The Pass X product schematics have never been released publicly. That's still current production for Nelson and he needs to pay his light bills and put food on the table.
As for what's in the X stuff, circuit-wise, I have made a few guesses here and there, but I don't know if they're accurate. For all that people seem to assume that Nelson and I have lunch together every day, I've never actually met him and have only spoken with him once on the phone--although I have been known to send him an e-mail once in a blue moon (Nelson, quit snickering...). Nelson has said that the basic X/Super Symmetry patent schematic is essentially the X-600 schematic, but then he's also said that he's moved on to other front ends that use quad symmetry. That translates roughly as taking a 2SK389 and a 2SJ109 and using them as complementary differentials. I believe he said he's using current mirrors after that. Yes, that's an amplifier front end, but amp front ends have this endearing tendency to also be good starting points for preamp circuits...and vice versa.
Okay, so where does that leave you in your search for a preamp circuit?
For starters, you're not going to be able to build an X preamp. The "UGS" is the heart of the thing and if you don't have that, then all you're left with is a power supply and some control circuitry.
You don't say what you find objectionable about the Aleph. If you can't quite describe what's bothering you, build most anything, then sit down and listen to it. Think of it as a learning experience. It may take a little time and effort, but you'll know intimately what different topologies can sound like. If you know what's bothering you, then perhaps you can begin making educated guesses as to what to try next.
The Pumpkin? I built something like that a few years ago, but with a follower output. It sounded pretty good. It has the advantage of being a relatively simple circuit that won't require a lot of fiddling to make it sit up and beg.
Cheff's UGS is an altogether different beast. It's a more sophisticated and elegant circuit that will take more parts and time to build. Given that simpler circuits often sound better, the question arises: Are the extra parts worth it? In this case, I think so. Again, I've built something kinda-sorta like it, but not exactly. In fact, I'm using something of that sort as the front end of the amplifier circuit I'm currently building. I've almost got that whipped into shape and may even start a thread on it.
The idea of asking people on DIY what sounds good is somewhat like asking people what's the best thing to have for breakfast. Some will say eggs. Others will say cereal. Biscuits, cinnamon rolls, and muffins will all have their proponents. And there will be a surprising number who don't eat breakfast at all. Given that I've seen quite a few people go nuts over some pretty humble circuits, I long ago reached the conclusion that a variation on Beranek's Law is at work here: If you chose the circuit, selected the components, put up the money to buy the stuff, built the thing, debugged it, and finally got a chance to listen to it, then to you it's the most incredible thing on the planet. I've never asked people for their assessments of how things sound and I rarely offer my own.
The shorter my posts are, the more likely people are to interpret them as cranky and ill-tempered. Hopefully this one is long enough to escape that fate.
Grey
As for what's in the X stuff, circuit-wise, I have made a few guesses here and there, but I don't know if they're accurate. For all that people seem to assume that Nelson and I have lunch together every day, I've never actually met him and have only spoken with him once on the phone--although I have been known to send him an e-mail once in a blue moon (Nelson, quit snickering...). Nelson has said that the basic X/Super Symmetry patent schematic is essentially the X-600 schematic, but then he's also said that he's moved on to other front ends that use quad symmetry. That translates roughly as taking a 2SK389 and a 2SJ109 and using them as complementary differentials. I believe he said he's using current mirrors after that. Yes, that's an amplifier front end, but amp front ends have this endearing tendency to also be good starting points for preamp circuits...and vice versa.
Okay, so where does that leave you in your search for a preamp circuit?
For starters, you're not going to be able to build an X preamp. The "UGS" is the heart of the thing and if you don't have that, then all you're left with is a power supply and some control circuitry.
You don't say what you find objectionable about the Aleph. If you can't quite describe what's bothering you, build most anything, then sit down and listen to it. Think of it as a learning experience. It may take a little time and effort, but you'll know intimately what different topologies can sound like. If you know what's bothering you, then perhaps you can begin making educated guesses as to what to try next.
The Pumpkin? I built something like that a few years ago, but with a follower output. It sounded pretty good. It has the advantage of being a relatively simple circuit that won't require a lot of fiddling to make it sit up and beg.
