Masterpiece

[Stefanoo]

Originally Posted by MiiB

I have built the paradise using Jfets and without the big caps... grainy and muddy compared to the Bipolar's, they have a warmer tone, but lacks the crisp and dynamic, so dull an warmer is what you get.

Sorry I don't understand the current mirror around the current source, it's a dead short, no need for that in the way you have designed this, only reason it works is the current running to and from the ground. your Jfets are running on IDSS.. In simulation that would sort of OK'ish as they are all the same...REaL-life..??

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.

[Stefanoo]

Originally Posted by buzzforb

Strip it down, as i suggested. There is plenty to learn with simpler circuits.

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.

[buzzforb]

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.

[Stefanoo]

Originally Posted by buzzforb

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.

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.

[MiiB]

True the gain goes down,with the Jfets, but I have a Decca London and another Paradise with a 45 dB gain (just a different Riaa network) so my listening results are valid.

I don't lack equipment, as I have Access to almost what ever I want... Don't want to make this thread about equipment.

[Stefanoo]

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.

[Stefanoo]

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?

[RCruz]

I believe there are no real alternatives nowadays

[Joachim Gerhard]

There are higher transconductance N-channels but the 2SJ74 is the only living boy in New York.

[MiiB]

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.