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Juma's LSK Preamp - through hole version
Juma's LSK Preamp - through hole version
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Old 1st March 2016, 07:48 PM   #271
SRMcGee is offline SRMcGee  United States
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Juma's LSK Preamp - through hole version

Funny, but my build has been, uhmm, sporadic at best. I have high hopes that the LSK preamp will supersede my beloved Aleph P 1.7, but at the rate I'm progressing on the project the LSK won't be finished until long after I've gone completely deaf.

Distractions, distractions...

Good decisions come from experience. Experience comes from making bad decisions. (Mark Twain)
also, Everyone has a plan, till they get punched in the mouth.(Mike Tyson)
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Old 5th January 2017, 01:17 PM   #272
brianco is offline brianco  Ireland
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Originally Posted by brianco View Post
Has this project petered out simply because everyone who bought boards is happy, or has it transpired that there is too much difficulty in getting them to work to expected standard?

I ask because I am considering - after all this time to health issues - building the set I bought at the outset of the GB.

[My boards are PS rev.2.7 and pre are rev.3.0]
I posted the above quoted almost a year ago; there has been no response as such.

Has anyone built a successful preamp of this circuit on the GB boards?
IF so then what are the comments on the pre in normal usage and what power amp is being used?

Many thanks,


Last edited by brianco; 5th January 2017 at 01:19 PM.
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Old 12th January 2017, 04:05 PM   #273
Tripmaster is offline Tripmaster  United Kingdom
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Strange that there are no replies
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Old 26th May 2017, 07:16 PM   #274
brianco is offline brianco  Ireland
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If anyone in Europe wants a set of boards please send me a PM.

.....I am not prepared to potentially waste time when builders are so reluctant to post their problems or recommendations.
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Old 27th May 2017, 02:43 AM   #275
jameshillj is offline jameshillj  Australia
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I'm part of your silent people as I bought the boards some time ago and then bought a used assembled board off one of the members here that had trouble reducing a troublesome dc offset on the output pins - thought I'd have some fun sorting this out but haven't got onto yet - recently, started assembling parts for the F6 amp (to replace the juma version F5) so the preamp (thru hole version) is back on the table

I don't know why it's not had a better support tho - it just didn't seem to 'catch on' and maybe, at the time, there was a lot if other 'stuff' going on

The juma variations to the F5 made a rather large change to the sound (I keep saying HUGE but ...) - I added different components and a better power supply, and the result was a much more relaxed, more musical sounding amp, just like juma originally mentioned

All the best ...
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Old 20th June 2018, 05:05 AM   #276
yeuclassa is offline yeuclassa
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Default Vds jfet bf862

I build a juma lsk preamp. But Vds of jfet bf862 about 1-2V. Help me? Sorry, my English are bad
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Old 20th June 2018, 05:46 PM   #277
xrk971 is offline xrk971  United States
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Juma's LSK Preamp - through hole version
Since you guys seem to be having no luck with support for this thread, may I offer Ann alternative?

If anyone is looking for a simple high performance DC coupled preamp, the TimS HPA design that I am developing now with JPS64 could work very well as a Preamp. It also uses BF862 and there are no hard to find or expensive parts.

Simple High Performance DC Coupled Class A HPA with sub PPM THD

We are working on an integrated stereo version with a built in dual rail PSU that doesn’t require wall mains AC.

Another option is the Aksa Lender Preamp, which sounds excellent and can drive an F4 to clipping, but it is AC coupled.

AKSA's Lender Preamp with 40Vpp Ouput GB

Both are/will be well supported throughout the build process.
XRKaudio https://www.etsy.com/shop/XRKAudio
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