"Too much gain"? (Cary SLP05 question)

@immatthewj Definitely think you will be happy with your decision. I went through the same litany of issues running SLP-05 into Pass X250.8. The Rothwell’s have worked out great. I usually run main volume pot between 10 and 1 with small. Balancing L/R pots at 100% and system is dead silent and very dynamic.

@harpo75 Thanks for the clear explanation on balanced gain, pot issues etc. i run balanced from the Cary to the Pass and my analogue from the phono preamp to the Cary. I actually loved the extra balanced dB bump on the mc cartridge. I am currently running rca from my 2.0 v digital source as I have not been able to hear a difference and I like the reduced gain even at the 2.0 volts( still run main volume between 10-12 for digital) I will revisit this again but since cables are different that clouds the comparison and I want to stay away from lowering main volume below 9 o’clock. Enjoy, looks like you got some great experienced advice here.

@immathewj

I have learned your issue the hard way having bought a power amp with 26db gain for my Cary SLP-05 (Pass Labs XA30.8).  Even when the Cary's gain is backed off to half (going any lower affects dynamics) there is too much gain in the system. 

I tried the 10db rothwell attenuators and did not care for the results.  

I also tried using the RCA outputs which drops the Cary gain from 24 db to 17db.  This definitely helped but I lost a lot of the 3-D huge soundstage when not using the XLR outs on the Cary, the balanced outs run through another set of tubes and the sound stage is much larger and the sound is ore dynamic.  

Ultimately an amplifier with 23 to 20 db gain works best- or an amp with adjustable gain like Parasound a21+ or JC5 which I run at about half gain.  

Hello all,

I thought it would be worthwhile to add to this thread as the unit does have a ton of gain that will severely limit use of the main volume pot. After reading through this thread and others, there has been some good information and some incorrect conclusions. I thought I would relay my experiences here to help future owners resolve the question of what to do with the excessive gain in a pre that they love.

First, let’s be clear what the circuitry is. ALL inputs, xlr (via input tube buffer) or rca get routed to the right and left input trim pots. The pots are a cheap Honeywell plastic potentiometer, 100kOhms. Recommended use for this pot from the Honeywell sheet is in ATVs, joystick controls, and more. Ruggedized for military standards. These Honeywell pots are directly wired to the two plastic potentiometer layers of the Alps 100 kOhm pots, which has a motor control. So you can use either the trim pots or the volume knob to control volume, or both. It doesn’t matter electrically, you just have 2 pots in series.

I have played around with the pots on the Cary, as well as digital attenuation. Re digital, some software driven attenuators are definitely better than others, but it seems like -10- to -15db is the limit where I don’t hear issues in volume matched back to back comparisons. Yeah, I know it shouldn’t be the case mathematically, but something is off. Besides, even -30 or -40 db digital attenuation isn’t enough to give you full use of the volume knob. So that isn’t the answer.

Playing with the pots is interesting, because you will quickly notice with volume matched testing that the balance trim pots are clearly filtering the signals. This shows up with low level information at all frequencies, but it is most easy to see with higher frequencies. Maybe a system runs a bit bright? Well ok, but the full spectrum loss of clarity and detail is not a favorable trade. Buy tubes that are rolled off on top, *cough* I meant warm sounding.

Playing with the Alps volume pot gives similar results, but with less severity. The channel imbalance near max attenuation is a problem though, as is the high frequency filtering which makes the bass seem exaggerated.

So what are the solutions? I guess you have to decide what you want out of this pre. Do you use the headphones a lot? The input trim will likely be important unless your tubes are perfectly balanced. Input trims are useful for troubleshooting, but that is limited case scenario when it is also easy to just pull a cable. Only use the volume knob and you just want it to work better?

If you want it all I would look at replacing the volume and the trim pots with high quality stepped attenuators. Goldpoint,Khozmo, or others are good examples. Yes they are expensive. But your $6-8k amp deserves better than 3$ and 12$ pots. I put in a 24 step mono 100k pots in place of the trim as I don’t use headphones. If you do, maybe see if 47 step will fit.. First off, night and day improvement in clarity at all frequencies, you will sit up in your chair. Second, with high quality pots you will notice that the Alps isn’t exactly bad. If you do most of the attenuation with your stepped pots, then you can run the Alps from 12o’clock to full on with good results. In messing with this configuration over the last month, I would say that the less the Alps is in the chain, the clarity improves but with diminishing returns. My next step will be to replace the Alps with a 47 step attenuator and call it good. The upper range of the 24 stepped input trim is just a teensy bit limiting in my system.

Motorized volume knob mandatory? Well there are solutions depending on the attenuator you choose, but they are expensive. I would go this route if you plan to keep the pre for as long as you can. I haven’t decided what to do yet, I might see if I can use the existing RC design and fabricate an adaptor for the new attenuator. We’ll see.

