Help and Advice Needed: Cary Audio SLP-05 Preamp RMA Disaster


First, I want to thank everyone. This forum has been one of the best sources for information about gear, and I have used it extensively for years.

 

I am in need of help and advice on how to proceed from here.

The preamp is a Cary Audio SLP-05 Ultimate w/ Kimber Kable Upgrades.

Does anyone have an issue with the volume on their SLP-05 not fully muting when the knob (not mute button) is turned to zero, and do they have significant crosstalk between the channels?

This is only with XLR in and XLR out.

In particular, I would like to hear from people with DAC's with a rated voltage of 4.5V or more on XLR. This is about every high end DAC like the Holo, Chord, Auralic, and even Cary offerings, as well as DACs from Matrix, and other entry level high-end DAC's

 

My Gear:

i9 based server running HQPlayer Embedded and Roon Core.

Sonore Optical Rendu, Holo May KTE DAC, Manley Snapper Monoblocks, 6Pi Cornerhorns.

 

The story is a bit long,

so here is a TLDR;

My SLP-05 preamp does not mute when the volume is turned to zero (mute button works fine), and has significant cross talk between channels. I can input a 1KHz test tone into the LEFT channel (not other inputs), and hear it clearly from the RIGHT channel with the volume turned to zero.

Here is an unlisted video that I sent to Cary demonstrating the problem.

Cary is claiming the issue is my gear. First, they claimed my amps have too much gain (it has less than the Cary amps), and too many watts (watts?!?), then my speakers are too sensitive (102dB). They finally fixated on my Holo May DAC having too much voltage at 5.8V on balanced (the Cary is rated at +/-3V, or 6V). They remained fixated on this even though I provided the above video using the Matrix DAC which is rated at 4.5V.

 

I measured the voltage coming out of the Matrix DAC as shown in the video at

    

pin1-pin2

pin1-pin3

pin2-pin3

Matrix DAC LEFT

1.085V

1.084V

2.170V

Matrix DAC RIGHT

1.083V

1.081V

2.164V

 

which is very close to what they claim is "standard."

Cary is being resolute in stating that they have sold thousands of these preamps, never had this problem, and my case is unique. It seems I am the only owner of a Holo May (or Chord, or Auralic, or...) and an SLP-05...

 

Advice needed:

Cary is proposing modifying the preamp as follows:

1) Relocate a capacitor that is getting charged via the ground plane near the input buffer tube, and isolate the input buffer ground.

2) Tie the floating XLR neutrals to ground at the relays (this will short the inputs when an input is not selected).

3) Add a 5:1 voltage divider across the input for XLR 1, and RCA 1 to reduce the inputs from 5V to 1V. I do not know what they propose to use for the ground reference here.

I would like some feedback on these mods. I think some of these are pretty questionable. Why tie the relays directly to ground when it might be better to tie them through a 1M resistor? Tying the XLR neutral to ground seems like an invitation for common mode distortion and might prevent the circuit from being fully differential. 

Moving the cap seems fine, but it does not address the core issue - why are we having ground plane issues in the first place?

----------------------

The story as briefly as possible

I want to be clear up front, that I never engaged in raging, yelling or name calling, I never made any demands other than "you have to make this right." I did express myself as being "very upset and angry," and in a later email, "Please understand that my trust is pretty much gone at this point."

I RMA'd my 2 week old SLP-05 because the volume would not fully mute with the volume control (mute button works fine). While they had it, I paid ($250.00 + $250.00 shipping) for the gain reduction mod.

They could not find anything wrong performed the gain reduction mod, and sent the preamp back to me.

When I powered on the preamp, it was DOA. It turned out FedEx dropped it hard enough to knock the rectifier tube loose, and break the straps holding the big power capacitor down.

I found the gain reduction had no effect that I could determine, it is too loud at 10:00, and almost impossible to adjust to a low listening level.

I found the signal still bleed through at zero volume, and I found that the left channel bled through to the right channel.

 

What ensued was a steady stream of what can only be called BS (or "nonsense" as I referred to in my emails) with the Quality Service Manager. When it became clear that not only was I being not being listened to and there was a lot of CYA going on, I called and asked for the contact info of someone in authority to monitor the situation. I was given the email of the owner, who it turned out was never told about the shipping damage. I was finally issued an RMA 3 weeks after getting my preamp back.

 

They once again could not find anything wrong.

I had to actually write out an experimental plan for them to duplicate the issue.

As far as I know, they did not test another preamp with or with out the upgrades to see if the issue is unique to my unit or not.
 

It is clear to me that Cary does not want to know if there is a problem.

I am at a near loss as to how to proceed from here, and I could really use any input you good folks could provide.

