[boozcool]

FWIW, having owned and extensively tested both the M^3 and Caliente, I recently upgrade to a Stello HP100. Although the M^3 and Caliente were impressive amps in their own right, I found the HP100 to offer a solid improvement across the board
For me, the M^3 had great synergy was a lot of cans, both high and low impedence, but there were also quite a few which did not have such great synergy and sounded significantly better with other amps. For example, my Denon D2000s had better synergy with my KICAS Caliente, while my Beyer DT770/80 Pros sounded significantly better with the M^3
The HP100, though, definitely had better synergy with a larger number of cans. I believe one of the main reasons is the fact that this amp offers more features which make it very versatile and gives you the ability to throw just about any cans you can think of at it
For power hungry cans, there is a high/low gain switch. More interesting, though, is the filter switch which has the ability to either tame some overly bright cans, or help darker cans shine. On top of everything, even the voltage is selectable, so no voltage worries wherever in the world its used
I've seen prices of an M^3 go from anywhere between $320 to $570 with and/or without the separate PSU. IMHO, though, the HP100 is just in another league, and easily worth its weight in gold
Just my two cents

 

[Shahrose]

Quote:

Originally Posted by boozcool /img/forum/go_quote.gif FWIW, having owned and extensively tested both the M^3 and Caliente, I recently upgrade to a Stello HP100. Although the M^3 and Caliente were impressive amps in their own right, I found the HP100 to offer a solid improvement across the board For me, the M^3 had great synergy was a lot of cans, both high and low impedence, but there were also quite a few which did not have such great synergy and sounded significantly better with other amps. For example, my Denon D2000s had better synergy with my KICAS Caliente, while my Beyer DT770/80 Pros sounded significantly better with the M^3 The HP100, though, definitely had better synergy with a larger number of cans. I believe one of the main reasons is the fact that this amp offers more features which make it very versatile and gives you the ability to throw just about any cans you can think of at it For power hungry cans, there is a high/low gain switch. More interesting, though, is the filter switch which has the ability to either tame some overly bright cans, or help darker cans shine. On top of everything, even the voltage is selectable, so no voltage worries wherever in the world its used I've seen prices of an M^3 go from anywhere between $320 to $520 with and/or without the separate PSU. IMHO, though, the HP100 is just in another league, and easily worth its weight in gold Just my two cents

The only problem here is that the comparison is unfair. I've found changing opamps in the M^3 changes the sound, often times, quite significantly. With some opamps I've found the M^3 a bad match with my headphones, while with others, very synergistic. I believe your impressions, but I can't say it's a fair assessment of the M^3, considering how variable its sound is, and therein lies its key strength IMO: the ability to tailor the sound.

That being said, which opamps did you try with the M^3?

 

[boozcool]

When I originally bought the M^3, it came with a whole bunch of opamps (Analog Devices AD8610 x3 and Linear Technologies LT1122 x3, LT1115 x3, LT1028 x3)
I also ended up buying a pair of OPA637 opamps separately since they were highly recommended
I found the AD8610 in the M^3 sound a bit thin with all the headphones tested, and ended up using the OPA637 on the L/R and LT1028 in the center in the end
But to be honest, since it took a minute to switch the opamps, its difficult to say with absolutely certainty that there was a significant difference between the opamps

I remember hearing from the previous owner that he didn't think "the op-amps are as important/influential on the final sound as other op-amp based amps. The M^3 only uses them for voltage gain duty. The output is actually discrete"

Since the HP100 is a full discrete, class A headphone amplifier with a host of other components not found in the M^3, I wasn't totally surprised that it offered a clear, solid improvement across the board

 

[Shahrose]

Quote:

Originally Posted by boozcool /img/forum/go_quote.gif When I originally bought the M^3, it came with a whole bunch of opamps (Analog Devices AD8610 x3 and Linear Technologies LT1122 x3, LT1115 x3, LT1028 x3) I also ended up buying a pair of OPA637 opamps separately since they were highly recommended I found the AD8610 in the M^3 sound a bit thin with all the headphones tested, and ended up using the OPA637 on the L/R and LT1028 in the center in the end But to be honest, since it took a minute to switch the opamps, its difficult to say with absolutely certainty that there was a significant difference between the opamps I remember hearing from the previous owner that he didn't think "the op-amps are as important/influential on the final sound as other op-amp based amps. The M^3 only uses them for voltage gain duty. The output is actually discrete" Since the HP100 is a full discrete, class A headphone amplifier with a host of other components not found in the M^3, I wasn't totally surprised that it offered a clear, solid improvement across the board

Being fully-discrete is not an absolute criteria for improvement. There are opamp-based amps that are better than discrete ones out there and vice versa.

