AudioCircle
Audio/Video Gear and Systems => The Lab => Topic started by: Freo-1 on 3 Mar 2012, 01:44 am
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Recently came across an amp design from Papa Pass that peaked my interest:
(http://www.audiocircle.com/image.php?id=58894)
This little gem is a Class A zero feedback amp. From the owners manual:
" The First Watt M2 is a two channel audio power amplifier delivering 25 watts per channel. It uses JFET and MOSFET transistors operating in Class A mode without negative feedback so as to produce a more musically life-like sound."
" The M2 is a simple circuit whose output stage consists of a pair of complementary power Mosfet followers biased into pure Class A mode. These devices are the current gain stage of the amplifier, very linearly following the musical signal produced by the voltage gain stage."
"Actually, this is the easy part, and I've done it many times before."
"The voltage gain stage which precedes the output followers is where you usually have the most problems with distortions of various sorts. This is because the mode of operation required (common-cathode, common-source, or common emitter) is the least linear, requiring both voltage and current gain. There are numerous approaches, but it usually boils down to either accepting higher distortion or more complexity."
"The M2 is different. It uses a passive voltage gain device, an auto-former. Like a transformer, an auto-former is a magnetically coupled circuit which changes the ratio of voltage and current while keeping the same amount of energy. In this case, it steps up the voltage by a factor of 5 in exchange for delivering 1/5 the current at the output. Since the input impedance of the output stage devices is very high, this is an equitable exchange."
I think this a somewhat unique and refreshing approach to obtaining the "tube sound" characteristics advantages without the limitations known with tubes.
Here is the explanation of the circuit design from the manual:
" So here we have a no-feedback Class A FET power amplifier with transformer voltage gain. Does it have any similarities to no-feedback Class A tube amplifiers with an output transformer? Yes and no.
It does have some of the qualities that SET aficionados look for. The auto-former does bring its own signature to the sound, although in smaller doses than we usually experience. The midrange has a lush, warm character that I associate with tubes and transformers, but subtly so. Part of this is due to the limited bandwidth of transformers, and part of it is the lack of feedback artifacts."
"On the other hand, there is considerably less harmonic distortion than with no-feedback SETs, and if you really do like that distortion then the M2 might not be what you want. Also, there is more power than usual and a relatively high damping factor, so the M2 is different in that regard."
"The M2 strikes a balance in the performance space between the extremes of big behemoth solid state power amplifiers and little tiny single-ended triodes."
I've always been a big supporter of Nelson Pass designs, and his support of the DIY community as a whole. This little gem has just enough power to push a wider variety of speakers than most of the low power SET designs.
Looking forward to trying one out next week. Will be using the M2 with a pair of speakers that are 90 db/w at 6 ohms. Should be fun.
If this goes well, may look at building a F5 clone for fun. Will also look at a similar design with J-FET outputs.
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Interesting. I'd love to hear it.
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Interesting. I'd love to hear it.
I'm going to post my observations after I've put it through it's paces.
I've always had a soft spot for the "tube sound", but have never been a fan of their limitations. So, been using class A solid state amps, which sound excellent, but not quite like a well made tube amp. This little gem is suppose to come very close, and still be reliable and long lasting.
The other cool thing is that most of the First Watt amps can be cloned fairly easily, and Papa Pass is great about offering help. He helped me with some issues I had with the bias circuits while resorting a Threshold 400A. Would up doing a total rebuild on the unit, and could not believe how much better the amp sounded after rebuilding the driver boards with new, high quality audio parts.
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If you don't mind, I think many of us would love to watch over your shoulder as you construct the amp. Well, at least I know I would! :) Wadaya say? Can we tag along? Please post progress if possible!
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Seems i have read that the J2 sounds more "set like" than the M2.
If that is correct, the J2 is the one i'd like to hear.
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No worries. If the M2 sounds as good as I think it will, I'll post pics of whatever First Watt clone that gets built.
Here is a pic of of the re-built 400A:
(http://www.audiocircle.com/image.php?id=58897)
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More photos, Freo, more! :thumb:
I'm with Josh in hoping you do a step by step photo journal of building your amp.
I love my Aleph, still have the boards for a mini Aleph, and the Peter Daniel boards for the F-2?
Lyndon
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Seems i have read that the J2 sounds more "set like" than the M2.
