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Old 23rd January 2014, 09:12 PM   #11801
Salas is offline Salas  Greece
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Quote:
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Hi Salas and all !!
These are my 117s sorted by IDSS

1. 5,77
2. 5,76
3. 5,70
4. 5,41
5. 5,27
6. 5,14
7. 4,86
8. 4,79
9. 4,69
10. 3,31

I would pair them as follows.


Q7 > 1,2
Q2X > 7,8 (with R6X 33R since I'm close to 5 ma)
Q3X > 3,4 (with R3X 6K2 since I'm over 5 ma)
Q5X > 5,6

am I right ?
Yes, you are OK.
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Old 23rd January 2014, 10:27 PM   #11802
Marinos is offline Marinos  Greece
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Thanks Nick

Next come 369s...

1. 12,52
2. 12,58
3. 12,42
4. 12,58

What Rs should I use ? 5R1 or 6R8 ? I'm in the middle you see..
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Old 23rd January 2014, 10:41 PM   #11803
Salas is offline Salas  Greece
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6R8
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Old 24th January 2014, 08:00 AM   #11804
Turbon is offline Turbon  Sweden
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Hi salas and others.

Changing the load resistors didn't make more than a minute difference - I have to listen more and switch between 47K and 220R to be certain.

I have used 100R, 220R, 470R, 1K and 47K. I settled at 220R per your advise for 103r.

The brand of the resistors have a noticeable larger impact on SQ though, hence the next question:

What about impedance and capacitance? What figures do you have for the folded both att input and output?

Regards
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Old 24th January 2014, 08:40 AM   #11805
Salas is offline Salas  Greece
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The output has a low about 50R source resistance, ~the K10BL RDS, bcs its a CCSed buffer. The input shows whatever load resistor you choose plus the Ciss of the 369(s) bcs there is almost no Cmiller due to cascoding. Small input+TT cable capacitance is not bothering low source resistance and inductance as the MC carts have.
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Old 25th January 2014, 12:02 AM   #11806
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Originally Posted by Salas View Post
Such good mechanical level TT and arm rotates and traces smoothly so the tip mass to vinyl resonance gets less excited and the load damping plays less role, that is why you don't feel much difference than level. They have obviously designed TT, arm, & cart as a coherent system for general resonance control. You have seen my humble Denon how controlled it got at last HF octave after the arm got upgraded etc. It was somewhat peaky before, more Q. First clue of good HF control on smooth TT systems is low surface noise. Imagine better control on yours which is designed and built as an F1 car. But setup has to be painstakingly immaculate, the more perfect the more demanding, exactly like in racing cars.
I agree with you about its design and revolutionary concepts. It has very attractive look and produce very nice sound. I got it from some guy lived in San Francisco who was in hurry to sale it due to his immediate relocation to South America. I do not remember the exact $, but I think it was like $1600 include everything, beside protractor. He just lost it. So, I got protractor from WB directly. The only thing I found wrong is just counterweight line o-rings. So, I got this from BW too. $1.5 a piece and I use 2.
About the adjustment. It is a pailful and time consuming process. No any type of indicators beside VTA mark on it. So, you need scales, protractor, blanket LP, and small thin mirror for the azimuth. Last time it took me just about 2-3 hours to set it up. BTW, I enjoyed the process in certain way....
However, it has one major disadvantage: no protection cover and its collect dust like crazy.
I thought to order some custom-made cover, but I did not see any attractive design there yet. I see just square aquarium like covers.
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Old 25th January 2014, 09:34 AM   #11807
Marinos is offline Marinos  Greece
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Default Matching episode X season Y

Fet matching is ending...
I have 2 questions

1. Weather changed and 369s readings have changed (i'm not kidding.. ). Now I have the following IDSSs
12,33
12,53
12,41
12,46
Should I keep the 6R8 for Rs ?
Nick, is there any rule of thumb selecting the Rs when we have intermediate values ? It will save the time to measure the 9ma expected bias afterwards.

2. My Q5s have 7.8 ma IDSS. I have a lot of 170s to pair them (Q6) with IDSS from 8 to 10 ma. What range is more appropriate ?
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Old 25th January 2014, 10:49 AM   #11808
Salas is offline Salas  Greece
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I know you are not kidding. The room temperature changed. High gain large geometry JFETs are very sensitive. That is why I have alerted Tea early before he offered them matched to only measure them in batches when his den has about same ambient conditions between days. You stay at 6R8.

For intermediate values go with the next higher Rs when they are +0.25mA or more from lower one IDSS tier. Safer, more controlled, you could only lose some negligible amount of gain in the MC versions.

For Q6 when you have 7.8mA Q5, any higher IDSS than that will do. I would say you use your most common IDSS to find in your stash so not to dedicate difficult to chance again pairs.

*The JFETs are not done by direct lithography, they are buried under the silicone surface and diffusion is used, less defined process hence the wide range, but they can benefit from lower noise also as they stay away from surface impurities.
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Old 25th January 2014, 04:41 PM   #11809
Marinos is offline Marinos  Greece
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You correctly "alerted" TB... My set, while excellently sorted was marked as 13 ma. I knew about the ambient related variations and that's why I didn't bother.

Thanks for the elaborated answer
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Old 25th January 2014, 06:13 PM   #11810
Salas is offline Salas  Greece
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Main thing is the matches to be done in same conditions so when they will go up or down due to temperature, to go along as a team. Also the different DMMs will differ in burden voltage and mA range accuracy if used in series.
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