ampllifier design

Mrtennis: From your previous posts, I thought you preferred rolled-off highs -- caramel coloration? Do you now look for balanced frequency response? What kind of sound do you seek?

hi 9rw:

i seek a balanced frequency response. in the past i have found that many components exhibited an emphasis in the 1000 hz to 3000 hz region. recently i auditioned two, the audionote kits l3 line stage preamp and an implementation of a sabre 32 bit dac chip, which i found balanced in frequency response. both components created resolution and lack of a euphonic signature which i found compatible with many of my problem cds. i can configure my stereo system to sound "soft" and subtractive in the upper mid/treble. when reviewing i attempt to create as uncolored a perspective as possible.

in terms of personal listening, i have, in effect two stereo systems. one is obviously colored, while the other is open, dimensional and relatively balanced in frequency response. the quad esl 57 (quads unlimited version) represents the "linear" sounding stereo system, while replacing the quads with magnepan 1.6 and replacing the vtl deluxe 120 monos with consonance monos creates the "color" .

you can read my review of the audionote preamp on audiophilia.com. the sabre dac chip has been set up in dac form, including a linear power supply and is currently under review. i welcome your feedback.

you can read about the sabre dac chip on www.esstech.com .

I likewise have good associations with the 6CG7, it's the long-tailed-pair phase-inverter tube in my Marantz model 2s . . . it's used effectively for this role in the 5 & 8 as well, and as a cathode-follower in the 9.

But if you're using EL84s as outputs, then the 6CG7 is kinda overkill as a driver tube, and you might have a problem making it work at its best as a long-tailed-pair from the lower B+ plate supply (Marantz had a higher B+ available because he was using EL34s as outputs). And for an input tube, the 12AX7 is a better choice because of the higher mu.

I personally don't feel that different tubes themselves have any "sound" at all - it's the circuits that they're used in that have certain "sounds" . . . and it's just that some tubes are traditional choices for certain circuits, and thus we have these associations. I also think our associations of NOS tubes as "sounding better" is because their manufacturing tolerances were much, much more consistent, so it was/is possible to make more precise engineering decisions about critical circuit parameters. Added to this is the fact that most of our tube data is NOS as well.

Interesting post, Atmasphere.

It might have been yet more interesting had you noted that you yourself used the 6DJ8 and 6CG7 in earlier versions of the MA-1, and then explained how you later came to the realization that these tubes did not provide the best performance.

Hi Jimjoyce25- bingo! We got great linearity out of them, but they would often ring like a bell. Handpicking them got the microphonics down, but never to the point that you can get with a 12A* series tube or 6SN7. I'd always been a fan of the 6CG7, but when I realized that it and the 12AU7 were evolved from the 6SN7 geometry, I decided to try the 6SN7. There was no looking back at that point.