In Reply to: RE: GRAAF GM 200 posted by Mark S Allen on February 26, 2012 at 14:58:22:
Hello to Mark S Allen and all.
I must ask your comprehention and tolerance with my english. It is not my mother language.
I read with much interest your long explanation on tuning up the Graaf 200 OTL.
I have one too. But the matching procedure is very long and very time consuming. I already did Graaf method but I can´t match well.
I was working with 65mA on Bias, but now have lowered a little bit further to 50m, just for precaution.
I have an Hickock 600 tube tester that tests the 27GB5 /PL504.
Most of the spare valves I have reads between 4000 & 5000 and try organise them like that in the amp, but when I try Graaf matching procedure direct in the amplifier ( those 15,5 & 17,5mV) everything get wrong. Is just like this proceedure contradicts the Hickock.
Most of the 4000 valves read 19-20mV and some 5000 reads 8~10mV. It crazy, and I don´t understand why.
Can you help Mark? It seems you have a lot of experience in this amp. I have other OTL amps that sounds much better. Perhaps I am doing something wrong. My speakers are Quad ELS 57 and YAMAHA NS1000M.
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Follow Ups
- RE: GRAAF GM 200 - ideiaprint 12:33:59 09/23/12 (13)
- RE: GRAAF GM 200 - Mark S Allen 12:37:05 11/26/12 (12)
- RE: GRAAF GM 200 - berni 06:16:21 04/07/13 (10)
- RE: GRAAF GM 200 - rhinohifi714 19:53:47 04/09/13 (8)
- RE: GRAAF GM 200 - berni 10:30:35 04/10/13 (6)
- RE: GRAAF GM 200 - rhinohifi714 05:40:49 04/11/13 (5)
- RE: GRAAF GM 200 - Frederichabert@hotmail.com 01:37:36 08/13/15 (0)
- RE: GRAAF GM 200 - berni 12:19:47 05/15/13 (1)
- RE: GRAAF GM 200 - berni 02:49:31 05/27/13 (0)
- RE: GRAAF GM 200 - berni 12:19:23 05/15/13 (0)
- RE: GRAAF GM 200 - berni 05:58:12 04/11/13 (0)
- RE: GRAAF GM 200 - berni 22:46:08 04/09/13 (0)
- RE: GRAAF GM 200 - berni 13:45:52 04/07/13 (0)
- RE: GRAAF GM 200 - berni 04:22:58 04/07/13 (0)