Hope this helps. Yes, get a professional to do the work and the usual disclaimers. I have no knowledge of EE or circuit designs, these conclusions are my own experience and you may get different results. Make modifications at your own risk.

Find this an interesting thread as I’m still looking at an SLP-05 as a second preamp.

Enjoythemusic dot com published a review of the Rothwells that say they do affect sound quality. Never used them myself but seeing here they seem quite popular.

@jaybe 

Having lived with the ins and outs of the SLP05 I am still enthralled with the sound quality of this preamp.  

The extra gain can be too much but there are two ways to satisfactorily work with it.  BTW the higher gain is a virtue as the resulting dynamics make for a superior sound stage and listening experience.   Also the rothwell 10db attenuators did not work for me either. 

The easiest way to deal with it is to use the single ended outputs which gives you 17db which is perfectly suitable for most amplifiers and just two db more than most preamps.  This is my current setup feeding my new gen McIntosh MC312 power amp and the sound is both dynamic and pristine. 

The second way is to use an amplifier with lower than usual gain and use the balanced outputs higher 24 db gain. I used it with the Pass Labs XA25 that has 20db gain with stunning results.  Also the Benchmark AHB2, many of the First Watt amps as well as Bryston models that have a two way gain switch one being 22 db.  

Its incredible what this preamp can do in stock form, even better with NOS tubes and rectfier.   Dont let the higher gain scare you away.  

I haven’t tried the Rothwells, so I cannot comment on those directly.

In regards to attenuators, there are some things that should definitely be pointed out.  First off, any attenuator that isn’t matched to output and impedance runs the risk of increasing roll off in the upper or lower frequencies.  Because attenuation works by dumping voltage to ground, and allowing the remaining voltage to pass to the input circuitry, current is also passing to ground.  I tried some basic 600ohm T style first because the case was reusable and I could always try different topologies, buy as many resistors as I wanted to find the sweet spot.  The 600 ohms dumped so much current the tubes were unable to drive any low frequencies.  Keep in mind that the 400 ohm output impedance of the Cary rises to 4000+ as the signal drops to ~20 Hz, as measured by JA in the Stereophile review.  This unit runs out of juice quickly unless you have a high input impedance amp.  50k+ would be my recommendation.   Note that OTHER highly regarded tube preamp makers state they can increase the cost with beefier output capacitors to match equipment.

I was able to find a resistor match that did measure tonally the same. However, and these are my listening impressions only and should not be regarded as a claim to anything but, I found after considerable testing that the XLR inputs and outputs of the Cary sound different (edit: compared to RCA).  With 6 identical tubes, the XLR pathway loses warmth, bloom, depth, microdynamics and more.  Some say adjust with the input trim.  That is BS, they are directly wired to the Alps pot.  Putting 2 cheap plastic trim pots in series serves no purpose except to allow balancing for mismatched tubes in the headphone stage where it will be most noticeable.   Regardless, both the input and output XLR circuitry both have the same character (edit, compared to RCA).

I did ask Cary about this issue and if they would recommend a local service place to diagnose the issue, and they didn’t reply.  Commonly held belief is that properly made RCA and XLR circuits should sound identical.  Indeed, in my other gear they do.  

Having said all that, running RCA with only 4 tubes (leaving 4 empty), replacing the Alps pot with Kozmo, Goldpoint, or other high quality attentuators and removing the input trim pots will leave you with the potential for glorious sound, as long as you buy exceptional tubes.  I did the work myself, but it will cost you around $1k if you get a tech to do it.  

The gain issue should not be ignored.  Running my XLR 4V outputs through the Cary into a Pass amp (+26 db) required the attenuators to dump 99% of the voltage to ground after the input tubes going by resistance level and L circuit configuration. Many users note minimal volume control issues.    Note also the alps is also the most susceptible to internal RMF signal interference at the bottom and top 1/4 of its range.  Note that with output relays turned off you can clearly hear an input signal at low and high volume, but not at 12o’clock.  So you have to be able to run the unit at 11-2 ish to get best sound.  Gain matching and impedance matching are critical to getting great sound with this unit.  YMMV, and others have reported great satisfaction.  

Cheers

Edited to remove ambiguity, and noted as edits

I found after considerable testing that the XLR inputs and outputs of the Cary sound different (edit: compared to RCA).

@khloebo , my impression is the complete opposite.  I have found that when comparing SQ of the balanced circuit vs the RCA circuit, that after listening to my system using the XLRs the sound stage seems  folded in or collapsed when I use the RCAs.  

Out of curiosity, and not that it would have anything to do with perceptions of balanced vs single ended ins and outs, does your SLP-05 have the Cary Upgrade package?  

@immatthewj   Hi there!  Good point for the discussion, no mine does not.  I bought it 2014 as well, it probably has around 7000 hours on it.  

