Masterpiece

[MiiB]

there's is also a Pspice model, that can be used in LT-spice, but as a sub-circuit, It's beyond my skills to build a working model from that. LTspice has a lot of op-amps built in also differential ones and sub-circuit ones, but finding the right "similar" one can be a hassle.

 

[buzzforb]

MiiB, i build many shunt RIAA stages with the OPA1632 and with my values the result was precise to plus-minus 0.1dB so input impedance of the OPA1632 is a non issue.

Juma, the guy who created this opamp also suggested the meed for a buffer

 

[Joachim Gerhard]

That opamp can push more then 100mA so why the need of a buffer ?
Can you show me the creators response ?
Juma did that opamp ? Unlikely.
This is new to me.
I have under certain circumstances experienced that this chip can get quite hot, that can be solved with a copper trace in the MOPS version and with a cooling profile in the regualr SMD version.

 

[buzzforb]

I probably misread or misunderstood. Wouldnt be the first time.
http://www.diyaudio.com/forums/pass...clotron-jfet-input-buffer-opa1632-2sk135.html

 

[Joachim Gerhard]

It has two buffers inside the chip. Juma, an opamp designer ?
No way.

 

[Stefanoo]

there's is also a Pspice model, that can be used in LT-spice, but as a sub-circuit, It's beyond my skills to build a working model from that. LTspice has a lot of op-amps built in also differential ones and sub-circuit ones, but finding the right "similar" one can be a hassle.

Yeah kind of arc to convert from PSpice to LTSpice.
I will have to find a suitable part to create a model for the circuit.

 

[Stefanoo]

FYI: Joachim sorry I have to catch back tomorrow morning with your posts as I was busy until now trying to prototype the older differential input stage as I was curious to see how it performs.

 

[Joachim Gerhard]

Good that you try the differential input. That can be for the benefit of the Paradise community.
Concerning the Masterpiece from my side there is no rush.

 

[jacco vermeulen]

... I will try those.

Ricarditto,

easier to find if you google punch Philips 60pF.
e.g. : Teflon trimmer 60PF van Philps -hf-electronics

or 2222-809 (-05xxx to -09xxx ,are the ptfe series of Philips/BC components)
e.g. : https://www.elfa.se/elfa3~tr_en/elfa/init.do?item=68-798-03

Or http://www.newark.com/vishay-bc-components/bfc280908002/capacitor-trimmer-4pf-38pf-300v/dp/98K7134
Same routine at ebay.

Or be a teflon cheapo : adjust a polyester trimmer cap to value, then exchange for http://www.diyaudio.com/forums/pass-labs/156397-pearl-two-8.html#post2251685
(as a part fetishist, my religious beliefs forbid such activities)

 

[buzzforb]

Thats very clever Mr Beatty.

 

[Joachim Gerhard]

There are some really cheep NOS air trimmers that do the job as well.
Air is even better then teflon but i refuse to use NOS parts in my professional products.

 

[buzzforb]

Mountain air is best.

 

[FdW]

Ricarditto,

easier to find if you google punch Philips 60pF.
e.g. : Teflon trimmer 60PF van Philps -hf-electronics

or 2222-809 (-05xxx to -09xxx ,are the ptfe series of Philips/BC components)
e.g. : https://www.elfa.se/elfa3~tr_en/elfa/init.do?item=68-798-03

Or BFC280908002 - VISHAY BC COMPONENTS - CAPACITOR TRIMMER 4PF-38PF, 300V | Newark
Same routine at ebay.

Or be a teflon cheapo : adjust a polyster trimmer cap to value, then exchange for http://www.diyaudio.com/forums/pass-labs/156397-pearl-two-8.html#post2251685
(as a part fetishist, my religious beliefs forbid such activities)

Just one NOS trimmer available ...

 

[jacco vermeulen]

Mr B

Oink to you (phonebooks find it hard to remain sane)

The ptfe trimmer caps are no longer manufactured, so whether it's Vishay BFC, BC components or '80s Philips 2222-809, it's all NOS to me.

 

[buzzforb]

Really was a clever idea. Ill use it on my RIAA.

 

[Stefanoo]

Joachin,

I have creted a schematic with the differential input stage you had proposed on Paradise thread and used folded cascode to have a fully DC coupled differential in/out.
I thought this would have been worth posting it here on the Masterpiece.

It simulates great and everything.
The only problem I was unable to solve so far is the servo for differential.
I have been thinking and playing around but I cannot come out with something that works symmetrically.

I hope someone here will have some idea.

 

[Joachim Gerhard]

OK, so this is more or less a Paradise with the new input stage.
Yes, i know. making a servo for this is a major challenge.
I did not find the time to look deeper into it.

 

[FdW]

Joachin,

I have creted a schematic with the differential input stage you had proposed on Paradise thread and used folded cascode to have a fully DC coupled differential in/out.
I thought this would have been worth posting it here on the Masterpiece.

It simulates great and everything.
The only problem I was unable to solve so far is the servo for differential.
I have been thinking and playing around but I cannot come out with something that works symmetrically.

I hope someone here will have some idea.

You can not make a single servo for a balanced circuit, you need to use 2 servos. R12 must be split for this.

 

[Stefanoo]

OK, so this is more or less a Paradise with the new input stage.
Yes, i know. making a servo for this is a major challenge.
I did not find the time to look deeper into it.

it is more less a differential input with mirrrors anyway....yes servo there is a challenge.
Don't you however think that this could reserve some good surprise over the OPA's approach or you still think the other way will yeald to a better result?

If we could design a servo here I could try it and see how it sounds and then report!

 

[Stefanoo]

You can not make a single servo for a balanced circuit, you need to use 2 servos. R12 must be split for this.

How would you split it? to in series with two servos one at each end?
Could youy show me the priciple?

I am aware that I need two servos in the schematic I have included just one but I was playing with the differential one as well.