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..
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?
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?
- 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
- 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
- So given 1 and 2 try a step up -- you may be surprised as I was!
- ...
- 49 posts total
@rauliruegas-
All system integration decisions involve trade-offs.
I do not have even a smidgen of the knowledge necessary to parse out the differential effect of load impedance on the various elements of the analog reproduction chain. I only know that I was able to hear the difference between very small variations in the load resistors placed across a very high quality SUT. Therefore, I've opted for a solution that eliminates the variables associated with an SUT by going w sufficient gain in the phono stage to allow a 0.25 mV LOMC to perform well. Maybe if I had some knowledge of electrical engineering and circuit design, I would come to a different decision. |
Raul & Michael (Swampwalker), you’re both right. Regarding the multiplication effect Michael mentioned, the transformer will of course step down the resistive component of the input impedance of the phono stage as it is seen by the cartridge, but at the same time it will step up (multiply) the input capacitance of the phono stage and the capacitance of the cable connecting the SUT to the phono stage, again as seen by the cartridge. That will tend to work in the direction of lowering the frequency and increasing the amplitude of the resonant peak in frequency response resulting from the interaction of cartridge inductance and the load capacitance applied to the cartridge. In the case of LOMCs that peak occurs at RF frequencies, but may affect sonics to the extent that the design of the phono stage allows audible frequencies to be affected by RF energy that is fed into it, and to the extent that the bandwidth of the SUT allows frequencies in the vicinity of that peak to be conveyed to the phono stage. Atmasphere has made similar points in a number of past threads. |
Don't mean to hijack this thread but this has me wondering. Is it worthwhile to add a SUT just to get about 12 dB of gain? I have a cart that puts out 1mv (Zyx 4D Mono) so it's just in the middle of the range - a bit low output for a MM stage, but high enough that it clips if I run it through the MC on my phono stage (Doshi Alaap). I'm using the MM stage now, but it seems to lack some dynamics (don't notice any extra noise though). I've emailed with Dave Slagle about making a low output SUT, but it seems like a lot to spend for only 10-14 dBs of gain, and maybe no corresponding sonic benefit. Anyone out there encountered this situation? thanks |
I believe it would make sense. Some of the best phono stages use a transformer gain stage first to match the cartridge. Take for example the Tenor phono stage which has a 4 Times (ie 6dB) transformer stage as the first step in amplification http://www.monoandstereo.com/2016/09/tenor-phono-1-review-by-richard-h-mak.html |
- 49 posts total