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Re: Sunn Coliseum PA to bass amp?

7/20/2005 10:32 AM
casajr
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Re: Sunn Coliseum PA to bass amp?
The Power amp of the Sunn PA is basicly a Dynaco Mark III with 2 more KT88's and an additional GZ-34 rectifier with a parallel choke. I've been using 2 Dyna's for years with my bass rig with an Alembic preamp and they sound fine the way they are.  
 
One BIG caution....  
 
The filter caps are rated 525V and are not sufficient for this amplifier. This is a well known flaw with the Dynaco. You will compound this by replacing the rectifier tubes with diodes and the voltage will exceed the rating and the cap (probably a single multicap) will vent (mine did).  
 
What I did is put in new filter boards from SDS Labs, which are availible from Triode Electronics. This raises the cap values from 30/20/20/20 to 50uf each and 630 volts. The board has instructions for both Dynaco and Sunn retrofit. Cost is about $50 and is money well spent. BTW, I kept my GZ34's and they are commonly found.