Search found 72 matches

by Hans
Thu Jun 30, 2016 4:40 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Shorting the input and measuring the output is great for literature but any real world installation will be multiple magnitudes greater. I fully agree. I would like to show an image, confirming what you mention, with a noise spectrum with: 1) input shorted 2) everything connected but cart still in ...
by Hans
Thu Jun 30, 2016 12:09 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

JR. wrote:Perhaps your choice of words is also contributing to animus.
That may certainly be the case, I try to do my best but it should be quite obvious that English is not my native language.
English is a complex language with all its understatements and double meanings.

Hans
by Hans
Thu Jun 30, 2016 11:50 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

High grade is subjective and not a bright line. I regard your design as high grade simply because of all the effort invested to what you have designed, i.e. extremely low noise, full balanced design etc. Noise is much lower than strictly needed and a full balanced design is also quite a step above ...
by Hans
Thu Jun 30, 2016 10:17 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Wanna link to some High End (?) circuits which you feel have lower noise, lower current bla bla and better "balance"? That would be a constructive contribution. Sorry to say, but I find your response to my open questions, meant to give a constructive contribution, rather harsh. Answerring your bla ...
by Hans
Thu Jun 30, 2016 5:50 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

I still have to think that MC carts capacitively coupled with huge capacitors to elevated transistor bases are going to see peak DC currents in the tens if not hundreds of uA at turn-on. After a good long warm-up and forming maybe a few uA. But if capacitor leakage specifications are consistent wit...
by Hans
Wed Jun 29, 2016 1:45 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Ever looked at these Fet's from Interfet ?

IF9030 0.5nV/rtHz
IF3601 0.3nV/rtHz

Hans
by Hans
Wed Jun 29, 2016 5:50 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

I tried to find a difference in THD and/or 2nd HD on test discs with IIRC, up to 100uA through the cartridges, but saw nothing. The real reason for the tests were to justify putting Ib of 5534/2 through a MM cartridge. I then tried some Ortofon MCs cos I expected their greater power efficiency woul...
by Hans
Tue Jun 28, 2016 9:05 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

The BF862 FET has 0.8nV/rtHz.
but maybe others are even better.

Hans
by Hans
Mon Jun 27, 2016 2:07 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

mediatechnology wrote:I made the Ios measurement pretty quickly.
At the time my expectation was that it would be high enough to measure directly.
Next time I have it powered on the bench I'll measure it through the output.
O.K.
And please see my contribution as a way to contribute in a positive way.

Hans
by Hans
Mon Jun 27, 2016 12:09 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 174980

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

To measure the Offset current accurately, you only have to measure between TP1 and TP2 with 1) the input shorted and 2) with the input open, i.e. only having the 2x 499 between the inputs. Subtract the two voltages, divide by 158000 (=50dB*499)and you have the Offset current in nano-amps. Thus 15.8m...