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Take a look at this Cary SLP-90 schematic

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Posted on November 13, 2014 at 17:38:31
Michael Samra
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 Notice the 560uf cap coming directly off the 6CA4 rect tube...I took both of those out and put in a pair of 35uf poly film caps and left the other stock and already the one with the polys has deeper bass and cleaner mids..I want to implement a 5h or 10H choke but the 22k resistors have to remain as they load the plates on the 12AU7s.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

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RE: Take a look at this Cary SLP-90 schematic, posted on November 13, 2014 at 17:52:07
vinnie2
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 Why would they have ever put that large a cap in there?

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 13, 2014 at 18:41:32
Eli Duttman
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 Yet another fucked up Cary design that BADLY abuses vacuum rectifiers. :>(( Grrr!!!


Eli D.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 13, 2014 at 18:57:20
Triode_Kingdom
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 I agree with other posters that the original caps are much too large for the rectifier. Nevertheless, how do you explain the phenomenon you're describing, that the bass became more powerful with smaller supply caps?

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 13, 2014 at 20:03:16
Michael Samra
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 Exactly and that's why I took them out and put in 35uf polys.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 13, 2014 at 20:11:00
Triode_Kingdom
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 OK, I've got it now. I thought this was a power amp, that's why I asked the other question. This is actually a Class A preamp. No wonder it sounds better with films!

 

Cary Audio always did/does this. look at . . , posted on November 13, 2014 at 21:25:22
John PA
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 some of the power amps with 1200uF after the rectifier and then they wonder why the rectifiers don't last and arc. The SLA 70 was like this. What is the deal with the huge caps. I put a theristpors in a few amps. Or just changed out the caps.

The Quicksilver Full Preamp was also hard on the dual 6X4's when it used them years ago. Those would arc after a while. Nice preamp though.


iBasso DX300MAX Ti. Focal Utopia and Stellia. iBasso SR2. Mr. Speakers, Ether II, Voce stats. Manley, Absolute headphone amp. LTA MZ3, Z10e electrostatic amp. Many other headphones, amps, cables etc.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 13, 2014 at 22:57:59
mr9iron
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 Wow, I was expecting the poly-film cap speech from you Samra where are all the statistics on their efficiencies? We all know you have surrendered yourself to poly filters:)

J

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 09:25:05
sonicboom
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 Michael, I'm sure you were thinking of something else, but the 22K resistors are power supply dropping resistors and are decoupled from the tubes' plates via the 470uF caps. If you can measure the current draw of these tubes you could then substitute both 22K resistors with Hammond's 153-159 series chockes that have the appropriate current rating. These will most likely end up being somewhere in the range of 15 to 30H and in addition they're small and inexpensive units.

Because the chokes' DCR values will be a lot less than the resistor values, you would then need to adjust the PSU's voltage by properly sizing the first cap. My guess for this would be anywhere from .22uF to 2uF. If you could measure the transformer's off-load voltage and DCR values at the rec sockets (with no tubes in), you could design a nice power supply having the desired output voltage in PSUDII. If and when you take said measurements, you could post them here and perhaps we could help a bit too. If not, we'll still be very interested in whichever way you decided to go.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 11:11:07
Michael Samra
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 But of course,especially in a preamp.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 11:17:59
Michael Samra
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 Thanks..When I saw the absence of the plate resistors on the paralleled follower,I somehow thought at glance that the PS resistors in that divider network acted as the load resistors...I like that idea that you've presented.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Cary Audio always did/does this. look at . . , posted on November 14, 2014 at 11:19:59
Michael Samra
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 John
Even in my CAry/AES set amps they have a pair of 1200uf series connected which I changed to a pair of 70uf parallel connected motorruns with great improvement.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 11:44:35
GEO
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 Probably leftover supply that they wanted to use up. Garbage.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 12:43:32
Caucasian Blackplate
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 I think the biggest improvement you could make would be to directly couple the preamp stages.

After that, use all that excess voltage to build a regulated B+ supply.

You might also try not having parallel triodes up front.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 18:10:32
Michael Samra
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 The paralleled triodes on the CF and paralleling them raises the transconductance and halves the output impedance.I thought about using one triode in the CF but I hate having one nonfunctional.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 18:12:49
Caucasian Blackplate
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 Paralleling the voltage amp halves doesn't really do anything beneficial.

How about paralleling 3 of the triodes for the cathode follower.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 20:16:59
Michael Samra
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 The two triodes in the CF if the line stage are already paralleled..Where are you getting a 3rd CF section? I agree that I haven't heard much sonic benefit to the paralled triode.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 20:19:42
Caucasian Blackplate
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 The voltage amp section also has paralleled triodes.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 22:45:24
Michael Samra
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 Yes but that isn't a cathode follower tho.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 14, 2014 at 23:15:20
Caucasian Blackplate
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 Yes, there are four triodes per channel. Two are voltage amps, two are cathode followers in the stock circuit. As a mod, you could take one of the voltage amp triodes and add it as another cathode follower triode.

 

amazingly similar to the SLP-98 ..., posted on November 15, 2014 at 05:26:56
Thom
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 right down to the component values in that line stage even though 6SN7 subbed in. PS is somewhat different as the divider network only goes two levels and the 47uF caps used as bypasses rather than decouplers.

+1 on direct-coupling and I also realized great improvement replacing those 560uF as per your suggestion.

What did your B+2 come to if I may ask?

 

The rub is I actually took the time to listen for an improvement with his move... there is none~nT, posted on November 15, 2014 at 08:08:44
Cleantimestream
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 ~!
The Mind has No Firewall~ U.S. Army War College.

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 15, 2014 at 14:19:40
Michael Samra
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Location: saginaw michigan
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 Wouldn't I lose gain tho?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: amazingly similar to the SLP-98 ..., posted on November 15, 2014 at 14:36:30
Michael Samra
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Location: saginaw michigan
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 The B+ was within +- 1.5v which is essentially the same.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Take a look at this Cary SLP-90 schematic, posted on November 15, 2014 at 15:05:36
Caucasian Blackplate
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Location: Seattle
Joined: June 18, 2004
 No. If you removed one of the parallel voltage amps, you'd double the cathode resistor and plate load. There would be no loss of gain.

 

B+2 as in after the 47k0 resistor .., posted on November 15, 2014 at 18:05:50
Thom
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 and feeding the first tube of the line stage. Your B+1 on the CF looks a good +150VDC over my SLP-98 and wondering what the B+2 is on your gain stage. Sorry if not clear :(

 

RE: B+2 as in after the 47k0 resistor .., posted on November 16, 2014 at 02:46:56
Michael Samra
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Location: saginaw michigan
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 Coming out of the 47k with the side the polys are on reads 114vdc and the side with the 560uf electrolytics it reads 111.3vdc.Part of that could be slight differences in the 6CA4s.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

thx ... hmm, interesting that SLP-98 runs very ..., posted on November 16, 2014 at 07:15:58
Thom
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 different voltages than yours with about the same B+ on both voltage amp and CF ... 193 and 196VDC respectively. Much lower on the CF and much higher on the voltage amp, yet component values the same.

 

Your right. . . , posted on November 16, 2014 at 15:18:08
John PA
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Location: The lower 48.
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 The SLA 70 was a set of two 1200uF in series. What were they thinking?



iBasso DX300MAX Ti. Focal Utopia and Stellia. iBasso SR2. Mr. Speakers, Ether II, Voce stats. Manley, Absolute headphone amp. LTA MZ3, Z10e electrostatic amp. Many other headphones, amps, cables etc.

 

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