Tom, thanks for releasing such a detailed review of the amp. It is very interesting to read and its not often to see a DIY amp fully specified.
A question though. How does the amp compare with others of a similar topology in terms of transistor count? There was a comparison with the JDS Atom, but my understanding is that the atom is op-amp driven with what, a 16 transistor equivalent circuit per channel? (From a quick schematic search).
A mercedes V8 will always sound better than a yamaha 2-stroke so I wonder how this amp compares to other 2-stroke amps?
A question though. How does the amp compare with others of a similar topology in terms of transistor count? There was a comparison with the JDS Atom, but my understanding is that the atom is op-amp driven with what, a 16 transistor equivalent circuit per channel? (From a quick schematic search).
A mercedes V8 will always sound better than a yamaha 2-stroke so I wonder how this amp compares to other 2-stroke amps?
So because it's entertainment to you and Nelson Pass, I'm not allowed to apply the scientific process? I do recognize that some parts of the world are undergoing a bit of a reverse enlightenment, but still... I would have thought there'd be room for science - even in audio.
You're free to disagree, but I don't see the entertainment value of "anti-resonance crystals", speaker cable stands, and similar products that are rooted in pseudo-science, junk science, or flat-out non-science. If those products were a few bucks, then maybe I could see the entertainment value. Similar to the entertainment value of a pet rock. But those products are thousands of dollars. That's not fun or entertaining anymore.
Similarly, you could argue that the T2 is only a few hundred bucks, so what's the big deal? Well, to some a few hundred bucks is a big deal. Further, I think people deserve to know what they're buying when they invest their money and time in a project. So when presented with the opportunity to measure one, I jumped at it.
I expressed my opinion on it in my review. I base my claims and opinion on science and data. The only subjective part of the review is my listening experience. I was a bit disappointed. You're free to disagree with me. We don't all have to like the same stuff. I'm pretty sure there's room for all of us on this here space rock.
Tom
You're welcome. I'm glad you appreciated it.
Good question. I haven't heard or measured other two-transistor amps than the T2.
I compared the T2 against the Atom on price and specs only. The Atom is $99 and provides vastly lower THD, IMD, etc. You can find measurements of the Atom on Audio Science Review.
Depends on the opamp. One opamp I worked on (LMP2021) had a lot more than 16 transistors.
In other opamps I've designed (building blocks in various other circuits), I've been able to get away with as few as 5-6 transistors (not counting those used in biasing)....or in case of analog circuits, a two-transistor circuit will usually have lower loop gain, hence, lower error-correction factor than an opamp.
I've designed precision circuits for a living since 2005 when I started working for National Semiconductor. I've tried tube circuits as well, but ended up preferring the clean sound of a precision amp. To get precision, you need loop gain, so I use opamps and composite topologies. That's me.
Mark seems to have wanted to design an amp with as few components as possible. Nothing wrong with that, but it's not a strategy that automatically lends itself to precision design. Then, precision was probably not his goal. I'll leave it for him to elaborate on what his design goals were, should he so choose.
Tom
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I’ve been proud to post about my projects in a couple of other people threads but I’m finding more and more that a few folks are doing it as a form of indirect advertising, it just seems it is a lot more prevalent over the last year or so.
And maybe some of you fellows could jump in on some of the First Watt or old Zen threads, measure a few simple amplifiers out to the nth degree, try and save all those DIYers from spending their money on inferior projects...
Can we just leave this thread alone and let people have some fun
And maybe some of you fellows could jump in on some of the First Watt or old Zen threads, measure a few simple amplifiers out to the nth degree, try and save all those DIYers from spending their money on inferior projects...
Can we just leave this thread alone and let people have some fun
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Out of curiosity last week I purchased a Chord Mojo new for £269.
I had seen a number of posters on different forums saying how good it was at driving the Sen HD800 direct so was keen to give it a try myself however I thought the combination a bit Meh personnally and its certainly not a combo I would use.
Yet technically the Mojo measures extremely well and on paper has more than enough power to do drive the hd800s.
My tube Bottlehead Mainline on the other hand which I am sure would measure terribally in comparison and has less power but sonics wise it just kills the Mojo with the HD800. Its not about coluration but in resolutuion, sound staging, texturing, spaciality.
