Preamp Layouts
As promised here are the eagle board files for the the PMA preamp I have been working on. I have also included the voltage regulator boards. I haven't yet had a chance to label everyting on these boards, feel free to do it and psot them again. You will notice that I made a few changes here and there. Mostly I moved the output so the traces were shorter, added pads for larger capacitors near the OPA's and also added pads for some caps near the input. I also removed the GND input near the DS1802...it was unnecessary and could have caused a ground loop.
I would like it if somone could help me modify the PSU boards to add a discrete regulator as Steeno suggested. I was looking at some designs last night for this...Pedja Rogic has a nice one on his web site...Alcaids is also very nice.
Anyway Enjoy! 😀
As promised here are the eagle board files for the the PMA preamp I have been working on. I have also included the voltage regulator boards. I haven't yet had a chance to label everyting on these boards, feel free to do it and psot them again. You will notice that I made a few changes here and there. Mostly I moved the output so the traces were shorter, added pads for larger capacitors near the OPA's and also added pads for some caps near the input. I also removed the GND input near the DS1802...it was unnecessary and could have caused a ground loop.
I would like it if somone could help me modify the PSU boards to add a discrete regulator as Steeno suggested. I was looking at some designs last night for this...Pedja Rogic has a nice one on his web site...Alcaids is also very nice.
Anyway Enjoy! 😀
Re: Discrete Regulator
Could you post the schemtic?
If it's a zener + emitter follower the output impedance decrease with increasing value of output capacitance, so yes you need a output cap.
Gcollier said:
Could you post the schemtic?
If it's a zener + emitter follower the output impedance decrease with increasing value of output capacitance, so yes you need a output cap.
Member
Joined 2002
Gcollier said:
This schematic is wrong : O ) The buf 634 sybol is wrong leading it with the pin's wrong also.
jleaman said:
You are absolutely correct...well sort of.
The schematic is correct if you are using the TO220 package...not the dip. Looks like i screwed it up on the PCB. I will re-route it with the proper pinout for the DIP8 package. Thanks for paying attention jleaman you saved me from making a big mistake. 😱 I'm working now on finishing up soldering some LM4780 boards so I likely won't be correcting this today...but likely tomorrow.Member
Joined 2002
send me the sch file ill fix it for ya : O ) I was extreamly confused when i was looking at your board and then yuor schematic : O ) then i got it Its de wrong one HEHE. Just wanted to help that's all..
J'
J'
Not sure if it's important to you or not, but I think the TO220 version of the BUF634 has better heat dissipation than the DIP-8 version, plus you could throw a heatsink on for better cooling if you like.
I can't find a datasheet for the mg2955/3055 - can someone pls provide a link?
Do these differ from MJE2955/3055?
Thx! I'm intrigued by this PS design...😀
edit - never mind! The board pic lists MJE2955/3055....
Do these differ from MJE2955/3055?
Thx! I'm intrigued by this PS design...😀
edit - never mind! The board pic lists MJE2955/3055....
No dual discrete bridge rectifiers?! I mean, c'mon. Everyone does those nowadays 😉 I mean, how audiophile can you get if you're not forced to get a transformer with dual secondaries?! Huh?!
Just kidding.
It might be smaller/spiffier if you could make each +/- voltage on a smaller, separate board. That way you have a flexible design (like the digi01 boards) that can be used for more stuff! (I'm being selfish here, 'cause I'm thinking about a way to replace my +/- 15v and +5v PSUs on my DAC)
Just kidding.
It might be smaller/spiffier if you could make each +/- voltage on a smaller, separate board. That way you have a flexible design (like the digi01 boards) that can be used for more stuff! (I'm being selfish here, 'cause I'm thinking about a way to replace my +/- 15v and +5v PSUs on my DAC)
Fat Dave said:
For a preamp, I don't think you'll ever be hitting the 250ma output capability of the BUF634. I use a ton of them to drive various different types of headphones and mine don't get warm to the touch in the SOIC or DIP8 packaging, let alone something that would require a heatsink 🙂
Why are you using two regulators is series, it's nonsens ! Sumary parametres will be worse, than with simply regulator with LM..., 'cos you haven't blocked zener diode, which generate noise. For opamps and buffer you need any " superstabiliser ", 'cos exist parameter CMRR - read something about this 😉 . How I see, most of amateurs are totaly confused by " audio wizards ".
Upopa, we all know you are a very knowledgeable guy🙂 I would love to see Gcolliers project to get near perfection😎 Could you please point us all to a better direction on this🙂 I think, considering the amount of interest in the GC preamp, that it would be a great help for a lot of DIY'ers😉
Thanks in advance
Steen🙂
Mea culpa, not CMRR, but PSRR 🙁 . OK, helping to DIY : making " superregulators " is for these application unnecessary. In these cases you are working with high levels and low gain, so with quite simply regulators you can get SNR over than 120 dB, refered to " CD level " ( 2 V RMS ). Ultra low noise regulators you will need for mic preamp ( in submarine sonar 😉 ) and in several other cases. Much more important is correct design of PCB and construction commonly - here I'm ready to help.
Uuups, I am afraid I put Gcollier to more work than needed, then
I have this thing with supplies though, they can only be bad😀 Or is that a bad attitude? I do not know for sure!! Happy you joined in on this Upopa🙂 As a matter of fact I have to come out of the bush on this
I had a dream! If Gcollier , with the help of this community, came up with a really nice design of his PCB, why not shout Groupbuy???With the strong interest on the GC preamp, (well not only GC), that would be a great oppertunity for our fellow DIY'ers to get a nice preamp for their poweramps. Lets make it happen 🙂
A pre and psu PCB for everyone, nice😎 😎
Steen.🙂
Member
Joined 2002
Ive always like A decent or if not perfectly constructed regulated psu for power amps and pre amp's and active-x-over's : O )
SO who's got the nice schematic for the regulated positive and negive Psu. : O )
SO who's got the nice schematic for the regulated positive and negive Psu. : O )
Member
Joined 2002
Steen, several times I was showing here a simple, but high quality preamp with opamp + buffer ( very similar to PMA's one ), with PS ( voltage regulators ) at the same PCB and which is fitable to preamp by screw jumper or by " computer " square pins connector. This PCB is quite universal, 'cos is ready for DIL and SOIC. Do you need more ?
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Joined 2002
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