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Author Topic: Adding 1-tube reverb  (Read 11637 times)

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Offline tubenit

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Adding 1-tube reverb
« on: October 22, 2009, 10:08:22 am »
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

« Last Edit: September 21, 2010, 06:07:56 am by tubenit »

Offline Heinz

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Re: Adding 1-tube reverb
« Reply #1 on: January 29, 2010, 01:50:24 pm »
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.
in tranquilitate vis

Offline tubenit

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Re: Adding 1-tube reverb
« Reply #2 on: October 23, 2010, 09:08:47 am »
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
« Last Edit: April 23, 2013, 04:40:05 am by tubenit »

Offline tubenit

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Re: Adding 1-tube reverb
« Reply #3 on: May 29, 2013, 05:48:39 am »
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
« Last Edit: May 29, 2013, 05:58:02 am by tubenit »

Offline tubenit

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Re: Adding 1-tube reverb
« Reply #4 on: November 17, 2013, 07:22:59 pm »
OK,  here is another one to consider .......................

I am NOT sure about having two pots for the reverb return?   That doesn't look right to me.  Probably would use just one pot and maybe try a 1MA?

With respect, Tubenit
« Last Edit: April 28, 2014, 10:24:30 am by tubenit »

Offline chocopower

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Re: Adding 1-tube reverb
« Reply #5 on: November 25, 2013, 05:05:39 am »
Just a quick question.
Will be possible-practical a stand-alone  1-tube reverb?
What changes should be done in power supply, signal chain?


David

Offline tubenit

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Re: Adding 1-tube reverb
« Reply #6 on: November 29, 2013, 07:53:47 am »
I don't see why you could not make this into a stand alone unit that plugs into a passive effects loop.

I made a active FX loop & reverb unit that did just that.

http://www.el34world.com/Forum/index.php?topic=10624.0

With respect, Tubenit

Offline chocopower

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Re: Adding 1-tube reverb
« Reply #7 on: November 30, 2013, 12:15:46 am »
Perfect!  thanks!
David

Offline charliem

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Re: Adding 1-tube reverb
« Reply #8 on: December 19, 2013, 02:50:26 pm »
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




I'd like to use this circuit but I'm a noob and have a few questions I'm sure will be irritating and stupid...

I have an 18w bluesbreaker type amp I built, the amp maker pp18. I have enough in the power transformer to run another 12ax7 so this seems perfect. I find the diagram (first one attached to this post) a little confusing. I'm sure I'll be asking the "wrong" questions here but... What are the specs of the trany here? and there are a couple of points (circled C D and E) that I don't really understand what they're for. R and R2 appear to become Rv and Rv2?



Put simply, I can see how most of this works but there are a few blank spots. I wonder if someone would be so kind as to help me work this out.

In case it helps here's a schematic of what I have...

http://www.ampmaker.com/images/ak03kit/ak03sc2.jpg

I do understand where to insert this, I'm not asking someone to create an entire set of instructions or anything, just a little confused and looking for a start point to work from.

Any help much appreciated.

Thanks

Charlie


Offline sluckey

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Re: Adding 1-tube reverb
« Reply #9 on: December 19, 2013, 06:25:22 pm »
Quote
What are the specs of the trany here?
It's a typical Fender reverb transformer. Hoffman has them right here.

Quote
and there are a couple of points (circled C D and E) that I don't really understand what they're for.
Those are just B+ nodes in the power supply.

Quote
R and R2 appear to become Rv and Rv2?
That's right.

Offline charliem

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Re: Adding 1-tube reverb
« Reply #10 on: December 19, 2013, 08:00:52 pm »
Thanks, OK I do believe I've got it. I get a maximum of 275v from my current power transformer so I either need a new one, a separate one or I need to play with some of these values. What do you think?

I notice the three B+ voltages at D and E are pretty close to each other in the second amp insert example. I guess there is an obvious reason for 3 close, yet different voltages?
« Last Edit: December 19, 2013, 08:08:13 pm by charliem »

Offline sluckey

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Re: Adding 1-tube reverb
« Reply #11 on: December 20, 2013, 12:06:25 am »
I think the reverb circuit will work with a wide range of B+ voltages.

Offline charliem

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Re: Adding 1-tube reverb
« Reply #12 on: December 20, 2013, 04:10:58 pm »
I think the reverb circuit will work with a wide range of B+ voltages.

Yes, I begun to realise that when looking at the inserted examples. I believe the max plate voltage on a 12ax7 is about 330v, I have a few voltages around that point in my circuit so it'll be OK, I reckon I'll be fine. I think I'll order up one of this reverb tranies soon and get it all in.

Thanks for your help getting me past the mental block.  :thumbsup:

Offline kagliostro

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Re: Adding 1-tube reverb
« Reply #13 on: December 28, 2013, 01:43:42 pm »
I've found this link and I think it can be of some interest also if it isn't an only one tube reverb

http://www.channelroadamps.com/articles/reverb_driver/


K
« Last Edit: January 10, 2014, 01:07:06 pm by kagliostro »
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Offline tubenit

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Re: Adding 1-tube reverb
« Reply #14 on: April 30, 2014, 05:57:24 am »
There was a thread that I started revisiting the one tube reverb using a 6BM8.   There was some thought that a regular Fender reverb trannie might work OK with 300v?   

However, it appears that using a trannie similar to what is used on a VibroKing that uses an EL84 to drive the reverb tank might be more suitable.   http://www.hammondmfg.com/pdf/EDB1750B.pdf

The project was not completed, but I think this would work well.

With respect, Tubenit

Offline kagliostro

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Re: Adding 1-tube reverb
« Reply #15 on: July 18, 2014, 04:37:51 am »
For those who are familiar with Hammond recovered parts (in this case the A0-24113-0 transformer)

a variation on the theme one tube reverb, see attached schematic

here all the explanations

http://www.tdpri.com/forum/shock-brothers-diy-amps/465389-possible-1-tube-reverb-add.html

K
« Last Edit: July 20, 2014, 09:41:08 am by kagliostro »
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Offline Ed_Chambley

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Re: Adding 1-tube reverb
« Reply #16 on: July 18, 2014, 08:24:50 am »
What determines the resistance between Rv and Rv2?  The different values I noticed.  I have only used 100K, but I am seeing 150K and 220K?
Thanks for the help!
Sincerely
Ed Chambley

Offline kagliostro

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Re: Adding 1-tube reverb
« Reply #17 on: July 18, 2014, 10:24:39 am »
I'm not able to give you an answer, I can only say that in commercial amp I've seen that resistor with a much more higher value (3.3M) and bypassed with a 10p capacitor


I don't know the exact explanation about the function of the resistor, I consider it acting as a sort of mix resistor between the wet and dry signal


K
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