Agree with Joachim, thats strange.... I was listening to your boards in stereo, they sounded like mine.... I didnt measure the offset though.
Implementing that trimmer should be no problem, I will wait for the feedback from Ricardo to see if it brings anything. I will put a 10turn trimmer just like in the shunts.
From the fact that you have 24V we can conclude that the shunt is working. From the fact that the shunt is working we can conclude that there is a high probability that the current source is working (the voltage across TP201 and TPO202 will show what its state is (the CCS)). Then there can only one reason be for the high voltage at the top of the CCS (at TP202), the voltage source around Q201/202 is not working/broken or/and the zener ZD201 is broken (the voltage at TP203 will tell that (I hope)).
Thanks guys for jumping in and helping Ricardo.
Fortunately the new version is much less temperamental, even fool prove.
I am still looking into the little output offset issue of the new one. If that is solved i see no reason the new version could not be build by just about any body that can solder and has some basic tooling and experience. It performs very well in listening tests.
Fortunately the new version is much less temperamental, even fool prove.
I am still looking into the little output offset issue of the new one. If that is solved i see no reason the new version could not be build by just about any body that can solder and has some basic tooling and experience. It performs very well in listening tests.
Hi Frans
Thank you for your help... I will profit to understand how the shunt works
Here are my measurements in the "bad" channel:
TP101 29.7V
TP102 25V
TP103 29.7V
TP104 0.5V
TP201 -43.4V
TP202 -44.6V
TP203 -44.6V
TP204 -0.5V
Vin = +-44.6V
It seems that the zener diode ZD201 is broken (it is not conducting, so no music), check the values of R201 and R202 and if they are as expected replace the zener.
The 5.1V will work, but given the high input voltage I would prefer something higher. The 5.1V is the minimum value to be used; it just allows the CCS to work properly. The voltage at TP202 should be the same as at TP203 minus Vbe(Q202). The next thing to do is check the value of R203 and replace Q201 and Q202.
Update from me
I got both chanels working and played a couple of tracks.
Is not good news, but reading the last post I may know what is wrong.
As it is now back ground noise is preaty HI.
I have set the voltages so to have 17.5 V at the suply pins of the OPA134 and that may be where I am getting wrong.
As it is, there is quite a lot of noise when the nidle is up off the record.
I managed to take it down a fair bit by adding a bit of capacitance and comon mode coke near the Phono Boards, My traffo and pre regulator are about 1 meter away in a separaye box.
Now seeing Riccardo and FDW posts I know that the voltages I am using are to low.
What shuld the various voltages be on a working board ?
I am wrong in wooring about the suply to the op amp, spec sheet say 18V max?
I have 35V from Pre-reguators +17.5 at TP1 and -17.5 at TP2
I got both chanels working and played a couple of tracks.
Is not good news, but reading the last post I may know what is wrong.
As it is now back ground noise is preaty HI.
I have set the voltages so to have 17.5 V at the suply pins of the OPA134 and that may be where I am getting wrong.
As it is, there is quite a lot of noise when the nidle is up off the record.
I managed to take it down a fair bit by adding a bit of capacitance and comon mode coke near the Phono Boards, My traffo and pre regulator are about 1 meter away in a separaye box.
Now seeing Riccardo and FDW posts I know that the voltages I am using are to low.
What shuld the various voltages be on a working board ?
I am wrong in wooring about the suply to the op amp, spec sheet say 18V max?
I have 35V from Pre-reguators +17.5 at TP1 and -17.5 at TP2
Yes, he has R2 boards. This is strange....
The 10turn pot went into the updated R2 board design, so the final boards will have offset adjustment possibility....
Hi Quick one before I get ready for flight to Venice.
Yes got R2 Boards
The noise is hiss, white noise.
There is no hum boards are realy good even with open box and fluereshent tube inches awayor moving things around there is none whatsoever the board design is absolutley brilant.
As Albert say it is strange and I think it's My fault seting up V at tp1 tp2
I have both a 25 25 Trafo and 30 30 trafo with 25 X 1.471 and diodedrops I got around 35 + - going in to the boards.
Once again I can change the V at the TP1 and TP2 (+17.5 - 17.5 at present) with the 2 k pots WHAT shuld it be set at please?
I am going to try to take it up to + - 25 at TP1 TP2
On regards to ofset I got 1.36 mV I tried the mod and it fit nice and easy on botom of boards.
It can be set to nothink and desapear with small loading resistor.
I like the space and the 2 set of pads round the imput pins Ideal for small caps and load resistor as needed by MC
Yes got R2 Boards
The noise is hiss, white noise.
There is no hum boards are realy good even with open box and fluereshent tube inches awayor moving things around there is none whatsoever the board design is absolutley brilant.
As Albert say it is strange and I think it's My fault seting up V at tp1 tp2
I have both a 25 25 Trafo and 30 30 trafo with 25 X 1.471 and diodedrops I got around 35 + - going in to the boards.
Once again I can change the V at the TP1 and TP2 (+17.5 - 17.5 at present) with the 2 k pots WHAT shuld it be set at please?
I am going to try to take it up to + - 25 at TP1 TP2
On regards to ofset I got 1.36 mV I tried the mod and it fit nice and easy on botom of boards.
It can be set to nothink and desapear with small loading resistor.
I like the space and the 2 set of pads round the imput pins Ideal for small caps and load resistor as needed by MC
I think (as Joachim noted) that you are using R2 and that runs at about 18V, Ricardo is using R1 (the original Paradise) and that runs of 24V.
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