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Cartridge gain overload - please explain

I am using a Lyra Delos on a JA Michell tecnodec, a Whest .30R phono stage,
an ARC LS25 linestage, ARC VT100 amp, and Rockport Mira Monitors.

I recently added the Whest to get more gain because the ARC PH3SE with 54dB was not enough, especially because the LS25 gives just 12dB of gain to single ended sources. By switching to the Whest, I was able to get more gain right from the phono stage, and also an additional 6dB from running balanced into the LS25.

Because I was coming in from a under-gain situation, I started with the Whest set to 66dB, thinking a bit more is good, and I could just turn the volume knob lower on the LS25. But there was that record pop / loud static discharge sound which was actually cartridge gain overload. When I changed the gain settings to 60dB, the problem ceased.

My question is, why does this happen? Whats wrong with an extra 6dB from the phonostage and just a little less output from the linestage to compensate? In my mind, that seems like it would work fine.

I would like to know more about this. Perhaps there will be even a benefit if I switch down to 55dB? But that seems counter intuitive, because I was getting too little gain before and I had to really ramp up the volume on the line stage, which caused a lot of noise.

thanks,
Mark
marktomaras
zd542
5,339 posts
 
Mark,

The one thing I see in your last post that gives me pause is your reference the position of your volume knob. I think you may be focusing too much on that. Given that you can adjust the gain on your phono pre and the LS25, your volume knob can be almost anywhere and not, necessarily be a problem.

If it were me, I would get the phono preamp dialed in first. You ask what you should be looking for sonically. The first thing, of course, is to get your gain set low enough to where there is no distortion. From that point, its up to you. Most people like to try a verity of settings and just pick what sounds best to you.

Once you find a gain setting on your phono that you like, then set the LS25. Just pick a setting that gives you the best control for how you like to listen to music. I wouldn't worry too much about the actual position of the volume knob. Once you take care of the gain issue with the phono, I don't see you having any problems with your LS25. Your phono preamp is a line level source. You can expect the same type of performance you are getting from any of your other sources.
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lewm
13,030 posts
 
There seems to be an underlying assumption that the Whest phono stage is a truly balanced device. It may have XLR input or output jacks, but I find no evidence anywhere to say it is balanced. For that matter, the same holds true for the ARC, altho in the latter case one can probably find out. Whest are so mysterious about their products that one can only go on the absence of a claim on their website, rather than on any real circuit description. Well, they do not claim that any of their products are balanced, so I am tending to think they are not. Ergo, subtract some db from your estimates.
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almarg
9,670 posts
 
01-18-13: Lewm
There seems to be an underlying assumption that the Whest phono stage is a truly balanced device. It may have XLR input or output jacks, but I find no evidence anywhere to say it is balanced. For that matter, the same holds true for the ARC, altho in the latter case one can probably find out.
Hi Lew,

I don't think those assumptions are being made. What is being assumed, which seems to be consistent with both the OP's findings and the specs on the various components, is that changing from an unbalanced connection between an ARC PH3SE phono stage (which only provides unbalanced outputs) and an ARC LS25 line stage, to a balanced connection between the Whest phono stage and the same ARC LS25 line stage, results in a 6 db increase.

Given the LS25's gain spec, which (quoted verbatim) is ...
Gain -- Main Output: Selectable for each input: 18db, 12dB, 6dB Balanced output. (12dB, 6dB, 0dB SE output)
... that would seem to be within reason, regardless of whether or not any of the components have internally balanced signal paths.

Also, looking at the schematic for the LS25 (which is shown at the ARCDB link that John provided earlier), it does appear that it has a balanced internal signal path.

Best regards,
-- Al
dover
2,243 posts
 
I think somebody is confused here.
Using the balanced OUTPUT of the LS25 increases the gain by 6db.
I presume you plug the phono stage into the INPUT, at least I hope so.
There is nothing to suggest that using the balanced INPUT on the LS25 increases the gain.
Changing to a balanced INPUT on the LS25 does however increase maximum input from 14Volts to 28Volts which could give more headroom.

Funny thing is my old Quicksilver preamp could take 60volts up its jacksie on single ended before overload, and my 1960 Marantz 7 can take 30volts up its jacksie without overloading. I guess they dont make preamps like they use to.

The other thing I dont understand is that my Marantz 7 has 60db of TOTAL GAIN INCLUDING LINE STAGE and I can use a Koetsu with 0.4mV output with no noise and gain to spare. What has happened to modern tube preamp design - more noise, less gain and lower overload margins.
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