Building the DS Unbalanced Phono Preamp
Hi Everybody!
Now that I have found this thread, I can stop pestering Doug via email
Actually @DouglasSelf - Thanks for the board and your quick responses!!!
I am building the unbalanced version of the Signal transfer phono preamp and am obviously having the same issues as everybody else in finding a supply of 2SB737 PNP transistors, as well as the TL072CN called for in the build. I ended up taking the plunge on these parts with two different suppliers on ebay out of California. Both say they have genuine parts, so I will see if my Peak Atlas DCA55 analyzer can sniff out a rat on those when they arrive.
I also looked at the ZTX951 as a substitute for the 2SB737. Other than the base and collector being switched between the 951 and the 737, would there be other component value changes needed?
Has anyone completed their phono preamp build yet?
Thanks in advance
-Glen
Hi Everybody!
Now that I have found this thread, I can stop pestering Doug via email
Actually @DouglasSelf - Thanks for the board and your quick responses!!! I am building the unbalanced version of the Signal transfer phono preamp and am obviously having the same issues as everybody else in finding a supply of 2SB737 PNP transistors, as well as the TL072CN called for in the build. I ended up taking the plunge on these parts with two different suppliers on ebay out of California. Both say they have genuine parts, so I will see if my Peak Atlas DCA55 analyzer can sniff out a rat on those when they arrive.
I also looked at the ZTX951 as a substitute for the 2SB737. Other than the base and collector being switched between the 951 and the 737, would there be other component value changes needed?
Has anyone completed their phono preamp build yet?
Thanks in advance
-Glen
Low Noise Transistors from Zetex and ROHM
Not cheap but the provenance is impeccable.
The TL072 is a jellybean and should be widely available. Do not get hung-up on the "CN"-- that's temperature and package. You do want DIP-8 thru-hole, but your LPs will melt/shatter long before your chips, and there are more letters today for Lead-Free, tape/reel, and other unimportant (to us) options.
For the US, Da Bear is a reliable supplier:
IC TL072CP - Small Bear Electronics
The TL072 is used as the DC servo and must be a JFET/CMOS opamp due to the high resistance values in that part of the circuit, a bipolar opamp like the AD797 would fail here due to the high bias currents. It doesn't contribute to the noise of the circuit as much as you might think (again circuit topology).
Something like the OPA1652 could be a more performant JFET replacement (though I don't expect the '072 to dissappear in the near future). Most modern replacements would require ceramic decoupling capacitor between its rails that the '072 doesn't need (in fact it doesn't need any decoupling IIRC).
Something like the OPA1652 could be a more performant JFET replacement (though I don't expect the '072 to dissappear in the near future). Most modern replacements would require ceramic decoupling capacitor between its rails that the '072 doesn't need (in fact it doesn't need any decoupling IIRC).
Answering my own question…. The Alps SPUN194700 appears to have the correct pin spacing for this board.
Hello Mark
Let me say a very belated thank you for this. It seems to work very well with an absolute minimum of hassle.
It appears you have to zip the various Gerber layers into one zip folder before it will display them, but no big deal. Thanks again.
Douglas Self
I'm very glad you like it!
My guess is: they expect the Gerber files to be collected together in a .zip archive file, precisely because that's the format which is accepted/required by the low cost prototyping PCB fabs. JLCPCB, AllPCB, Elecrow, OSHPark, PCBway, etc.
BTW a fun and easy way to do price shopping comparisons is to try out the website
www dot pcbshopper dot com
Just enter your board's dimensions, number of layers, quantity desired, FR4 color, and copper plating (HASL, ENIG etc). Boom! Twenty price quotes along with total turnaround time and shipping speed options. To your country and in your country's currency.
_
My guess is: they expect the Gerber files to be collected together in a .zip archive file, precisely because that's the format which is accepted/required by the low cost prototyping PCB fabs. JLCPCB, AllPCB, Elecrow, OSHPark, PCBway, etc.
BTW a fun and easy way to do price shopping comparisons is to try out the website
www dot pcbshopper dot com
Just enter your board's dimensions, number of layers, quantity desired, FR4 color, and copper plating (HASL, ENIG etc). Boom! Twenty price quotes along with total turnaround time and shipping speed options. To your country and in your country's currency.
_
Last edited:
Which email address did you use?
The valid address is the on on the front page of my website.
NB, I haven't looked at this forum for some time.
I will go back and see if there are any other communication issues.
Just thinking aloud... this thread is quite limited in its appeal (as in the audience you have now is pretty much it I would think) and so if you want to go down the route of promoting and selling your boards then perhaps a new thread in the Vendor area would be more fruitful listing what was avilable and so on.
Also your own site has headers and links still showing the Signal Transfer Company as the place to get boards from. I think I would look at distancing yourself from that given all the problems over the last few years.
Carry on
Also your own site has headers and links still showing the Signal Transfer Company as the place to get boards from. I think I would look at distancing yourself from that given all the problems over the last few years.
Carry on
I will buy the Load Invariant and preamp + phonostage when in stock. I am very excited about this. Thanks for making this available again!
I appreciate this is not the place for purely commercial advertising. I was just hoping it would contact unhappy would-be customers, and it seems to have done that. I will certainly look into the Vendor area.
Also your own site has headers and links still showing the Signal Transfer Company as the place to get boards from. I think I would look at distancing yourself from that given all the problems over the last few years.
Carry on
Not sure I follow you here. The Signal Transfer Company (in the shape of me only) is still the place to get boards from. I have updated the website with new addresses, contact details etc. If there's anything on it I have missed I'd like to know so I can fix it.
Last edited: