Too Much Gain the Issue ? (preamp and amp)

Update- sold the Pass XA30.8, simply too much gain to sound the best with my 24db gain preamp.  

@audphile1 

thanks!  

as an update to this thread the sound was decent with my cary slp 05 preamp feeding the pass labs xa30.8 by compensating for the gain missmatch using the single ended outputs and lowering the level controls to aprox 30 percent.  the preamp single ended gain is 17db while the balanced gain is 24db.  

the sound from the balanced connection was unrefined and unacceptable no matter what i tried. 

however the single ended output seemed to lose much of the magic.  it was still not as refined sounding as i like, the soundstage was smaller and lower in height, possibly because the balanced out goes through another tube stage and dynamics were not as good, possibly by throttling the preamp level controlls too much. 

i bought some rothwell xlr attenuators which reduces the balanced output by 10db, down to 14 db net gain.  

this did the trick with no apparent negative impacts to the sound.  the huge sound stage and dynamics are back along with a more refined sound.  

moral of the story is that too much net gain between preamp and amp has a bad influence on sound quality.  

i am not sure how to make a rule of thumb but 44db total gain is about perfect and i have had success with 39 db net gain with other systems and now 40 db with my current attenuated system.  50 db net gain is definitely too much and 35 db is too little and anemic.

 @avanti1960 good! Nice effort to make it work!!! It’s an excellent amplifier. 

After some interconnect cable swaps, using the single ended 17db output and adjusting the level controls on my preamp to 3/8 of a turn the sound is now very good and at times excellent.  

I have ordered a pair of Rothwell 10db balanced attenuators so I can use the balanced connections again and that should improve the sound even more. 

Thanks again for all suggestions. 

+1@pmm.  When the (10dB) attenuator is used between the preamp and the power amp, quote (in Rothwell) "... not only is system gain reduced by 10dB but also the signal to noise ratio is improved by 10dB.  This pushes the noise floor down enough to create an inky black silent background from which the music can emerge with better resolved fine detail and transparency. This applies to even very high-end and very expensive pre/power amps." end quote.

Harrison Lab carries -12dB rca inline attenuator too and has good feedback but no xlr.  Also, I have used the variable attenuator a bit more expensive though.

i am willing to try attenuators but are they any more effective than the front panel level controls?

Evidently, those level controls on the front your pre are not helping. You have nothing to loose by buying a pair of Rothwell Attenuators and putting them in the inputs to your amp. As far as the sibiliance is concerned, try swapping tubes.

Maybe, if you give Cary a call, they may give some advice on how to remedy the problem. This may be the best course of action.

@stevehuff is running Cary SLP-05 with XA60.8 amps  

@avanti1960 may be worth reaching out to see if Steve observed something similar to what you’re running into. 

The Cary is already producing the gain; attenuators can help push noise floor hiss (NOT hissy treble) down and enable more volume control range but OP didn't complain about those issues, and they likely won't do anything to address the reported sibilance. Getting a super-low output MC to force a "need" for the high gain is also unlikely to resolve the issue here.

As OP reports clean smooth sound with XA25, he probably already has his answer - the Cary & X30.8 might just be a bad match. 

I use Rothwell 10db XLR attenuators and they work wonders between my tube pre and power amp..  I bought them new from Analogue Seduction on EBay and received them from the UK in less than a week.  

Here's a USA purchase source for Rothwell, but I'm not familiar with them (purchased mine almost 20 years ago).

They are listed under accessories and I think that I paid $40/pair ages ago.

I went for less expensive as the AI preamp was a loaner from a friend.

DeKay

sibilant in the upper midrange - several issues can cause this

1-gain

2-bias adjustment

3-source

Happy Listening.

@avanti1960 sounds like you have a good plan. 

Hay @avanti1960,  I also own the Cary SLP-05 and my power amp is the Parasound JC5, which has an input gain dial for both channels.

There is no question that the output gain from the Cary is very high.   When I got my Cary earlier this year,  I was playing around by adjusting the output gain dials of the Cary and the input gain dials of the JC5.   

Parasound suggests the gain dials to be set a the maximum position whenever possible.  I do seem to agree with them.   I feel like I'm getting more bass, when the input gain dials are set at their max.

I finally settled on setting the output gain dials of the Cary at around the 3 o'clock position, and leave the JC5 input dials at max position.  I found that anything less than 3 o'clock on the Cary makes the sound a little lifeless.   Whereas setting them higher can sound a little bright on my system.

I'm pretty happy now with this settings.  My usual listening level is between 8 and 10 o'clock on Cary's volume dial.   It doesn't bother me that I can't use a wider range on the volume.  Anyway, the days of listening to loud music is over for me.  I need to preserve my aging hearing for as long as possible. 😀

BTW.  Cary support did tell me once that they have a gain reduction modification, which will bring the gain of the Cary down by 6db.  It costs $140 bench fee, plus labor and parts.   I didn't go for it.

Anyway, good luck, and hope this helps.

Buy a very low output MC cartridge to soak up some of your excess gain.

Buy some really inefficient speakers.

Most people would kill for the gain you have.

But the Cary preamp gain is mad high.

Preamp tubes are optimized- all spots have early 50’s Sylvania 6SN7 GTA. Smooth as glass.

Tried putting the EH, Ken-Rad and Raytheon in and no help.

