[sdiy] demagnetising spring reverbs

[cheater cheater]

A typical (running!) desk fan will demag anything it's held against I
think. Try and see.

D.

On Wed, May 12, 2010 at 18:00, Barry Klein <barryklein at cox.net> wrote:
> You didn't say how it sounded with the resistor back to original value...
>
> I wonder if the author is correct suggesting the driver transformer
> magnetics
> get permanantly damaged.
> I think the truth is you will get distortion by saturating the driver
> transformer -. much like if you
> over saturate the inductor of a DC/DC converter.  By doing so you would see
> the current (with a current probe)
> waveform change as amplitude is increased.  You then also can just be
> overdriving the transducer, resulting in a
> distorted signal passing through the reverb spring.  Lastly you could have
> an issue with the frequency
> profile of the driver circuit...
> You could instrument tests for this but your ear is probably a better
> diagnostic tool.
> A pickup has a magnetic core but a reverb driver transducer will not.
>
> Barry
>
>
>
> ----- Original Message ----- From: "James Dunn" <james at 4thharmonic.com>
> To: "synth-diy at dropmix. xs4all. nl" <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, May 12, 2010 03:04
> Subject: [sdiy] demagnetising spring reverbs
>
>
>> Hi list,
>>
>> Some time ago I came across a suggestion to increase the signal to noise
>> ratio in the ARP 2600 reverb unit by reducing the value of R273 by half. I
>> tried this mod and it was indeed louder but after a while the reverb seemed
>> to deteriorate. It now sounds very muddy and distorted. I looked at the
>> signal being sent to the reverb tank on a scope and it was also distorted,
>> although it only had a minor glitch when I disconnected the tank. So I
>> concluded that the tank must be faulty (probably by overdriving it). This
>> <http://sound.westhost.com/project34.htm> website would seem to confirm this
>> - it says:
>>
>>> ...but you must be very careful, because overdrive causes the small pole
>>> piece to become magnetically saturated, leading to gross distortion that
>>> increases with decreasing frequency
>>
>> So my question is how can I demagnetise it or otherwise repair the tank? I
>> know there was some discussion a while ago about repairing tanks, but not
>> specifically demagnetising...
>> On the other hand, should I just buy a new tank? Where can I get one?
>>
>> many thanks
>>
>> James
>>
>> PS - the transducer input impedance is 175 ohms and I temporarily
>> connected another tank which worked fine.
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