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Old 10th March 2014, 02:52 PM   #1241
Salas is offline Salas  Greece
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Exchange the 550 also.
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Old 10th March 2014, 03:29 PM   #1242
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Thank you for all the help Salas. Found the bastard :-)

While building the DCB1, I only sampled one of the resistors in the package to be correct. Seems there was actually ONE wrong resistor and this one was soldered onto the PCB. Instead of the 47k I had around 800R, thus the BC517 and 550 got damaged.

After exchanging those 3 parts as you suggested, I get an Offset of -1.7mV and -1.2mV.

Seems ok? :-)
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Old 10th March 2014, 04:06 PM   #1243
Salas is offline Salas  Greece
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Old 10th March 2014, 04:17 PM   #1244
Turbon is offline Turbon  Sweden
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I also managed to solve my V+ issues I had a few weeks back. It was Q6 (closest to A/C input). I thought I had changed Q6 but there was bit of confusion about schematics at the time. Now both voltages are a bit below +-10V with 6mV mismatch. I can live with that

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Old 11th March 2014, 08:21 PM   #1245
lithos is offline lithos  Norway
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Default 2SK170 vs LSK170

Hi
Building a Mez on blue PCB. I have 10 2SK170s and 8 LSK170s.

Now, Murphy being ever-vigilant, I have one good pair of 2SKs at 7,79/7,80 and a not so good pair at 10,29/10,33. There's not a single close match among the LSKs. Earlier in the thread it was advised to use closely matched buffer pairs, so I would like to know if these are too far apart - I also seem to remember that IDSS over 10 mA was unwise.

On the other hand, if I can mix and match among both 2SKs and LSKs, I can make a nice pair of an 9,02 2SK and a 9,04 LSK. Is the LSK170 a true clone of the 2SK170?

Thankful for advice!

Lithos
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Old 11th March 2014, 08:40 PM   #1246
Salas is offline Salas  Greece
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Andrew could reply that more securely since he had been matching LSKs in the past and has experience on those.
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Old 11th March 2014, 09:21 PM   #1247
WalterW is offline WalterW  Netherlands
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NicMac has measured both and I thought the LSK has lower Yfs than the original Toshiba's. But if that's a problem for this buffer?
I think not, especially if you use the LSK part as the CCS JFET.
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Last edited by WalterW; 11th March 2014 at 09:24 PM.
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Old 11th March 2014, 09:48 PM   #1248
Salas is offline Salas  Greece
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If used like you say, no. Not a problem.
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Old 11th March 2014, 10:24 PM   #1249
WalterW is offline WalterW  Netherlands
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Some pictures of my build so far...

I tried to match every component to the best. Have a lot of 2SK170's so why not
Also hot-rodded it a bit

I used matched JFets for the positive and negative shunts. Also matched all the LED's with their corresponding JFet in that position in the circuit.

For the four matched JFets in the buffer section I used for the left channel two 2sk170's with 7,67 and 7,68mA Idss with the same date code '2I' which gave me an offset of 0.0mV
For the right channel I used two JFets from different date codes with Idss of 7,82 and 7,83 but when warming up the offset seems to get worse, and it ended up to 3,5 mV. So I changed them for two JFets with the same date code of '1H' and Idss of 7,88 and 7,80mA which results in an offset of 0,4mV warmed up.
I can get a better matched pair, and so probably better offset, but then the difference in Idss for the left and right channel will be much larger.... but if that's a problem???

Oh, and I did the 'leg-trick'.

The results:
+ Vout= 9.88V and current through R1 ( 10 Ohm/2W) = 175mA
- Vout= 9.85V and current through R1 ( 10 Ohm/2W) = 178mA

Offset left: 0mV
Offset right: 0.4mV

Sound: Perfect! I can not hear a difference between this remote controlled DCB1 or a straight interlink

In the pictures you see the DCB1 between my DDAC1794 and my F5Tv3.
Nice thing is, because I used orange and yellow LED's, it is giving a nice tube filament like, glow in the dark

@Salas; THANKS for all your effort and support !

I listened a few days to the not 'leg-tricked' version with around 0,5 Volt difference between + and -.
What should I have heard in difference? Some more second or third harmonics? Some warmer sound?
Asked by someone without 'golden ears' I don't hear it.....

Walter
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Old 11th March 2014, 10:37 PM   #1250
Salas is offline Salas  Greece
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Well done. Your offset is practically perfect. Maybe you could hear the leg trick or not in a low current cool CCS build at signal peaks, bit warmer. But its subtle. Its no problem the normal Mez mode for those worrying as you saw.
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