Thanks for your input.
Hi Uriah. That is very interesting about capacitive coupling on the LDRs. My supply is perhaps already similar to what you suggested (see circuit below). Do you think the Oscons are ok as final filtering elements? Any other suggestions for mods are welcome.
I think the problem I had might have been exacerbated because I use an LC filter after the rectifier bridge. This caused a weird looking waveform on the output of the bridge which seemed to also upset the transformer and produce some additional ringing on this and other windings.
The snubber I fitted is shown on the diagram. The waveform there is still strange, however the sharp resonances noticed on all windings are gone.
As an interesting bonus this snubber even eliminated the minor ringing on other windings which was generated independently of this circuit.
Jeremy
Hi Uriah. That is very interesting about capacitive coupling on the LDRs. My supply is perhaps already similar to what you suggested (see circuit below). Do you think the Oscons are ok as final filtering elements? Any other suggestions for mods are welcome.
I think the problem I had might have been exacerbated because I use an LC filter after the rectifier bridge. This caused a weird looking waveform on the output of the bridge which seemed to also upset the transformer and produce some additional ringing on this and other windings.
The snubber I fitted is shown on the diagram. The waveform there is still strange, however the sharp resonances noticed on all windings are gone.
As an interesting bonus this snubber even eliminated the minor ringing on other windings which was generated independently of this circuit.
Jeremy
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Problem located and fixed
The hum problem is located and fixed.
It was a grounding failure on the psu pcb in my F5!
Thanks and best regards to all,
Oliver
Hi Albert,
i tried that. A bit better like the Nordost cables i had tried, but the hum is still there...
The hum problem is located and fixed.
It was a grounding failure on the psu pcb in my F5!
Thanks and best regards to all,
Oliver
Hi dvb-projekt it seems reading your link I was on the money, though of course I didn't give any pointers as to where to look in the amp for the problem. Glad you got it sorted
Tony.
Well I went ahead and cut the DCB1 PCB in half and now have a SALAS Shunt Reg that I can use with my B1.
I've reduced the series resistors to 10R and added heatsinks.
Question is - Why are the resistors so massively specified ?
By my measurements with the original 22R resistors VR = 1.4V.
Now that I have 10R, I=E/R so I = 1.4/10 (which equals 140mA)
The resistors are only going to be dissipating I^2R = 0.14x0.14x10 = 0.2W
I/ve used 10W because that is what I happened to have.
I've reduced the series resistors to 10R and added heatsinks.
Question is - Why are the resistors so massively specified ?
By my measurements with the original 22R resistors VR = 1.4V.
Now that I have 10R, I=E/R so I = 1.4/10 (which equals 140mA)
The resistors are only going to be dissipating I^2R = 0.14x0.14x10 = 0.2W
I/ve used 10W because that is what I happened to have.
Attachments
Under test VR has crept up slightly on one rail to 1.77V but stays at about 1.58V on the other.
That means that I am running 177mA +/- 10% on one and 158mA +/- 10% on the other.
I'm letting it cook to see how warm it gets.
(The tolerance by the way is the tolerance of the power resistors).
That means that I am running 177mA +/- 10% on one and 158mA +/- 10% on the other.
I'm letting it cook to see how warm it gets.
(The tolerance by the way is the tolerance of the power resistors).
Just doing a bit of mental maths to make sure everything will be OK.
As heat transfer and everything else is linear.
Currently my heatsinks are 8 Degrees above ambient - nice and cool.
If I triple the current will this triple the heat - ie heatsinks 24 degrees above ambient ?
If everything stays linear the sinks will then run at about 43 Degrees.
????
Unfortunately I have no idea what the dissipation figure for these old reclaimed sinks is.
As heat transfer and everything else is linear.
Currently my heatsinks are 8 Degrees above ambient - nice and cool.
If I triple the current will this triple the heat - ie heatsinks 24 degrees above ambient ?
If everything stays linear the sinks will then run at about 43 Degrees.
????
Unfortunately I have no idea what the dissipation figure for these old reclaimed sinks is.
The best of both Worlds
After a great deal of playing, I've now settled in for this weekend with my B1 running with the Salas Shunt reg. set at 180mA.
I do think that 600mA might get a bit warm in there but I might try 500mA later.
The B1 is a far more forgiving board when it comes to laying it out and is completely silent. A correctly laid out DCB1 is silent too, don't get me wrong.
I can use my wonderful Obbligato 10uF PIOs in this layout which suits me as I have a DC coupled amp.
The B1 doesn't need the dual reg, but, hey I'd built it anyway so I'm just using is as a 19V DC supply.
No humming, no buzzing and no distortion. Just pure listening pleasure. No relays, No turn-On thump, just everything as I would like it.
After a great deal of playing, I've now settled in for this weekend with my B1 running with the Salas Shunt reg. set at 180mA.
I do think that 600mA might get a bit warm in there but I might try 500mA later.
The B1 is a far more forgiving board when it comes to laying it out and is completely silent. A correctly laid out DCB1 is silent too, don't get me wrong.
I can use my wonderful Obbligato 10uF PIOs in this layout which suits me as I have a DC coupled amp.
The B1 doesn't need the dual reg, but, hey I'd built it anyway so I'm just using is as a 19V DC supply.
No humming, no buzzing and no distortion. Just pure listening pleasure. No relays, No turn-On thump, just everything as I would like it.
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Jeremy,
Your supply should do the trick. Oscons are nice. I find them expensive. A Nichicon or Panasonic will give you the same effect. Dont forget to throw a film on the electrolytic's leads.
Uriah
Since you had output capacitor in service anyway, a good config decision. Enjoy.
Great. I found the Oscons in my parts bin and thought "what the heck". Best I delve back in their for a film cap too.
Thanks for the advice.
Jeremy
I have a partial kit for the DCB1 mesmorize available if anyone is interested.
http://www.diyaudio.com/forums/pass-labs/207646-help-where-i-can-buy-dcb1-kit.html#post2925027
http://www.diyaudio.com/forums/pass-labs/207646-help-where-i-can-buy-dcb1-kit.html#post2925027
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