The upgrade package reportedly has a complete capacitor overhaul, which could affect the SQ in a number of ways (especially driving 20k input impedance).  However, I have not read anyone doing a direct comparison between the two, which is not surprising.

Also, and this is just a giant guess as I haven't created a circuit design and asked an EE about it, but if the ultimate upgrade improves the capacitors, AND the circuitry that converts the balanced signals to unbalanced (and vice versa for output) then it absolutely should be better in technical performance and adding input tubes should add tube character. 

One of the reasons why I replaced the input trim pots with Goldpoint attenuators is so that I could figure out some issues I discovered with tonal shifts during digital vs analog attenuation.  Long story short, both the cheap honeywell pots and the Alps act as low pass filters when attenuation is nearing the max.  IE, they remove high frequencies.  Thus sound is perceived to be rich in mids with fat bass.  Using XLR and low volume controls increases this effect.  It can be very pleasing and rich!  However, it comes at the expense of clarity and dynamics.  Listening to a bunch of systems over the last couple years with tubes left me unsatisfied with mine, so I tinkered.  The Goldpoints allow tons of clarity, richness, detail, space and everything else through.  I keep the Alps at max so it is out of the circuit for music, it only gets used now for TV volume.

Having said all that, nothing needs to be done when you love the sound, XLR or RCA.  New purchasers should definitely try the unit before buying or with a full return option.   It is an interesting box that needs the right situation to sound at its best.  

@khloebo , from reading your posts I have no doubt that you are way more tech savvy than I am (and in case that sounds like it might be snark, I am totally sincere) and I didn’t put as much science and knowledge into the comparisons that formed my perceptions as you have.

I acquired mine in ’21 from Cary’s preowned page, and from my memories of the emails I exchanged before I pulled the trigger, it was 8 years old at the time (it is one of the ones with the indentations on the power supply for the preamp feet to sit on, although I don’t have mine set up that way).  When I called Cary on the phone (they will talk to you on the phone if you want to buy something) to close the deal, I decided that I may as well do The Ultimate Upgrade at the same time, and an added "bonus" would be free shipping (no free shipping on preowned, but if one was to send a preamp to cary for the upgrade, Cary would send it back after the work for "free") even though that meant that once the upgrade was done I owned it even if I didn’t like it.

But to understand where I am coming from with my perceptions of the SQ, up until that point I had been listening to a SLP-90 which I had owned since ’99.  And the SLP-90 replaced a B&K digital HT preamp, so as you can see, my experience playing with high quality preamps is, to say the least, limited).

The SLP-90 was a huge upgrade in SQ from the HT preamp, but it was starting to sound as if it was getting tired.  So the fact that I was listening to a 30 year old preamp probably has a lot to with why I like the SLP-05 as much as I do, although I will say that the SLP-05 sounds a bit (or maybe more than a bit) cool and clinical in comparison with my SLP-90.

As far as my balanced input tubes, that’s something else I am doing different that makes RCA vs XLR not a fair comparison.  A friend from another site turned me on to a literal plethora of PAIRS of vintage 6SN7s (note that I emphasized ’pairs’) so after playing around with those in the balanced slots, I did note that some of them really really shined.  At the moment I have a pair of National Union 6F8Gs (obviously with adapters) in those slots, and they really do it for me some nights.  And prior to putting those in, I was giving a pair of Sylvania ’52 Bad Boys an extended spin, and they were making me happy, but for different reasons.  I also found two different pairs of VT231s  in that plethora that I thought were audibly better than the rest, with my favorite being a pair of black glass RCAs which made detail and separation stand out much more clearly and cleanly. (There were also pairs out of that fore mentioned plethora that I was not sure if I heard any discernible difference or not, and there are actually pairs of both 6sn7s and 6F8Gs that I have yet to even try.)  

So with that all typed, I realize that you were making your observations re XLR vs RCA with all tubes being equal.  

Back to the pots:  what you typed about using the input level pots in conjunction with the main Alps pot was quite interesting, because in my near field environment I am usually at 9 o-clock + or - a bit, and that, of course, is with the input level pots turned all the way up.

My vision is not very good anymore and also I am a bit dense when it comes to understanding  this stuff, but it sounds as if what you have been saying is that to get the best SQ given some of my other limitations also means lowering the gain and if I am stubborn about XLRs the next best would be to upgrade the two input level pots and use them for volume control with the main pot turned all the way up?  Or at least set the upgraded inputs low enough so I can run the main Alps at 12 o-c-clock or close to it?

Forgive me  if that is not what you have been saying. 

(Okay, so now I note that you said that basically the Alps is not at its best at the bottom OR TOP quarter . . . meaning that I would not want to run it all the way up if I was combining it  with the input level pots for volume adjustment.)

