Phono stage gain setting to match preamp and power amp capabilities


Hello All,  I have a Whest PS .30R phono stage, with adjustable gain settings.  My Audio Research LS-25 preamplifier also has adjustable gain settings (high 18db, medium 12db, low 6db; I have been using high at all times as I believe this is the best sound quality & "native" setting).  The Whest gain options are 43, 50, 55, 60, 65, 72.  It also has adjustable load settings of 100, 220, 470, 1k6, 15k, 47k.

The cartridge is Lyra Delos (Output voltage: 0.6mV@5cm/sec.) The power amp is an Audio Research VT100 (100wpc).  The speakers are Rockport Mira Monitors ( somewhat low sensitivity at 85 dB SPL/2.83 v)

The reason I am looking for advice here has to do with how much I have to turn up the volume control on the preamp up to get to the loud volume that I like to listen at when I am in my loud listening moods.  In order to get to the point of a dramatic concert style experience in my living room, when playing vinyl, I have to turn the preamp volume to the 3 o'clock position. Once I get the volume control this high, the noise floor (am I using the term correctly?) or background hiss increases audibly.  I do not get loud volume without that hiss.  Of course, when the music is full, you cannot hear it.  But when the music is lean, the hiss is there.

For the past year or so, I had the Whest set to 60db and 220 ohms.  I arrived at 60 because I didn't want to over amplify the signal in the phono stage and get more hiss.  But then I had to crank up the preamp volume.  Now I just set the Whest to 65, and as expected, the volume control on the LS-25 can be backed down a little.  I haven't had the chance to really listen critically or for long enough time to determine if the hiss has diminished.  But I will log the listening time soon.

Can you give me any advice on the proper way to set these options?  Should I go to full gain on the Whest and back down on the LS-25 volume control even further?  Or is a lower gain on the Whest a better way to go?  Also, can you help me understand the nature and source of the hiss I hear?  What is it, why is it there, and how do I get it to be 'inky black' as some reviewers like to say?

Thanks!
Mark
marktomaras
Hi Mark,

First, kudos for stating your question so thoroughly and well.

Clearly the hiss is being caused by something upstream (ahead of) the volume control mechanism in the preamp. Looking at the preamp schematic at arcdb.ws I see that the volume control devices are located not far in the signal path from its input connectors, with only the input select switches and a few resistors and associated switches (which provide the gain select function) in between.

Noise performance for vinyl sources will often be limited by circuitry in the phono stage that is at or near its input, since a given amount of noise generated by that circuitry will be greater in relation to the signal amplitude than a similar amount of noise generated further downstream. But without knowing the details of the Whest’s design it’s hard to predict how such noise will vary as a function of its gain setting. If I were to guess, though, my suspicion would be that lowering its gain to 55 db would be more likely to help than raising it to 65 db. Despite the somewhat low sensitivity of your power amp (1.9 volts; 23.5 db gain into 8 ohms) and your speakers, the 18 db gain setting you are using on the preamp coupled with the 0.6 mv rating of the cartridge should enable you to do that while still being able to drive the amp to full power on high volume musical peaks, without running out of range on the volume control.

In addition to the phono stage’s intrinsic noise performance, though, there are some other things that might be causing or contributing to the issue:

1)I see that you have the power amp located close to and in between the phono stage and the preamp. It seems conceivable that the power amp is coupling noise into either or both of them. As an experiment, at least, you might try relocating those components such that the power amp is as far away as possible from the other two components, especially the phono stage (and also the cable connecting the phono stage to the preamp).

2)A ground loop issue between the phono stage and the preamp could conceivably be contributing, even if there is no perceptible hum. You might try temporarily using a cheater plug (a 3-prong to 2-prong adapter, with the safety ground not connected to the outlet) on the power plug of one or both of those components. That would break any ground loop that may exist between them.

Good luck. Regards,
-- Al

I don't think there's a perfect answer to your situation, but based on the cartridge's output I would set the Whest at 50 or 55dB gain and then adjust the preamp accordingly.  I wouldn't be worried about the position of the volume control as long as it still has some extra adjustment range.  If you are trying to achieve concert hall levels (95dB+), then you probably need a larger amp with your current loudspeakers.

Let's us know how your listening goes.
More gain on the Whest less gain on LS-25 since the Whest is solid state it will be quieter when turned up 100k is best for me with Transfiguration Proteus but it depends on the cartridge.Good luck enjoy!!

Is there a way to listen and measure the noise properly?  As in, can I turn the volume up, have the input selector on phono, and just listen with nothing playing?  Or is that not a way to isolate and listen to noise only? If I could do something in that ballpark, I think it would be easier to hear the changes that you all are suggesting.  Either that, or perhaps play a track on the turntable that is extremely sparse and allows one to hear the background noise.  Suggestions?
To recap, some say lower the phono stage gain, and some say raise the phono stage gain.  Does anyone want to back up their argument with some supporting evidence?

Almarg, As for amplifier interference, I take it you saw my system photo. Is there anyplace on the rack where the amp would not interfere?  I ask this because the speaker cables are not long enough to have the amp anywhere other than in the center position.  The only option would be to put the amp on top of the rack, next to the turntable, or, reconfigure the shelf heights and put the amp on the bottom, with the preamps on the raised up center section.  If you think this is not adequate, then unfortunately, I don't have much of an option.  Of course, if I am looking for the source of the hiss, and that is it, I can put the amp on the floor in the middle of the room as I have some longer interconnect, but I think I will save that for the last test.