If that is correct, the J2 is the one i'd like to hear.
I think it's the other way around. (Depends what one reads). :D
I'm keen to listen to a J2 as well. The reason I went with the M2 was power output, as it is 40 wpc @ 4 ohms, while the J2 is more like 13W at 4 ohms.
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+1 on a build out thread! Sounds like you know what your doing.
I bought an Aleph clone and its my favorite amp so far.
I've been tempted to try to build an F5. I've never built anything before and its a little daunting. I hadn't seen this M2 before.
FYI...Just noticed an M2 pop up on the 'gon.
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I think it's the other way around. (Depends what one reads). :D
I'm keen to listen to a J2 as well. The reason I went with the M2 was power output, as it is 40 wpc @ 4 ohms, while the J2 is more like 13W at 4 ohms.
iirc, Mark at Reno hifi told me that -- been awhile tho -- i could have it bass ackwards .... lol
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There are not too many designs available that provide an amplifier with passive voltage amplification and no feedback.
To be able to get the sonic benefits of "tube like sound" without tubes is a pretty neat achievement. This amp is touted to be one of the most reliable designs out there.
The First Watt approach is really cool. It allows audiophiles to experience different sonic results based on varied amplifier design approaches.
To me, amps like those from First Watt are testaments to the fact that “amplifiers can and do sound different”, based on a whole host of factors. There a number of articles written by Mr. Pass that explain the effects of feedback, how to get circuits and devices to operate in their “sweet spot”, class of operation, etc. all of which help to explain how they work, and some supporting information as to why this happens.
Best of all are the articles on how to DIY projects like the F5 turbo. (very cool).
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The M2 arrived today. First impressions are very positive. For 25 wpc, it seems to have plenty of drive for the speakers (91 db at 6 ohms).
Will post observations after some time listening, but one thing that is obvious: Anyone who thinks "all amps sound the same" would have to re-think that after listening to this amp for awhile.
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Great amp, love mine. It will drive darn near everything.
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Great amp, love mine. It will drive darn near everything.
How inefficient a speaker have you tried with the M2 TONEPUB? Surprised to see "drive anything" in a thread on a 25WPC into 8 ohms amp.
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Great amp, love mine. It will drive darn near everything.
Glad to hear it. So far, I'm really happy with this.
What are your impressions of the M2 compared to the F5? (I'm assumimg you have you have listened to the F5).
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After listening to the First Watt M2 for about a week now, let me state that this is perhaps the most enjoyable amplifier I’ve ever sat down and listened to. This amp is proof positive that “all amplifiers do NOT sound the same”. With the right speakers, some types of music from this amplifier often sound closer to a live event than one will generally experience with an audio setup.
To be sure, this amp is not for everyone. It outputs 25 wpc@8 ohms, and 40 wpc@4 ohms. So, as long as the target speakers have sufficient sensitivity, the amp will play music as loud as most of us would listen comfortably.
What this amp does right (and not all that many do) is the ability to re-create the entire frequency spectrum without any undue emphasis for any one area of the spectrum. The bass is extremely natural, and has sufficient heft, weight, and damping to sound accurate, without calling undue attention to it. The midrange has a clarity and natural harmonic tonal character that VERY FEW amps get right. Vocals from the amp sound more natural than one generally hears. String instruments very realistic with the right recordings and low level details are easily heard, but are heard in the correct proportion. Some equipment can be “too analytical” when one hears more low level detail than one would hear in a live setting.
Where this amp really shines is the upper registers. The treble from this amp is easily some of the best I’ve heard from any amp at any price. There is no trace of HF emphasis or solid state “crispness” that plagues many amps.
I would suspect that may tube audiophiles would think they were listening to a new state of the art tube amp when hearing music played through the M2. The passive transformer gain stage, which provides 15 db of passive gain, has a lot to do with the sonic signature of the M2. There is a total lack of glare with the M2. This is one of the very few amps on the market where the listener will not experience any listener fatigue. I think the fact this amp is a Class A unit with zero feedback also is a big reason why the amp sounds so natural.
From a noise standpoint, there is none discernible with the speakers I’m using (91dbw@ 6 ohms). The amp is very quiet (quieter than most tube amps by a fair bit).
