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On Step Ups and the Importance of Managing Gain

The past several weeks have been some of the most eye opening in my entire audio journey. Despite over 30 years listening to LPs across a range of setups it seems I've only just stumbled across one of the secrets of analog reproduction -- the step up transformer AKA the importance of managing gain across the analog reproduction chain.

To understand what I mean you need to start with an understanding of my gain cascade prior to my most recent changes. My cartridge is an Acoustical Systems Palladian which is a relatively low output MC at 0.33mV. I've been running it into an ARC Ref 2SE Phono and then an ARC 40th pre. Both are connected balanced so the gain is 51dB (for the phono stage) plus 12dB (for the pre) = 63dB at the LO gain setting -- I tried listening to the HI gain (74dB) setting on the phono but found the added FET amplification added an edge to the sound, amplified hum and restricted dynamics. I'd therefore learned to live with having the Ref 40 volume control on the high side (about 70-80% of range) and "thought" I was getting good sound - great clarity, sound-staging and frequency delineation.

However with a pending upgrade in my phono stage to the VOSS phono, a pure 40dB only single ended affair, I was forced to add a step up to my setup. I've always sworn off the added complication and additional switching and cables so had assumed it would not do anything to improve things. How wrong I was. The model I have is the Music First Audio Classic V2 in a custom configuration built for me with two inputs (one for my mono arm and cartridge) and fixed 20dB gain (1:10 ratio). It also has a three way ground lift switch so any hum issues can be addressed at source (which works btw). At about $3K it's not cheap (and MFA have cheaper options) but in the scheme of things actually much less than the list price of the interconnect I needed to add to connect it to my phono stage (so in the context of my system a stone cold bargain). 

My gain cascade is now 20dB (step up) plus 45dB (phono, now single ended) plus 12dB = 77dB and the volume control is at 40-50% of range. Once I'd realized that running a step up into 200 ohms is not going to work at all and switched the ARC Ref2SE to 47K I was off -- and was I surprised! All of the sudden the soundstage opened up by 50% side to side, front to back and up and down. Dynamics on individual instruments suddenly snapped into focus and the overall presentation was transformed in a way I would not believe possible. One instance can serve as a sense of what I mean -- the two opening cuts on Joni's Hejira, "Coyote" and "Amelia", are mostly similar sounds layered over one another and can be pretty hard to sort out. With the new step up in place it's as if everything now makes sense and each instrument is positioned in space perfectly in location and scale with all the others.

So what's my take away and potential advice to any reading this?
  1. High gain (i.e. 60dB plus) phono stages are, as we all know, problematic so if you can avoid going that way consider looking into it, BUT
  2. Don't "push your gain" i.e. try to under drive a stage, you may not know it (as I didn't) but trying to amplify .33mV with "only" 51dB is probably losing a lot of detail into the noise floor of your amplification stage and/or giving you problems down stream if gain is set too high
  3. So given 1 and 2 try a step up -- you may be surprised as I was!
Not sure if this experience matches with others and would love some perspective from amplifier designers as to why I may have had such a bad (in retrospect) experience with my prior gain cascade.
128x128folkfreak

Showing 5 responses by rauliruegas

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rauliruegas
12,851 posts
 
Dear @folkfreak : Yes, I agree with you that the SUT is a valid option but not necessary thwe best one for the cartridge signal. As you said it needs additional IC cables with additional connectors where the signal must pass.

I'm not against SUTs per sé, as you said is a valid option but there are better options. 

Problem with active high gain stages resides in its design where the designer has to have a real deep knowledge levels and skills to that kind of " problematic " design and that's why exist not many active good designs and when the design comes of tubes the " solution " is a SUT inside that tube design because tubes levels of noise preclude to design an all tube active high gain phono stage. Other designers of tube electronics decided that the first gain stage be handled by SS devices.

The use of external SUTs can produce in the audiophiles several questions and normally came by the cartridge needs of load impedance when the LOMC cartridge is no sensitive to changes in load impedance as I staed here and where @almarg gaves a wider explanation about and where other gentlemans in other threads repeated the same several times.

Of course that always exist people that read but understand nothing, just never learn. Are ignorants for say the least.

Anywa, again SUT is a valid option.



Regards and enjoy the MUSIC NOT DISTORTIONS,
R.


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rauliruegas
12,851 posts
 
Dear @folkfreak : Not really, the best phono stages has not transformers in its design, are active high gain designs.

Tenor is not of the best out there. In its design the transformer is a must to has but this transformer does not means is one of the best because it's not and for very good reasons.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.
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rauliruegas
12,851 posts
 
Dear @swampwalker : The cartridge it self is no sensible to load impedance. What is sensible to load impedance changes si the phono stage dpending on the quality of that design..


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rauliruegas
12,851 posts
 
Dear @folkfreak : What defines the maximum is the phono or line stage overload figure.

Now, the whole subject it's not if your SUT is outstanding ( because it's not. ), it's a good SUT. A SUT is not a rocket science design. I'm not trying to diminish your SUT only to put our foots in the floor. I'm sure your SUT is a good design. I think I tested over 30 different SUT's over my audio life and many of them really good as the Denon 1000  or the top Technics where both has the wider frequency range I seen in any SUT but even that can't even a SS active design in this regards. The Denon is something to listen and to caryy because it weigths 10 fully kilos.

Anyway, What you are experienced tells me that the ARC designs are not up to the task against your new items. I posted " every thing the same " a fullfunction high gain unit beats its counterpart with passive unit as the SUT. EVERY THING THE SAME.

Problem is that you had not a really good design. It's not easy to design it.

Checking levels of quality performance alone needs better electronics designs.

Now, the very important subject is that you are satisfied as never before, good ! !


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.
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rauliruegas
12,851 posts
 
Dear @folkfreak : Agree with @lewm in that you can't diminish an active high gain phonolinepreamp..

If I remember there is other thread that appeared months ago with the same problem as you with ARC electronics ( I can't remember if was you in that thread. ).

Anyway, problem belongs to ARC design, weird as @almarg pointed out. Normally inside a same manufacturer trys that its models can stay matched when used together. here with the HG option the line stage puts in clipping condition.

Everything the same a high gain phonolinepreamp always outperforms the one passive one ( SUT. ), even this SUT's can makes very good job.

The main disadvantages of a SUT are the frequency range limitations at both frequency extremes ( especially in the low bass. ) and noise levels.

I own  an active high gain phonolinepreamp and rigth now I'm using/testing through a SUT and performs good.

I'm speaking of a full function phonolinepreamp that always beats separated phono stage and line stage. It's better a phonolinepreamp it does not matters if use a SUT to cope LOMC needs.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.


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