Let me answer first to the current mirror's topic.
You can also strip that down and correct directly on the common source i.e. directly on the signal path rather than house keeping.
However I don't find that as refine as correcting through a current mirror IMHO.
You made a good point regarding different Idss.
On the SE Paradise servo works just fine and on the balance every asymmetry on the input devices would not being able to be corrected.
In simulation, you can simulate 2 not properly matched devices in the following ways:
a) create a new part with slightly different parameters
b) change one or more source resistors (which is more catastrofic than point a. )
Per point b) on rev5 when I thought that one servo would be able to correct any unbalancy, I tried to play with source resistor and found that it wasn't true.
However with this new arrangement, at least simulation wise, it looks to work just fine as the two resistor in searies allow isolation between common mode of the two halves thus the servo corrects separately.
Again I have not tried that yet, as I am trying to build the paradise for starters.
Nex step is to build the balance version.
Now, let's comment on your point regarding BJTs vs. JFETs.
Thank you very much for sharing this point.
Like I said I have never tried one over the other, I like JFETs but I don't disregard BJTs of course.
However even Joachim suggested that JFETs are probably better sounding to his ear.
I have the following question for you:
1) you said you build a JFET version WITHOUT ELCAP, thus even if you parallel 4 of them, you won't reach 60dB gain but a rather disappointing 45dB-isch, are you using the stage with MM cartridge or with MC?
2) Just to get an idea what is your set up in terms of turntable, cartridge, tonearm etc etc down to speakers? I am asking that to kind of understand if we have the same taste that's all
Thank you for your post and feel free to mark up the schematic and re-post it with your ideas that way it is clearer and more straightforward what you exactly mean.
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can you show me how you would strip parts of the circuit down (please circuit schematic or mark ups and not just description) and tell me the reason why it should work better? I might evaluate that if makes sense.
Stefanoo,
I am just suggesting a path of how to get where you are going. I am not going to tell you what to do or how to do it, even if I could(I cant). But I think you are missing something. Youhave knowledge that allows you to look at someone else's design and cobble pieces together for an idea. Not saying that won't work, but you may be missing something along the way. The fact that you assume that the current mirror additions will improve things shows this, I believe. How do you know. Perhaps ig built and listened to, you would find they are unnecessary. Most complicated does not infer best design. You love your Pass amps, yet seem to miss what is his overall design concept of "as simple as possible, but no simpler". You may very well end up where you stand now, but you will haev done so because a series of choices and listening sessions, not just simulations. If it doesnt sound good, how do you know what to fix? You started at the end, not the beginning. I am not trying to be a pain, just offering a different overall design approach. Good luck. I will leave you alone and watch progress.
I am just suggesting a path of how to get where you are going. I am not going to tell you what to do or how to do it, even if I could(I cant). But I think you are missing something. Youhave knowledge that allows you to look at someone else's design and cobble pieces together for an idea. Not saying that won't work, but you may be missing something along the way. The fact that you assume that the current mirror additions will improve things shows this, I believe. How do you know. Perhaps ig built and listened to, you would find they are unnecessary. Most complicated does not infer best design. You love your Pass amps, yet seem to miss what is his overall design concept of "as simple as possible, but no simpler". You may very well end up where you stand now, but you will haev done so because a series of choices and listening sessions, not just simulations. If it doesnt sound good, how do you know what to fix? You started at the end, not the beginning. I am not trying to be a pain, just offering a different overall design approach. Good luck. I will leave you alone and watch progress.
No thanks. I appreciate your comment and I think it also makes sense.
You know me
I am very much about listening.My goal here is to have a concept design and perhaps more than one idea to implement, listen and perfect.
It is not a short process unfortunately and you can't take big shortcuts.
Again I appreciate your comment so don't feel like a pain because again what you said makes sense.
Thanks.
wooo nice!! Good for you! And thank you for the thought of not making this thread a debate on equipment, you are smart!
So you are pretty sure that using J74/K170 yeals to a more grainy?
