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.
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!
This would be a good option, yes
I just checked the cost of attenuators and I froze
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.
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.
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).
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).
I soldererd a lot of these good old ELMA audio attenuators.
Attachments
Yours are stepped attenuators that have always a chain of resistors in the signal path. Mine only one resistor at each step. A couple of years ago I purchased the last two from a British distributor. They seem to be hard to find meanwhile and if you get some, they are quite expensive.
But have a look at these high grade attenuators from Poland: High Quality Audio & Industrial Attenuators and Passive Preamplifiers
Mine? I have got none yet.
You mean a shunt attenuator, i plan something like that.
They had mixed quality issues, so I prefer to go with Elma.
Mine? I have got none yet.
They had mixed quality issues, so I prefer to go with Elma.
What kind of quality issues?
I have read the comments at http://www.diyaudio.com/forums/parts/149049-khozmo-48-position-stepped-attenuators-6.html.
Sounds good, at least in my comprehension...
can i repeat my "newbie" question ? what is the effect of this input capacitance and how to cure it on the Sit ?
The effective input capacitance and the output impedance of whatever drives it form a low-pass filter with cutoff = 2*Pi*R*C
So, driving the SIT with a 600 Ohm source gives:
6.28 * 600 * 2E-9 = 133 kHz
And, for example, hanging a linear 50k volume pot on the input, set at 50%, gives:
6.28 * (600+12500) * 2E-9 = 6 kHz (which is hi-fi for humpback whales)
So, driving the SIT with a 600 Ohm source gives:
6.28 * 600 * 2E-9 = 133 kHz
And, for example, hanging a linear 50k volume pot on the input, set at 50%, gives:
6.28 * (600+12500) * 2E-9 = 6 kHz (which is hi-fi for humpback whales)
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From Michael's calculation I get that a 1k pot would be ideal to not have HF rolloff.
My source is very low impedance so I could use a 1k pot, the problem being it unobtainium
Therefore i'll build a stepped attenuator taking advantage of the 10k (which i erroneously called inpout resistance) in it.
My source is very low impedance so I could use a 1k pot, the problem being it unobtainium
Therefore i'll build a stepped attenuator taking advantage of the 10k (which i erroneously called inpout resistance) in it.