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Old 5th November 2009, 02:48 PM   #31
MRupp is offline MRupp  Germany
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I find your design very intriguing and I am surprised that you do not get much response. People are either scared off or the title plus the low number of visitors on this particular forum are the reason for this.

In the latter case may I suggest a little marketing and to use Syn08's approach of intentionally posting a design in the wrong but much more frequented Solid State forum
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Old 6th November 2009, 01:02 AM   #32
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Today i fished the second channel and was able to measure it and listen breefly.
I work late hours so everybody at home was sleeping when i came home so i could only listen at low volume to a diet of Casandra Wilson and Diana Krall.
Measurements first:
There are diffences between the channels but most of them can be explained.
One channel (the new one) has 0.8dB more gain. that may come from the MAT02/MAT03 being different on the channels. I had selected the cascode transistors for hfe but could not do that for the MAT´s. I am using a PEAK Consult transitor tester for this and the revers bias diodes in the MAT`s fooled the PEAK. I could of cause measure the hfe directly but i was to lazy. I may change to other input transistors anyway. The gain difference can of cause be adjusted by R7.
The RIAA on that channel had a 1dB loss at 20Hz. That can be expained by the use of poorly matched 10% carbon resistors. The servo is also a bit different in the new channel and has a series resistor of 1Mohm instead of 750kOhm on the first channel. That does not explain the difference because in both servos the brakepoint is very low.
I used a 0.47uF MKT on both channels. Help !!! i am running out of resistors !!!!!
I also put C6, C7, C8 and C9 into the new circuit (value 2200uF) and that lowered distortion a lot. 3rd went under -100dB at 0dB/U output (aka 1V RMS) and 2nd went down from -75dB to -90dB so this modification is recommended. it also lowers the noisefloor somewhat by a theoretical -3dB.
I then mounted some capacitors also in the older channel and got an improovement too but 10dB less on the 2nd and 4dB less on the third then i got on the new channel. higher harmonics (4th, 5th) are also present but very low in value.
i can only explain that behaviour in the context that i used different types of electrolytics. The new channel has SMD polymer Nichicon 6V and the other channel has through hole Nicicon polymer 4V. Why they behave so different i do not know. This part of the circuit is very sensitive to biasing issues so i will try other caps too. One thing that occured to me is that polymer electrolytics of that high value have a very high leakage current in the order of 1mA. Elna and others are making low leakage types that have less then one muA. Wet tantal whould be ideal in that sense although they do no have particalar low ESR. Unfortunately the 2200uF i found from Kemet at Farnell cost a staggering 300,- € each !
Sound :
i listed to Casandra Wilson and Diana Krall at low volume.
The MPP certainly works and what comes out resembles music.
High frequency noise is very low but there was some noise in the deeper ranges that sounded like distant firecrackers. Not objectionable in the listening seet but something to worry about. The circuit is really starving on that primitive powersupply and i will try a well regulated active supply on the weekend.
I had some strage clicking noise on the right channel when i changes volume but in the lab the DC offset of both cannels was under 0.1V.
Maybe my tubeamps are giving up after long use. I already experienced some problems with focus and soudstaging with my fully developped reference phonostage. I use the Goldstandart as Pre-Pre and the MM stage of the soon to be released Quantummusic Telepath phonostage.
Be it as it may, on this weekend i am on the Klangbilder High End Show in the Hilton Danube in Vienna and will play the prototype of the MPP after hours. The Goldstandart, The Hypnosis and The Telepath are also playing.
I hope to take home my repaired and updated Mace Amp to do some more tests when i am home.
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Old 6th November 2009, 01:16 AM   #33
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Hi MRupp !
i do not care at that moment if this particular thread gets a lot of attention but many thanks that you care.
I will develop it for my own pleasure and hope that it will prosper in terms of quality.
Certainly when the design will be mature i will put it in some quite spectacular casework
with some inovative mechanical solutions that will benefit the sound i hope.
I know how to get attention but this is more like raising a child.
The only thing that disapponts me a bit that nobody is commending on the circuitry so i am on my owm here. i hoped to get some input concerning the optimisation of the topology in terms of speed, noise and distortion. me being trained in the 70th are not so good at simulating but usually a mix of intuition, basic math and experience get´s the job done. Again thank you for your attention.
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Old 6th November 2009, 03:03 AM   #34
anatech is offline anatech  Canada
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Hi Joachim,
I think that many of us are reading and learning as you go. Once you have things at a certain level, the questions will begin. So the number of other members posting at this point may be completely irrelevant. There are no metrics that I know of that tell us how many are currently viewing this thread. For example, I've been following, but I'll have to go over everything once more. It's always been late and I don't fully grasp the concepts since I'm tired.

