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Old 18th November 2009, 02:44 AM   #141
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next comes the Quantummusic Goldstandart my best commercial efford. Watch the extremely low noise in the Paris. The Goldstandarts actually sold have 4.5 to 6dB less noise because of massive paralleing. Shown is my lab sample.
The Goldstandart has a copious amount of shunt feedback in the first stage and massive NFB in the second stage so the measurement of a Head-Amp with parallel NFB is missing here but i expect no miracle. Actually it gets a bit boring. I get more and more the impression that conventional distortion measurements are sufficient to discribe the performance if the design is not totally incompetent so draw your own conclusions.
Yes, they all sound different my son tells me that still can hear up to 20kHz in his young age. Why will always remain a mystery. that is where the "Art" part comes in for me.
P.S: sorry , i can not find the squarewave test on the USB stick.
i promiss i send it tomrrow
Attached Images
File Type: jpg Goldstandart TIM noise method.jpg (95.8 KB, 554 views)
File Type: jpg Goldstandart Belchertest.jpg (122.4 KB, 537 views)
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Old 18th November 2009, 02:45 AM   #142
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Tip:
if you push the mouse in the left side down of the plots they are magnified even more
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Old 18th November 2009, 07:20 PM   #143
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here comes the squarewave TIM measurement of the Goldstandart.
I show the Paris here again for comparison (2nd picture from left)
the picture on the right shows the MPP output stage.
Attached Images
File Type: jpg Goldstandart TIM squarwave method.jpg (99.2 KB, 508 views)
File Type: jpg Paris TIM Squarewave method.jpg (93.5 KB, 486 views)
File Type: jpg IMG_0503-klein.jpg (188.1 KB, 545 views)
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Old 18th November 2009, 10:34 PM   #144
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Joachim,
I have sent you a personal measage via the forum - have you received it?

Top right hand corner of the page should show it.

Regards, Allen
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Old 18th November 2009, 10:59 PM   #145
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hi allen !
i got the message and i have answered immediately. did you not get it?
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Old 18th November 2009, 11:28 PM   #146
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So the MPP works now. What to do next ?
If i whould build it the next time i whould certainly thermocouple the input-stage because there is still a little bit to much DC fluctuation. the servo is quite slow so it can be up to 10mV at the ouput at times. Today i tried a DC adjustment on the cascode stage that can minimise DC offset from the input stage but the cartridge has to be connected and the amp warmed up for say 20 minuts to do the adjustment. a servo could be used on the inputstage but i rather would like to avoid that for simplicity sake. and i really whould like to spare me the discussion if a servo could do any harm at that point of the circuit.
also i may not use the MAT02-03 in my next build because i fried an expensive set during experimentation. i also have the SSM parts that are also low noise matched pairs and they are considerable cheeper although some people claim that they do not behave the same (they are not so easy to source any more but with some patience you can get them). If you are prepared to pay a premium take the MAT02/03 for piece of mind. they are excellent and have prooven to work well in this topology. there is a THAT chip that has 2xPNP and 2xNPN on one chip and could be interesting too. i also have a big collection of low noise bipolars from ROHM and Toshiba so i should have some luck to find well matched octets.
I plan to build the unballanced version next and will eventually make a stuffed and tested PC bord of that version availlable in different quality levels.
it will be interesting to compare the two versions soundwise. the unbalanced version certainly has a 3dB noise advantage and much simpler topology but my reference is the Goldstandart that has a balanced input and is sofar the best sounding device i made.
i also started to look at a powersupply for the MPP and Salas is helping me here.
for the time being i used 9V alcaline batteries buffered with Low ESR Elcaps. Today i switched to a low noise supply from LC audio that works well too and is not expensive. i think they charge around 57,--€ plus tax and shipping for a +- 12 V supply (actually it is adjustable) and it comes with transformer too.
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Old 19th November 2009, 01:35 AM   #147
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I slept some hours after work and awoke fresh. I currently have a strange illness and i do not know where that comes from. Circuit diagrams are appearing in my mind and beg for drawing.
seriously i am quite happy with the MPP how it is. I reached my target of -80dB distortion (0.01%) at 1 V output and it is mostly 2nd. i think that is quite good for an open loop design and will do the sound no harm in my opinion. on the contrary, i expect a little anhancement in the form off added liquidity and full tonal palette. Still for some this performance is still not good enough and i have seen in a recent paper from National Semiconductor that 1PPM is the way to go (-120dB) to make absulutely shure that the circuit is transparent. they make the amasing statement that 10 (or was is 100) stages in series with that specification would still add up to inaudible distortion. I think that is marketing hype but anyway made me think if it is possible to lower distortion even more just for the sake of it. yes, i said that in another thread, it is possible. When i build the next version of the MPP (unbalanced) i will use ROHM transistors that have a much better Gain match of NPN and PNP devices then the MAT02/03 combination has. I expect some cancelation of 2nd harmonic from that. to get to REAL low values the standard method is to raise the open loop gain and then pad it down again. in the case of the MPP i use current feedback in the form of a simple resistor. looking at the process alternatively the resistor makes a current-voltage transfer. So how can we raise the open loop gain in the MPP? well, first i substituted most resistors with constant current sources. then i equipped the folded cascodes with seperate current mirrors that float on bootstrapped current sources. the bootstrap increases the output conductance by current gain of the bootstrap transistor. this stage gives enormous forward gain and leaving out error feedforward and bias cancelation is the current state of the art. OPs like AD797 and LT1469 have circuits like that and are the lowest distortion devices currently on the market. i show the transimpedance variation but this can be done to the other circuits i have shown here and also for the common long tail pair. Will i ever build it ? maybe. i think i have to hone my simulation abilities a bit before i start a project like that. i feel comfortable with the MPP like it is but is shurely shown the path to the future. i call it the MPP ultimate
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File Type: pdf MPP Ultimate Basic Structure.TSC - TINA.pdf (88.1 KB, 294 views)
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Old 19th November 2009, 07:44 AM   #148
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Quote:
Originally Posted by Allen Wright View Post
Joachim,
I have sent you a personal measage via the forum - have you received it?

Top right hand corner of the page should show it.

Regards, Allen
This is a forum, share it with us,

Reinhard
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Old 19th November 2009, 09:45 AM   #149
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I asked Joachim if he would be interested in a listing comparison between his phono pre and my hybrid (bipolar + tubes) phono pre.

He replied, that he would.

Joachim, I did get your message - after I had written to you...

Are you ever in Schaffhausen CH?

Regards, Allen
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Old 19th November 2009, 12:32 PM   #150
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Quote:
Originally Posted by Joachim Gerhard View Post
I reached my target of -80dB distortion (0.01%) at 1 V output and it is mostly 2nd. i think that is quite good for an open loop design and will do the sound no harm in my opinion. on the contrary, i expect a little anhancement in the form off added liquidity and full tonal palette.
Not sure about the "sound" part, but it would certainly be interesting to find out about distortions vs. output voltage, at 20Hz, 1KHz and 20KHz. I don't think it's realistic to rely strictly on 1V output only.

Quote:
Originally Posted by Joachim Gerhard View Post
Still for some this performance is still not good enough and i have seen in a recent paper from National Semiconductor that 1PPM is the way to go (-120dB) to make absulutely shure that the circuit is transparent. they make the amasing statement that 10 (or was is 100) stages in series with that specification would still add up to inaudible distortion. I think that is marketing hype but anyway made me think if it is possible to lower distortion even more just for the sake of it.
For a MC cartridge amp, less than 0.01% distortions is nonsense. In my experience, headroom is the most striking audible factor. I found that not enough headroom makes the vinyl pops so much stronger and interfering with the program. Beats any distortion and/or RIAA errors in audibility.

Quote:
Originally Posted by Joachim Gerhard View Post
When i build the next version of the MPP (unbalanced) i will use ROHM transistors that have a much better Gain match of NPN and PNP devices then the MAT02/03 combination has.
You can bet on that. Because of the manufacturing process, all ultra low noise devices (ROHM, Hitachi, Toshiba, Sanyo) have little spread of beta and it's even better if they come from the same batch. I recently got a small stock of ROHM devices and, while they are not in the highest beta class, they match within 5%. Sorting for 1-2% is a breeze.

I think I've mentioned somewhere that, set aside the outrageous price, I am totally unhappy with the MAT and THAT dispersion and P/N matching. Such a dispersion is normal for double diffused devices.

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Originally Posted by Joachim Gerhard View Post
i feel comfortable with the MPP like it is but is shurely shown the path to the future. i call it the MPP ultimate
Looking forward
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