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Millet Hybrid MOSFET-Max or MiniMax for HD600 headphones

post #1 of 7
Thread Starter 

Greetings people,

I've being researching the net on amps to get the best match for my headphones (Senn HD600). Unfortunately I want to keep this hobby kind to my wallet, that means, I don't want to build/buy more than 1 amp nor swap my headphones, maybe the next year.

I want something like these in this priority order:
1- Sweet (warmy) Musical mids for clarity on female voices.
2- Fast, defined, precise bass yet musical.
3- natural highs for nice classical music listening
4- enough soundstage to identify instruments position, yet not a far away sounding experience, something on the fourth row at most maybe.

I don't know yet how a tube amp sounds, maybe my chance is on a hybrid amp with 2 different flavour outputs. I tried a Lehmann Black Cube Linear amp on the HD600 and HD650 when I bought my headphones. The HD650 were the most sweet experience with slow music like lounge/new age music, but after listening to all my tunes I decided on the average better performance on the HD600 for an all around use. That's what I'm also looking, an all around amp! Something to recover the sweetness on the HD650, rather something still better; while keeping the tighter bass response on the HD600 which I liked for Trance and Metal music. I listen to about anything!

 

So far I'm tempted on the Millet Hybrid MOSFET-Max, the MiniMax or even an Aikido. I haven't found anything about the sound on the Aikido, if anyone has something to say about the Aikido it would be a plus. BTW, I need something not "flashy" since it's for my work (I almost not hear music on my house as I'm not commonly there). I beliebe I can hide the tubes on the Millet amps with some MTB Bike spacers lol, the point is I have discarded options like Bottlehead amps for this simple reason.

 

I read from Tomb on a post that MOSFETs could sound warmer and with more slam on bass than BJTs, but someone else says: "MiniMax is better with Senns while MOSFET-Max is better with Grados" ... oh well ... here is what I believe is the preference on the person, maybe he likes something more balanced. I wrote my experience with the Lehmann and the HD650/HD600 so that someone could help me out maybe what I would like more. Maybe not a Millet and something else? I can't test/try amps on my country before making a decision, I don't know people around on this hobby.

 

I was also considering a KICAS Caliente, but after reading that a Woo Audio 3 and an AMB M³ are better and that so I believe a MOSFET-Max could be at the level of an M³ or better, I'm considering the MOSFET-Max at the top of my list, help me hear with any impressions on sound please on the HD600. I'm expecting to keep it below the $400 range.

 

Thanks!

post #2 of 7
Quote:
Originally Posted by Gauss1777 View Post

So far I'm tempted on the Millet Hybrid MOSFET-Max, the MiniMax or even an Aikido. I haven't found anything about the sound on the Aikido, if anyone has something to say about the Aikido it would be a plus. BTW, I need something not "flashy" since it's for my work (I almost not hear music on my house as I'm not commonly there). I beliebe I can hide the tubes on the Millet amps with some MTB Bike spacers lol, the point is I have discarded options like Bottlehead amps for this simple reason.

 

I read from Tomb on a post that MOSFETs could sound warmer and with more slam on bass than BJTs, but someone else says: "MiniMax is better with Senns while MOSFET-Max is better with Grados" ... oh well ... here is what I believe is the preference on the person, maybe he likes something more balanced. I wrote my experience with the Lehmann and the HD650/HD600 so that someone could help me out maybe what I would like more. Maybe not a Millet and something else? I can't test/try amps on my country before making a decision, I don't know people around on this hobby.


This has nothing to do with preference, the Senns DO sound better on the Minimax due to the way the BJTs work. Someone can correct me if I'm wrong, but the Mofsets put out more current, which is preferred for low impedences. At any rate, I'm listening to HD650s on my Minimax right now, and they sound wonderful. I don't think the amp looks too flashy either, with the tubes recessed halfway into the amp. The only reason I'm selling mine is because I purchased a Speedball Crack.

post #3 of 7

There is a simple physical limitation with the MOSFETs and voltage (regardless of what amp they're in).  There is specific turn-on voltage (gate voltage) that's required for MOSFETs to operate.  For the MOSFETs used in the MOSFET-MAX or M3 (Z24 and 9Z34), that's anywhere from 2 to 4 volts.  Anyone who's built both types can easily see the difference in operation on their DMM's when measuring Class A bias - the MOSFETs are actually dead until a certain threshold is reached when adjusting voltage - then they start registering.  BJT's on the other hand, are alive from the start - with some little bit of voltage and current regardless of the bias setting.

