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5751's in a PAS 3

69.142.97.141
Posted on September 26, 2009 at 14:34:12
gilpi
Audiophile

Posts: 5
Joined: March 11, 2009
 Came across a few 5751's and thought I try them in my PAS 3 line circuit and what I noticed is cleaner highs and bass not as boomy, now from what I read the 5751 tube is a lower gain than 12AX7?

Just wonder if others here have tried these tubes in their preamps as a replacement for the 12AX7's and the results.

RE: 5751's in a PAS 3, posted on November 9, 2009 at 12:27:47
Ross
Audiophile

Posts: 282
Joined: January 24, 2000
 I have a VA modded PAS 3. Using a 5751 in the phono stages alters the frequency responce of the phono circuit as it is designed for the gain of a 12ax7. Use of a 5751 in the line stage is fine and may make it easier to connect to a more modern amp.

Best,

Ross

RE: 5751's in a PAS 3, posted on September 28, 2009 at 07:07:15
xaudiomanx
Audiophile

Posts: 978
Joined: August 16, 2004
 When using another tube make sure your filament voltages are correct. Electrically the tube can be the same with lower gain but there are other factors that have to be taken into consideration. If you don't need the gain you are better off. Maybe with the 5751's the sonics are more of what they are supposed to be. All these vintage preamps were designed around analogue use with much lower outputs from a phono cartridge. If the preamp is to be used with a CD player then all that gain isn't needed. As a matter of fact an active gain preamp isn't needed at all(in my opinion). That is an argument that will never end with a right or wrong answer but if you ask yourself why add more gain just to attenuate it. Who knows? Some say with a passive stage you lose dynamics. Dynamics or gain? We shouldn't mistake the two. It mostly depends on the gain of the power amp whether you need the gain up front or not. Most anything I ever modded or built I never needed an active stage with gain for CD playback. Phono is another issue totally.

Just my "0" cents worth!

Paul

RE: 5751's in a PAS 3, posted on September 26, 2009 at 21:31:01
GP49
Audiophile

Posts: 113
Location: No Cal
Joined: April 21, 2009
 I found much the same on my PAS. However note that it's not a stock PAS, but has the circuitry of the Van Alstine Super PAS Three.
GP49
RE: 5751's in a PAS 3, posted on September 27, 2009 at 06:37:40
gilpi
Audiophile

Posts: 5
Joined: March 11, 2009
 My PAS is all stock with just the caps replaced no mods going into a SAE A502 amp and while the upper highs and highs seem more opened and detailed with the 5751's, its also a bit more laid back in the upper range.

Gil

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