Tube project needed for spring reverb tank

[biggy boy]

Hi there.
I'm looking for some help with a project that would use a spring reverb that I pulled out of my now dead 1971 amp.
Its a small one 4"x 2"x 1" the reverb tank that is!!!
Any way Id like to use it with a tube or tubes the mini tank has two transformers built right into it, there real small.

Here's a picture of the schematic that it came from.

The big oval is drawn around the reverb circuit and the small oval is just the reverb tank showing the two transformers and the spring.

I'd like to use it with my Valvecaster. I'm hoping to use it like how the Vibracaster is incorperated into the Valvecaster.

It was running at around 34 volts or so when it was in the amp.  I'm hoping I could run it at a lower voltage?





OK so any help or tips would be great!

Glen

[petemoore]

  First thing would be start with a tank of known input and output impedances, these will determine amp factors.
  It'll take:

A  Power supply.
2  Buffer / Split A/B.
3  Smplifier drives reverb spring through transducer.
4  Basically a signal line just goes over to the output mixer after a gain stage.
5   The output mixer.
  That's 'all'.  Example:
  http://www.kbapps.com/audio/schematics/tubeamps/fender/reverb6g15.html
  I'd use a power mosfet for the buffer stage.
  And Low Voltage tube amp for the amp.
  Same for the mixer.
  The power supply..current consumption of the heaters...perhaps adjusting the filter cap values.
  Otherwise if you can get a 1/2 watt going that should wiggle the spring driving transducer with authority.
  See 'Stage Center Reverb' at GGG. 

[biggy boy]

Thanks Pete!

I was thinking of jamming the tank in between two tubes either a pair of 12au7s or 12ax7s
I don't know ---- signal in ---- tube #1 ----- tank ----- tube #2 ----- signal out -------

Or going the stage center setup and incorporate it into my valvecaster some how. I need to learn more 



Glen

[biggy boy]

Ok I have this schematic here that I made up not sure if the resistor values are correct, will have to try it.
So what do you think? should I try it and see if it works???






Glen

[frequencycentral]

I think you should try it - looks a very interesting project. Good luck!

[petemoore]

  Impedance matching, the tube plate and the spring drive transducer coil determine how well the tube drives the spring, although everything in the build is nice and may be of some use, committing to a chassis / layout now may prove to be less rewarding.
  Somehow, determine the impedance of the driver first.
  I would take a look at some of the amplifier projects FC and others have been working on for the driver amplifier, the transducer is similar to a small speaker except it's designed to drive the spring, and may require or benefit from more 'push' than stage shown provides.
  the Fender tube reverb is the bees knees, the SCR gets reverb going, compare how many stages of gain and cathode followers compared to these and get an idea what you have there compares to.
  Since the SCR uses an LM386 [capable of making a little speaker cry], and the fender uses a HV output tube amp capable of making a little speaker fry [really small speaker probably would beg], getting that driver controlled with authority [draws current] makes the spring vibrate right, the rest of it is just boost / recovery and mixing, fairly simple 'dressings', but they do require space.

[biggy boy]

Hi Pete
I've looked at most of that stuff before good info there...... Yes may need to use a cathode follower for impedance reasons, will be doing it on the bread board to try it all out.
My tank is real small   The transformers are like 1/2 inch by 1/2 inch big. I don't know, don't think they will need much current to drive them

I must finish my Valvecaster/ vibracaster setup and it's enclosure before I start testing the reverb tank. I'm hoping to put the reverb tank into the same enclosure.

Glen

[frequencycentral]

You might find that the triode driving the reverb transformer needs to see a few more volts to get a meaningful amount of volume.

[biggy boy]

You might find that the triode driving the reverb transformer needs to see a few more volts to get a meaningful amount of volume.

I have 12, 28 and 157 volts Dc available on the board that It will be attached too. I have the Valvecaster tube fed with the 157 volts.
I was thinking of starting with the 28 volts first and slowly going up in voltage to see what happens.

[thomas667]

Has anybody tried this design?
I am very interested in it...
Any info is welcome before I try to gather parts...

Thanks!

Ok I have this schematic here that I made up not sure if the resistor values are correct, will have to try it.
So what do you think? should I try it and see if it works???






Glen

[mth5044]

Seemed like a work in progress back in 2009. You'll probably want to breadboard before committing to an enclosure.

[amptramp]

I recognize that schematic - I have quoted it several times when discussing the simplest possible tremolo and I happen to have a U65RN.

I would advise keeping the input coil AC coupled through capacitors to avoid getting any DC on the coils.  You can match the output to a tube amp if you want by putting the characteristic resistance across the coil because the tube stage input should be high impedance.  It doesn't require much drive but a cathode follower should be able to drive it easily.  It should be able to run at lower signal voltages but don't go too low or you may get excessive distortion caused by friction.

[thomas667]

Interesting! Thanks for the input.
Any guess on the tubes I should use, and how much the heater current should be? SRPP can take up to 30V I read somewhere?
Indeed DC on the coils seems like a really bad idea...
I am trying to build a stereo tube reverb from scratch to use in a studio, so I liked the pretty straightforward design on that schematic... Do you think the output gain stage should be tweaked?