JLH 10 Watt class A amplifier

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#261
input capacitor

hi,

thanks Tim for your descriptions,

last week i gave the new Mundorf "Silver Oil capacitor" a chance.
my experiences: first i had a mundorf tin foil, which was realy satisfying.
i replaced it with Siemens MKV type, which is in my crossover nearly as good as a jensen paper in oil, but not in my JLH`s.
when i build in the silver-oil, sound was only bit better than with tin foil.

after only 10 hours burning in i could hear it getting better and better(smoother, warmer, more detailled) human Voices , guitar, piano (depending on recording) are incredible...

But i think the improvements are also because the jlh was running about twenty hours and is also still burning in.

the longer the amp is burned in the better it gets...

A high-end Freak visited me to listen to the JLH.
He was so impressed and told me, that that was the sweetest Musik, reproduced by an amplifier he ever heared.
(He is owner of Wilson Audio Watt/Puppy)
He asked me to build two amps for him.


TIM:

i am curious about your capacitors:
if i would send to you the money for 10 pices in secure letter, would you be kind to send me them?

Greets,
Ralf
 
#266
Re: PSU question

chris ma said:
Hi,

Is there any problem or just waste of money and effort if I put a large bank of caps(say 100000 uf) after the LM338K regulator before the amp board of this mono amp? I am refering to Fig.2 here

http://www.gmweb.btinternet.co.uk/jlhesl.htm

Thanks,
Chris
Click to expand...

With this overkill large bank of caps (100.000 uF) the LM338K will have a hard work at power on...and if it's not very well protected internaly ,it can evenctualy fail...

So ...not a recomended design pratice...😉
 
#268
Re: Re: PSU question

Tube_Dude said:


With this overkill large bank of caps (100.000 uF) the LM338K will have a hard work at power on...and if it's not very well protected internaly ,it can evenctualy fail...

So ...not a recomended design pratice...😉
Click to expand...

Is this the same logic of reasoning why nobody would do the following type of regulated power supply;


after the bridge rectifier then pi-filter (CLC or CRC) then LM338K and then another pi-filter (CLC or CRC) then to amp circuit

Thanks,
Chris
 
#271
Thanks Erik,

But I was a bit confused with all different versions of the cap multipler in the The Capacitance Multiplier page. And also the said updated version with dual supply. I guess it must be the Fig2 but with a bridge rectifier per secondary supply, split the 0V line, one for each secondary and join them at star ground. Similar to the LM388K schematic in terms of +ve and -ve rails?

I have a few 2n3055 left from the dismantled JLH1996 I can recycle them here and save the LM338K for future use.

I am not 100% sure here, any help will be greatly appreciated.
Thanks,
Chris
 
#272
paulb said:
I think you're solidly into the area of diminishing returns. Why not save the other caps for your next amp? Unless they're so cheap you can afford to buy more next time (or you're Bill Gates).
Click to expand...

Hi paulb,
Bill Gates! hehe I wish. I was just wondering why no pi-filter after supply regulation, was there a technical reason thats all.

Chris

🙂
 
#273
Pi filter after the regulator

Chris,

You'd have to figure the output impedance
(with frequency) of the LM338 alone vs. series
combination of the LM338 + your proposed pi
filter. Lowest through the audio band is good.
Lowest and still flat is conceivably better.

Going back to the cap multiplier idea, have you
looked at the one on Rod Elliot's page?
See especially figure 3. He gives some good
practical advice on what it does and how to go
about connecting it.

Erik
 
#274
CAPmult

hi,

i build my capmult as in picture but with 4x10000 BC , 4x2000 in middle, and 2x10000+2x6,8+2x200nf in output.

i hav tested the against two psu of 600000! uf.
Result with capmult no hum hearable on speaker, but hearable with 600000uF!

As Tim recommends to use higher grade capacitors i will try in future.

Has anyone ideas how to better the capmult (perhaps more capacitance?.....

Greets,
Ralf
 

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#275
HI Erik

snip...
Going back to the cap multiplier idea, have you
looked at the one on Rod Elliot's page?
See especially figure 3. He gives some good
practical advice on what it does and how to go
about connecting it.
Click to expand...

Yes I have study it for a little bit, but I would like to use two bridge rectifiers per transformer per channel. Will there be any different in wiring the pass transistors if I follow the similar way of the LM338K supply schematic on Geoff's site but doing the cap multiplier?

Ralf,
May be we can build a better bridge recitifier with all those soft recovery diode ideas discussed in the forum.

Chris
 
#276
Transistors

Does any one know if there is a MJ15003 in a flatpack case like TO247 or similar? Im not so keen to work with TO3.
Also I have some Toshiba 2SC3281 and I have read on Geoffs site that they may be prone to oscilations, whilst on another post somewhere on this board he suggests them as substitutions.
And where I can get 2SA1358 and 2SC3421 in quantites less than 500🙂
 
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