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Old 10th January 2013, 11:45 PM   #1561
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Originally Posted by Telstar View Post
Happy new year to everyone!

I'm starting to prepare things to build a scaled-down version of the l'Amp with CCS for use with lowZ headphones.

The first question is about the input impedance of the K82. Since I would like to use a 10k pot, i would have to raise the input resistor to 100k - is this ok?

Second, if someone -possibly in EU- has a pair of IXTH6N50D2 that could sell me.
Otherwise I have to order from digikey.
Do you mean a 10k volume pot? The effective input capacitance of the 2SK82 under L'Amp operating conditions was a couple thousand pf as I recall.

Most of my samples have a microamp or so of leakage current.
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Old 11th January 2013, 06:53 AM   #1562
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Originally Posted by Telstar View Post
???

a private joke... he make the LDR passivepreamp i use . see the Warpspeed thread...
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Old 11th January 2013, 07:01 AM   #1563
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Originally Posted by Michael Rothacher View Post
Do you mean a 10k volume pot? The effective input capacitance of the 2SK82 under L'Amp operating conditions was a couple thousand pf as I recall.

Most of my samples have a microamp or so of leakage current.
what is the effect of this ? limited band witch? bias problem stability ?

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Old 11th January 2013, 07:18 AM   #1564
generg is offline generg  Germany
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Originally Posted by Blues View Post
Ahem...



Generg,

Going thru the question and answer related to Nelson's answer above, I think he mistook your 100k for frequency(Hz) instead of the 100kohms that you meant so if you clear this up we might get a better answer.
I think you are right, Blues!

Thanks!
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Old 11th January 2013, 10:16 AM   #1565
protos is offline protos  Greece
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Originally Posted by Telstar View Post
This would be a good option, yes
I just checked the cost of attenuators and I froze I think diy is the only option either way.
I agree Telstar plus perhaps with HP's you do not need so many settings as with speakers in the volume control - perhaps only 6-7.
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Old 11th January 2013, 11:11 AM   #1566
Telstar is offline Telstar  Italy
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I need at least 24 steps, cutting away the outer zones (i.e. choosing resistors to provide fine control in the normal listening level).
ATM I'm choosing the switch to use, and i'll order next month.
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Old 11th January 2013, 11:53 AM   #1567
protos is offline protos  Greece
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I think you will spend more time soldering the attenuator than on the rest of the amp.
Good luck and keep us informed. What headamp will you compare it with ?
I have a PPA.
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Old 11th January 2013, 12:48 PM   #1568
Telstar is offline Telstar  Italy
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Originally Posted by protos View Post
I think you will spend more time soldering the attenuator than on the rest of the amp.
Hell yes! but i found one already mounted with Holcos... is my time soldering it worth 20£? i think yes.

Quote:
Good luck and keep us informed. What headamp will you compare it with ?
I have a PPA.
For comparison:
-modded CK2III
-Marsh Headamp (to build right after L'Amp)

Same regulated psu (varies only voltage and transformer size, type is the excellent Nuvotem potted).
The SIT is the bigger of the lot, I think I'll order a 100VA transformer for mine (+35v/0.5A bias).
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Old 11th January 2013, 12:52 PM   #1569
Telstar is offline Telstar  Italy
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Originally Posted by protos View Post
I have a PPA.
I'm playing with discrete designs so far, other 2-3 further down on the list (a JLH 69, an italian project called VHF-N and an F5 or aleph redux with laterals).
When I'm done with all the ones I think are worthy, I'll check opamps (not many output ones high current types avail).
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Old 11th January 2013, 01:04 PM   #1570
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Originally Posted by Telstar View Post
I need at least 24 steps, cutting away the outer zones (i.e. choosing resistors to provide fine control in the normal listening level).
ATM I'm choosing the switch to use, and i'll order next month.
I soldererd a lot of these good old ELMA audio attenuators.
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