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RE: Futterman Story w/ Ted Hammond

Hi Anthony,
as far as changes to the original circuit in the h3aa and the 509s version pictured there are several, and I only know a few, the addition of pots for alignment as in the otl-3's was installed for easy alignment, as well as hexfred diodes, several bypass caps on both power and speaker caps. also bypass caps on the 4-way bridge rectifier. but that's all I know, I have only played the amps a few hundred hours since I got them from Ted, I had planned to take them back to Croton and he was going to go over all the mod's with me. There is no complete schematic for that amp, only handwritten notes concerning the changes.
Since then Ted has been undergoing chemotherapy for cancer off and on for the last year and a half. Hopefully when he gets better I'll get copies of the changes.
Concerning the 509s tube:
I was there when Ted performed max output at clip, the amps put out 95 watts into 8 ohms, so as far as them being up to the challenge in that design they appear to work ok. One thing I noticed though was when doing the alignment that I was near the max settings to get the 300 ma idle current recommended in the procedure, I think that may be a sign of the lower factory spec on the tube. When I tested the tubes in my Amplitrex to the same setting as I use on the 6lf6's they all showed to be considerably low compared to good 6lf6's, the problem is that all I have is the tubes in the amps and 6 spares. I think that there is a chance that they were just off the shelf tubes not premium examples.
There is a seller on e-bay that I contacted who said he could match sextet's of them and would guaranty they met the factory spec for mutual conductance, I need to make sure he is testing them using fixed not autobias settings to achieve those numbers.
Not sure I told you anything that will help you out.

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