That is interesting as pretty much everybody thinks that these Jfets are one of the best sounding device (not) avaialable.
I did listen a little bit to the phono yesterday and it sounded really nice to my ears.
Thanks for your contribute.
So you are pretty sure that using J74/K170 yeals to a more grainy?
That is interesting as pretty much everybody thinks that these Jfets are one of the best sounding device (not) avaialable.
I did listen a little bit to the phono yesterday and it sounded really nice to my ears.
Thanks for your contribute.
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Little update on this subject.
I have one channel of the MasterPiece up on my bench.
Offset is extremely good so far.
The only thing I can't get is gain. Accordingly to the simulation I should be able to get about 61dB of gain @1KHZ while on the real circuit I get a mere 55-56dB.
I am using J74/K170 BL GRADE. I am wondering if with the V grade, unfortunately I don't have them, I would be able to get more gain out of it.
Also, I know this is kind a retorical question, but isn't there any JFET out there that has a higher transconductance with linear characteristic and pretty complementary N/P CH? 
I have one channel of the MasterPiece up on my bench.
Offset is extremely good so far.
The only thing I can't get is gain. Accordingly to the simulation I should be able to get about 61dB of gain @1KHZ while on the real circuit I get a mere 55-56dB.
I am using J74/K170 BL GRADE. I am wondering if with the V grade, unfortunately I don't have them, I would be able to get more gain out of it.
Also, I know this is kind a retorical question, but isn't there any JFET out there that has a higher transconductance with linear characteristic and pretty complementary N/P CH?
Best way is to accept the Caps and stick to the bipolars... Reason why caps have a bad reputation is when they are used in a zero crossing position. In the paradise there's no zero crossing, as the caps are always charged. When used like this the drawbacks of a cap is very very minute, and The cap can of course be bypassed with film, but in reality the MHz loss in the El-co is not unwelcome. quite confident that you'll have a lot better result with the Bipolars, than with the much too hard to get Jfet critters.
you can also boost gain by adding current gain in the mirrors. but you have to watch dissipation of the Lower mirror transistor.
you can also boost gain by adding current gain in the mirrors. but you have to watch dissipation of the Lower mirror transistor.
MiiB,
thanks for your reply.
If I use 16 JFETs for the balance at the input I get to a dumb 59dB.
However I am sure I can squeeze out 2-3 dBs, I am convinced that this arrangement won't sound any good.
One other thing I have noticed is that frequency response, of the SE Jfet with no caps, is very narrow for some reason. and significantly drops down at 80KHz, and I was unable to trace this problem down nor understand why it would do that also because on simulation it doesn't show having this issue at all.
Going back to bipolars and capacitors.
It sounds really nice. However I Can say from tests I have conducted that ELCAP has a much bigger impact than what you think it doesn.
Simply enough, just changing the type and/or arrangement significantly changes the overall sound, which obsiously highlights the fact that cap there is introducing somehow a clear sonic signature as expected.
Unfortunately it looks like in order to do it much simpler with JFETs, you will have to find devices with at least 5-6 time the transconductance of the K170/J74 and I am not sure is a possible tasks
How come devices like those don't exist? I can't imagine why they wouldn't make them or made them at a certain point?
There are a ton of BJTs but very limited JFETs.
Clearly JFETs is an evolution of the BJT came after than and I Don't understand why this technology is only used on IC but not available discrete.
Maybe some custom military or NASA parts...I am sure they must have something like that.
I remember talking to a hi-end manufacturer in my country who was explaining to me that in prder to create his very fine electronics he had to haunt down parts from NASA (don't know if it is true) devices with extremely high gm and linearity which allowed him to only have one gain stage.
What do you guys think of it?
There are much steeper J-Fets from Interfet for example. This one has 80mS and there is even one with 350mS.InterFET Corp. Page Selector - IF9030 datasheet
Again the problem is that there is no matching P-Fet.