In summary, this amp is tremendous performer. It’s easy to see (and hear) why the M2 is popular in the Asian market. If you are looking for an amp that provides the best aspects of tube amp reproduction, but still desire a more natural bottom end that is the purview of solid state (not to mention reliability), then give the M2 a try.
You will not be disappointed.
8)
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Thanks for the review, Freo-1.
Have you spent enough time with any other First Watt or Pass Labs amps in your system to allow some comparisons?
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Thanks for the review, Freo-1.
Have you spent enough time with any other First Watt or Pass Labs amps in your system to allow some comparisons?
No worries.
I was a little late coming to the First Watt camp, as only recently discovered its virtues. However, now that I’m there, I’ll be staying in that camp for some time to come.
I currently own a Pass Labs X2.5 preamp, and that is what I’m using with the M2. The gain from the X2.5 is set to low. The source for the music is a Modwright Oppo BD-95 tube unit. The speakers are Source Technologies 277SE.
I have heard a couple of other offerings from Pass Labs, but not in an environment that I sufficiently trusted to use for evaluation.
After having the M2 in the system for awhile, am now considering making a pair of F4 amps vice an M5. The high gain from the X2.5 will work just fine with the F4, and could get 100 watts a channel as monoblocks.
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More photos, Freo, more! :thumb:
I'm with Josh in hoping you do a step by step photo journal of building your amp.
I love my Aleph, still have the boards for a mini Aleph, and the Peter Daniel boards for the F-2?
Lyndon
OK.
Here is a photo of the inside of a Threshold S300 which was restored, and converted to a SA/3.
It turns out the driver boards for the S300 and SA/3 were the same, and the optical bias model power transformer supports both rail voltage. So it was a simple matter of using the alternate voltage rails, bump up the bias, and change out the rail fuses, and presto, a 50 wpc Class A is born.
(http://www.audiocircle.com/image.php?id=57610)
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Whoa. Didn't realize the F4 does 100W in mono. Into what load?
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Whoa. Didn't realize the F4 does 100W in mono. Into what load?
From the First Watt website:
" As a stereo amplifier with single-ended inputs and outputs, it will deliver up to 25 watts into 8 ohms with a damping factor of 40. It will do 50 watts into 4 ohms, and as a mono-block amplifier with parallel inputs and outputs, it will do about 100 watts into 2 ohms. As a mono-block amplifier with balanced inputs and outputs the power output rating is 100 watts into 8 ohms at 1%.
The amplifier operates Class A to 25 watts (50 peak), and the distortion is 2nd and 3rd harmonic in character, rising or declining in proportion to the output power. The amplifier has a direct coupled input and output, with a -0.5 dB rolloff around .1 Hz and 200 KHz. It does a clean square wave at 100 Khz."
Pretty cool, eh? 8)
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F4's are 100w mono into 8 ohms. I built a pair and ran them balanced. They're very nice as long as the preamp can output enough voltage comfortably.
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Damn.
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But needs to be a balanced input for monoblocks?
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F4's are 100w mono into 8 ohms. I built a pair and ran them balanced. They're very nice as long as the preamp can output enough voltage comfortably.
Right. The Pass Labs X2.5 should work quite nicely in the high gain setting.
Well done on building your own, by the way. Papa stated that it was one of his fav sounding amps.
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But needs to be a balanced input for monoblocks?
Yes (for 100W).
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I think it's the other way around. (Depends what one reads). :D
I'm keen to listen to a J2 as well. The reason I went with the M2 was power output, as it is 40 wpc @ 4 ohms, while the J2 is more like 13W at 4 ohms.
M2 is 40 into 4ohms, according to the Firstwatt site. J2 only 13 into 4 ohms.
M2 is PP, while J2 is SE.
http://www.firstwatt.com/prod.html
Russellc
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Thought I would bring this up to date:
After obtaining a Conrad/Johnson clone preamp, decided to try it with the M2, which was on duty in a HT setup.
The take away is that the M2 LOVES a tube preamp. The combo sounds very close to a all tube playback system, with a few minor deltas. The overall sound stage is wide and deep, and 3D. The midrange has a special quality that does remind the listener of a high end SET setup. The bass is tighter than a SET, which is the delta that is noticeable. The C/J clone is a better match for the M2 than the Pass Labs X 2.5. (Back to this synergy issue here.)