 

[K3cT]

The HP100 also costs a bit more than the M^3 and S11 PSU though so a definite improvement is to be expected I guess?

Anyway, comparisons between the M^3+S11 and Mini MAX anyone?

 

[doping panda]

Quote:

Originally Posted by Shahrose /img/forum/go_quote.gif Being fully-discrete is not an absolute criteria for improvement. There are opamp-based amps that are better than discrete ones out there and vice versa.

x2. It all depends on the design. Discrete doesn't necessarily mean better. A well-implemented opamp design is easily as good as a good discrete design. Opamps have some characteristics that make them very good for certain applications that you won't be able to beat without a very good discrete section.

Quote:

Originally Posted by K3cT /img/forum/go_quote.gif The HP100 also costs a bit more than the M^3 and S11 PSU though so a definite improvement is to be expected I guess? Anyway, comparisons between the M^3+S11 and Mini MAX anyone?

Price isn't an indication of quality either. With commercial gear, there's mark-up, overhead, etc. that can make the price of a product vary significantly depending on which company produced it and which dealer sells it. In general, diy gear offers better value because the designs are open, the exact cost of parts is known, and the builders aren't necessarily motivated by profit margins. I haven't heard the HP100 myself so I can't say how it would compare to the M^3+S11. Hell, I haven't listened to the M^3+S11 enough to have a well-formed opinion, but what I little I heard was good. I'm just speaking in general terms here.

 

[boozcool]

I definitely agree
The quality and type of components of an amplifier are ( usually

) also a criteria for improvement
According to the manual which comes with the HP100 http://hifi500.com/imgs/HP100_manualEN.pdf
Class A Operation discrete circuit
HP100 has adopted pure class A operated discrete push pull circuits
Super low noise J-FETs are used for the input stage of the preamplifier section
The output for the preamplifier as well as headphone amplifier use pure bipolar transistors
Input impedance is designed at 1 Meg Ω
And all the circuitries except the DC servo control of the headphone section are full discrete circuit which is possible for only those high-priced preamplifiers.
Premium Quality Components
Main components of HP100 are world best WIMA polyprophylene capacitors and all the resistors are super low noise 1% grade level.
All input/output connectors are gold-plated connectors.
Decoupling capacitors are Audiophiler (by Mundorf of Germany)
Main volume is Blue Velvet form ALPS
Powerful Power Supply
25VA custom-made toroidal power transformer is used
And the regulation circuit has a very low output impedance (20mΩ@10Khz) to support the high quality of output power supply for the circuits with its super low hum and riffle characters.
Versatile and handy functions
Comes with Neutrik XLR type headphone jack to adopt special-made XLR type headphone jack as well as the normal headphones

 

[boozcool]

Oops, double post, SORRY!

 

[geremy]

when they say class A push-pull, do they really mean class AB?

 

[amb]

Quote:

Originally Posted by geremy /img/forum/go_quote.gif when they say class A push-pull, do they really mean class AB?

No. Class A is class A. You could have class A in a single-ended output stage configuration or in a push-pull configuration. All that is required to remain in class A is that the output transistors do not cut off at any point in the signal swing, while delivering the maximum rated output current into the load.

See a discussion about the various class A topologies (and their inefficiencies) in Nelson Pass' A40 amplifier article. Btw, the A40 is push-pull class A.

EDIT: By the way, an important point to remember is that a single-ended class A output stage will simply go into clipping if it's called to deliver more output current than its quiescent current. Whereas push-pull class A would not clip under similar circumstances, but simply fall into class AB operation. Also, "single-ended" here is not to be confused with balanced/unbalanced signal transmission and amplification. It refers to a specific amplifier output stage topology.

