I am very happy to hear that!!! All the hard work in putting in all the improvements and fixes finally pays off.... I will prepare the final touches now, and start the group buy hopefully by end of next week.
Here is the anti-RIAA that I used, please see attached. The values are the exact same values, only that I built 4 of these, to use two per channel for symmetry.
One way to limit the servo working hard is to pre adjust the buffer.. Different IDSS JFETs in the current source can give different buffer offsets.
Also the resistors in the current mirrors are a bit critical...to match the currents totally One could go for 0.1% tolerance.
I have selected rather high resistor values in the servo's circuit connection, this to shield it max from the signal path, but it's really overkill as it is already shielded behind a high impedance mirror, by lowering the resistor values the the servo gets more authority.
Also the resistors in the current mirrors are a bit critical...to match the currents totally One could go for 0.1% tolerance.
I have selected rather high resistor values in the servo's circuit connection, this to shield it max from the signal path, but it's really overkill as it is already shielded behind a high impedance mirror, by lowering the resistor values the the servo gets more authority.
Thanks, Michael, i will try that. It is not a big deal anyway but output offset could be a bit more stable.
I measure exactly 1.444V over all current mirror resistors ( i checked only one channel ) and Idss was matched in the buffer, again not better then 10%.
I will try to lower the resistors after the servo for more authority.
I listened more with my son and his friend yesterday night. We had a lot of fun.
Harry Bellafonte, Level 42, Joni Mitchell, Dido, Luis Armstrong and Duke Ellington, SOS Band and more. Today i will listen to classical and Jazz. I have played some classical and it worked fine.
I measure exactly 1.444V over all current mirror resistors ( i checked only one channel ) and Idss was matched in the buffer, again not better then 10%.
I will try to lower the resistors after the servo for more authority.
I listened more with my son and his friend yesterday night. We had a lot of fun.
Harry Bellafonte, Level 42, Joni Mitchell, Dido, Luis Armstrong and Duke Ellington, SOS Band and more. Today i will listen to classical and Jazz. I have played some classical and it worked fine.
nano void jfet.... mini tubes aparently 
Hi Joachim, I noticed a generous reduction in input offset just by connecting a Denon cart... I will listen to the rig this week (hopefully).
As for output offset, It exists but in a small scale... I will wait for the outcome of your experiments with opamp feedback resistors
Hi Joachim, I noticed a generous reduction in input offset just by connecting a Denon cart... I will listen to the rig this week (hopefully).
As for output offset, It exists but in a small scale... I will wait for the outcome of your experiments with opamp feedback resistors
Yes, i will look into the offset issue today. Good that the input DC level went down.
By the way, the Paradise and the Pardise R2 are not biased optimally for the Denon DL103. It is more optimized for cartridges under 10 Ohm. Lowering the bias would lower the input offset but then we would also run out of steam to drive the RIIA.
By the way, the Paradise and the Pardise R2 are not biased optimally for the Denon DL103. It is more optimized for cartridges under 10 Ohm. Lowering the bias would lower the input offset but then we would also run out of steam to drive the RIIA.
Here is a list of the Benz cartridges :Benz-Micro Cartridge Specs & Prices
The ones under 20 Ohm should work fine.
The ones under 20 Ohm should work fine.
Simply put a 40 Ohm resistor parallel to the input ( without cartridge connected ) and then you see. The last time i measured a Denon DL103 it had 28 Ohm but 40 Ohm are shown in the data sheet.
There is a website called Vinyl Engine:Technics | Cartridge Data | Vinyl Engine
There you can see at lot of information.
I heard good things about the Technics MCs from the 70th and 80th. Pristine examples you can find on e-bay and others for 100 - 200 $.
There is a website called Vinyl Engine:Technics | Cartridge Data | Vinyl Engine
There you can see at lot of information.
I heard good things about the Technics MCs from the 70th and 80th. Pristine examples you can find on e-bay and others for 100 - 200 $.
As i reported some time ago input offset pushes the cantilever of the cartridge a bit out of the middle point of the magnet system. That can be partly compensated with down pressure. I found that under 0.1mV it does no harm. You can of cause use a capacitor at the input.
Say you load the input with 10kOhm. Then a 220uF elcap is fine.
You can also use an oversized one in bipolar plus a foil shunt, say a 1000uF 25V Nichicon ES with 1uF shunt.
I do not say that this is the most elegant solution but there will not be much distortion with the elcap because of such low level. This gives you at least the possibility to check out if the little offset there will remain does harm or not in terms of sound.
Frying the cartridge is unlikely. I build a lot of transimpedance inputs with much more offset and never destroyed a cartridge.
Say you load the input with 10kOhm. Then a 220uF elcap is fine.
You can also use an oversized one in bipolar plus a foil shunt, say a 1000uF 25V Nichicon ES with 1uF shunt.
I do not say that this is the most elegant solution but there will not be much distortion with the elcap because of such low level. This gives you at least the possibility to check out if the little offset there will remain does harm or not in terms of sound.
Frying the cartridge is unlikely. I build a lot of transimpedance inputs with much more offset and never destroyed a cartridge.
As far as i can tell the Boboli has 1.5mV nominal output. Plus 20dB can be cut at certain frequencies so it will put out 15mV on the highest peaks. Say we have 60dB of gain, we end up with 15 V at the output ! The Paradise can throw 15V P-P so on the highest peaks it will just not overload but you end up with a lot of voltage before the preamp. The 150 Ohm may certainly need a coupling cap.
Ouch.
What happened to our dutch connection ?
Stuffing german highways with these cute little boxes
they use to attach in the back of their cars ?
He was away for a short 'away mission' but he's back. Some mail has to be answered, and that will be done during the weekend.
I see that here all is well, all constructed power supplies are working as expected, and function in one go. As are the P2's, well done! Also I see some very promising listening reports, I cannot wait to hear it myself (and maybe even compare it to my http://www.diyaudio.com/forums/anal...t-all-dc-coupled-riaa-preamp.html#post2162960).
On this front here (you know I did show the boards some weeks ago), all parts have arrived, and my frame/chassis builder has delivered the first (beta) chassis. So I have to start building... BTW the top/back/internal-enclosure plates will be copper plated-polished-lacquered