Regardless, unless I am totally misreading, upgrading the input level pots is definitely recommended.  Even though I make no claims to be a tech, I do have experience soldering and de-soldering . . . how tricky a job is replacing the pots on this unit?    

Having said all that, nothing needs to be done when you love the sound, XLR or RCA. 

Well, there are nights that I am in love.  But who doesn’t want more and more love?

Hey, thanks for your contribution to this thread!

@khloebo 

very nice description of the workings of the SLP 05.  

right now my system sounds so good with the stock SLP non modded or upgraded.   For anyone interested I do have 3 matched pairs of a specific variety of Sylvania 6SN7s running every slot except the headphone amp.  The rectifier is a NOS made by mullard GZ34.   fyi the RCA smoked glass did not work out and neither did several other NOS notables.  

the tubes and rectifier made such an upgrade I recommend them to anyone with or thinking of an SLP05

@immatthewj   It sounds like we have essentially the exact same unit (depressions and all), excepting the ultimate upgrade.  I am curious, but the cost is definitely a factor.

The mix and matching is truly the appeal, with the variety 6sn7s out there.  If I dream and ignore consequences, it would be fun to remove the headphone stage, drill another pair of holes, then be able to choose from 3 input tube stages!  Crazy talk... 

Yes you have it, you could replace the pots with quality stepped attenuators.  I had to enlarge the holes a bit to fit the goldpoint 24 steps.  I thought about doing 47 but size was scary close, and digital attenuation below 20dB is totally fine if you want to go that way.  The main benefit was the improvement in clarity.  Running the alps at 12-2 o'clock wasn't bad, and if I did volume matched comparisons no Alps was better, but I will admit it was getting close enough that blind testing might prove me wrong.   But yes, I run digital -6db to -25db for music, the girls do the remote control Alps volume for TV roughly at 12 o'clock.  Input pots never change

I'm currently smitten with the Linlai e6SN7 tubes as a quad. 

@avanti1960 Now that you mention it, I should go back and see if the rectifier tube actually does anything for me.   I swapped in a mullard copper edge from Vintage Tube services, but didn't notice anything different at the time.  The time to swap just makes anything short of night and day really difficult to see.  Sounds like fun!

Glad everyone is enjoying happy listening though.

@khloebo , although you addressed this to  @avanti1960 

 I should go back and see if the rectifier tube actually does anything for me. 

I have rolled three 5AR4s (the original Sovtek, a GL, and a Mullard with Amperex brand on it) and I cannot say that anything reached out and slapped me on the face.  But with that typed, I do not possess golden ears and there may have been a difference that was subliminal, meaning the way I believe  my ear/brain connection works is that I may be enjoying something either more or actually less, but it is a subconcious type of thing that results in either pleasure or displeasure.  If that makes sense, because it is a concept that is hard for  me to put into words.  And it makes A/Bs hard to do for me.  

I also have a couple of 5AR4s that I picked up that I have yet to try yet--an actual Dutch Amperex and a Japanese tube . . . maybe a Nakamichi?  I’d have to go back and fid it and look at it.  Someone on ebay was once selling some 5AR4s that they were saying were the "Japanese Mullards" (which I had heard of before) and the way I was doing ebay binges,at the time, I am surprised now that I didn’t buy one of those also.

A PS on edit:  hogging out those holes for the upgrade pots makes be a tad nervous, I will have to think about that.  I may try to get back to you on this project.

Please note that Cary’s preamp gain is done BEFORE it reaches either the trim or main volume control.  The only thing that trim pots and the main volume control do is attenuate the signal.  The volume controls will not alter the noise floor as it has already passed through the gain stage. However, as one poster has pointed out, cheap volume pots have the ability to act as a filter.  
 

If Cary really wanted to offer an Ultimate Upgrade, they should address the volume pots which is the SLP 05 Achilles heal. 

@immatthewj  Good advice on the 5AR4s.  As long as the power rectifier circuit was well designed any change of tube should have a minimal effect.  At that point it should be noted that variations in tube production over the years might also have just as significant an effect, positive or negative.  My Sovtek had ~6000+ hours on it, figured getting a Mullard to try couldn't hurt. I will likely buy a backup 5AR4 from new production, unless the Mullard clearly shows it is better.

Yeah, the holes are a bit of an issue.  If I did it again I would get a step bit or reamer and practice on some scrap first to make sure it remains perfectly circular and centered.  I suppose I could have made a jig to get it on the drill press without total disassembly too.  Meh.  I had to do some hand filing in the end to get it where I wanted.  The soldering is super easy, and if you remove the mounts temporarily on the headphone stage there is enough room to do all the work.

@testpilot I totally agree.  The honeywell trim pots are a couple dollars each and are made for ATV controls, among other gross implementations.  The Alps you could buy for under $25 with the remote motor.  There is a ton of room inside the case for upgrades.  It should be an option to go stepped or switched relay.