"Too much gain"? (Cary SLP05 question)


A few days or so ago, someone had revived an old Cary SLP 05 thread, and common to that discussion seemed to be the subject of too much gain. 

My first question is:  does compensating for too much gain by simply adjusting the volume knob knob down degrade the sonic quality?

My second (2 part) question relates to this quote from one of the replies in that thread:

 A quick note to Pass Labs and they suggested a pair of Rothwell 10db balanced attenuators into the amp’s inputs.

What exactly do balanced attenuators do to resolve this issue, and if placed between the preamp and the amp, would they degrade the signal path & therefore the sonic result out of the speakers?

I am a relatively new owner/operator of a SLP05 and it is in front of one of the earlier Cary V12s.  I did find those balanced attenuators on ebay for (I think I remember them being) $89 a pair, which I find totally doable.  I am lsitening in a (very) near field room right now, and it seem as if I do have a lot of gain.  Generally the big knob is on 9 o'clock plus or minus a little bit depending upon the source material I am listening to.  I am using the balanced ins and outs to & from my SLP05 and I have been given to understand that using RCAs would reduce the gain somewhat.  I do have some RCAs (I am presently using Kimber Silver Streak balanced interconnects) but my collection of spare RCAs is Kimber PBJ and Monsters. 

For $89 should I try putting a pair of those  of Rothwell 10db balanced attenuators into the balanced amp’s inputs?

 

immatthewj

@xcool’s statements are perfect.  Love it. 

Although the Cary support person is very nice, sometimes he doesn’t give me a straight answer [. . .] He never really answered my question.

“Haha. Yeah. There was a time when I used to rave to anyone who would listen to me about Cary Audio’s telephone tech support. I will say no more on that subject.”

Yes, absolutely right!  Now the answers are just cut and paste.  Dan and Marc used used to be great on the phones there but there’s no more phone support as many companies are doing.  And Dennis Hadd’s statement still holds true and now even more so.  The two balance pots are even cheaper ones then they used to use.  Years ago they used the Clarostat  pots in that position.  Then when those got more expensive they change to some very cheap generic pots which are terrible. At least they still use the Alps Blue Velvet in the main volume position.  
 

Also glad you didn’t go for the lower gain mod.  Part of that mod is already in your ultimate upgrade when they change the cathode resistors. The rest is simply adding four resistors in the line gain stage to reduce the signal and I didn’t think the preamp sounded as good then.  Just lost its life. 
 

If you want to keep the two balance controls and improve the sound quality get a couple of high quality mono pots for that position.  Like a couple of the mono version Alps Blue Beauty or better.  Or better get the Khozmo or whatever.  There isn’t a lot of room there before it hits the pc board so you’ll have to measure things.  As I mentioned the value of the pots are stamped on the back of it their values. 
 

Another answer that is better then two pots, find the position that sounds best on the balance pots and, that gives you some master volume adjustment freedom, measure the resistance of the balance pots and install to high quality resistors in there place.  That will sound better then most any pot.  Of course then you have no control over balance.

 

What to understand in the way the 05 is that the gain of the tube circuit is set.  It’s just on.  What you are controlling is how much of the signal coming in from your source you are going to allow to go forward into the circuit and be amplified.  Now the balanced input circuit (6SN7 tubes 3&6) of the SLP-05 produce gain also.  About 9db on ultimate upgrade units and 12db on a standard one.  So the balanced input gets amplified and then routes through the balance controls and then the volume control, then on to the line stage circuit consisting of the four 6SN7 tubes 1,2,4,5. The single-ended inputs route in from the switching relays directly to the balance and volume controls.  That is one reason why there is so much gain on the balanced inputs.  Along with twice the signal from the +/- phases.  I’ve heard of people trying and I’ve tried lowering the gain into the balanced inputs from the source but I’ve really noticed a lack of dynamics and overall sound quality then. They need the +/-2V in for best sound.  Another thing to be careful of is how much input goes into the balanced inputs.  They overload the tube if you go much more the 2V per phase of the balanced signal.  Meaning balanced +2V and -2V.  Like once you hit about 2.3V to 2.4V per phase you will start hearing it distort/clip. Things get hard and bright first then fully distort.  So be careful of your balanced source components. To understand better, those two tubes are “full on” and there is no volume control in front of them. It was designed in the day when the standard source component output was 2V.  

All right sorry!  I always explain too much. 

@immatthewj 

with the left / right gain controls each at 50 % (sounds best) 

the volume control is at 9:00 to 10:00 or so most often, moderate loud, for my higher output digital sources and 10:00 to 11:00 for my turntable.  

@harpo75   Are you saying the balanced gain total  for the ultimate upgrade is now 21 dB rather than 24 dB? And does the gain get lowered with a totally single ended input as well?

 

Also any comments on the sound of the headphone amp in this preamp?

All right sorry! I always explain too much.

@harpo75 no, not at all! Thank you! I like the sound of tubes when everything is running good, but I really do not have the mind for comprehending a lot of this stuff.

It almost sounds like you would agree with the previous advice that @russ69 offered, which was to use the RCAs?

I guess I am feeling stubborn about that because of the $ I invested in my balanced Kimber Silver Streaks. If I do go to my RCAs, the best I have on hand (right now) are my Kimber PBJs.  (I also have a bunch of Monster, but I don't think that was ever very good interconnecting.)

I am going to continue to be redundant and reiterate that I can, in fact, find a place with the big knob where the I am good with the level--but my question was related to whether the quality of that level would be better if I could achieve it at a higher than 9 o-clock setting of the volume knob.

Thanks again!

LISTEN TO THE DAM PREAMP!

The balanced connections sound noticeably better (pre outs). The balanced circuitry passes through another set of tubes. Just do a quick AB comparison. That is all it took for me. The balanced soundstage is huge and more open with distinct separation between instruments, it is really something.

Using the RCA outs the sound stage is instantly collapsed and less exciting, very obvious.  

I choose balanced every time. Give it a try from your listening position.