OK, that's fair and sorry I doubted you! I have 1950s Sylvania 6SN7GTA in my collection, and can confirm they're smooth. I was hoping you were using EH because that would have given you an easy move in the right direction.

I roll several components in my main rig, and some combinations just don't work great for whatever reasons. Sometimes you can mitigate a bit with tube-rolling, but it's most important to find components that mesh well together. And it's not always JUST the amp & preamp pairing either - upstream (phono / SUT / cartridge) and of course downstream (speakers) are also big players in whether the whole system gels together. 

@mulveling

Preamp tubes are optimized- all spots have early 50’s Sylvania 6SN7 GTA. Smooth as glass.

Tried putting the EH, Ken-Rad and Raytheon in and no help.

I am also experimenting with cables. I have tried everything. The sound is like a slightly scratchy upper midrange that sounds a bit too strong and distinct.

I love the sound of the XA25, it really lives up to the hype.  If I cannot get the 30 to work I will move it on...

@mulveling +1 on tube rolling definitely worth exploring

Also, in my experience, rarely anything is a “direct replacement” when it comes to swapping components in the system that’s been tuned over time to have a specific sound. And introducing a different amplifier is not a small change. I won’t be surprised if you might need to work with speaker placement and toe in as well as revisit the cabling.

You have a tube preamp and I am the only one advising you to roll those tubes 😂

I believe these preamps ship (at least they used to) with Electro Harmonix tubes which are great to liven up a dull/dark system but could very well be a bad match in yours. Adding attenuators can lower the noise floor but won't help the main issue you cite. 

@audphile1 

not new, a few years old.  

i am willing to try attenuators but are they any more effective than the front panel level controls?  which are variable resistors, no?

@avanti1960 is the XA30.8 brand new?

I remember posting a similar question (Cary SLP 05 & lots of gain) and at the time I thought that the consensus was that a attenuators simply added another volume control(s) in the signal chain?

@avanti1960 Wrote:

thanks so far.

couple things-

not really a brigtness issue, more like slightly hissy treble.

my pass xa25 sounds perfectly clean

cary can adjust the gain but i am not willing to go down that road

That’s because the Voltage gain is lower, on the Pass Labs XA25 amp which is 20dB gain and the Pass Labs XA30.8 amp is 26dB gain lower, gain less hiss. 😎

Mike

Try some cheap pads. I think you will find that it is NOT a gain problem.

What attenuators are recommended?

I used inexpensive Rothwell's between an AI Mod 3A an Audion Silver Night years ago and they seemed to work/sound fine.

Think they were rated 10dB.

DeKay

thanks so far.

couple things-

not really a brigtness issue, more like slightly hissy treble. 

my pass xa25 sounds perfectly clean

cary can adjust the gain but i am not willing to go down that road

Best is to consult your Carry dealer if the gain can be lowered to 12-18db (se-balanced), or lower hitting a total of early 40db max. I expect that would be sufficiently enough with speaker sensitivity between 88-91db.

Erik:

You are correct.

DeKay

I am so not a Pass fan, but what I have read from those I respect is that  these amps are very sensitive to speakers, and with the right speakers will sound full range.

I will say that when I repped InnerSound (ancient history) I took speakers to a dealer and for whatever reason the Pass with those transmission line speakers could not produce any bass at all.

@Dekay

Based on the link below, you misread.  I quoteth:

The Cary preamp needs to be used with power amplifiers having input impedances of 10k ohms or greater if the bass is not to sound a little lean.

As you point out, the input impedance of 50k Ohms listed on the Pass site is more than enough.

@avanti1960 I experience zero brightness, harshness or any type of sibilance issues with my XA30.8. I pair it with a Pass XP-12 preamp (9.3db total gain) using XLR cables.

Could be a combination of mismatched impedance exacerbated by too much gain. 

The input impedance of the Pass is too high for the SLP-05.

10K ohm is recommended (per a Stereophile review/measurements) and the Pass is 50K/100K depending upon single ended/balanced connection.

The mismatch will theoretically give a leaner sound (less bass).

DeKay

24dB is an awful lot of gain for a preamp. 26dB is sort of a surprisingly high gain for a 30 Watt SS power amp. Yeah, that might not be the most optimal match - but the volume attenuator on the preamp should keep the amp's input stage from getting overloaded and causing the sort of sonic issues you describe. So as @erik_squires mentioned, your main artifact of too much gain should just be noise floor. 

The Cary is tubed - LOTS of 6SN7 - so you can tube roll to try and mitigate some of that sibilance. If you have Electro Harmonix 6SN7 in there now, then starting to replace them with any decent vintage tube should help a lot. 

In modern era, preamps with gains over 20dB (almost always tube based 6SN7s or 12AX7s) are sort of an awkward fit. 

@pmm 

Thanks, how does using attenuators work better than using the level controls on the front of the Cary?  

@pmm +1!

An indication of too much gain is how much you need to turn the volume knob to achieve room filling sound. Say, for example: some here, find their volume too loud, when the volume knob is at the 8 or 9 o`clock position.

Two ways to rectify this. One, send your preamp back to Cary, and have them change the gain of the preamp. The second, cheaper way, is to purchase inline attenuators and insert them at the amp inputs.

PS - This is exactly my complaint wiht Pass amps, always and forever. :)

The 26 dB of amplifier gain is the convention/standard.

It's not gain.  Too much gain usually causes noise.