Jay,
When JLH first published this design in 1969 it was called "Simple Class A Amplifier"
I have not built DOZ and do not intend to so cannot comment on that. I still adhere to many elements of the design philosphy that JLH developed over the years he was designing . . . which for me can be summarized as "as much OLG gain and "speed" as possible to give reasonably low HD and a very good stability margin" and "enough bias to avoid audible crossover / switching distortion".
This, coupled with keeping all possible sources of noise as low as possible seems to produce results that my ears prefer although I'm aware that other ears seem to prefer different approaches.
The Name DOZ seems to imply that if an amp design has more that one transistor it has the potential to sound better than a mono device design. I prefer designs to be as simple as possible but as complicated as it takes to sound as good as possible.
I agree that everything counts but for me some things count more than others
When JLH first published this design in 1969 it was called "Simple Class A Amplifier"
I have not built DOZ and do not intend to so cannot comment on that. I still adhere to many elements of the design philosphy that JLH developed over the years he was designing . . . which for me can be summarized as "as much OLG gain and "speed" as possible to give reasonably low HD and a very good stability margin" and "enough bias to avoid audible crossover / switching distortion".
This, coupled with keeping all possible sources of noise as low as possible seems to produce results that my ears prefer although I'm aware that other ears seem to prefer different approaches.
The Name DOZ seems to imply that if an amp design has more that one transistor it has the potential to sound better than a mono device design. I prefer designs to be as simple as possible but as complicated as it takes to sound as good as possible.
I agree that everything counts but for me some things count more than others
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I don't think I fully understand your words (re: Simple Class A is better than DOZ), but may be I understand the question. But this difference is only subtle for most and can easily be considered as a voodoo thing. In essence, I don't want to discuss the voodoo thing
DOZ is a simple class A amplifier, like JLH, and keeps its promises. So the voodoo thing doesn't exist. We have nothing to discuss.
Yes I know DOZ can blow away many simple MOSFET designs by the sound it produces.
Did you actually check the schematic of DOZ before saying that?
Or may be the JLH is too simple as the Zen? Do you think the DOZ can also be called a DOJ (Death Of JLH)?
Shouldn't you check the DOZ article on Rod Eliott's site before asking these here? There you can see and realize the truth, here- only voodoo.
Everything counts. Yup, you know that's why even ZEN uses some global negative feedback(which is considered to be a succabus that sucks the life out of music and leaves a husk, devoid of soul) minimize distortion to acceptable levels. People still use ZEN and praise it, with it huge amount of distortion for the topology it uses. If "everything" does count then ZEN would be considered one of the worst amplifiers, but the story is not so. To hear the sweet sound it produces people spend lots of dollars and time to build a system with it, ignoring many factors including damping factor, peaks and dips etc. which are important parts of "everything". They are not all mad, are they? Also, if you are looking for the best possible topology for a small power amp, then ZEN may well fail in this criteria, because it is the simplest, not the best.
For your kind information DOZ is nothing but JLH '96 with a different current source which stabilizes Iq without using some kind of voltage reference, like the JLH '69. Do you see the point? It's as simple(and complex) as the JLH.
Techs aside, I have built and listened ZEN V1, ZEN V4, JLH '69, JLH '96 and DOZ . EACH of them sounds different and unique in the same 8 ohm speaker. The DOZ and JLH '69 sounds almost identical and very pleasing. So does the ZEN V4, but it has poorer supply hum rejection than JLH or DOZ, plus a more complex current source. The simplest and true Class-A ZEN V1 sounds AWFUL into my 8ohm speakers(and it's not voodoo, clearly audible, just like the great Mr Pass said in the original article; ZEN may not be happy with some speakers. Is this still the best possible, even if it is the simplest?).
PS. DOZ is nothing but JLH. It's useless to call it Death of JLH or DOJ. The name "Death of Zen" is a mock on Pass's naming of his ZEN series amplifiers and preamplifiers, nothing more. And if you have those $200 16ohm fullranges then you don't need DOZ, trust me, however, I am pretty sure DOZ can make those expensive things sound equally pleasing.
Ah, I see.
I built the DOZ because of the tendentious name, after I built the ZEN variations. The first time I listened to it I thought "Ah, this is just another JLH". (I have been long a mosfet fan, and don't like the typical bipolar amps, including the JLH).
Don't forget about linearity. I think it is the key word determining the sound of bipolar amps. Just my guess.
Power supply ideas and the knowledge about the effect of power supply were not so advanced by then. But JLH choose (may be) the fastest transistor back then.
I prefer designs to be as good as possible, simple or complicated. Experience and knowledge only help to limit the options.
I agree that everything counts but for me some things count more than others
Sure, but sometimes we run out of some things. And simple things (e.g. ccs) can easily become the weakest link.
The first time I heard about this was from your post. If you can draw the schematic I think many will try it (CFP has unique sound yes).
It is a phase splitter anyway. Types of transistor may also count. I mean, today we have many good transistors compared to that era when JLH thought a CFP based splitter will improve performance. At least, I guess we're going to use NPN input transistor instead of the PNP as used in current JLH, aren't we?
Well from here you can see what a cfp is, Sziklai pair - Wikipedia, the free encyclopedia.
I dont think it is any major change changing the phase splitter transistor to this, I cant post here the page dedicated to this from a JLH book but think of the input impedance and output impedance the change makes as well as the positive effects it would have.
I dont think it is any major change changing the phase splitter transistor to this, I cant post here the page dedicated to this from a JLH book but think of the input impedance and output impedance the change makes as well as the positive effects it would have.
