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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
marktomaras OP
544 posts
 
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...

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almarg
9,670 posts
 
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

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

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