My Oppo pm3 on the other hand while it sounds good using the Mainline out of the Mojo it is just amazing the best I have heard it.
Very impressed with the little Mojo it offers a lot of peformance for essentially peanuts if you can live with its lack of connectivity.
Looking forward to getting my T2 up and running not much more to do now.
I had seen a number of posters on different forums saying how good it was at driving the Sen HD800 direct so was keen to give it a try myself however I thought the combination a bit Meh personnally and its certainly not a combo I would use.
Yet technically the Mojo measures extremely well and on paper has more than enough power to do drive the hd800s.
My tube Bottlehead Mainline on the other hand which I am sure would measure terribally in comparison and has less power but sonics wise it just kills the Mojo with the HD800. Its not about coluration but in resolutuion, sound staging, texturing, spaciality.
My Oppo pm3 on the other hand while it sounds good using the Mainline out of the Mojo it is just amazing the best I have heard it.
Very impressed with the little Mojo it offers a lot of peformance for essentially peanuts if you can live with its lack of connectivity.
Looking forward to getting my T2 up and running not much more to do now.
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I am a pretty analytical guy, with an electrical engineering background, but over the years I have a soft subjective side and its the love of listening to great music and to witness how present day technology allows me to have a great musical experience.
When the O2 came on the scene I got on the spec bandwagon BIG time. But over time I learned there are some unscientific reasons that come into play that affect this enjoyment. I mean with such a perfect amp how could other people have a great musical experience with anything else than an O2? Especially when it was a $100 amp.
How could anyone in the past 20-30 years have a great experience with tube amps? All those Dynaco's out there etc...with lousy specs. There are folks on other sites that if yu mention a tube amp your in some alternate universe. If it doesnt measure VERY well, well its going to "sound" or "not sound" crappy.
Recently I bought a set of new headphones, and after rotating thru my 10 amps all of them for some uncanny reason they seem to mate the best according to my ears to one of the SS amps. All the other amps provided a good musical experience, even the T2, but this one amp just works better with these cans....why? Does this mean that the other amps are bad? No.
I have a set of HD600's that on this same amp that works well with the new cans sounds not as good and when I use the HD600's on a Bottlehead Crack amp. Why? Well As an engineer I would like to know if the science can explain it to me. But I have never found anyone that could, even the specmanship folks at ASR.
One issue folks will have with high end amps is the cost. There is a lot of time and effort that goes into designing a good amp to have it be a very low distortion / noise free and all that gorp....and folks want this performance at a low price....aka the $99 amps out there that have some pretty good measurements....that is a dilemma that is hard to overcome. Even the new kids on the block the $400 THX amps...
But I have to add that using a very good measured amp can provide a great musical experience as well.
When I first built the T2 and listened it was my 20+ build and it really worked very well here sonically. Made me smile alot. Then when I see that its been measured and its rather mundane, I am wondering how can this amp be that bad when it made me smile etc...and I have a lot of stuff here that I can easily compare it to.
I think it might be that the specs may not be as important as I objectively thought for all these years. That said I like things built well, not in plastic cases, but with great knobs, billet aluminum, neat flashing leds...I am just as vain as most. Yeah the T2 isnt in a aluminum 1/4 thick billet case, but it still makes me smile!
Alex
When the O2 came on the scene I got on the spec bandwagon BIG time. But over time I learned there are some unscientific reasons that come into play that affect this enjoyment. I mean with such a perfect amp how could other people have a great musical experience with anything else than an O2? Especially when it was a $100 amp.
How could anyone in the past 20-30 years have a great experience with tube amps? All those Dynaco's out there etc...with lousy specs. There are folks on other sites that if yu mention a tube amp your in some alternate universe. If it doesnt measure VERY well, well its going to "sound" or "not sound" crappy.
Recently I bought a set of new headphones, and after rotating thru my 10 amps all of them for some uncanny reason they seem to mate the best according to my ears to one of the SS amps. All the other amps provided a good musical experience, even the T2, but this one amp just works better with these cans....why? Does this mean that the other amps are bad? No.
I have a set of HD600's that on this same amp that works well with the new cans sounds not as good and when I use the HD600's on a Bottlehead Crack amp. Why? Well As an engineer I would like to know if the science can explain it to me. But I have never found anyone that could, even the specmanship folks at ASR.
