[raduray]

Last spring I discovered this site and have subsequently spent too much money, though I was able to recover some of it by reselling some of the items on the For Sale forum.

Some months ago I picked up a used LaRocco PPA based on the original PPA board and with LaRocco Diamond Buffers and 627 opamps. It was powered by an Elpac PS. This was coupled to my HD650 and gave me excellent performance.

But I had read about the M3 and, although pleased with the PPA, could not resist the urge to check one out. So, just recently, I purchased a used Rockhopper M3 with a STEPS PS in a separate box. It came with AD843 opamps installed and with a set of 627/637 for rolling experiments. It also has a crossfeed circuit that, so far, I've left turned off.

Both boxes are very well constructed, but the M3 set up is significantly larger. Also, the M3 combo was 50% more expensive.

As to the sound, I do not have a trained ear, but can report the following preliminary reports. The M3 has a deeper bass extension, but is a bit muddier (not as crisp) at the low end than the PPA (Jewell's latest release on Rhapsody). On the treble side, the M3 is warmer and is less fatiguing (Beethoven Violin Concerto, Kathleen Battle singing Mozart).

I think that the M3 will serve better for long listening sessions but the PPA is probably more accurate.

I wonder if anyone can explain the warmer sound of the M3 vs the PPA. What exactly is going on with waveform? Is there some sort of distortion or harmonics that warm up the sound, and is that a result of FET over bi-polar output stage.

Has anyone set up a signal generator and scope and run some sine waves through both these units?

Radu

 

[ATAT]

M^3 is MOSFET output, the PPA is chip buffer, PPA v2 is discrete BJT output. (i think)

That would be why.

 

[SK138]

That's an excellent question. I too sold lot of my amps (Woo3, Mapletree, Gilmore, HP100A, etc.) to simplify my listening enjoyment with W5000. I have very neutral (almost dry sounding), and detailed source (MF A3.24 DAC). Having M^3 in my system chain is great for overall synergy with often consider "bright" W5000. The AT HA5000 amp is also based on MOSFET design similar to M^3...accept the price of HA5000 is over $1k.

As you stated...with M^3 amp you can listen to it for long period...and that's exactly what I like about it...to get lost in my music

 

[amb]

Quote:

Originally Posted by raduray I wonder if anyone can explain the warmer sound of the M3 vs the PPA. What exactly is going on with waveform? Is there some sort of distortion or harmonics that warm up the sound, and is that a result of FET over bi-polar output stage. Has anyone set up a signal generator and scope and run some sine waves through both these units?

Both the PPA and the M³ measure with exceedingly low distortion and have a straight-as-ruler frequency response. Have you looked at the Specifications section at the M³ website? There are benchmarks and test results posted there. Also check the PPA's test results at tangent's PPA site. These measurements cannot fully describe the "sound", of course, but the difference you hear is definitely not because one amp has less distortion than the other. The distortion of the headphones dominate over the amps by several orders of magnitude.

Sometimes the difference could be partially psychological. If someone tells you that amp A is supposed to sound "warm" and another is "analytical", one could probably be influenced into "hearing" those characteristics. Let many people have similar comments and these amps "acquire" a reputation of a certain type of sonic character. I am not saying that this is necessarily the case here, and there has always been debates about the sound vs. the measurements. But I wonder whether in most cases these differences might disappear when the listener is subjected to a blind test?

 

[hciman77]

Quote:

Originally Posted by amb Sometimes the difference could be partially psychological. If someone tells you that amp A is supposed to sound "warm" and another is "analytical", one could probably be influenced into "hearing" those characteristics. Let many people have similar comments and these amps "acquire" a reputation of a certain type of sonic character. ...I wonder whether in most cases these differences might disappear when the listener is subjected to a blind test?

I know I use this a lot but the thought-provoking "Do all amplifiers sound the same" article caused me to re-evaluate my belief system in this context. This is in itself an act of psychological manipulation i.e you read a credible article that implies that all amps sound the same and what happens you believe that all amps sound the same - brilliant really !.

In the old days (1970s when I first got interested in hifi) an amp was just a straight wire with gain anyway.

 

[purk]

I have a maxed out PPA (v.1) with Larocco Diamond buffer and steps PSU...and love it. IMO, the PPA and M3 sounds remarkably close....and I will be happy with either one.

 

[raduray]

I decided to try the OPA627/637 in the M3 described at the top of this thread. I found them significantly more forward (bright) than the AD843. Listening to Linda Ronstad's Mas Conciones album was fatiguing after a while with the 627/637 but the sound mellowed out when I went back to the AD843's. I had read that the 843's shone with female vocals, and it's true. The downside is that you lose a bit of the tightness in the low bass.

In this case I don't think the difference is due to the pshychological power of suggestion AMB mentioned. It may be that a lot of the differences between the PPA and the M3 I mentioned earlier was due to the different op-amps.

I'm going to leave the 843's in the amp.

Radu