Cheff's UGS is an altogether different beast. It's a more sophisticated and elegant circuit that will take more parts and time to build. Given that simpler circuits often sound better, the question arises: Are the extra parts worth it? In this case, I think so. Again, I've built something kinda-sorta like it, but not exactly. In fact, I'm using something of that sort as the front end of the amplifier circuit I'm currently building. I've almost got that whipped into shape and may even start a thread on it.
The idea of asking people on DIY what sounds good is somewhat like asking people what's the best thing to have for breakfast. Some will say eggs. Others will say cereal. Biscuits, cinnamon rolls, and muffins will all have their proponents. And there will be a surprising number who don't eat breakfast at all. Given that I've seen quite a few people go nuts over some pretty humble circuits, I long ago reached the conclusion that a variation on Beranek's Law is at work here: If you chose the circuit, selected the components, put up the money to buy the stuff, built the thing, debugged it, and finally got a chance to listen to it, then to you it's the most incredible thing on the planet. I've never asked people for their assessments of how things sound and I rarely offer my own.
The shorter my posts are, the more likely people are to interpret them as cranky and ill-tempered. Hopefully this one is long enough to escape that fate.
Grey
One of our blue boardmakers from Croatia briefly had a circuit for an "X-_" preamp on his website (I don't remember if it was X1 or X2). Knowing the value of knowledge, I stored away copy of the circuit diagram in my "greedy boy" files.
Only two things to consider:
1) I have no way of knowing if it is the same circuit used by the Pass Labs X-_ preamp.
2) Given Grey's thoughtful comments above, I would not post it without Nelson's permission.
JJ
Only two things to consider:
1) I have no way of knowing if it is the same circuit used by the Pass Labs X-_ preamp.
2) Given Grey's thoughtful comments above, I would not post it without Nelson's permission.
JJ
well - few (as always full of wisdom ) words from me ....... :
I dunno if its Chef's or any other UGS Diyaudio circuit same as Papa's ;
same - I dunno if its
same as some Papa's preamp ;
but - from my knowledge about Papa's published circs - I have impression that :
-he certainly made already that combination ( at least every combination which arrive on this board now and then)
- he certainly made it simpler and less complicated .
that must be truth from few reasons :
-he's awesome engineer ,
- he have uber sense of humor ,
- he is not ( at least not anymore ) victim of high end approach .
look at Shunty ; Papa is certainly smart enough to make Shunty's Shunty ;
at least to my knowledge - he isn't so nutz to implement gadget like this in his apparatus-es .........just from one reason ..... why bother ...
I will be pleased to see that X preamp schematic , but not to build one ..... but to see few more witty crumbs from Papa .....
on the other hand - I'm not so greedy boy to expect to see it in public forum ...... we still must show some respect and sensibility ..
I'm sure that Babo's reaction have that meaning
edit:
is it better than UGS ......... ?
it is , when paired with Shunty , driving F4 to clipping ;
is it - driving normal amp , with same PSU ........... ?
naah.............
I dunno if its Chef's or any other UGS Diyaudio circuit same as Papa's ;
same - I dunno if its
same as some Papa's preamp ;but - from my knowledge about Papa's published circs - I have impression that :
-he certainly made already that combination ( at least every combination which arrive on this board now and then)
- he certainly made it simpler and less complicated .
that must be truth from few reasons :
-he's awesome engineer ,
- he have uber sense of humor ,
- he is not ( at least not anymore ) victim of high end approach .
look at Shunty ; Papa is certainly smart enough to make Shunty's Shunty ;
at least to my knowledge - he isn't so nutz to implement gadget like this in his apparatus-es .........just from one reason ..... why bother ...
I will be pleased to see that X preamp schematic , but not to build one ..... but to see few more witty crumbs from Papa .....
on the other hand - I'm not so greedy boy to expect to see it in public forum ...... we still must show some respect and sensibility ..
I'm sure that Babo's reaction have that meaning
edit:
is it
better than UGS ......... ?it is , when paired with Shunty , driving F4 to clipping ;
is it - driving normal amp , with same PSU ........... ?
naah.............
It's not all that difficult to build a preamp that meets the basic criterion for an X circuit--a simple differential with feedback can do the trick. Topologically, the X circuits are just somewhat more complicated differentials...with all the extra stuff hanging off the two sides of the input differential like the limbs of a tree. They hang in mid-air, supported by the trunk. Like sap, the signal comes in at the trunk and flows to the most remote portions of the circuit.
