Rockhopper M^3 - The Review - Page 9

What About...

What about adjustable gain - is it required to properly drive a range of phones - Senns, Grados, ATHs and Denons??? Is it needed to use the OPA637s, successfully?

And... are the OPA637s really needed? And... if so... what is the minimum gain and voltage required of the PSU to safely use them?

I've experiemented with them in my Maxi Moy, and found they have only very, very slightly greater detail / resolution than the OPA627s, which are superb by themselves. I'm not sure they're really noticeably better than the OPA627s... and... they have some design requirements the OPA627s do not.

I've used the m^3 to drive senns and grados and iems and never had any problems with gain.

and I havent done any experimentation with opamps so I cant really help you there. Supposedly, opamps dont really have a big effect on the SQ. YMMV of course

I have a gain switch on mine. Gain of 5 (or 6 I can't remember) and the other at 11. If you decide to use the OPA637+627 then you will need a gain higher than 5 otherwise the 637 could oscillate and interfere with SQ. I find the gain settings useful for driving different headphones, depending on their impedance and sensitivity. The M^3 is usually set to 24V if you get it from Rockhopper, which is a good voltage setting for the OPA637+627. Should you decide to get a higher volt M3 built, you would have to use different opamps depending on the exact voltage. All of this info can be found on AMB's website where Ti lists all the opamps and their respective optimal voltage values.

BTW, BOTH the OPA637 and the OPA627 can be used simultaneously on the M3, and it's a great combination I've found.

As for your other question about the layman choosing the M3 over the Gilmore Lite or Caliente. Well, the reason why most have been hesitant to answer that directly is because they likely have not tried all 3.
Why did I personally go for the M^3? I based it all on what I read on Head-Fi and other forums. I also compared the specs of all three (and also with the GS-1). In the end, for the price, the M^3 offered the most...for example, it had the highest power output of all of them (especially compared to the KICAS), it had an active ground channel, it had a customizable sound (with opamps), it was a tried and tested design known to yield great results, it was compared favourably to really high end amps like the Dynahi and GS-1. It also tested better with RMAA than the Dynahi and Beta22 across the board. Then factor in the price...and you really do get a winning combination. Ideally, I'd have tested all the amps out and made a decision from there, but TBH, I actually found that the opinion of other owners coincided with mine when I got the M^3 and it turned out to be better than I expected.

Yeah...

Yeah... you're findings and experience seem consistent with my research. I'd just like to find someone who's compared the M^3 to the KICAS, which apparently is superior to the PPA, as well as a lot of other amps.

RE: your gain adjustment... it sounds like you have a switch with two options (toggle switch) vs a POT with variable gain adjustment - correct? I would think a good switch, or two headphone jack circuits (one hi and one low) would be superior to a POT (less likely to develop noise issues).

Have you found it necessary to use it much with low vs high impedance phones - especially Grados, and Denons at the low setting??? I would think that with the amp's very, very low impedance... that a variable gain switch might not be really necessary - that a moderate setting of about 6, or 8, might be fine with all phones. And... I wouldn't think many would be so inefficient that a higher setting would be required.

My interest in trying either a Caliente, or M^3 is growing... if I thought either could provide a SQ close enough to a "tube" sound (even with a tube buffer like the GF B-283), and drive all types of phones really well. I know it can be done... because my Maxi Moy (with OPA627s) and GF B-283 combo is so close - just needs a wee bit larger soundstage, and perhaps very slightly more resolution.

The PPAv2 is a very good amp, with a sound/SQ close to the M^3 but more neutral and brighter/colder. I haven't seen anyone compare the KICAS with the PPA(v2), so I'm not sure if it's better.

Yes I do have a switch (so 2 gain values) as opposed to a pot. I'm not sure if having a pot would necessarily degrade SQ, but you'll have to ask Ti (AMB) or someone more technically versed to verify.

TBH, I haven't found it necessary. However, switching to low gain with low impedance headphones does help me use a wider range on the volume pot.

I know the M^3 with the OPAs is a warm/dark amp and I've read the same about the Caliente's sound signature. But the M^3 is a better amp technically speaking.