Hehehe none of the Pass amps are my options
If NP was to design the best amp, you will never find such a wide variety of amps. But he has to come closer, i.e. moving forward not backward. The BA3 shows what I mean.
Haven't I mentioned that for most, the difference is subtle, or doesn't exist. Saying that DOZ is different than JLH can be a voodoo. I love voodoo
Try ZenV9. The funny thing about DOZ is as if NP didn't know what he was doing.
Oh, I know what a Sziklai pair is. I thought the CFP is the second transistor in the pair. If what you meant was adding another transistor to make up a pair for the phase splitter, yes, there will be no major change like I thought.
But still, the existence of better device than the 2N1711 (faster, low Cob) might dismiss the need for extra transistor.
Think this carefully over again, Jlh knew what he was talking about, he wouldnt recommend something if it didnt improve things.
BTW the specs on 2n1711 are terrible, easily surpassed many times with mordern components.
So if it is a simple modification and you think it will improve things, you must have built and listened to it. What do you think of the sound?
Jay, why do you you suggest me to build a ZEN V9 when you have built and listened to it and it still isn't your option and I know that the V4 is equal with the JLH?
BTW, I am interested in the CFP phase splitter. Currently simulating, soon will build a JLH around it and post results here.
BTW, I am interested in the CFP phase splitter. Currently simulating, soon will build a JLH around it and post results here.
So if it is a simple modification and you think it will improve things, you must have built and listened to it. What do you think of the sound?
I dont think, I know, that with regards to measureable performance. As to what it sounds like I have no idea but I suggest someone to try and see.
I have long discarded Class A designs, no interest whatsoever, too much wasted power.
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I used to feel this way. But then I got to thinking - I notice most DIY Class A amps are rather low power. An ideal Class A push-pull amplifier wastes 50% of the power but most don't get that close, maybe 30% in the case of the JLH. They are often used with more sensitive speakers where high power is not required. Not many people leave them turned on because they get hot.
But most DIY Class AB amps are usually of quite high power, usually 50 - 100W minimum. They are not used in the range where they are most efficient and in reality don't do much better than 60%. They are often used with multi-way speakers with relatively low sensitivity. People often leave them switched on because they believe they use relatively little power.
So yes, the JLH wastes more heat, but overall I'm not sure the gap is that large.
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Just to let you know that things get "better" with Pass amps
BTW I'm surprised that you think ZenV4 is equal with the JLH!ZV4 is the first Zen with Aleph CS. ZV9 also uses it. ZV4 solves the low Zin issue with mosfet buffer. ZV9 has different approach to making a good sounding amp, a more proper way. But all Zens have high Zout as a result of simple circuit (which is the idea of the Zen series). This calls for FB which is not a good thing when we are after the best. Even Aleph CS is not a good thing, as it fix issues that should have not been there.
But such a use of power JFET to help balancing the operation of the main mosfet has been proven to be preferred by many. So is the J2. An "extreme" approach (actually not so for those seeking the best possible) is in the BA3.
But you like to build amps (and not focusing on the best only), so suggesting a few amps should not be a bad thing I guess
All of us were told many times, that there is no such a thing, as best amp in the world. But, if one discards a need to produce loud sound at parties and disco, than some preferences become more definite, and they tend to class A SS or tubes. Also, at less power, one has no need in paralleling output transistors, one has more freedom with providing power supply, and this contributes in a positive way. One could go to very top of sound quality along this way, but it seems that quality of recordings preclude this permanent perfectioning, above definite properties of the system recordings become a "bottleneck". As for power efficiency, when it goes about realization of personal dreams, it must not be that important.
You don't have low power 2-way bookshelf speaker? I have discarded Class-A amps also, but I have too many heatsinks
And I cannot pretend that class-B is as good as class-A.A-ha! Eight transistors at the output of the JLH! That's what I have been thinking to build (at least 0.65mA each). How/why do you come up with that circuit?
I think if we see the JLH as a single ended collector "follower", the CFP splitter should do no harm but good, even if the distortion spectrum is different. I will build this hopefully within next month
With mosfet, paralleling output device means higher capacitance, which is a drawback. But with bipolar I want more devices
I disagree. I know this "get better" is the "truth" for many. But I have found the truth to be different.Just to let you know that things get "better" with Pass amps
Here is the voodoo Jay, you are surprised to see that I can't actually hear things you can. Hahaha...
Jay, despite the high Zout the ZenV4 sounds identical to JLH(i.e VERY good, I know this kind of opinion often hurts certain people). BTW, Which one do you think I built in the wrong way just because they "should" not sound the same? voodoo Jay, voodoo.
But you like to build amps (and not focusing on the best only), so suggesting a few amps should not be a bad thing I guess
Jay, I discarded the Pass designs the day I built my first MOSFET based source follower pure SE class-A amplifier(the project-83 MOSFET power follower in ESP site coupled with DOZ preamplifier) which sounds marvelous. What I believe now is that the pass amps are simply not my cup of tea. You can not convince me otherwise no matter what you say, do or suggest, until the day comes on which I get my hands on a $200 fullrange with 96dB sensitivity.
I decide the "best" ONLY after building an amp myself and listeing to it. So the amps I consider to be good or bad have already been built by myself. BUT, I will never suggest you anything I built and found to be good because I don't consider other's "best" as something suitable(let alone be best) for me.
Jay, how do you focus on the "best" only and know that an amp is "best" before building it? Just by looking at the design? Or the simulation results? Or because Stereophile said it is?
Please stop suggesting anything other than JLH variations, like the CFP type phase splitter suggested above, this is the JLH 10 watt thread. PM me if you have to suggest anything else.