Problem solving
Hi steenoe !
The pot is definitively not the problem. It seems that your power supply has difficulties in delivering the required supply current. Therefore you have some undesired coupling between the two channels and between the bias circuitry and the output stage.
Please use a 10000uF/40V cap near to the PCB.
Hi steenoe !
The pot is definitively not the problem. It seems that your power supply has difficulties in delivering the required supply current. Therefore you have some undesired coupling between the two channels and between the bias circuitry and the output stage.
Please use a 10000uF/40V cap near to the PCB.
You are right Alexander, thanks. I saw that earlier and it has been corrected. I will try and place a big cap close to the board as ILA suggested, and check my grounding scheme too. I am looking forward to hear what this circuit sounds like
Let us know what you think about it, Alexander
Steen
Let us know what you think about it, Alexander Steen
IRF 610 reversed
If you have reversed the IRF610, you have probably damaged T101/201=ZTX753. Please check the Vbe of this transistor, it should be around 0.65V. I know that well, because one day the same happened to me. The board still worked - sounding a bit strange. It turned out, that the above transistor had a Vbe of 1.3V. Unbelievable but true.
Ivo
If you have reversed the IRF610, you have probably damaged T101/201=ZTX753. Please check the Vbe of this transistor, it should be around 0.65V. I know that well, because one day the same happened to me. The board still worked - sounding a bit strange. It turned out, that the above transistor had a Vbe of 1.3V. Unbelievable but true.
Ivo
Thanks, ILA It works. It must have been the ZTX753 in the opposite side, I would never have guessed it could be that one I put in a new, and voila! Well, it actually sounds good too I didnt have time to listen a lot to it, but it sounds very promising. The supply I made isn't good enough, as suspected.
Its too noisy.
ILA, do you have any suggestions for a suitable supply?
Thanks for posting this fine, little circuit
Steen
It works. It must have been the ZTX753 in the opposite side, I would never have guessed it could be that one I put in a new, and voila! Well, it actually sounds good too I didnt have time to listen a lot to it, but it sounds very promising. The supply I made isn't good enough, as suspected.Its too noisy.
ILA, do you have any suggestions for a suitable supply?
Thanks for posting this fine, little circuit
Steen
Power supply
Hi steenoe !
The power supply dependes on your application. If you use the board with the original BOZ board, I would suggest to tab the zener-diodes chain (the one that mister Pass likes best), take another TIP29 and don´t forget the 100uF between base and ground.
My own solution is a good old LM317 as 25V preregulator, decoupling the output with a resistor - say 10 ohms or so - and then a bank of 10000uF capacitors.
Ivo
Hi steenoe !
The power supply dependes on your application. If you use the board with the original BOZ board, I would suggest to tab the zener-diodes chain (the one that mister Pass likes best), take another TIP29 and don´t forget the 100uF between base and ground.
My own solution is a good old LM317 as 25V preregulator, decoupling the output with a resistor - say 10 ohms or so - and then a bank of 10000uF capacitors.
Ivo
ILA, thanks for the supply suggestions. I made a kind of BoZ supply with 24V and it works allright! Well the RIAA stage sounds just great!! You can safely build that one if you consider to I have a small thing with hiss though! I didnt excactly excpect total silence, but the hiss is quite detectable! Between tracks at fairly high level, its not too good
Any suggestions?
`Steen
I have a small thing with hiss though! I didnt excactly excpect total silence, but the hiss is quite detectable! Between tracks at fairly high level, its not too good Any suggestions?`Steen
Noise
Hi !
The IRF610 is not a low noise semiconductor. The SiO2 gate insulator inherent in every Mos - Transistor (lateral / vertical) causes some flicker noise in the audio band (high 1/f corner). At high volume settings you will hear this as hiss.
Nevertheless I do not find this as a problem because the background noise from your vinyl is still dominant.
The solution to this problem is to use a medium power JFet. A suitable JFet must meet the following requirements:
gm @ 10mA = min. 100mS
Idss = min. 50mA
Ciss = max. 150pF
Vds = min. 20V
Ivo
Hi !
The IRF610 is not a low noise semiconductor. The SiO2 gate insulator inherent in every Mos - Transistor (lateral / vertical) causes some flicker noise in the audio band (high 1/f corner). At high volume settings you will hear this as hiss.
Nevertheless I do not find this as a problem because the background noise from your vinyl is still dominant.
The solution to this problem is to use a medium power JFet. A suitable JFet must meet the following requirements:
gm @ 10mA = min. 100mS
Idss = min. 50mA
Ciss = max. 150pF
Vds = min. 20V
Ivo
Vey interesting phono stage. I may try to build one. Reguarding the power supply, one of the best supply for phono stage are LM317 follow by CRCRC filters. See this thread for very good discussion on phono preamp supply. I made a text resume at the thread end that resume most of the discussion. There is a section on power supply.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=28957&perpage=10&pagenumber=1
Bye...
http://www.diyaudio.com/forums/showthread.php?s=&threadid=28957&perpage=10&pagenumber=1
Bye...
Lovoltech JFet
Hi Jürgen !
I have looked through the lovoltech product catalogue. The LU1014D has to much input capacitance. This will result in mid band peaking and high frequency cutoff with an ordinary MM cartridge.
The L8S220N may be a good choice - is anybody willing to buy 1000 pieces?
Ivo
Hi Jürgen !
I have looked through the lovoltech product catalogue. The LU1014D has to much input capacitance. This will result in mid band peaking and high frequency cutoff with an ordinary MM cartridge.
The L8S220N may be a good choice - is anybody willing to buy 1000 pieces?
Ivo
Thanks for the advice, ILA. I will try and find a J- FET.
I have that nasty habbit, putting my ears to the speakers when I have built something new
I am a bit focused on hum, which I dont like at all. This little RIAA stage sounds pretty good
Could you make that with 4 paralleled SK170BL J-fets instead of the big mosfet?
I think ILA said it is possible. Thanks for the link with info on the supply. Steen
Hi steenoe !
It is a bit difficult to get the required transconductance out of the 2SK170BL. You will need at least 4 devices (as you said) in parallel. In this case the matching procedere will be painful - or you can use up to 8 devices with individual source resistors (10 - 22 ohms).
A single monolithic device such as 2N6550 or L8S220N would be my personal favourite if the noise floor from the IRF610 is not acceptable.
Unfortunately these devices are hard to obtain in diy quantities and not what I call a bargain.
Ivo
It is a bit difficult to get the required transconductance out of the 2SK170BL. You will need at least 4 devices (as you said) in parallel. In this case the matching procedere will be painful - or you can use up to 8 devices with individual source resistors (10 - 22 ohms).
A single monolithic device such as 2N6550 or L8S220N would be my personal favourite if the noise floor from the IRF610 is not acceptable.
Unfortunately these devices are hard to obtain in diy quantities and not what I call a bargain.
Ivo
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