Grey
P.S.: Interesting factoid--trees are only net producers of oxygen during the daylight hours. At night, they are net producers of carbon dioxide. Their oxygen contribution during the day, however, outweighs their carbon dioxide production at night, or else none of us would be here to fret over electronics.
Or we would have very different metabolisms.
Grey
P.S.: Interesting factoid--trees are only net producers of oxygen during the daylight hours. At night, they are net producers of carbon dioxide. Their oxygen contribution during the day, however, outweighs their carbon dioxide production at night, or else none of us would be here to fret over electronics.
Or we would have very different metabolisms.
GRollins said:
Thanks Grey for your post.....you were very clear and helpful.
I can describe what i find objectionable with the Aleph P....
I compared it to my reference preamplifier (ECI-4) which is a direct coupled with differential j-fet input.
The sound? well the the aleph doesn't seem to be as controlled and deep on the bass frequencies as the reference.
The midrenge is also not as clear and "silent" as the ECI-4 but conversely the sound-stage SEEMS to be more opened.
The high frequencies don't seem to go so high and is not as crispy as my reference.
In general it lacks with regard to the sense of the music.
An last the pre is also not as fast as i would have expected to be.
Wit the reference i can hear the player tapping the skin of the drum and all the harmonics of the instrument.
Therefore ... In the end....the difference seems to be vwey big.
I might be wrong by saying that i don't think that by changing capacitors i will obtain the desired result.
This is just my guess.
But i want to go till the end and i might buy the parts and finish the project and see what happens.
You are right with regard to the learning experience.
Right now...since this is the first thing i ever built i don't have any other reference and therefore i don't know what another topology would sound like.
That is why i would have liked to build something else like the X2 using the chef UGS or the pumpkin.
You caught the point with the example of the breakfast and each one's personal preferences...so i might just build other things and starting gathering experience on making things and on how different topologies sound like and find my own preference.
i think i'm going to start from the pumpkin and then after that try the UGS.
In the meantime i will really look forward to see your project that i'm sure will be an interesting thing.
Hope you can open it up soon.
thanks grey for your comment.
my best regards,
Stefano.
Three quick comments:
--Do not underestimate the difference caps can make.
--Do not try to use less than the recommended capacitance. More is okay.
--When people begin speaking in terms of 'crispy' highs, I tend to wonder if the design is using a lot of negative feedback. Differing rates of feedback can produce enormous differences in sound quality. This is the kind of thing that can get certain sorts of people really upset, so I'll just say that from where I sit, the less feedback, the better. The referent isn't what a meter says, nor is it another piece of audio equipment--the referent is what unamplified music sounds like. All else should proceed from there.
Grey
P.S.: The Panasonic 10uF metallized polyester caps are frequently used in DIY circuits because they're reasonably priced and widely available. Unfortunately, they're okay in the bass, but tend to lose steam as the frequencies climb. There are any number of boutique caps out there that sound very good, but they're also hideously expensive. For a little more than you'd spend on the Panasonic caps, you can try the WIMA polypropylene MKP10 caps. They've got another, similar cap that I haven't tried--I think it's called an MKP4. For even better results, bypass the WIMA with a small polystyrene.
--Do not underestimate the difference caps can make.
--Do not try to use less than the recommended capacitance. More is okay.
--When people begin speaking in terms of 'crispy' highs, I tend to wonder if the design is using a lot of negative feedback. Differing rates of feedback can produce enormous differences in sound quality. This is the kind of thing that can get certain sorts of people really upset, so I'll just say that from where I sit, the less feedback, the better. The referent isn't what a meter says, nor is it another piece of audio equipment--the referent is what unamplified music sounds like. All else should proceed from there.
Grey
P.S.: The Panasonic 10uF metallized polyester caps are frequently used in DIY circuits because they're reasonably priced and widely available. Unfortunately, they're okay in the bass, but tend to lose steam as the frequencies climb. There are any number of boutique caps out there that sound very good, but they're also hideously expensive. For a little more than you'd spend on the Panasonic caps, you can try the WIMA polypropylene MKP10 caps. They've got another, similar cap that I haven't tried--I think it's called an MKP4. For even better results, bypass the WIMA with a small polystyrene.
