help with audio resesrch d76

I like the D-76 a lot. I'm working on a D-90B right now. Both are great but the D-76 with new caps actually sounds better then when it was new as all the poor twist lock lytic caps get replaced with current technology filter caps. The D-90B uses different output tubes as well. The B version utilized 5881/6L6's vs. the D-76's 6550's as well as a servo circuit which is somewhat audible. Also for reliability reasons, the white relay in the D-90B should be removed as the audio can hum for a few seconds after the relay closes. Some people find that objectionable.

I own both....very similar driver circuits. The reason ARC came out with the D-90 is that Mr. Johnson's favorite sounding tube was the 6l6 (personal communication) That is one of the reasons he used the 6L6 in the ARC/Dynaco ST70-C mod. He told me his ARC guys always pushed the higher power 6550. Tube brands have a larger effect on sound than the different circuits. Mr. Johnson liked the GE 6550 in the 76/a and GE 6l6 in the 90B. The JJ 6l6 and the mesa boogie STR440 sound similar to the GE 6l6. The 90B set up correctly has the power to "float" an orchestra...as HP use to say. The 76 is gorgeous sounding especially in the midrange...but the 90b has BALLS!! ;)

The original D-90 had 6550 outputs.

...also the D90 did not have a servo in it. The D90B does.

Thanks HifiGeek!! I have never looked at the schematic for the original D90. Clearly shows matched GE6550s. I was fooled by the http://www.arcdb.ws/D90/D90.html website. Has a picture of D90 with GE6l6s in it. must be D90Revised...oh those ARC guys. When I talked to Mr. Johnson he said there was a heated debate between himself and his "engineers" between the 6550 and 6l6, but I did not realize they produced a 6550 version. Mr. Johnson seemed pleased he produced an amp using 6l6s. Also, I have an amp stamped on the back with D90-B and it does not have the servo in it. Leonard at ARC finally told me that it was at a dealer and was sent back for the B update and they took a little short cut... ;) Thanks again for the audio trivia. Larry