As for the ground loop, just so I understand properly, I disconnect my power conditioner from the wall outlet, plug in the cheater plug, and replug into the wall, and listen for a hiss change/reduction?  Is there any danger to my equipment for this test?

Thanks!
Can I turn the volume up, have the input selector on phono, and just listen with nothing playing?
Absolutely. In fact, that is what you should be doing. Additional noise that occurs just while a record is being played would be a function of some combination of the turntable, tonearm, cartridge, cartridge and tonearm adjustments, and the recording. And for a given playback volume would not be affected by the gain settings.
Some say lower the phono stage gain, and some say raise the phono stage gain. Does anyone want to back up their argument with some supporting evidence?
As I said, it’s hard to predict without detailed knowledge of the Whest’s design, and perhaps also without published measurements being available. But FWIW my instinct is that more often than not lower phono stage gain will correlate with better noise performance, **everything else being equal.**
If I am looking for the source of the hiss, and that is it, I can put the amp on the floor in the middle of the room as I have some longer interconnect, but I think I will save that for the last test.
Yes, I was just suggesting moving things for experimental purposes, to see if it makes a difference. So this sounds like a plan!
As for the ground loop, just so I understand properly, I disconnect my power conditioner from the wall outlet, plug in the cheater plug, and replug into the wall, and listen for a hiss change/reduction? Is there any danger to my equipment for this test?
No to both questions. Regarding the first question, as I indicated the cheater plug(s) should be placed on the power plugs of the phono stage and/or the preamp, to eliminate the possibility that a ground loop between those two components may be contributing. (Putting a cheater plug on the preamp’s power plug would also break a ground loop between the preamp and the power amp, although it doesn’t seem as if that is an issue here, since the noise is volume control sensitive).

Regards,
-- Al


P.S: Regarding the phono stage gain question, you may find the following thread to be of interest:

Gain vs. Volume

The bottom line, as stated in that thread by Atmasphere:
A simple way to look at it is to use the least amount of gain that you can to get the job done, as the more gain, the more can go wrong.
I am citing this in regard only to the phono stage in this case, however. Not in regard to the preamp, due in part to the examination of its schematic that I mentioned.

Regards,
-- Al

Al, would you mind a brief phone chat with me? 

Thank you!
Mark
305-775-3020
I use a Whest and find that I enjoy the sonics with as much gain as I can use for a particular cartridge to have the resulting volume comparable when switching source from CD to turntable on my preamp.  I've gone as high as 65db with medium output MCs to great effect but when I go too high, it's obvious to my ears that I am overloading my pre-amp.  With your cartridge, I'd live with 65db and see what you think over time. I don't know your preamp but having owned two Whests now, I consider them pretty quiet. Maybe go to 72db just to hear what max gain sounds like too, it'll be a reference. MY guess is you'll be most happy at 65db on the Whest, and less volume on the preamp.
Al, would you mind a brief phone chat with me?
Thanks, Mark, but my preference is to participate just via the forum.  Hope you'll understand.

Also, I'm not sure that I can add anything at this point beyond what I've posted above.

Regards,
-- Al
 
No problem Al, thank you very much for your valuable input so far!  I have completely rearranged the rack, components, and cables to move the phono stage as far from any other power supply as possible, and I am being particularly careful to route cables smartly. I'll report what I find when done.

Thanks Oscar, I think I will do that eventually as well, start at high gain and work downward.

ill report my findings soon.


So, I moved the entire rack around.  Hours of fun!  You can see what I did here https://systems.audiogon.com/systems/5421 if you look at the 1st and 2nd photos, you'll see the changes.  It doesn't look as pretty as it did before, but perhaps I can refine it a bit.

I was super careful to keep the signal cables away from power cables, and I was successful to a very large degree.  There is not a single signal cable that touches a single power cable.  They get close only once or twice, and even then it is an intersection that does not touch, nothing parallel.

I noticed the hum get completely eliminated, probably by separating the phono stage from the amplifiers, thank you Almarg for this suggestion.

The hiss is still there, but I do have an older tube preamp, is this just the way it is?  Besides, I can no longer hear it at listening position.  Is there a way to quiet down the LS-25 a bit more?

I am still investigating the right gain setting on the phono stage,  I think I will go to maximum, listen, minimum, and listen to define the boundaries, and then find the right point in between.

The other bonus to this process was that I think the system is more well defined.  Generally better in the detail than it was before.  Maybe the phono stage was getting more interference than I thought from the location near the power amp?  Maybe I had some power cables messing with the signal cables, either way, it is sounding really good.  Now to figure out those gain settings...

Sounds like good progress!

If the remaining hiss varies with the setting of the volume control, as it did previously, the fact that the volume control mechanism is located not far from the "front end" of the preamp’s internal signal path would seem to suggest that the hiss is probably being introduced primarily by either the phono stage or by a ground loop between the phono stage and the preamp.

A quick experiment that may be useful would be to disconnect the XLR cable that connects the phono stage to the preamp, and assessing the hiss under that condition. As well as trying the cheater plug experiment I had suggested.

Also, try disconnecting power from the DAC and the Mac Mini, to verify that they are not radiating or coupling digital noise into the phono stage or the preamp.

Good luck. Regards,
-- Al

I tried the Whest at 72db gain, and it overloaded the preamp.  loud popping sounds from the speakers... Ouch!