Stefanoo said:
Many possibilities here. Are you sure the 1.7 performs optimally? A picture may answer some questions.
- does it not oscillate?
- what is the output attenuator type?
- are the passive components at least on par with the Electrocompaniet? Is the PS? Remember, low/zero nfb circuits are generally more influenced by component quality. The ECI-4 has something like 500VA power transformer
- You may really not like the sound of cap-coupled circuits
- You may really not like the sound of low nfb circuits
Why don't you analyse/reverse the ECI-4 preamp section?
thank you all for your answers.
I'm going to answer in order:
Grey,
- ok i won't underestimate the rule of the capacitors.
- Actually i am using the value prescribed on NP' s project so 10uf for the IN and 30uF for the output.
I am a little shamed to say what type of caps i have on now, because i know you guys will scold me for that
I' ll change them and see what's new..
I was actually thinking at the beginning of using Auricaps but they are a little pricy.
Then, along the way, I decided to switch to Zen caps on Nelson's suggestion.
- I'm sure you know the Aleph P schematic...and if i' m not wrong it should be a 0 feedback circuit.
You made a correct statement by saying that our reference must be live music. I agree with you.
What can i say? Last week i had a very nice SACD hooked to my stereo system (i'm very mad at who decided that it needed to die.....it stinks!).
All the people that were there had the impression that nothing/nobody was between us and the recorded music (obviously we were using a very good recording by chesky). and that is what i like the most when i listen to a stereo chain...and unfortunately that didn't happen too many times
Just understand i am a total newbie with regard to building and making circuits but in these past 12 years i have been listening to alll sorts of things like jeff rowlands..spectral....avalon....klimo...vpi....vtl....and so on....so i got kinda of idea on what high level hi-fi sounds like (and i can anticipate that i don't share the sound philosophy of many of them)
Anyways after this long chat....The result?
When i tried to use the aleph P as a preamplifier i liked it...as every mother likes his child........but i couldn't find it better.....in therms of music and the sense of realism that i have when ECI is hooked up to B&W.
I think that i need to build more thing to find what topology satisfies me better.
I have on my head what music would have to sound like and obviously i aim to make something better then what i have now to make it " the new reference" and keep improving.
I know....my post was definitely too long....sorry for that....
I'm going to answer in order:
Grey,
- ok i won't underestimate the rule of the capacitors.
- Actually i am using the value prescribed on NP' s project so 10uf for the IN and 30uF for the output.
I am a little shamed to say what type of caps i have on now, because i know you guys will scold me for that
I' ll change them and see what's new..
I was actually thinking at the beginning of using Auricaps but they are a little pricy.
Then, along the way, I decided to switch to Zen caps on Nelson's suggestion.
- I'm sure you know the Aleph P schematic...and if i' m not wrong it should be a 0 feedback circuit.
You made a correct statement by saying that our reference must be live music. I agree with you.
What can i say? Last week i had a very nice SACD hooked to my stereo system (i'm very mad at who decided that it needed to die.....it stinks!).
All the people that were there had the impression that nothing/nobody was between us and the recorded music (obviously we were using a very good recording by chesky). and that is what i like the most when i listen to a stereo chain...and unfortunately that didn't happen too many times
Just understand i am a total newbie with regard to building and making circuits but in these past 12 years i have been listening to alll sorts of things like jeff rowlands..spectral....avalon....klimo...vpi....vtl....and so on....so i got kinda of idea on what high level hi-fi sounds like (and i can anticipate that i don't share the sound philosophy of many of them)
Anyways after this long chat....The result?
When i tried to use the aleph P as a preamplifier i liked it...as every mother likes his child........but i couldn't find it better.....in therms of music and the sense of realism that i have when ECI is hooked up to B&W.
I think that i need to build more thing to find what topology satisfies me better.
I have on my head what music would have to sound like and obviously i aim to make something better then what i have now to make it " the new reference" and keep improving.
I know....my post was definitely too long....sorry for that....
analog,
- it doesn't seem to be oscillating to me.
If i have a sine wave at the input i can see a stable sine at the output.
