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tschrama 11th April 2002 09:49 AM

JLH 10 Watt class A amplifier
Well... just a thread to say that at last I finished my JLH 10Watter last weekend... I dicided to buy a commercial lab-powersupply.. this made things alot easier..

The results: Great!

Sound is a difinite upgrade from my Sony integrated amp .. more instruments are comming through even in loud part of the music.. high's are excelent .. well at least for me they are.. and supprisingly the bass somehow has more detail.. I experienced the new sound like I experinced my first Grado headphone listeing, but now with the stereophonic effect working..

The amp was easy to build, I even flipped a transistor around but the amp still worked.! just a little noisy.. Iq is set at 1.2A@ 27Volt, the 4 heasinks get hot but can be touched for more than 10 seconds.. well permanent actually higher voltages and Iq goes really hot!

10Khz square wave looks crystal clean but a 50KHz reveals the assymetric slewrate.. bandwidth goes from 10Hz to beyond 200KHz...

conclusion are that it is a very simple amp to build, no PCB used, no instability of any kind.. and sound is quite revealing.. highly recommended

but then again, my initials aren't H.H. ;)

ralf 11th April 2002 02:06 PM

I have build one half a year ago.

I can tell the Hiraga monstre ist one of the best amps in the world, when your sppeaker-snsitivity is high enough.

Nevertheless i have build a Pass SOZ, which is equal, but with more watts and costs 10 times more, wights ten times more..) a bigger monster!


NickC 11th April 2002 02:09 PM

I built the amp. Great amp
i built mine on +22,-22 volt. No cap at the output
You could change the 2n3055 to MJ15003 makes alot of difference but the cost would be twice of 2n3055 plus mj15003 has a bigger Safe Operating Area they can withstand 250 w instead of 115 w of 3055. I wouldn't say 3055 are bad but they almost antique stuff :) but still in production mj15003 would be the upgrade to it. Better bass, treble and midrange evident when change. If can get the 2n1711 that would be a bonus ( another exotic transistor from where i come from). Apart from that, caps and resistor exspecially the feedback caps are good to be change. Hey you try a choke and cap filter forming a LC filter. Looks good on simulation. I will get back to you when i build the LC filter. BUt first, enjoy the music. MOst important part in audio some people might actually forget its importantance

tschrama 11th April 2002 02:32 PM

Thanks for the tip!.. I would like to try those output transistors soon .. just need to find them first :-) ... I did use the 2N1711.. Hfe was something like 300.. the input transistor bc560 had a Hfe of 360, I also checked a bunch of BD139's: they all had a Hfe of 110 to 130 ..
the 2N3055 were matched at Hfe of 80/89 and 260(!)/340(!)... which brings me to a question?

I test my transistors with a simple multimeter: I that usefull, since the thansistor will be used at (much) higher currents than my multimeter uses..?

tschrama 11th April 2002 02:41 PM

any suggestions for the feedback capacitor.. I now have a general electrolytic 470uF/50V installed..


NickC 14th April 2002 04:23 PM

Not bad, my 2n1711 was only 130 tested from the multimeter too funny. Well For transistor testing try looking up Rod design a simple circuit to testing transistors in generally. The current can be set for small signal like the bc560 to 2A for the 2n3055. Well for the 2n3055 of hfe of 260 and 340 is quite high. Could be defect, i am not sure though. Well for my mj15003 hfe was only mere 40. Also for good a sound try( I am saying this if money grows on trees in your area) matching them almost identical like both channels at around hfe 80 i guess you get almost identical characteristics. But to do this you need alot of transistors. Any upgrades of caps material of resistor will invoke the law of diminishing returns on you just for you to note. Well for the input cap of 470nf i used a film and foil polyprop. My has not particular brand. If you really want hi-fi try hovland music cap will cost a bomb. and for 470 uf try blackgate non-polar i think the model is NX or something else as usually a bomb but the voltage of the cap you choose can be at 6.3 volt. Hence using a non-polar at that high value is possible and not so costly. But test the voltage first mine was a dual supply. Well you could try to change the 220 ohm resistor connecting to the 470uf to maybe to something better. That's the feedback resistor that's what i heard. Experimenting must done to check this out cause i build mine using good resistor here. Hope this helps

Sidney 14th April 2002 08:45 PM

Just thought I'd add my 10c, as I've finished-up the final version of my Rod Elliott DoZ amp (Project 36), a JLH variant, and just love this amp!

Initially I had tried some different makes and gains of the 2N3055 in a DoZ prototype and had just thought the glaring mids and too-bright top-end were a function of using surplus parts and paying no attention to gains. So in my final version of the amp I used hq parts and matched 2N3055's with Hfe's of 200 for the output trannies and 160 for the 2N3055 current sources (per the JLH site better to have the one lower than the other). However I was dissapointed, once again it seemed lacking - mids and highs dominating. So I replaced the 2N's with MJ15003's (with gains of 60 & 55 respectively for output & source) and there is an absolutely unequivocal significant improvement - so would highly recommend. (And to whomever said somewhere on this forum something about the DoZ amp lacking deep bass I can happily state - you're completely wrong! EBTG's Temperamental was shaking the floor last night.)

Other substitutions if interested: I've used NTE373's selected for high gain for the BD139 (JLH - 2n1711) drivers . (I also have just aquired some high gain MJE180's (hfe - 250) that I may try sometime, as they have a better Ic operating range than the 373's and worked fine in the prototype). Input transistors are matched Motorola 48-869412's (with Hfe's around 300), a BC559C or NTE234 equivalent.

P.Lacombe 15th April 2002 12:22 AM

2N3055's are old designed, cheap transistors, totally unsuitable,
unusable for high fidelity amplifiers...

Regards, PL.

tschrama 15th April 2002 09:01 AM

Thanks every one... I know the 2n3055 are old and considered not suiteble for quality audio.. I also read that in D.Self's book.. so I would like to switch to the MJ15003's.. I just need to find them first:(

Dear P Lacombe

I don't want to be annoying but do you have any explanation why the 2n3055 are totaly unasable besides that they are:
-old designed (that doesn't make them bad)
-cheap transistors? (that is a good quality :) )


mrfeedback 15th April 2002 01:51 PM

2N3055 = Slow, noisey & bad gain linearity, and not robust WRT modern types.
Output stages with these DO sound lousy WRT better modern types.
Flatpack versions of MJ15003 are easier to implement.
Also MJLl1302A and MJL1381A even better maybe- u need to check soar.

Maybe this helps.
Regards, Eric.

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