I would highly encourage anyone interested in a Low Wattage setup who wants the qualities of a SET playback system, but does not want to fool with the power amp bottles, to give the M2 a listen with a tube preamp. You will be pleasantly surprised.
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An M2 arrived from Reno HiFi today, which I will be comparing to my Rogue Stereo 90 during my 10 day trial period that Mark at Reno offers. Details to come.
But to whet the appetite, the preamp is a Musical Fidelity kW (a hybrid design), and the speakers are VonSchweikert VR-4 Gen IIs (91dB, nominally 7 ohms, biwired).
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An M2 arrived from Reno HiFi today, which I will be comparing to my Rogue Stereo 90 during my 10 day trial period that Mark at Reno offers. Details to come.
But to whet the appetite, the preamp is a Musical Fidelity kW (a hybrid design), and the speakers are VonSchweikert VR-4 Gen IIs (91dB, nominally 7 ohms, biwired).
Sounds like you are in for a good experience. I have two M2 amps, one for use bi-amped to the center channel speaker, and one for the rear speakers, to go with a XA 30.5 for the mains. They are a great match, and work wonderful together.
The front end is a Modwright Oppo BDP-83 Nuforce, with a Classe SSP-300. The nice thing about the Classe is NO OPAMPS (all discrete for the 7.1 input).
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Yes, Freo-1 I knew you were a fan. Look forward to hearing how it works with these speakers compared to the tubed and higher powered Rogue.
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As long as your speakers are efficient, it should sound outstanding.
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91 dB, so we will see...
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That should work. Is it 91db at 8, 6, or 4 ohm nominal? I tried it with the Cary Silver Oak Model Ones, which are 88 db/w at 6 to 8 ohms (plus a subwoofer), and it worked great. The Cary's were running full range.
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7 Ohm nominal, but my understanding is the bass module is 4 ohm, while the upper is closer to 8. I biwire these, so am not sure how the separate impedance affects things, vs the amp just seeing the nominal 7 ohms.
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Well, here goes with first impressions on my VR-4 Gen IIs in a 13x15 room. Listening at between 60-70dB levels, with the amps level-matched with a dB meter:
I don't see the M2 giving me anything that I am not getting with my Rogue Stereo 90 (4 Ohm tap in ultralinear mode, with KT88s). And the Rogue seems to be doing better in the bass (a surprise considering accepted SS vs. tube differences in the bass). But I am also seeing the Rogue shine in terms of air and the notes of the decay. Not that the M2 sounds poor with the Von Schweikerts. It is as if things on the M2 are a bit muted. I am just not drawn into the music in the same way.
And this isn't coming from a hardcore tube fanboy. I have owned a First Watt F1, F2, F3 and F4. And I have had chances to audition in my system an F2J, as well as a clone F5. Though all of these auditions were with far more efficient speakers (Zu Superflys, and DIY speakers with a 12" Common Sense Audio driver).
This is just the first impression, based on the Fleet Foxes' S/T album (which I know inside and out).
And it occurs to me that these thoughts might be in line with Freo-1s suggestion of pairing a tube preamp with the M2s. While my kW preamp is a hybrid, I wouldn't characterize it as particularly tooby (I do oh so love this preamp tho for the detail and oomph it provides).
It always bears repeating that synergy is everything.
More to come.
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Totally agree that synergy is everything :thumb: As they say in the UK, its "horses for courses"
Is your M2 a demo, or is it new? I have noticed that they do sound better once broken in, and definitely after an hour or so once broken in.
Thanks for the feedback. Please post your impressions as you continue to audition. More than I would like to think, my initial impression of a product often times is not my final impression.
Lastly, I have learned the hard way that an optimal impedance match between the preamp and power amp is essential to evaluate the overall system sound as a whole.
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All good points for sure.
The M2 is used, so presumably broken in.
More to come.
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I just finished my Pass Approved M-2 from a group buy on the Pass forum over on DIYaudio.com. Very nice amp. Also recently built the F-6, another one with a transformer on the amp board. It uses it differently than M-2, which uses the transformer for gain. I also have built the Pass DIY BA-3 power amp, F-5 power amp, BA-3 preamp, B-1 preamp as well as the Diy Pass Pearl 2 Phono preamp.
All of the Pass stuff is dynamite in the sonics category, and not a single piece of it makes any noise or hum. All units are quiet as the grave.
Lots of support on the diyaudio site if anyone is interested.