I don't know....now i' m on bed with fever so as soon as i'll be better i'll post some pictures as i can misunderstand the concept of oscillating thinking that it is something big that would affect the entire output when in the reality i can'tr be a small entity visible only at idle condition.
The only thing that i have on the Aleph that i would like to fix...but that i don't think it greatly affects the sound.... is a little hiss on the tweeter... and it is probably due to the not shielded output cables.
-To not degrade the output signal, since i didn't have a good output switch , i decided to use a fixed resistor and i eventually modify he volume of the CD player...but i actually put a "good listening level resistor" so that i don't have to modify the volume.
-Right now to make things fair...i was using the same ECI power supply that has a +60V (same suppy as the aleph).
By the way the toroid is a 600VA but it is shared with the power amplifier too since it is an integrated amplifier.
I still don't know what a cap's coupled circuit sounds like...and you are right i might not like it....but i still don't know.
Can you shortly describe me what a caps coupled circuit sounds like in comparison with a direct coupled circuit?
Why people here keep making caps coup circ? aren't they more demanding due to the variable quality of the coup cap?
If i'm not wrong both...aleph and EC are 0 nfb so i'm sure a like the 0nfb
I have the schematic of the ECI but as i said above .....i aim to make something better than that.... (by the way it is a j-fet differential input circuit...so i trust better the pumpkin over the aleph because i think jfet circuit are superior...but i might be wrong)
- it doesn't seem to be oscillating to me.
If i have a sine wave at the input i can see a stable sine at the output.
I don't know....now i' m on bed with fever so as soon as i'll be better i'll post some pictures as i can misunderstand the concept of oscillating thinking that it is something big that would affect the entire output when in the reality i can'tr be a small entity visible only at idle condition.
The only thing that i have on the Aleph that i would like to fix...but that i don't think it greatly affects the sound.... is a little hiss on the tweeter... and it is probably due to the not shielded output cables.
-To not degrade the output signal, since i didn't have a good output switch , i decided to use a fixed resistor and i eventually modify he volume of the CD player...but i actually put a "good listening level resistor" so that i don't have to modify the volume.
-Right now to make things fair...i was using the same ECI power supply that has a +60V (same suppy as the aleph).
By the way the toroid is a 600VA but it is shared with the power amplifier too since it is an integrated amplifier.
I still don't know what a cap's coupled circuit sounds like...and you are right i might not like it....but i still don't know.
Can you shortly describe me what a caps coupled circuit sounds like in comparison with a direct coupled circuit?
Why people here keep making caps coup circ? aren't they more demanding due to the variable quality of the coup cap?
If i'm not wrong both...aleph and EC are 0 nfb so i'm sure a like the 0nfb
I have the schematic of the ECI but as i said above .....i aim to make something better than that.... (by the way it is a j-fet differential input circuit...so i trust better the pumpkin over the aleph because i think jfet circuit are superior...but i might be wrong)
You seem to have addressed most of the issues.
"Hiss on the tweeter" is probably not the result of unshielded cables - they usually lead to hum.
The 1.7 has quite a lot of gain, could this be the reason for hiss?
It will be nice if you can measure the output noise (with the input shorted) so we get an idea of the nature of hiss. IIRC i had some issues with oscillations once. After increasing the gate stoppers it was fine.
It is supposed to have less than 5uV of noise at output!
Cap coupling, at least to my ears, always has some subjective effect of curtailing and rounding the lowest frequencies. The 1.7 has not only two caps in series with the signal but they also need to be huge in value because of the design.
It is also possible that the "Pass sound" is simply not what you are looking for. From several diy projects and commercial amps i've heard i wouldn't say it is the type of sound characterised with razor sharp separation, lightning speed and crushing dynamics. It is more a type of calm and romantic sound.
Keep in mind that relatively few diyers are also audiophiles. Which is probably obvious as both hobbies are very time consuming. Diy, is of course, much more expensive in the long run.
You may also be right about the Jfet inputs. Mosfets have generally higher input capacitance and a tendency to sound darker.
Does the ECI use a servo?
"Hiss on the tweeter" is probably not the result of unshielded cables - they usually lead to hum.
The 1.7 has quite a lot of gain, could this be the reason for hiss?
