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Old 2nd April 2013, 04:00 AM   #1411
EUVL is offline EUVL  Europe
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Join Date: Oct 2003
I have been advocating the use of batteries for the SEN / CEN since day one. So I have to admit I don't understand the problem.
In our own IV (using batteries), it is so dead quite, that you cannot hear anything at max. volume even with headphones.

If one insists on using transformers, Joachim Gerhard also posted a schematics for a floating supply with common mode choke before.

Zen -> Cen -> Sen, evolution of a minimalistic IV Converter
Zen -> Cen -> Sen, evolution of a minimalistic IV Converter

But as Nic found out, batteries are still better.

In any case many thanks for the link to the Murata article.
Very good reference.




Patrick
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Last edited by EUVL; 2nd April 2013 at 04:19 AM.
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Old 4th April 2013, 04:12 PM   #1412
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Patrick,

After many months (years?) I have decided I really must put my Sen V18 together; so looking at everything I have one question springs to mind.

I have the pack of matched jfets and associated document which details Channel against Upper / Lower; other documentation refers to Q1 thru Q4 with Q1/Q3 and Q2/Q4 being thermally coupled.

Would I be correct in thinking that Q1/Q2 form the Upper set whilst Q3/Q4 form the Lower?

There is a second question! I have the heat sinks for two jfets, should I thermally couple the heat sinks for q1/q3 and q2/q4?.

Alan
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Old 4th April 2013, 04:18 PM   #1413
EUVL is offline EUVL  Europe
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Alan,

The transistor designations are indicated on the PCB.
Q1/Q2 are the upper pair, Q3/4 the lower.

Thermally the upper should track the lower.
So heatsinks are for Q1/Q3 & Q2/Q4.

You actually figured out all the answers already.


Patrick
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Old 12th April 2013, 09:40 AM   #1414
q-rz is offline q-rz  Austria
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Hello,

sorry to hijack this thread, but i had a quick question. I've simulated the SEN with paralleled BF862's, results are attached. I thought distortion would be lower. Could please somebody check if I've done something wrong?

Thanks,
Peter
Attached Images
File Type: png sen_ckt.png (15.3 KB, 532 views)
File Type: png sen_fft.png (37.9 KB, 533 views)
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Old 12th April 2013, 10:16 AM   #1415
EUVL is offline EUVL  Europe
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I spiced the same circuit as yours without the R4 and got :

2nd harmonics 2.1e-5
3rd harmonics 1.9e-6
4th harmonics 1.5e-6

In general BF862 has a higher dependence of Id on Vds, so best used when cascoded.
See :

Zen -> Cen -> Sen, evolution of a minimalistic IV Converter
Zen -> Cen -> Sen, evolution of a minimalistic IV Converter

"Cascoded SEN using BF862 cascoded with J111"


Patrick
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Old 12th April 2013, 11:40 AM   #1416
q-rz is offline q-rz  Austria
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Thanks for your quick reply.

Without R4, the distortion levels are slightly better. Would it mean that the SEN does not like the PCM1704's lowish output impedance? The CEN with SK170/SJ74 sims way better.

Peter

PS: Forgot to mention that cascoding didn't help with R4 present.
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Old 12th April 2013, 12:15 PM   #1417
heb1001 is offline heb1001  China
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Quote:
Originally Posted by q-rz View Post
Thanks for your quick reply.

Without R4, the distortion levels are slightly better. Would it mean that the SEN does not like the PCM1704's lowish output impedance? The CEN with SK170/SJ74 sims way better.

Peter

PS: Forgot to mention that cascoding didn't help with R4 present.
For good sim results, try #1375 with more parallel pairs to get the input impedance down. Not sure if anyone has actually listened to #1375 working though...
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Old 12th April 2013, 12:51 PM   #1418
EUVL is offline EUVL  Europe
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I am not sure whether a current source in parallel with a 1k resistor represents the PCM1704 correctly.
And simulation is only a tool, not reality.


Patrick
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Old 12th April 2013, 01:06 PM   #1419
q-rz is offline q-rz  Austria
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I'll try both SEN and CEN this weekend, and post the results.
I completely agree with your opinion regarding validity of simulations. The only thing what bothers me is that reality is almost always worse than simulation.
Patrick, did you try SEN with PCM1704 yourself? If yes, what performance did you achieve?

Peter
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Old 12th April 2013, 01:09 PM   #1420
regal is offline regal  United States
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There are tricks to the PCM 1704. One is doubling them up, twice the current even thuogh it halves the output impedance seems to help. The other thing that is a must is large caps for BPO and DC servo pins, this makes it sound more like a PCM63.


My problem with the Sen is the batteries, I am just too absent minded. I thought about 4x Li-ion 18650 batteries, these are 4.7V each fully charged, have a much lower output impedance than NiCad. But you have to charge them individually which is a pain. I used LiFePO4 batteries on one project but blew it up when I inserted the battery backwards!


Has anyone thought a bout using a rechargeable drill battery and charger? 18V is a common Voltage for these. Could fab a socket on the chassis and just plug it in, swap a pair back and forth. Would look silly but it would be practical.
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