Check out the KICAS thread, around page 15 or 16 there are some brief comments comparing the Caliente with M^3, I think Sbulack heard them both maybe you could ask him directly?

I was trying to decide between these two amps myself, I concluded that M^3 might be the superior amp but I went with the Caliente for fun sound, with price and availability also influencing my decision.

M^3 + PSU + shipping would be around $600, Caliente is $325 shipped. Even if the M^3 is superior in some aspects, the Caliente represented better value for me.

but m^3 with psu is quite different from the m^3, without the psu the price diference isnt that much

^True, but the M^3 benefits from the PSU and the Caliente didn't, according to what I read.

Agreed. It's good that you brought up pricing. At twice the cost of the KICAS, one would expect the M^3 to be a better amp and so it doesn't take anything away from the Caliente. In fact, considering how sbulack actually preferred the Caliente to his previous M^3, I'd say it represents an excellent value at the price point.

Yes...

Yes... I saw that... which is why I'm hesitant about the M^3... thanks for reminding me of those comments.

"What drew me to the Caliente was the combination of:

1) The size, unity and stable definition of the soundstage it presents and the clear definition of the placement of every musical voice within it.

2) The enviable dynamic range, in which even the faintest musical event is fully formed (spatially and timbrally), and the strongest musical events are presented in their fullness without stepping on other concurrent events or taking on any limitations or (even timbral) distortion (other than that imposed by the recording or production).

3) The lifelikeness of all musical voices - human, instrumental or otherwise. It can be downright spooky how present people and instruments can sound using this amp in my "Bedside Rig" - in my sig.

4) This amp produces THE BEST presentation of a variety of styles of Rock and Pop (through HD650's) than any amp I have ever or currently own... The Caliente bests my "main rig" Mapletree for what accounts for a substantial subset of my music collection.

5) The depth, transparency, well-formedness and amount of bass that is provided by the Caliente is just a sonic delight to my ears. Because of how transparent and well-formed the bass is, it's not too much, even with the "dark" or "prominent bass" of the HD650... the abundance of gorgeous bass is an aural thrill that I have experienced with no other amp I own or have owned. Given the depth of the bass, I feel it down to the bottoms of my feet. In addition to gorgeous highs and lush, rich lifelike mids that other amps envy, the Caliente provides truly visceral bass - yep, actually felt throughout the viscera.

Conclusion: The Caliente represents great value, a BIG bargain compared to the list of stationary amps I own or have owned, is very versatile across genres and phones with different voltage/current demands, and offers THE BEST presentation of a variety of styles of Rock and Pop of any amp that I own or have owned. - Besides the Mapletree in my sig, I HAVE OWNED (and sold off) a PPA w/ Larocco Discrete Buffer and a Rockhopper M^3 with Blackgate power caps and high-bias for max current - both powered by a 24V STEPS PSU. If only the Caliente had been available back in late 2003 when I was buying my first amp (the PPA but without the discrete buffer and powered by a 24V Elpac)."

- Sbulack

From those comments... I assume he preferred the Caliente.

Pricing is a big influence as is availability, amp builders would move more amps if they had an ebay store with a "buy it NOW" button.
Look at Keces and Little Dot, so many times I had to stop myself from ordering because I was waiting for Rockhopper or Purity Audio to make their amps available.
I got in the KICAS group buy, but I keep staring at the Rockhopper M^3 that is about to be released, any day now...

I'm Considering...

I've been considering another builder also - which will adapt it to my preferences (e.g. particularly the case, etc.). If I were to get one... I'd want it to have a "commercial" look in brushed aluminum.

Based on all the research... other than the case... I've pretty well concluded the stock M^3 with the OPA627s and the S11 PSU is pretty much the "sweet spot." Possibly with a gain switch - but... not even certain of that. Adding various other options, doesn't appear to really improve the sound much at all... and from what I've learned the addition of "high-end" caps makes no difference - so that isn't necessary.

But... my biggest hesitation is that the Caliente may actually provide equivalent, or better, sound for $300 less.