improvement was the use of an inductor instead of the power resistor. I used the primary winding of a small power transformer which is cheap and readily available.
I used a PCL86/14GW8 (6GW8 is the 6V heater variant) which is a power pentode and a signal triode similar to a 12AX7 in one bottle. An ECL82/6BM8 will also work but needs a higher input signal level. With these two-in-one tubes you can build a 1-tube reverb without transformer that can be added to any amp just as tubenit's circuit.

I have attached a schematic of my reverb module. A coupling cap may be needed at the input, depending on your circuit.
Sorry, I only have it in JSchem format. You can download JSchem from http://dhost.info/jschem if you don't have it already.

[tubenit]

Here is another idea using a 6BM8 one tube reverb. I have not tried this, so I have no idea how well it works?

Tubenit

Pignose amps used the 12AX7 one tube reverb.  Also look at the Gibson Scout for another factory example.

Here is one from Zendragon using a 6DX8

[tubenit]

I thought this was a very interesting application of the one tube reverb.

Note the low values of the gain pots being used.   Also note the low value resistor to ground  4.7k  after the 3rd gain stage. Unusual values from what I normally see.

And especially where the reverb insertion points are.

How does it sound? Maybe something like this :  

Cornford Hurricane - PRS Standard 22 - Noodling

With respect, Tubenit