One issue folks will have with high end amps is the cost. There is a lot of time and effort that goes into designing a good amp to have it be a very low distortion / noise free and all that gorp....and folks want this performance at a low price....aka the $99 amps out there that have some pretty good measurements....that is a dilemma that is hard to overcome. Even the new kids on the block the $400 THX amps...
But I have to add that using a very good measured amp can provide a great musical experience as well.
When I first built the T2 and listened it was my 20+ build and it really worked very well here sonically. Made me smile alot. Then when I see that its been measured and its rather mundane, I am wondering how can this amp be that bad when it made me smile etc...and I have a lot of stuff here that I can easily compare it to.
I think it might be that the specs may not be as important as I objectively thought for all these years. That said I like things built well, not in plastic cases, but with great knobs, billet aluminum, neat flashing leds...I am just as vain as most. Yeah the T2 isnt in a aluminum 1/4 thick billet case, but it still makes me smile!
Alex
I've said elsewhere that although I appreciate Tom taking time to do a full set of measurements on the T2, it would be better if he kept the subjective commentary to a minimum as it seems contradictory to his objective ethos (even more so as it's now evident the T2 is the only amp of its type he's measured). This is compounded by the fact that he has just announced his own headphone amp as his first official retail offering and is actively promoting it.
Comments like 'reverse enlightenment' are not helpful.
The T2 is a fun and easy build that makes for a great entry to the hobby and sounds good, too. A nice change from SMD-based projects with tight spaces, lengthy BOMs, and pricey chassis considerations (my achilles heel since I can't do drilling at home).
Comments like 'reverse enlightenment' are not helpful.
The T2 is a fun and easy build that makes for a great entry to the hobby and sounds good, too. A nice change from SMD-based projects with tight spaces, lengthy BOMs, and pricey chassis considerations (my achilles heel since I can't do drilling at home).
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I was about to echo that sentiment, it has no place here. As Mark and Patrick know I have no problem with the Zen/Pass Labs approach even though I spent 42yr. in precision IC design (>$900,000,000 in sales). Audio does not lend itself to the same standards, speaker technologies and room issues taint things to the point that the obsession with electronics performing to absurd accuracy becomes silly. Besides that I have met folks with vast knowledge and passion for music as art that prefer these "compromised" components/systems.
Tom you need to put your own standards up to full scientific DBT, I have never seen any evidence that -100dB vs -130dB ordinary THD amplifier performance (IMO of little use) is audible.
It's a bit OT but IME the 120 ohms output impedance of the Crack definitely imparts a particular character to the hd600 (by affecting its frequency response). I once tried to compare an hybrid amp with an input stage almost identical to the Crack but a "better" SS output buffer. The distortion profiles were very similar but until I added an output resistor to the SS buffer, the amps didn't sound similar.
Same could be said for this thread.
The PCB will be available from the DIY Audio Store soon. You may have noticed that I refrained from posting a link to my review here. I certainly could have done that, but I chose not to. Unlike some, I don't derive any satisfaction from pulling people's pants down in front of their followers, but I do believe the world is better off if more information is available. So I posted the review to my website and moved on. You can read it – or not – as you wish.
Olive & Toole have a bunch of research available and published through AES (and in Toole's book and Olive's blog). That'd be a good place to start. There's also Belcher (1973 if I recall correctly) who looked at the audibility of THD and IMD. Belcher (1973) actually proposed to use a multi-tone test (though multi in his case was 3) as he found evidence for IMD being a stronger correlate of the perceived sound quality.
I do agree that at some point the specmanship becomes a numbers game. I'm not aware of any evidence to support that -100 dB vs -130 dB THD should sound better or different, only that equipment that measures better tends to be rated as sounding better in blind tests.
That said, at -65 dB THD, the T2 will be the dominant source of distortion in a digital system. Even a $25 eBay DAC will reach nearly -100 dB THD. -65 dB is likely audible (Belcher, 1973). Some like distortion. Great! I'm not one of them. Before I posted my review, we had no data on how the T2 would perform. Now we do. This allows people to make informed choices. I think that's a good thing. You're free to disagree.