It will be nice if you can measure the output noise (with the input shorted) so we get an idea of the nature of hiss. IIRC i had some issues with oscillations once. After increasing the gate stoppers it was fine.
It is supposed to have less than 5uV of noise at output!
Cap coupling, at least to my ears, always has some subjective effect of curtailing and rounding the lowest frequencies. The 1.7 has not only two caps in series with the signal but they also need to be huge in value because of the design.
It is also possible that the "Pass sound" is simply not what you are looking for. From several diy projects and commercial amps i've heard i wouldn't say it is the type of sound characterised with razor sharp separation, lightning speed and crushing dynamics. It is more a type of calm and romantic sound.
Keep in mind that relatively few diyers are also audiophiles. Which is probably obvious as both hobbies are very time consuming. Diy, is of course, much more expensive in the long run.
You may also be right about the Jfet inputs. Mosfets have generally higher input capacitance and a tendency to sound darker.
Does the ECI use a servo?
are you sure?
I would be very glad of that.
Unfortunately right now this is not the case.
is there anything wrong? i still don't know.
The only thing that i can think of is the very bad quality capacitors (i'm going to change together with the other parts).
Have you ever tried the Electrocompaniet ECI4? (this is the modified version i put very nice diodes as extra-boast. i can tell very clearly the improvements with the modification -output stage, dc control, diodes power supply)
Don't get me wrong i ABSOLUTELY do not think that better can't be done.....i'm just waiting and working for that moment.
I would be very glad of that.
Unfortunately right now this is not the case.
is there anything wrong? i still don't know.
The only thing that i can think of is the very bad quality capacitors (i'm going to change together with the other parts).
Have you ever tried the Electrocompaniet ECI4? (this is the modified version i put very nice diodes as extra-boast. i can tell very clearly the improvements with the modification -output stage, dc control, diodes power supply)
Don't get me wrong i ABSOLUTELY do not think that better can't be done.....i'm just waiting and working for that moment.
GRollins said:
ah, intresting.
I am missing something....but is this a NP release?
I mean is it a service manual of a commercial NP product or a diy version?
Because i have been searching on internet for aleph P but the googling would only report me diy versions!
With regard to the Feedback......is the feedback resistor the 221k place across gate and drain of Q16 (Q19)?
analog_sa said:
yes i have been read that...i mean hiss can be also caused from a too high gain.
I actually have soldered in a 240ohm resistor....(hiss appeared after a little short i cause by switching different gate stopper resistor...so some of the components inside might have a problem...i don't know)
I have on the output a 4.7kohm res.
Unfortunately...and i want to outline this fact.....my scope has a power supply problem so doesn't allow me to have precise measures in fact when i would reduce the volt/div scale...i would see noise even without input signal....so i doubt i'll be able to make a reliable measure of 50uV...or even 5uV.
the only thing that i can ear is a little bit of oscillation if i touch the mosfet casing with my fingers but the noise would rise up for awhile and be steady to a certain value ....it wouldn't keep increasing and go out of control.
I have tried to increase the gate res but it seems to worse a little bit.
I was planning on ordering from mouser the fairchild part for the 9610.
What do you suggest me for the 610?
with regard to the coupling caps...don't shoot me...i am using tantalium capacitors..and therefore i need to change them to make a better evaluation and i except a sensible variation.
As far as i have read magazines ...unfortunately i have never heard one of NP's products because here in my city there are not pass's dialers...but from the reviews these products seems to privilege the transparent and neutral set up more than the romantic aspect that you describe me.
Bus as i said i never had the opportunity to listen to one of his product (i'm shamed!)
The EC has a DC servo on the output of the power stage that controls the input differential stage of the VAS.
It is a very nice project and most it sounds very nice.
Stefanoo said:
Stefano, with respect - but seems to me that you are biting too much for your knowledge level ;
it's completelly fine asking and wishing to know more , but - most important thing is knowing one gadget before going to another ..... only then you can understand difference between them .
try to remove flaws in your present preamp, then move to another one , if you stiil need that .......
post schematic here ( that's your homework, not anyone else's - to chase it) and then we can discuss it - where you (maybe) miss something and what you can improve.
point is - that preamp is still one of most cherrished in DIY world, not without reasons
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