Most of these amps can be scaled up for more power. I plan on a pair of Balanced BA-3 mono blocks next, they are easily over 100 watts. It should be kept in mind that these are class A amplifiers, and 50 watts is a lot. These amps get HOT, and expensive heatsinking is required
Russellc
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Indeed, 50w class A is a lot. I just sent a whole amp package to a fellow in Indonesia because his F5 was baking the cabinet he uses.
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Very old topic here but hey!
I am wondering if anyone still has an M2 in their system? If you guys moved on up the road from the M2, what have you moved on to? Any regrets? Has anyone that had the M2 gotten to compare it to some other pass models (f7/j2/pass ...)?
I would love to hear how this developed for you guys. Also any synergistic preamps?
I have an M2 and am enjoying it. I have run it with a passive volume control, with a gain stage (parks puffin) and a tube pre. All sound great.
Hopefully this brings back some memories.
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I too want to know more about this amp. I have the opportunity to buy one.
I also have very efficient ZU Audio speakers.
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I too want to know more about this amp. I have the opportunity to buy one.
I also have very efficient ZU Audio speakers.
Stereo PushPull 25W 8 ohms 40W/4 ohms,
JFet + Mosfet, No NFB, RCA input,
https://www.firstwatt.com/m2.html
Owner Manual
https://www.firstwatt.com/pdf/prod_m2_man.pdf
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I've heard most of the Pass and First Watt designs, and the one to beat, IMO, is the Burning Amp 3:
https://www.firstwatt.com/pdf/art_ba_3.pdf
and the build thread with pictures:
https://www.diyaudio.com/forums/pass-labs/258301-ba-3-amplifier-illustrated-build-guide.html
Now, I can hear you asking "Wait, Tyson, do you actually like this amp better than even the (in )famous SIT amps?" Yes, I like it better than even them. The BA3 is an astonishingly great amp.
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Interesting, what are the BA-3 specs ?
Its not that 5W amp?
Only found its 40W 8 ohms, found more now:
It use 3 transistors pairs p/ch, without listen them I could choose the Odyssey Stratos, just 2 Sanken pairs per ch.
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I've heard most of the Pass and First Watt designs, and the one to beat, IMO, is the Burning Amp 3:
https://www.firstwatt.com/pdf/art_ba_3.pdf (https://www.firstwatt.com/pdf/art_ba_3.pdf)
and the build thread with pictures:
https://www.diyaudio.com/forums/pass-labs/258301-ba-3-amplifier-illustrated-build-guide.html (https://www.diyaudio.com/forums/pass-labs/258301-ba-3-amplifier-illustrated-build-guide.html)
Now, I can hear you asking "Wait, Tyson, do you actually like this amp better than even the (in )famous SIT amps?" Yes, I like it better than even them. The BA3 is an astonishingly great amp.
Thanks
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The one I built is 25 watts and is the closest to a tube amp type sound I have ever heard from an SS amp. It's incredibly good.
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Great, do you could post inside photos?
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Great, do you could post inside photos?
The amp pictured in the build guide I linked to earlier is my actual amp that Jim (6L6) and I built together.
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Thanks these are great macro photos.
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And for about $700 in parts from the diyaudio store you get one of the best amps in the world (if you are a tube lover like me).
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How do you could compare his SQ with the Odyssey Stratos?
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How do you could compare his SQ with the Odyssey Stratos?
I don't have a Stratos to compare it to, but I do have the Kismet mono's and I'll say this - the Odyssey amps are smooooooth and very powerful, great bass and outstanding dynamics. The BA3 is softer and sweeter and with a deeper soundstage. The Odyssey sound like outstanding SS amps, the BA3 sounds more like a tube amp. I'm glad I have both because they each have different strengths and are each excellent in their own way.
To expand the comparison further, the BA3 sounds more like a tube amp than any other amp I've heard, including all the other First Watt designs (and definitely more tubelike than the Pass Labs stuff).
And at 25 watts pure Class A, it runs about as hot as a tube amp too, haha.
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I built the First Watt M2x a couple of years ago. It was just my second build, the first being the Amp Camp Amp. I needed help from the more experienced builders at diyaudio.com but I got it done. It really is a wonderful amp. It has a natural organic kind of sound. It does run hot, though.
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Thanks guys I appreciated your first hand report :thumb: