Mpp

[Audiofanatic]

This looks cute!

I'm gonna make one asap and will report to you guys.

Thanks again!

Best regards,


Audiofanatic (José)

[Joachim Gerhard]

Thanks Jan for the nice words, and we had fun too !
I have worked further on the Headphone Amp and the Self RIAA.
I am posting the new circuits later.

[iko]

Joachim, if you do, will you identify the parts as well or are you leaving the component names as an exercise to the reader?

[Joachim Gerhard]

I can identify the parts and you are right, i waited until somebody asks me.
I will help if you like to build one of my circuits.

[Salas]

Bravo Joachim. Wasn't expecting less than good third party testimonials.

[iko]

I would be interested in analyzing your headphone amp a bit first. Thanks!

[jan.didden]

Originally Posted by Salas

Bravo Joachim. Wasn't expecting less than good third party testimonials.

We listened to Joachims units on my system consisting of a predecessor of my paX error correction amp (in fact this is the amp that was tested by Hiraga in 1998 in La Nouvelle Revue du Son and got 39.5 points out of 40).
Speakers were vintage Martin Logan Sequell II's, response-corrected via an Australian DEQX PDC 2.6.
Joachim is very meticulous about taking care of his vinyl and there was an almost total absense of any ticks or pops or surface noise. I like my music clear, clean, analytic, strong bass and no coloration, and that is the reason that I often am disappointed by records. Not this time though; it was as clean and with strong, articulated bass as I could wish. And this was not a high-end turntable!
I attributed it to the combination of Joachims excellent electronics and the very good cartidge (a Lyra Helicon).

Edit: forgot to say: there was NO noise audible, nothing, nada, zilch. Very good design!

My subjective impressions

jd

[Joachim Gerhard]

Thanks again Jan. Record care is very important and part of the hobby. Send the record back to the seller if it is not ok.
I promissid compleet information about my Headphone Amp and here it comes.
I did some further tweeking but this will be the final edition for some time.
My audiophile ears where very happy with the sound of the PSG buffer but my engineer brain was not totally happy with the distortion measurements. Usually i go for -80dB or even -100dB so i redigned the buffer, the biggest source of distortion in the original version. I now use a modern form of the JLH buffer that should measure much better.
The parallel symmetric nature surpresses second harmonic and the bipolars bootstrap the fets and provide lokal feedback. This circuit is also much cheeper to make then the costly Linear Systems double Fet i was using.
I raised the output idlle current to 50mA. I build little cooling plates from 5cent pieces.
The output transistors run quite hot now so tomorrow i ad a second plate to each transistor.
The AKG701 now sings smoothly. The circuit can deliver 3V in class A into that can.
The 701 does 105dB with 1V so i think this is ample.
The JG Headphone Amp can deliver 150mW in class A and the AKG701 can stand 200mW of max power so i think it is a good match.
The output trasistors have to transfer 0,6W each into heat for that performance.
I am very happy with that design now. It sounds clear, dynamic and smooth, very good for late night listening.
On the photo i am posting you also see my new home mini lab.
I got a little 40MHz digital scope and a 20Mhz generator.
I can measure distortion with my Praxis system on my laptop but only down to -90dB.
I use an M-Audio Transit soundcard because of portablity but that limits resolution.
Dos anybody know a better portable soundcard that does better then that ?

[Joachim Gerhard]

I started to build my version of the Self phonostage.
First, the circuit i posted had two errors : i forgot one 10nF cap and i called a 47kOhm resistor a 200 Ohm. Sorry, the version posted now corrects this errors.
I will use the JLH buffer and because i can not let good enough, good enough i will try darlingtons this time with potentially even less distortion.
I am not sure if i need the servo still but i kept it in the diagramm.
First i build the filter banks and the good news is that the Self trick works. Paralleling several caps with 1% tolerance gives a cap with better then 0.5% tolerance.
The 10nf´s added to absolutely the same value ( 49nF ) , bejond my measurement limit and the 4.7nF bank was better then 0.5%.
I lowered the corner frequency of the subsonic filter to 14Hz / -3dB.
John will recocknise the famous pink Röderstein MKC as used in vintage Mark Levinson equipment.
I also found some "real" cooling profiles for my headphone amp.
I will install them and listen a bit before i go to bed.

[iko]

Originally Posted by Joachim Gerhard

I promissid compleet information about my Headphone Amp and here it comes.

Thank you Joachim.