 

[Beefy]

Quote:

Originally Posted by K3cT /img/forum/go_quote.gif Anyway, comparisons between the M^3+S11 and Mini MAX anyone?

I'm sorry that I don't have time to explain all the minutiae...... but all things considered, my MMM is a marginally better amp than my MiniMax. The MMM did cost more.

IMHO, either of these amps is FAR better value for money than any of the commercial amps recommended in this thread.

 

[boozcool]

Thank you for the clarification, amb. Since the HP100 also operates as a pre-amp, is it possible when used solely as a headphone amp that it would be called to deliver more output current than its quiescent current? Or is that a function reserved for pre-amp applications?
Unfortunately I haven't had any experience with the MiniMax to offer any input, so I won't speculate

Beefy, could you elaborate a bit more. Compared to the HP100 (or Caliente), what did you particularly like about the M^3 to make a FAR better value for the money?

 

[K3cT]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I'm sorry that I don't have time to explain all the minutiae...... but all things considered, my MMM is a marginally better amp than my MiniMax. The MMM did cost more. IMHO, either of these amps is FAR better value for money than any of the commercial amps recommended in this thread.

Thanks, beefy.

I assume this is with the S11 PSU in equation yes?

 

[amb]

Quote:

Originally Posted by boozcool /img/forum/go_quote.gif Thank you for the clarification, amb. Since the HP100 also operates as a pre-amp, is it possible when used solely as a headphone amp that it would be called to deliver more output current than its quiescent current? Or is that a function reserved for pre-amp applications?

I don't know about HP100's internal design or operating points so I can't comment.

By the way, as mentioned in the Nelson Pass article I linked to, for a push-pull class A output topology, as long as the quiescent current is more than half the peak output current, it will remain in class A.

What this means for the M³ (push-pull MOSFET class A, default quiescent current of 80mA/ch), is that it would remain in class A with virtually any headphone load while playing at any practical listening levels. And it would be very deeply in class A when serving as a preamp.

 

[tomb]

I'd have to agree with Beefy (about DIY amps in general). From the looks of the HP 100's PCB, one would have to say the M3 has superior technology:

First, let me say that the HP 100 appears to have significant quality in the PCB design and parts installation. Very few commercial headphone amps look this clean, IMHO. It's a very nice piece of work. There's no wiring at all to speak of - just that pair of leads going to a Molex connector at top left. There could be a lot more underneath, but still ... from all appearances, an immensely clean design. And I'm very attracted to quality, completely packaged PCB designs, which is something we strive for in the MAX/MiniMAX amps.

However, when it comes to the actual circuit, it appears to me that a basic M3 would have to be considered superior. Looking at the pic above, the only thing mounted on heat sinks is that "two-stage" voltage regulator power supply at the top left. It appears to have two-channel dual JFET-input on the right, with the two-channel output stage on the left toward the volume knob side ... and there are opamps ... probably there to zero out offset in the buffer. No doubt some of the signal passes through those opamps on the way to zero-ing the offset (admittedly not much, probably). The fact that the output transistors are mounted directly to the board means that the Class A operation is limited - probably to 30ma. Further, those huge film capacitors in the input stages at right imply that the input is filtered, probably a prudent measure in a commercial amp/preamp, but they will definitely have a sound signature. That's a lot of conjecture, admittedly, but I think that's the way the circuit is setup from appearances.

Anyway, the M3 has none of that in its circuit path. The output buffers are fully heat-sinked MOSFETs that run a minimum of 80ma Class A current. Perhaps most significant, the M3 is an active ground, three-channel amp. That provides a super-low impedance for return currents from the headphone load, meaning a very high damping factor and absolute control of the headphone drivers. It's the closest you can get to pure-balanced and many people will tell you that the difference from a fully-balanced design is hardly worth mentioning.

Add to that the other enhancements such as the bass-boost circuit option and the S11 or STEPS power supply and you have a superior, IMHO, more flexible setup. As stated above, the M3's minimum Class A current is 80ma, but I believe AMB will tell you that's only limited by the size of the heat sinks and there are speaker-power options with larger heat sinks. Designed several years ago now, it still represents one of the 3 or 4 best solid-state headphone amplifiers available for DIY.

Nevertheless, that PCB up there and the work that went into it is very pretty. As I said, one of the best I've seen.