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Old 20th February 2013, 10:20 AM   #1491
FdW is offline FdW  Netherlands
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Originally Posted by Abraxas336 View Post
Wenn I started the regs the first time one side of LEDs of one channel didn't light up, I checked and noticed I shortended two legs of either the J310 or BC327, don't remember. Could be that channel - any ideas?
If the J310 has been shorted, then the BC327 will be damaged.
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Old 20th February 2013, 10:54 AM   #1492
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by Salas View Post
Finished a channel today powered by a bench linear supply. Which is stable and clean enough for taking measurements. The current draw is 70mA per side and the preamp gains about 62dB @ 1kHz. Can zero the input for DC but the output hops about the zero point. Between +/-30mV most of the time, but has wayward periodic moves also. I could pick its momentary min and max DC offset and there is also a very slow deep memory scan I captured on the scope for you to see an averaged move of signal area about DC level over enough time.
While all the DCV bias test points are closely symmetrical for +18.2V and -18.16V PSUs, I get 0.1V asymmetry across sides of the 82R. Is that in acceptable range?
A spot check on the Riaa curve at 1kHz and 10KHz indicates my build is +0.4dB treble hot VS textbook for 11n and 9K1 I used (measured on LCR). I will have to fully verify the curves with FFT in another time. The DCV on main output concerns me especially when it can overshoot 3.55V at power on and has a long & high DC cycle at power down. Now where is that DCB1 & F5 system to hook it up when I am bored with some badly chosen woofers?
Hi Salas
IMO, when using a 9k1 resistor the 11n cap should be raised to 11.98 (12nF)
The 33.3n cap should alo be increased to 34.95 (35nF).

We can neglect miller effect because the output stage is a buffer.

The bass resistor needs some down trimming also to avoid bass rise below 100Hz
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Old 20th February 2013, 12:42 PM   #1493
hesener is offline hesener  Germany
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Quote:
Originally Posted by Salas View Post
Finished a channel today powered by a bench linear supply. Which is stable and clean enough for taking measurements. The current draw is 70mA per side and the preamp gains about 62dB @ 1kHz. Can zero the input for DC but the output hops about the zero point. Between +/-30mV most of the time, but has wayward periodic moves also. I could pick its momentary min and max DC offset and there is also a very slow deep memory scan I captured on the scope for you to see an averaged move of signal area about DC level over enough time.
While all the DCV bias test points are closely symmetrical for +18.2V and -18.16V PSUs, I get 0.1V asymmetry across sides of the 82R. Is that in acceptable range?
A spot check on the Riaa curve at 1kHz and 10KHz indicates my build is +0.4dB treble hot VS textbook for 11n and 9K1 I used (measured on LCR). I will have to fully verify the curves with FFT in another time. The DCV on main output concerns me especially when it can overshoot 3.55V at power on and has a long & high DC cycle at power down. Now where is that DCB1 & F5 system to hook it up when I am bored with some badly chosen woofers?
hahaha, thats a good one!

Yes you are up and running, the DC movements should come down over time, but yes they appear to be part of Paradise, albeit very low frequency. Suggest to let it settle for a couple weeks and take another look. Have you tried it in your system, what's the sound?
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Old 20th February 2013, 02:56 PM   #1494
Salas is offline Salas  Greece
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Originally Posted by RCruz View Post
Hi Salas
IMO, when using a 9k1 resistor the 11n cap should be raised to 11.98 (12nF)
The 33.3n cap should alo be increased to 34.95 (35nF).

We can neglect miller effect because the output stage is a buffer.

The bass resistor needs some down trimming also to avoid bass rise below 100Hz
I already have 34.7nF cap. Another 1nF FKP2 it can only be installed underneath the "treble" caps area, its tiny and it can go there. A parallel to trim down the "bass" resistors combo can be botched up easily also. But lets finish the whole and listen to it with originally intended bit "loudness" curve first.
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Old 20th February 2013, 03:15 PM   #1495
Salas is offline Salas  Greece
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Quote:
Originally Posted by hesener View Post
hahaha, thats a good one!

