|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
71.191.198.166
In Reply to: RE: Mac 1500 vs Fisher 500c. posted by Michael Samra on November 28, 2016 at 22:42:53
I did not think that the 7591 was all that tough to drive. I thought the 12AX7 while weak was up to the job. Many that is why my Scott 222D and Dynaco SCA35 use pentodes for drivers.
Dave
Follow Ups:
Full pentode mode "finals" are easy enough to drive. It's the "fixed" bias grid to ground resistance limit of the 7591 that's the sticking point. Fisher used 330 Kohm parts that have drifted upwards, over time. The data sheet gives 300 Kohms as max. From the beginning, Fisher was "out on a limb". :> ( Current production 7591s are intolerant of the liberties Fisher took.Mikey is on the right track in thinking 12DW7/7247. AAMOF, Fisher used the 7247 in the X-100. Then, "bean counting" set in. Reduce inventorying costs by stocking "only" 12AX7s. Never mind the fact that the high R P 'X7 triode must work into a high net AC impedance.
I'll upload the relevant X-100 schematic fragment, later today.
Eli D.
Edits: 11/29/16
Eli D.
Schematics start on page 7.
I never owned a Mac 1500, but a few Fisher 400s & 500s. The Fishers are nothing special in stock form. A little muddy IMO. But, after some simple mods & tube upgrades, the Fishers are great & very musical. They sound like a live performance. They are better than a modded Scott 340B too.
They are better than a modded Scott 340B too."
I would love to see the mods you used because I haven't found that to be the case at all. I agree that they are muddy and distorted but I would love to try Danny's mods or ones you used. The 340A I really like and the 340B is good as well with proper upgrades.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Michael, see my post above.
Fisher phono sections are notorious for poor bass extension. Reworking the phono section to use the tweaked RCA setup deals with that and allows the recording O/Ps to have respectable drive level.
Eli D.
Sony, have you ever tried any of the below tweaks that I put a link to in my below post? I still have to order the stuff to fix the riaa curve but the buffer after the volume really was a positive.
Edits: 11/29/16
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: