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Old 22nd April 2010, 12:14 AM   #1211
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I am building a preamp for a friend. For many years he was listening to CD and never wanted back to Vinyl. Until the day i brought my turntable and phonostage to his home.
Now he gets a preamp with High Z Capacitive MPP, Tentlabs volume control ( he wanted remote) and PSG buffer. That buffer improved the sound of his AudioAero CD player a lot.
Eather someting is wrong with the digital volume control on that player or the PSG adds some extremely pleasing distortion. We cranked the volume control on the CD player full and then added the buffer with a conventinal TKD pot as an experiment and he was blown away. Anyway for his Pre i choose the Placid PSU from Twisted Pear. Actually this is my first experience of a Shunt PSU on my equipment and i tested it out on my Headphone Amp. Compared to the LC Audio with inductor i heard an improvement but it was not night and day. The Headphone Amp has superb PSU rejection and even with simple 9V blocs there is no hiss or humm at all. The placid had a slightly softer sound i prefered because most CDs are a bit hot and compressed to say the least. The Placid made CDs more pleasant to listen too. Quiet pasages where more quiet so to say and i heard some micro details that escaped me with the LC Audio PSU. Bass was on the other hand was more clear and detailed and even a bit tighter and extended.
See also a picture of my frieds Turntable that i have around for adjustment. Its a Clearaudio with magnetic bearing and for 2000,- you get it with a good arm and cartridge. I substituted the cartridge with my Lyra Helicon and will that replace again when the new Delos comes. It sound really great and i was surprised how little the difference to my 35.000 monster is. Well the little Clearaudio does not reach the mastertape precission of my setup but it is very dynamic and alive sounding and makes lots of fun. Rumble is extremely low courtesy of the magnetic bearing and speed stabilty is good. I have it sitting on a simple Ikea table but touching the surface with my hand, vibration was very low. That simple silicon feet that are fitted work exceptionally well.
Attached Images
File Type: jpg Placid PSU.jpg (97.9 KB, 488 views)
File Type: jpg Clearaudio Turntable.jpg (97.2 KB, 489 views)
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Old 22nd April 2010, 11:03 AM   #1212
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With the help of Sigurd we developed the discrete Opamp further. The first version is ready and the results are very good. Open loop bandwidth is 40kHz (-3B), gain is 54dB,
distortion is under 0.01% up to 10kHz and around 0.02% up to 100kHz (open loop).
We call it JG OPamp 2.21. I can be usefull for many things. Linestage, filter etc.
I will try it as the second stage in my High Z Capacitive MPP.
We are working on a second version, working title 3.1, and will decide later what to use.
Attached Files
File Type: pdf JG_Discrete_OPamp_ver_2[1].21_REV_A.pdf (13.9 KB, 140 views)
File Type: pdf JG_Discrete_OPamp_ver_2[1].21_THD_REV_A.pdf (19.0 KB, 98 views)
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Old 22nd April 2010, 11:30 AM   #1213
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Here is a simulation of the High Z Capacitive MPP and the Ina.
Values are mathematically correct. If you take the closest standard values and 1% parts
precission "detorientates" to +- 0.1dB.
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Old 23rd April 2010, 12:37 AM   #1214
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Today the stuffed adaptor boards with the LME49990 arived from Stephan Horwege so i was able to build the Balanced INA input for the JG Self. I wish Holger whould be here.
The slightly rough and ready sound of the simple Phonoclone is gone replaced by a much more smooth and liquid sound with great bass and very good micro detail resolution.
This is not the lowest noise phonostage i ever designed. The discrete circuits i have shown here have the edje but up to medium high volume noise was not audible at the listening seat with my 96dB efficient MPL. At very high volume it was slightly audible but had a very "benign" quality with very little agressive treble content. This latest generation Opamps come fritening close in sound to discrete circuits so i am even more motivated to come up with a superiour discrete Opamp. One advantage of the INA topology is DC precission and i measured only 2.5mV at the output of the INA. A Servo is not necessary i think. Before the subsonic filter i am measuring 600mV now instead of 270mV and i think that is still fine. i decoupled all three Opamps in the INA with one pair of ELNA Silmic 2 330uF 25V and put only one 0.1uF Roederstein MKP from PIN 4 to Pin 7 of each Opamp. I talked about that in the "Best sounding OPamp" thread but got so much critique that i sopped to post on that thread for a while. Both the LME49990 and the ADA4627 are very fast but i have no troube with oscilation at all.
See the picture. You see the 3 0.1uF MKPs ( blue rectangles) directly soldered over
the OPs at the input. I left the Phonoclone in for the ocasion that somebody wants to here the difference.
One other notewothy thing. Allen Wright of Vacuum State will visit me on sunday. He brings some tube equipment, so this will be interseting to compare with what i have.
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File Type: jpg JG Self INA.jpg (99.8 KB, 438 views)
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Old 23rd April 2010, 12:58 AM   #1215
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Hi Joachim,

This looks nice

I'll get back to you later, I need to get up at 7 and the only thing I do is reading posts on DIYAudio

Cheers,


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Old 24th April 2010, 12:21 AM   #1216
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I am very happy with the sound of the Balanced INA i added to the JG-Self. It sounds much more natural then the simple Phonocone i used before. The Phonoclone is very dynamic and direct sounding but lacks liquidity and is a little stessfull sounding over the long run. I will convert that stage into a simple balanced input and see if that sounds better.
I also redesigned the linestage. I raised the current in the buffer after Sigurd made some simulations to gain linearity and i will add a Mono-Stereo switch. I have separate pot meters for left and right , so this will help me to find the center position more easily. Sigurd and i have more or less decided on the topology for the discrete OPamp but do not expect something new until next week. I really goes into the details now.
Attached Files
File Type: pdf DSJG Simple Balanced Input.TSC - TINA.pdf (39.6 KB, 115 views)
File Type: pdf JG Self Linestage Mono-Stereo.TSC - TINA.pdf (61.2 KB, 112 views)
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Old 24th April 2010, 01:44 AM   #1217
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Default OPAmp's

Hi Joachim,


I ordered the Opamp's and as soon as they arrive I'll start building your RIAA and compare it to my own passive phono amp.

I was wondering what the DC resistance is of the inductors after the LC Audio PSU you use. If I remember correctly it was a 27 mH inductor?

I use a J-fet as a MC head amp cause my phono is a MM type.
With tube's! I've used a SUN Audio transformer befor but this J-fet is faster than the SUN sound wise.

I'll read your posts tomorrow, it's late again

All the best.


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Old 24th April 2010, 10:19 AM   #1218
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The inductor i use has 27mH and 4 Ohm.
I posted a lot of RIAA circuits here so which one do you like to try ?
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Old 24th April 2010, 01:24 PM   #1219
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Hi Joachim,


I meant the DSJG.TSC The one with OPA1642 and LSK 389 and LME 49713.
The reason I want to try it is because I never liked OPAmp's in the past.
But looking at the specs of the new models I think it's time to be a bit more tolerant to those little creechurs ;-)

I'll order also a LC Audio PSU and start building your RIAA.

I'll report later when I'm done.

Thanks again for sharing.

Cheers,


Jos

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Old 24th April 2010, 05:10 PM   #1220
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I optimised the buffer a bit. See my recent posts. The LSK389C is quite costly and my new buffer has better specs. Sonds great though, maybe because it has only second harmonic.
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