Stack Audio footer was fifth or sixth ones that I have tried in the past three years. Previously I like Orea Bordeaux over VooDoo pods under PSA gears, then I liked XSSH metal footers with ceramic bearing under transport and DAC. I have also tried Herbies gliders.
Once Stack Audio arrived, it became the clear favorite under all components, including Gryphon D333 amp and PowerZone. The one makes the most difference is AUVA100 under FR30, but now I am using a combo of XSSH and Stack AUVA100 under FR30, a great combo for speakers that gave a little tighter definitions than with all Stacks.
I have replaced Mapleshade giant brass cones (better than Stack EQ) with four AUVA 100 under Grimm MU2 own feet, and I like it quite a bit better. In fact, I like the SQ better than PMG 512 even.
Sorry did not respond to my earlier post a lot sooner. So many comments were made - which included equations. By posters much more knowledgeable than I am.
The 30 watts class A voltage in the m400 amp refers to its bias voltage. So I googled it and this is the response which AI gave me. Hope this helps:
The way I read it, yes, the bias voltage stays the same, but the amp will still try to increase current if the load drops to 4 ohms. If the current increases some, then the wattage will increase. How much is the question.
@Chris_Brunhaver can possibly measure this when he is not too busy putting all of these together with their team.
Yes the current will increase from 8ohm to 4ohm load, but it will increase in class A/B not class A. The class A power will be cut in half on a class A/B amplifier.
“You are conflating the amplifier’s total voltage capacity (its total Class A/B envelope) with the physical limits of its static bias current.”
Since you are much more knowledgeable than I am in this area, I had to look these terms up.
In a stereo amplifier, the total voltage capacity refers to the maximum peak-to-peak output voltage the amplifier can deliver to each channel, considering its Class A/B envelope — the range of output voltage swing allowed by the power supply rails and the amplifier’s design.
In short, static bias current is the DC current that keeps the stereo amplifier’s output stage ready to amplify without distortion. Proper setting balances low distortion, stability, and thermal management, and is critical for both sound quality and component longevity.
All of these above relationships depend on several variables related to the amplifier design. The M400 uses a newer design philosophy to achieve PSA desired results. This implies the actual Class A wattage into 4 ohms could be slightly different than simply dividing by 2?
This could be true if PS audio is using some sort of dynamic bias, but this very uncommon in class A/B amplifiers. I know that Krell uses Ibias which monitors the output stage so it takes the impedance of the load into account, their old sustained plateau bias did this on the input stage, so it didn’t take the load impedance into account.
I have been using four Stack EQ1 under Gryphon D333 since day one. But one time I took them out and I remember there was a slight loss on the preciseness of imaging, and bass was not as well defined. It was not easy to place EQs back under its feet so I only did it once. Gryphon amps are extremely well made so I was a little surprised the footers did improve SQ a little.
When I had PSA M1200 amps, XSSH footers, and later Stack EQ1 did made a noticeable improvement. However, these footers help transports and DACs more than amps from my experience. I even use metal footers under some power plugs too, there are various degrees of success on plugs. Some well made plugs such as Stealth power cords, I could not hear much SQ difference.
No, this is correct. The amps double power into 4 ohms vs 8 ohm (and are 2 ohm stable but don’t double again). However, for the reasons mentioned (the static bias current) the class A watts are proportionally less into lower impedances.
It’s not something I would get super hung up on (all of the amps sound really great) but, if you want the largest class A range, the monos have much more of it.
You’d be surprised at how loud a watt is though . Buy a multimeter and try playing a test tone at 2V or 2.83V. It’s loud & most of an amps power is just for dynamic peaks.
I haven’t been in contact with an ML2 since the late 70’s. The HiFi store I worked at (gave my paycheck to) was a Levinson dealer. Best amp available for a long time but much has moved on, including Mark Levinson and John Curl, the designer.
The ML2 still sells used for about what it originally cost, $4.5k, for the few that are still out there. Technology and component advances would probably put these beasts well in the rear view mirror. I soon will have the M800’s to test this opinion. Anyway, thanks for putting me in the
Way Back Machine to a heady time in HiFi.
How many modern amplifiers with a linear power supply have regulated voltage rails, I’ll bet if you compared a totally rebuilt Mark Levinson ml2 with a similar power rating not much has really changed.
M400’s, PMG preamp, Aurender N30SA and NH10, Berkeley 3P DAC. Had to improvise to side by side, because the M400’s can’t be stacked on my special amp holder. This is before adding the OREA feet.
Anita listened to several of her songs and she says they are keepers. That is about as good a recommendation as I can give for now.
P.S. She is still listening down in my stereo room for the past 2 hours. She likes them vs the Krell’s, which actually were already very good.
My Krell Solo 375XD monoblocks are that iBias type and their Class A is 375 watts at 8 ohms, and 600 watts at 4 ohms. Not double but not cut in half either. I now have the M400’s to play with and they provide plenty of volume from the FR30’s so far.
