Anybody who's not a complete idiot would be able to figure out my explanation was simplified. Thanks for adding a bunch of useless info to make it more confusing.
I had similar problems with my first build with spooky IPS, the bias was sky high using the parts from the BOM including 200r trimmer. After changing to 500r trimmer I had no problem to get the bias down to 0mv. I need multiple turns before the bias start increasing.
Can you confirm that R107 is 470 ohms? Maybe you built it with 47R instead?
Can you confirm that R107 is 470 ohms? Maybe you built it with 47R instead?
I have taken some measurement. Many of them are the same that tonza have taken and wrote about in post 2054. But first of all I changed R23/24 to 3k9 since I use +/- 67V DC power. With this value I got 54.8 V = 14.05 mA trough R23/24.
I could easily set R10/19 to get 3.8 mA. With 100 ohm to NFB I measured 5.85 mA.
Over R14-17:88 mV - 90 mV.
Over R 25/R31: 1.282V = 8.54 mA
Over R8/9/20/22: 1.857V- 1.893V
Schema says 7.5mA over R25/R31, so 8.54 mA might be a little bit high, but dont explain the high bias I have told about in an earlier post(??).
So far I have not tried to increase R107 on my OPS. I will wait for any comments on what I have measured so far.
Eivind S
I could easily set R10/19 to get 3.8 mA. With 100 ohm to NFB I measured 5.85 mA.
Over R14-17:88 mV - 90 mV.
Over R 25/R31: 1.282V = 8.54 mA
Over R8/9/20/22: 1.857V- 1.893V
Schema says 7.5mA over R25/R31, so 8.54 mA might be a little bit high, but dont explain the high bias I have told about in an earlier post(??).
So far I have not tried to increase R107 on my OPS. I will wait for any comments on what I have measured so far.
Eivind S
What voltage are you getting across D5 and D6?
Do you have the jumper installed instead of D102 in the output boards?
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Sorry Jeff for the late reply.
Yes ,the feedback resistor's gnd connected to lifted gnd, gnd of the bipolar capacitor connected to star gnd.
The 1khz spike peak is the testing level not at 0db.(max. sound card output level=0db= max amplifier output level). When an amplifier driven with this 0db sound card out level may be goes to clipping levels.A clipping indicator or a scope is useful when a full power test required.
Look at picture one left bottom , where testing level is written.
Someone ask for a 4R load test.
Here it is,picture 2.
Attachments
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Thx for your postings can you show some pictures of the setup?
What version of the spooky are you building?
☺
Thanks Thimios.
In the version of WinAudioMLS that I'm using I can adjust the 0db reference point to the 1k peak point. I think this would allow for more normalized testing results? The sound card I'm trying to use for testing isn't very good so I haven't done much yet though.
My second Slewmaster is now "up and run ". No real listening test so far. I have used my vario tranformer to start up. There us no room in the chassis for slow start unit. So I will try with one CL 60. The transformer is 2.2 KV. Will it be a good idea to use two CL 60 with a transformer that big?
Eivind S
Eivind S
the "bigness" of the transformer is not really the issue.
A higher VA transformer needs a lower added resistance for an effective soft start.
It's your supply voltage that is the real issue.
Higher supply voltage needs a much higher added resistance for the same VA.
2200VA on a 230Vac supply can use a T10A fuse
That 10A fuse will survive many restarts if the start up current does not exceed 20A
For a limit of 20A, the total resistance in the 230Vac primary circuit needs to be ~11 to 12ohms.
An added resistance of ~10r will allow a 2200VA to start up reliably from 230Vac with a 10A fuse.
A higher VA transformer needs a lower added resistance for an effective soft start.
It's your supply voltage that is the real issue.
Higher supply voltage needs a much higher added resistance for the same VA.
2200VA on a 230Vac supply can use a T10A fuse
That 10A fuse will survive many restarts if the start up current does not exceed 20A
For a limit of 20A, the total resistance in the 230Vac primary circuit needs to be ~11 to 12ohms.
An added resistance of ~10r will allow a 2200VA to start up reliably from 230Vac with a 10A fuse.
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What are you using for divider?
I haven't any experience,Win Audio MLS looks like a great program but is a commercial one.
Fuses in the secondary side have to survive the initial charging of the capacitors fitted after the fuses.
Let's say you have 15mF for the smoothing but this is before the secondary fuses, then that 15mF does not blow the fuses
Let's say you have a total supply rail decoupling of 1320uF. This has to be charged through the fuses.
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I just built a divider on perf board to try it. There's a lot to learn with the software. Lots to adjust (and get wrong).