Just to be safe i designed a good sounding phono stage with only high Gm N-channel J-Fets some time ago. It must not be parallel symmetric, there are alternatives.
Again the problem is that there is no matching P-Fet.
Just to be safe i designed a good sounding phono stage with only high Gm N-channel J-Fets some time ago. It must not be parallel symmetric, there are alternatives.
I would do a differential stage with only high Gm N-channels, sure. That P-channel thing is simply impossible to solve. Linear Systems simply does not make them available.
The disadvantage is 6dB more noise with the same amount of input devices. Bob Cordell solved it by paralleling 4 LSK389 and got the noise down to 0.7nV/qHz. That is ok but i would go for 0.5nV/qHz. That is possible with the Interfet parts without paralleling that much. I know you are not a fan of paralleling but i simply have no better idea when you do not want the noise to be audible at the listening seat unless you take the super high Gm parts. Bob also converts in the input stage from balanced-In to unbalanced-out.
I would do the same or you need really tight matching of better then 0.1% of all parts.
If you do not do that you throw your common mode rejection out of the window.
There is also the risk that your double RIIA cancels in part in the micro details.
The disadvantage is 6dB more noise with the same amount of input devices. Bob Cordell solved it by paralleling 4 LSK389 and got the noise down to 0.7nV/qHz. That is ok but i would go for 0.5nV/qHz. That is possible with the Interfet parts without paralleling that much. I know you are not a fan of paralleling but i simply have no better idea when you do not want the noise to be audible at the listening seat unless you take the super high Gm parts. Bob also converts in the input stage from balanced-In to unbalanced-out.
I would do the same or you need really tight matching of better then 0.1% of all parts.
If you do not do that you throw your common mode rejection out of the window.
There is also the risk that your double RIIA cancels in part in the micro details.
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Here is one clever way to make a balanced-in, balanced-out stage with only N-Channels AND only one set of RIAA parts so it can be done :schematics
OHH, sorry, it has some coupling caps and a transformer, something you do not like too.
Coming up with a way of eating the cake but also keeping it is not easy but that is what i would like to see.
OHH, sorry, it has some coupling caps and a transformer, something you do not like too.
Coming up with a way of eating the cake but also keeping it is not easy but that is what i would like to see.
so basically it wouln't be a full balance topology, am I right?
Could you post a link to the schematic by BC you are referring to in this discussion?
Also, what would be the disadvantages of using a super high gm device if this brings you less noise, less parallel device and more gain?
On your comments you make is sound like a possible alternative, rather than a better solution.
I posted while you were posting.
Ok got the schematic, very interesting however, like you can imagine, I dislike transformers on the signal path.
Also, why would you want to convert to unbalance out to then re-convert it balance out?
If you have a decent matching, I am assuming you could get a cancellation of 2nd harmonic by keeping it balance throughout, while this way you just end up summing up, thus having more unwanted distortion.
Am I saying something wrong?
The high Gm parts have only the disadvantage to be very expensive but that did problem did not hinder you to buy the super expensive Teflons.
There is a super high Gm N-Fet with 0.3nV/qHz that could do the job with only pair.
I have somewhere on MPP designed a hypothetic phono stage with that parts, but that topology was more similar to the Pink Triangle Pip.
You have to browse the Intefet web page to find it. Sorry, i do not have enough time today to find it.
Bob Schematic is in Jan Diddens Linaer Audio 4 so i can not simply scan it and post it here.
I recommend to buy that issue anyway. There is a lot of interesting material about phono in there, also MM stages and tubes.
There is a super high Gm N-Fet with 0.3nV/qHz that could do the job with only pair.
I have somewhere on MPP designed a hypothetic phono stage with that parts, but that topology was more similar to the Pink Triangle Pip.
You have to browse the Intefet web page to find it. Sorry, i do not have enough time today to find it.
Bob Schematic is in Jan Diddens Linaer Audio 4 so i can not simply scan it and post it here.
I recommend to buy that issue anyway. There is a lot of interesting material about phono in there, also MM stages and tubes.
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