Yes you are up and running, the DC movements should come down over time, but yes they appear to be part of Paradise, albeit very low frequency. Suggest to let it settle for a couple weeks and take another look. Have you tried it in your system, what's the sound?
Its a dangerous situation if there is way for the DC to pass a system chain and get boosted. Especially in non informed hands hooking it up here and there and powering up and down randomly it can blow things up. It either needs an output coupling capacitor or a turn on/off safety output relay and tighter operational drift. Luckily I got a bootstrapped 6V6 valve buffer pre with a Teflon cap at input and I will be able to finish & listen to it without further additions as soon as I will get couple of small electrolytics values hopefully in 105C and the BJT semis I need for its local PSUs. Can I use MJE15030/MJE15031 that I already got instead of the D44H11/D45H11?
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Old 20th February 2013, 03:54 PM   #1496
FdW is offline FdW  Netherlands
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Originally Posted by Salas View Post
Can I use MJE15030/MJE15031 that I already got instead of the D44H11/D45H11?
Yes MJE15030/MJE15031 will do fine.
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Old 21st February 2013, 09:40 PM   #1497
Salas is offline Salas  Greece
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Originally Posted by hesener View Post
hi Salas, please just go ahead with the values as published. The output voltage will show low frequency fluctuations of ~100mVpp upon first turn on, and when the whole thing settles that voltage will come down.

This voltage is driven by the low frequency noise of the input dransistors, forming of the 6800uF elcaps, and thermal variations around the input stage. If it is too much, you could e.g. reduce the capacitor of the servo. Reducing the 150k resistors R43a/b is only necessary when there is too much (DC) offset in the amplifier, and the servo output (pin 6) is very high.

If the remainder of your system is not DC coupled, you should have no issue whatsoever.

hope that helps.....
I did a couple of experiments about the offset issue. First I installed a 1K trimmer parallel to the 82R servo correction injection point. That could reduce the min max instantaneous peaks when playing and the power-on huge peak, both by far. But it could not do much for the average +/-30mV I had before. One bad hint was that the channels current draw tended to ask for 10-20mA more when the trimmer was homed in. So I took it out. Then I put 10K resistors in parallel to the 150K ones. That dropped the play at about +/-4mV max but the power-on peak is again there in the volts. The power-off DC ramp down is still there in the hundreds of mV.
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Old 22nd February 2013, 03:30 PM   #1498
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I have now fixed the "noisy regulator rail" by exchanging Q102 and Q104. Even though the transistors tested without problem after I removed them the channel is now down to 2mV like the other three.

Frans though it might be worth mentioning here that I did not have to remove my heat sink because of a "precaution" I took for such occasions - I mounted it on 5mm spacers and as a result i do not have to remove it to access the parts underneath it.

The spacers are standard stuff available in all lengths.

Regards
Sven

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Old 22nd February 2013, 04:08 PM   #1499
FdW is offline FdW  Netherlands
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Originally Posted by Abraxas336 View Post
I have now fixed the "noisy regulator rail" by exchanging Q102 and Q104. Even though the transistors tested without problem after I removed them the channel is now down to 2mV like the other three.
Sven, "end well, all well". This is the first time I have seen proof that the BC's are actually making the thing oscillate, who would have thought. Still we do not know why (I’m still thinking too much gain), or what the defect is (tiny Nano bots not observing stop signs on level crossings).

I need to tell (let you all know) that this was not the same problem as earlier, which was fixed by adding the compensation capacitors. It was a 'new' phenomenon, and well documented by Sven.

So it goes, you learn something every day, a perfectly (measured) functioning BC can exhibit bad behavior.

It still is probable/possible that it relates to the, earlier fixed, oscillation problem (in fact it may be the source). A bad behaving device could easily ‘ignite’ oscillations, if the circuit is ‘on the brink of’ instability/insanity (and that is fixed by adding the compensation capacitors). Now the same oscillation shows itself as a 12mV noise signal. My, for now provisional, conclusion is; some BC’s are badly behaving and ‘ignite’ oscillation’s. This may also be the explanation why not all PSU’s are oscillating.

Just some thoughts

More information here http://www.direct.gov.uk/prod_consum.../dg_191922.pdf

Last edited by FdW; 22nd February 2013 at 04:12 PM.
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Old 22nd February 2013, 04:56 PM   #1500
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Hi Sven which brand BC are you using and HFE please?

Nice idea for the spacers I may copy that
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