In Reply to: RE: Heathkit AA150 posted by fstein on April 2, 2012 at 19:59:00:
You may find that the Heath power section has too much gain. The pentode section of the 6AN8 partially makes up for losses in the tone control circuitry and also produces the drive needed by the "finals".
FWIW, I'm not at all surprised by the poor preamp remarks being made. Heath's tone controls SUCK. Really good tone controls need to be 100% out of circuit, unless the rare recording that's actually helped by them is being played. They also have to be "unity" gain, which requires a fair degree of circuit complexity.
Were it my amp, the tone controls would be eliminated and I'd retain the power section small signal topology, but switch to a 6GK5 voltage amplifier and a section of an ECC99 as the phase splitter. The 6AU6 would go, as its gain is completely unnecessary, when the tone controls are eliminated. A 6GK5 would go into the socket currently occupied by a 6AU6 and an ECC99 would go into the socket currently occupied by a 6AN8. Set the ECC99s up so that each channel uses a different section. When the ECC99s show signs of wear, flip/flop them and get double the service life.
A proper DC supply for the phono section heaters can be constructed around an inexpensive AnTek model AN-0212 toroidal trafo.
Eli D.This post is made possible by the generous support of people like you and our sponsors:
Topic - Heathkit AA150 - fstein 19:49:40 04/01/12 (18)
- Mine is great, really great, after a full recap - ToddM 18:47:08 04/02/12 (0)
- RE: Heathkit AA150 - Ross 16:22:59 04/02/12 (8)
- RE: Heathkit AA150 - fstein 19:59:00 04/02/12 (7)
- RE: Heathkit AA150 - Eli Duttman 18:14:19 04/03/12 (4)
- RE: Heathkit AA150 - ecir38 08:15:58 04/05/12 (2)
- RE: Heathkit AA150 - Eli Duttman 16:51:14 04/05/12 (1)
- RE: Heathkit AA150 - ecir38 07:45:28 04/06/12 (0)
- RE: Heathkit AA150 - ecir38 19:59:44 04/04/12 (0)
- RE: Heathkit AA150 - rmyauck 21:30:49 04/02/12 (1)
- RE: Heathkit AA150 - Ross 05:30:39 04/03/12 (0)
- RE: Heathkit AA150 - fstein 19:52:10 04/01/12 (7)
- RE: Heathkit AA151 - Ron Oehlert 15:44:13 04/02/12 (0)
- RE: Heathkit AA150 - Eli Duttman 07:35:12 04/02/12 (5)