Posted by SteveBrown [ 75.185.102.13 ] on February 17, 2008 at 10:11:32:

In Reply to: Re: 100,000 ohms! Uhhhhh, maybe not. posted by Bill Epstein on February 17, 2008 at 00:34:09:

Well, very interesting. On the preamp I'm building right now, I actually have it switchable: 47k, 100k and 1M. So I can try different settings. I'm betting different music may work better w/different cartridge loading, but not sure. By the way, why 1M?? Well, I have a Grado Sonata that likes a 47k impedance but being a 0.8mv cartridge, I have to use a step up transformer for it. Since the primary impedance the cartridge sees is reflected from the secondary, and in this case stepped down by a good size factor, starting w/1M on the secondary will give me closer to the loading the cart wants to see. At some point I'll try to build a hybrid phono stage (FET + tube) to eliminate the need for the step up transformer. Oh, and the pre that is under construction should be fun, it is an all octal pre based on the Octal Coronet (Hagerman) design, then going to a 6SN7 line stage. Even the rectifier is an octal. I've tried octals (6SL7's) in the phono stage before and they can be very microphonic, but I think I've got that licked this time by using a Russian equivelent to the 6SL7. In some tests I've done I can rap the glass envelope with a pencile while it's working and not get any microphonics. Sounds great so far, too!

Replies: