Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BigE on June 21, 2010, 01:34:06 pm

Title: Reverb Tank Replacement Options
Post by: BigE on June 21, 2010, 01:34:06 pm

Hey guys.  I've got someone that has a single spring Accutronics Reverb tank that he wants to replace with a 3 spring tank.  The code is 1DB3C1C which according to the Accutronics site correlates to this:
type 1
Input impedance 250 ohm
Output Impedance  2250 ohm
Long Decay
Input insulated/Output Grounded
No Lock
Vertical Connectors UP

I can't find a 3 spring short tank that will match the In/OUT impedance exactly.  How close/important is it to match those values?  What would YOU use for a replacement tank?

Title: Re: Reverb Tank Replacement Options
Post by: phsyconoodler on June 21, 2010, 01:41:50 pm

It has to match.However I've never seen a 'one spring' reverb tank.Don't you mean it has one spring left and the other one is broken off?
  The reverb won't work if the impedances don't match.

Title: Re: Reverb Tank Replacement Options
Post by: BigE on June 21, 2010, 02:11:28 pm

You are correct,yes.  He actually has 2 of these tanks.  They are out of a couple of Polytones.  Both have only 1 spring.  But after looking at them, 1 tank doesn't even have the little mounting clips for the second spring and the other does, but just looks like the spring has been removed. 

any ideas on finding a 3 spring short with those input impedances?

Title: Re: Reverb Tank Replacement Options
Post by: sluckey on June 21, 2010, 02:37:40 pm

http://cgi.ebay.com/Accutronics-Reverb-Tank-Medium-Decay-8DB2C1D-Marshall-/160399014609?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item255886bad1

Title: Re: Reverb Tank Replacement Options
Post by: BigE on June 21, 2010, 02:48:47 pm

Will that tank work even though the impedance values aren't exactly the same?  Psyco said they have to match or it won't work.  what's the scoop?

Title: Re: Reverb Tank Replacement Options
Post by: phsyconoodler on June 21, 2010, 03:23:15 pm

50 ohms in either direction should work just fine.Any more than that may not work.

  A huge difference is what i meant.250 ohms to 310 ohms is a pretty small difference.
Same with 2250 to 2575.
  It will likely work.

Title: Re: Reverb Tank Replacement Options
Post by: PRR on June 21, 2010, 10:07:06 pm

Changing from "8" to "1K" or "250" to "6K" will be unhappy.

Changing from 4 to 8, or 5K to 10K, or similar ratio, is unimportant. The impedance actually varies a LOT over the audio range. The sensitivity will change but you just dial-up a happy sound. And changing from a cheap 1-spring to a lush 3-spring will make more difference than a 2:1 ohms change.