Tom
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In your mind only, the folks you are talking about have been totally open about the distortion profiles of their circuits. A comment like this has no place here.
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Specifications are most useful for comparison. Like you, I am not convinced that the difference between -100 dB and -130 dB is going to be audible.
I assume you know about the physiology of the ear and the principles of psychoacoustics. Our hearing did not evolve to listen to speakers in a rectangular room. Our hearing is adapted to help us find prey, and avoid predators. In general, we're very good at locating the source of sounds and differentiating frequencies. In regards to amplitude and frequency response our ears are very nonlinear.
Equipment does sound different and it's these characteristics of our hearing that are sometimes responsible. I'm very objective in my approach to design; I wear out at least on slide rule a month
. But I cannot deny that I can hear a difference in "soundstage" (I think it's really just minimizing diffraction) when I move my speakers around, or switch speakers, or even switch preamps. How do you measure that? My buddy has some big old Sony "party" speakers. They're loud, lots of boomy bass, they work but sound garbled to my ear in every way. He said there's no way I could build an 8" two way that played loud and sounded better than his speakers. Well of course I did, and I spent months tweaking the crossover to smooth them out, and they play so crystal clear and plenty loud, not as loud as disco boy's 1970s boomers but you never get tired of listening to them. And the reason they sound so good is that you can hear every instrument individually, you can hear people in the audience talking and it sounds like they're in the room with you, you can hear everything. And this plays into what our ears evolved to hear - location, identify the source, hear very quiet sounds in the environment.
Sorry if I'm long winded, but I wanted to highlight what traditional specs don't address in regards to the actual listening experience.
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Oh? Did I miss the distortion measurements of the T2 somewhere? I don't recall even seeing simulation results that showed the distortion profile, but am more than willing to stand corrected should I have missed them.
Tom
I disagree with this statement:
"Before I posted my review, we had no data on how the T2 would perform."
The data we did have was several builders stating they had a good listening experience with the T2.
IMO this is as valid as the data you get from an analyzer etc..and to some for years and years it was all that they had....and not having actual analyzer data didnt stop folks from using and enjoying their less than stellar stuff.
I would hope we all can just move on and let this horse lay down for a rest....
You all folks that dont like the T2 and how it measures fine, its been stated so just move on, life is too short.
You all folks that enjoy the T2, great enjoy it and go do some more DIY!
All the best
Alex
"Before I posted my review, we had no data on how the T2 would perform."
The data we did have was several builders stating they had a good listening experience with the T2.
IMO this is as valid as the data you get from an analyzer etc..and to some for years and years it was all that they had....and not having actual analyzer data didnt stop folks from using and enjoying their less than stellar stuff.
I would hope we all can just move on and let this horse lay down for a rest....
You all folks that dont like the T2 and how it measures fine, its been stated so just move on, life is too short.
You all folks that enjoy the T2, great enjoy it and go do some more DIY!
All the best
Alex
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Same could be said for this thread.
Tom
Agreed. I also had ‘X’ in mind as much as anybody when I wrote down my first comment....
No the Pass Labs circuits in general here you can read for yourself. This stuff has been discussed for years, you are being deliberately thick. You are not informing anyone of something that was not already known about these simple low/no feedback circuits.
FIRST WATT
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I apologize for holding you to the same standard as you hold me. You're absolutely right. There is no place here for personal attacks.
Nobody lost their minds when I reviewed the O2 and the Sjöström QRV08. In fact, Sjöström thanked me for providing measurements and many thanked me for providing the O2 measurements.
Years later, I review the T2 and everybody is upset. I think it may be prudent with a reality check here. There's plenty of room for all of us on this here space rock. Also, if measurements are irrelevant for audio, why would anyone be upset that a set of measurements exist for the T2?
At least I had enough respect for Mark to not post a link to my review on this thread. I don't see any reason to rain on his parade, but do believe that those who are data/measurements inclined should have the data made available to them.
Tom
Sorry Tom, I have to disagree. Low distortion amp will preserve driver acoustic distortion while a carefully designed amp will cancel some of the driver acoustic distortion. Other method such as current sense feedback rarely used also reduce acoustic distortion.
Your stated preference to low distortion amp indirectly shows your preference to the native acoustic distortion of the driver.
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