Another distinct possibility, respect. Allowing you to bring your design and ideas forward with no interference from the peanut gallery.

This project / thread should be done for your own enjoyment anyway. Otherwise it's too much like work!

-Chris
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Old 6th November 2009, 03:41 AM   #35
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This are wise words and actually i have watched a lot of forums before i decided to post here. There are other good ones but this has the nicest tone and highest level of sofistication so i already enjoy what i am doing more then i thought.
I will explain more how the circuit works in detail but eventually it will even get more complex. This is one of the reasons i do not plan to do it as a commercial product. It will simply be extraordinary expensive to make. I am still contemplating how i will make it available if there is any need for it but this is not important at that stage.
So today i post more buffers in various orders of complication (perfection ?) and ad my own design although i never actually build it. but maybe...
Other good ones i found but did not include here because excellent documentation is available are the Borbely and Per-Anders Superbuffers.
Attached Files
File Type: pdf Pedja Rosic Buffer.TSC - TINA.pdf (40.8 KB, 469 views)
File Type: pdf Jung Buffer.TSC - TINA.pdf (44.3 KB, 429 views)
File Type: pdf Sofisticated Buffers.TSC - TINA.pdf (69.6 KB, 507 views)
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Old 6th November 2009, 09:29 PM   #36
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Before leaving to Vienna i was able to work further on the MPP.
Having prooved that it plays music i was still puzzelt why the two channels are so different. One thing i found was that the bateries on one channel where nearly empty and i had forgotten to do one groundconnection on the new channel. Now both channels work much more similar. They have only a 0.2dB difference in gain now and the RIAA curve is exactly the same with the 1dB of lift at 20Hz i already talked about. Distortion is also the same now until 500mV but a new problem has developped on the new channel. It has more then 3V DC offset and i was sofar not able to cure that. I looked at the servo and other parts of the circuit but i have not found the cause until now.
Anyway i am going to Vienna now where i meet a friend who has the latest generation Audio Precission analyser and is also a very good engineer. I hope we can find some time after hours to repair the new channel. Maybe a component is faulty because i could not find a topology mistake. Stay tuned.
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Old 6th November 2009, 09:45 PM   #37
anatech is offline anatech  Canada
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Hi Joachim,
Remember, good technicians and good engineers are never stumped by difficult problems. It's always the very simple things that trip them up. ... from many years observing people.


Have a good time and you don't have to tell us what the problem was.

Quote:
There are other good ones but this has the nicest tone and highest level of sofistication so i already enjoy what i am doing more then i thought.
Thank you! That's the same reason I joined. It's everyone together that makes or breaks a place.

-Chris
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Old 6th November 2009, 10:52 PM   #38
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Joachim,

Most interesting assessment. Those noise figures are wonderfully low. Your design is most ingenious. I was trained in the sixties, so I know where you are at. That is very good test gear you have, you will be amused to hear one day how I developed the Paris......

Hugh
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Old 6th November 2009, 11:56 PM   #39
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Can`t wait to hear the story.
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Old 8th November 2009, 04:54 AM   #40
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It`a little off topic here because i try to make a transimpedance circuit without NFB in the input stage. On the way to Vienna i designed a voltage feedback version during a break that has voltage feedback and hence less distortion.
I posted it on Syn08`s thread "HPS 4.0 Phonostage " under "Solid State" with more explanation and details.
Anyway here is the basic circuit.
Attached Files
File Type: pdf Sans Pareil Basic Structure.TSC - TINA.pdf (105.8 KB, 525 views)
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