 

At any rate, that turn-on voltage threshold for MOSFETs means that the available voltage swing from the power supply is decreased by that amount.  With low impedance phones (like 32ohms), that voltage decrease is insignificant compared to the current impulse capability that the MOSFETs offer.  Conversely, with high-impedance phones, current is secondary compared to the voltage swing needed.  For instance, at 300 ohms a 500mW signal would require only 41ma but 12.25V.  At that same power level, a 32 ohm headphone would require 125ma but only 4V.

 

Unfortunately, it almost gets into an after-market cable discussion when trying to determine how much power is needed by a headphone.  Certainly, steady-state voltage and current levels are very, very low for most headphones to reach levels that will damage your ears.  However, audiophiles are interested in every nuance of the recorded music and are thus interested in every peak, regardless of how transient the signal.  Then it becomes much more difficult to say how much instantaneous power is really needed for a headphone's given impedance and efficiency (ever heard of "music power" ratings?).

 

At any rate, from the simple calculation comparison it should be easy to see that MOSFETs are optimized for low-impedance and BJT's for high-impedance.  The comparison is perfectly analogous - M3 to PPAV2 vs. MOSFET-MAX to MiniMAX.  Do they do well with most headphones regardless of impedance?  Of course.wink.gif

post #4 of 7
Thread Starter 

Thanks Bob for reading. Thanks Tomb for the detailed answer. From what I read both would be great for HD600 then, maybe I would just go with the MiniMax and speed thigs with a full kit.

 

Bob just for curiosity. do you already own the Crack or are you waiting for both (Crack and speedball)? I'm wondering if the speedball could give tighter and speedier bass response to the Crack, maybe tube rolling. Oh well.... maybe at the middle of the year I could try this one and set it as a bed rig... maybe the S.E.X. instead. 

 

At anyone: Do MiniMax has PSU upgrades?

post #5 of 7
Quote:
Originally Posted by Gauss1777 View Post

Thanks Bob for reading. Thanks Tomb for the detailed answer. From what I read both would be great for HD600 then, maybe I would just go with the MiniMax and speed thigs with a full kit.

 

Bob just for curiosity. do you already own the Crack or are you waiting for both (Crack and speedball)? I'm wondering if the speedball could give tighter and speedier bass response to the Crack, maybe tube rolling. Oh well.... maybe at the middle of the year I could try this one and set it as a bed rig... maybe the S.E.X. instead. 

 

At anyone: Do MiniMax has PSU upgrades?


Yes, the MiniMax has a STEP like power supply (correct me if I'm wrong). Owning both the MOSFET-Max as well as the MiniMax, I can tell you that Sennheiser HD6XX definitely sounds better on the MiniMax, it was VERY obvious with my HD650 :)

 

BTW to speed things up even more (also saving some dough), you could just pick up Bob's MiniMax that is for sale wink.gif. It was essentially built by Tom so you know it will be of good craftsmanship.

post #6 of 7
Quote:
Originally Posted by dizzyraider View Post

Yes, the MiniMax has a STEP like power supply (correct me if I'm wrong). Owning both the MOSFET-Max as well as the MiniMax, I can tell you that Sennheiser HD6XX definitely sounds better on the MiniMax, it was VERY obvious with my HD650 :)

 

BTW to speed things up even more (also saving some dough), you could just pick up Bob's MiniMax that is for sale wink.gif. It was essentially built by Tom so you know it will be of good craftsmanship.

 

Well, some people simply like building things. 

 

Quote:

Originally Posted by Gauss1777 View Post

 

Bob just for curiosity. do you already own the Crack or are you waiting for both (Crack and speedball)? I'm wondering if the speedball could give tighter and speedier bass response to the Crack, maybe tube rolling. Oh well.... maybe at the middle of the year I could try this one and set it as a bed rig... maybe the S.E.X. instead. 

 

At anyone: Do MiniMax has PSU upgrades?


I don't own the crack yet, but there was a group buy recently and I'm waiting for them to ship it out (maybe another week or two). From what I've read, the Speedball Crack might be better suited for the HD650s (but it costs quite a bit more with the Speedball add on and new tubes), but I really just want too build a new amp. If it sounds better, cool. If it sounds worse, I'll sell it. Just a word of advice, If you don't plan on owning 5-10 different amps by the end of next year, buy one that's already built. DIY will have you building many different amps.

 

Also, the power supply in the Max Is very high quality. I wouldn't worry about PSU upgrades.

post #7 of 7
I can personally attest to the wonderfulness of the minimax, it is a very well put together kit, and the one I built my step mother as a gift went together very quickly, was fairly easy as diy kits go, and sounded phenomenal. I just finished a MOSFET max, and while it does not sound quite as good as I remember the mini sounding, it is improving with burn in, so I am hopefull it will settle into the same signature. I am using a pair of M-50's at the moment, witch are low impeadance if I recall. The Millett design seems to be quite well refined, so while I have not heard any of those other amps, I feel confident in recommending it.
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