Hi Kofi,
I've just started building my own Uniamp.
Done differents choices for the parts and transformers (James OPT that I really appreciate) but your BOM is really close to mine!
This topic (from the next door forum) may help you for choke,ground,phase splitter connection, etc...
DIY Audio Projects Forum • Millett UniAmp Build Thread
This answer from Pete Millet about grounding is interesting:
Quote:
It's rather hard to see, but the "RECT CT" pin on the PCB is wired to the center tap of the HV winding on the power transformer. There is also a wire from the CT (at the transformer) to a ground lug that is located right next to the white power resistor (I think the black wire). This lug is the chassis ground point. Wires (green) also run from there to the (-) side of the output jacks (and also, on this particular power transformer, a shield/ground pin).
The resistors were an afterthought. The B+ was too high using the transformers I had, so one of the resistors (the white one) is in series with the choke, and the brown one is connected from B+ to GND (big bleeder resistor). This is just to drop the B+. You'll also note I removed the first filter cap so the way I built it it's actually a choke-input filter.
Pete.
I hope this could be helpful
And sorry for my english (I'm french and quit school long time ago)
Cheers
Pascal.
I've just started building my own Uniamp.
Done differents choices for the parts and transformers (James OPT that I really appreciate) but your BOM is really close to mine!
This topic (from the next door forum) may help you for choke,ground,phase splitter connection, etc...
DIY Audio Projects Forum • Millett UniAmp Build Thread
This answer from Pete Millet about grounding is interesting:
Quote:
It's rather hard to see, but the "RECT CT" pin on the PCB is wired to the center tap of the HV winding on the power transformer. There is also a wire from the CT (at the transformer) to a ground lug that is located right next to the white power resistor (I think the black wire). This lug is the chassis ground point. Wires (green) also run from there to the (-) side of the output jacks (and also, on this particular power transformer, a shield/ground pin).
The resistors were an afterthought. The B+ was too high using the transformers I had, so one of the resistors (the white one) is in series with the choke, and the brown one is connected from B+ to GND (big bleeder resistor). This is just to drop the B+. You'll also note I removed the first filter cap so the way I built it it's actually a choke-input filter.
Pete.
I hope this could be helpful
And sorry for my english (I'm french and quit school long time ago
)Cheers
Pascal.
Hi Kofi.
If you use a choke input filter (like Hammond 193J or 193H) the first supply cap (C11) is not necessary (never mind what PSUD II simulate).
R6 must be jumpered (as you done) but R7 must be open (short only for unbalanced input).
For your ground wire (the black wire you've soldered under the board to the C11 negative pin) I think it's OK and you can attach it to your chassis.
But an e-mail to Pete about C11,R6,R7 and grounding could be safer (if we are lucky and if he's not too busy he will answer quickly!)
Cheers.
Pascal
If you use a choke input filter (like Hammond 193J or 193H) the first supply cap (C11) is not necessary (never mind what PSUD II simulate).
R6 must be jumpered (as you done) but R7 must be open (short only for unbalanced input).
For your ground wire (the black wire you've soldered under the board to the C11 negative pin) I think it's OK and you can attach it to your chassis.
But an e-mail to Pete about C11,R6,R7 and grounding could be safer (if we are lucky and if he's not too busy he will answer quickly!)
Cheers.
Pascal
I'm not using a choke input-- see the attached image. This is my PSU.
Oh! I totally misread that! I thought it would need to be shorted for unbalanced.
Thank you so much for catching this!
That's good news.
Uh oh. You mean there's something not safe about this? Can you elaborate?
Ugh.
Kofi
Attachments
I think there's some confusion here. I am indeed using a CLC filter in the PSU. The first filter cap will be 1.2uF which, although lower than the value on Pete's schematic, is necessary for me to arrive at the proper supply voltage.
The 8H choke comes after the 1.2uF cap. The 400uF (100uF x 4) cap completes the PSU.
Does that make sense?
Kofi
The 8H choke comes after the 1.2uF cap. The 400uF (100uF x 4) cap completes the PSU.
Does that make sense?
Kofi
Kofi there's no confusion!
I have seen your first simulation on the first page of this thread and understood that you put C11 (1.2uF instead of 47uF) to reach 370V on B+.
But don't forget that's only simulation and that PSUD2 is not perfect with constant current source.
Pete told several times and in his schematic that C11 must not be installed with choke (LC filter,only choke and 400uF caps!).
Tomorrow I will send an e-mail to Pete just to be shure for R6,R7,C11 and grounding.
Cheers.
Pascal.
I have seen your first simulation on the first page of this thread and understood that you put C11 (1.2uF instead of 47uF) to reach 370V on B+.
But don't forget that's only simulation and that PSUD2 is not perfect with constant current source.
Pete told several times and in his schematic that C11 must not be installed with choke (LC filter,only choke and 400uF caps!).
Tomorrow I will send an e-mail to Pete just to be shure for R6,R7,C11 and grounding.
Cheers.
Pascal.
Kofi,
Pete has responded this evening (he's a nice guy) to my 3 questions:
1.For RCA input (using the Sowter 3575 without Negative FeedBack)the good place to solder it on the board is INP and ING1 (with R6 jumpered and R7 open)?
2.Is it possible to adjust B+ by decreasing the value of the first cap of CLC
filter(C11)?
With a choke of 10H/65 Ohms,when I simulate it on Duncan's PSUD2,to reach 370 Volts on B+,C11 must be around 1,5uF (instead of 47uF).
3.Is it necessary to ground the board to the chassis?
If so,what's the best place?
the answer is clear:
So easy
Pascal
Pete has responded this evening (he's a nice guy) to my 3 questions:
1.For RCA input (using the Sowter 3575 without Negative FeedBack)the good place to solder it on the board is INP and ING1 (with R6 jumpered and R7 open)?
2.Is it possible to adjust B+ by decreasing the value of the first cap of CLC
filter(C11)?
With a choke of 10H/65 Ohms,when I simulate it on Duncan's PSUD2,to reach 370 Volts on B+,C11 must be around 1,5uF (instead of 47uF).
3.Is it necessary to ground the board to the chassis?
If so,what's the best place?
the answer is clear:
So easy
Pascal
Wow. So, I had a few issues today with getting the board in the chassis. I didn't take into account the height of the electrolytics and it initially looked like I was going to wish I was dead.
Luckily, i was able to perform a few Cirque du Soleil moves and got it in perfect. Then I realized I wouldn't be able to solder the transformer leads with the board installed.
Super great day.
Anyway, I got all the rubber grommets on the chassis and installed the transformers and front panel done. Pretty nice.
Kofi
Luckily, i was able to perform a few Cirque du Soleil moves and got it in perfect. Then I realized I wouldn't be able to solder the transformer leads with the board installed.
Super great day.
Anyway, I got all the rubber grommets on the chassis and installed the transformers and front panel done. Pretty nice.
Kofi
Attachments
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