 

Thanks you,

-Josh

joshua43214

Just a few ideas for you from a person that has worked on some SLP-05’s. 
It’s possible the volume control needs to be replaced.  That should have been the first thing they tried. 
Kimber Kable has no shielding and so does have more leakage to the other channel.  Even though it sounds pretty good not having a shield does increase the issue. 
The balanced inputs on an SLP-05 can’t take much more the 2V per phase (4V balanced) ore it can overload the input tubes.  The balanced input signal is applied directly (after the switching relays) to the two tubes.  No volume control in its path so going much over 2V per phase can overload the input.  This shouldn’t cause the volume leakage but just so you know.  
The single ended inputs go directly (after relays) to the volume control.  

I would try replacing the volume control to see if that rectifies the issue.  
If that doesn’t do it I would think it’s a problem with the Kimber Kable leaking signal.  Because there is so much more signal on balanced.  Maybe moving the wiring around a bit might help. 

@gs5556 exactly, I brought this up earlier and OP went right back to justifying XLR again instead of re-evaluating this as a serious option, look for lower-gain source and preamp gain particularly with high sensitivity speakers. Try again with RCA!  

Hi Josh,

I don’t have any experience with Cary but I just got a Zesto Leto Preamp to pair with my SS Krell 300 XD Duo.  I’ve got a MHDT Balanced Pagoda DAC.

I have a similar issue, there is a hum when I use the DAC and even with volume set as low as possible still some sound.  Also some bleed over if I have another input and volume really high.  Sound wise, I like the pre and it’s pairing.  I searched forums, chats and found Cary specifically referenced for this issue.  It seems to be caused by fully balanced DAC’s and a mismatch in gain / voltage between the pre and amp.  

I got attenuators that sit between my pre and amp, they actually plug into the amp and the XLR into the attenuator.  When introduced, reduced the hum quite a bit, I could adjust the volume to about a quarter turn.  Still not a correct match but better.  My solution since I like my DAC, the Pre & Amp is to have a custom attenuator box built that has 3 different voltage / gain settings along with a bypass mode.  This will enable me to adjust the voltage / gain with different devices.  Root cause in my set up is the higher voltage / gain in the DAC which is at its best run fully balanced, signal to the Pre is hot and the Pre has a voltage / gain too high to match the sensitivity of the amp.  The mismatch creates the hum and other issues.  I could send the Pre in to have the voltage / gain / DB adjusted but even at it’s lowest setting would likely still be a mismatch.  
 

Try attenuators, sounds like you would need at least -20 db, maybe - 30 db.  If they reduce the issues, give you more flexibility on the volume control, you found and solved the issue.  Search on Audiogon, US Audio Mart and other forums.  You should find some of the threads I did that led me to my findings.  
 

Should you want a box like I’m having custom built, Pine Tree Audio is great to work, deal with.  Jesse is awesome.  

@gs5556 I saw that article when I first started looking online for others having my experience. I agree, I think Cary knows this is an issue and is doing everything they can to keep their heads in the sand. 

 

@harpo75 Your discussion mirrors some of what Cary has shared with me, in particular that the signal passes through the input buffer before it goes to the pot in XLR. They say that because of the "extreme" voltage, the signal is leaking into the ground plane and energizing the rest of the circuit.

But as you say, this should not cause any volume leakage, at least it shouldn't if the circuit is properly designed. So, somehow, signal on the ground plane is getting up into the plate and getting amplified.

Good info about the Kimber Kables, I did not know they where not shielded.

This just tells me they are selling a poorly designed input stage and/or a poorly implemented ground plane.

 

@decooney 

 I brought this up earlier and OP went right back to justifying XLR again instead of re-evaluating this as a serious option, look for lower-gain source and preamp gain particularly with high sensitivity speakers. Try again with RCA!

Not sure what you are referring to. @avanti1960 asked about RCA, and I provided an answer, not a justification. Consider also, I just spent $9600.00 on this thing, is it not reasonable to expect it to work with out compromise? There are a ton of equally good or better preamps out there that are RCA only for much less money.
I answered your question about how they replicated the issue.
I am happy to answer any questions on the subject, I am really hoping for a solution that can get me back to enjoying my preamp.

 

@mm1tt77 Thanks. I have considered attenuators, I have even heard some claim they improve the sound, though I expect this is from providing more headroom before clipping.

Adding an attenuator is certainly preferable to letting Cary hack in an 80% voltage reduction.

@joshua43214 I was reading an application used with Kimber XLR and one ground wire used thus allowing noise. Earlier, was attempting to understand if you only experience the noise issue with XLR only, and not with digital RCA coax. If you already stated this or someone else did, I missed it.  Agree it should hopefully work for the price you paid, however something in the chain of components is pushing capability beyond the design limit, it seems or maybe the cable is a contributing factor. I was wondering if the use of XLR was elevating the voltage somehow inherently by by design. I had gain with subtle noise in my former SS preamp and amp and defaulted back to RCA for signal, just for this reason alone.  One other XLR I tried did help some.   Just for grins, by chance have you borrowed or tried a different shielded XLR cable design with a different type ground configuration to eliminate the cable itself as a potential culprit?