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★★ Free PCB for JLH 2005 Class-A Amplifier
★★ Free PCB for JLH 2005 Class-A Amplifier
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Old 10th August 2016, 09:45 PM   #291
polsol is offline polsol  South Africa
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Quote:
Originally Posted by balle123 View Post
Nice amplifier..
No chassis grounding
Chassis grounded directly under the IEC power input socket - Roxburgh EMC RIR-022H-H. Green wire from the IEC input earth to the metal sub chassis (top right). The sub chassis is attached to the case by 4 S/S bolts.
The Roxburgh metal case is also part of the ground and connected via 2 bolts to the rear chassis panel - so basically 3 connections to earth.
A 'ground lift' is used for the audio earth connections (the copper bus bar top right).

Should be OK?
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Old 11th August 2016, 09:03 PM   #292
ferret is offline ferret  South Africa
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Hi Tony,

Sorry, I've been away for two weeks so only just saw your reply. Agreed, a very nice build. Know the feeling of too small a space. I still need to get my stuff assembled et al. Will post a picture when I get to a certain point in the build. I've opted for the capacitance multiplier board, as well as a decent reservoir cap bank, but I'll probably have to re-assess my PSU to make all things fit comfortably in the cases I have. Your comment about the "rat holes" I have side-stepped, by slowly building up my own small workshop. Took a damnably long time, but finally set to get my a**e in gear.

Regards, Kevin
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Old 14th August 2016, 08:06 AM   #293
polsol is offline polsol  South Africa
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Hi Ferret,

Is that the cap multiplier ex Siliconray or another (I'd like to try one myself)?
Haven't been able to get onto siliconray's website for some time. Still seems to be down/hacked.

I have a small workshop too but only have a table top drilling machine (Makita). Not sure how well that would do for holes in 10mm Al front covers. I think one requires a milling machine for that purpose?

Otherwise if you need any details then please let me know.

Cheers
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Old 14th August 2016, 06:33 PM   #294
ferret is offline ferret  South Africa
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Hi Tony,

Yes it is in fact SiliconRay's board. Looks their website is not going to be back anytime soon. The board never cost a farthing (well actually 1 cent each) it was just a few components I ordered too, and the postage from HK. I can scan the board and send it if you want. They did after all get it from a dude in Australia.
I also only have a table top drill press, but I got myself a stepped drill with 1mm increments, which has been quite invaluable for getting accurate holes in 10mm alu.

Thanks for the offer, I'll drop you a PM if necessary.

Ciao for now

Last edited by ferret; 14th August 2016 at 06:34 PM. Reason: finger fault
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Old 16th December 2016, 11:36 PM   #295
Shamron is offline Shamron  Norway
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Hi siliconray, and you others☺

I've got 4 pairs of these cards now all working, two are configured as monoblocs. but replacing vital components, have proven essential.

right now, I'm looking at replacing vr1-3 with multi turn pots.

am I correct if i think they are 50ohm, 200ohm and 20Kohm?
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Old 17th December 2016, 12:10 AM   #296
e_fortier is offline e_fortier  Canada
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★★ Free PCB for JLH 2005 Class-A Amplifier
I have built this amp and the multi-turn pots are

VR1; 2k
VR2; 50R
VR3; 20k.

BR,
Eric
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Old 17th December 2016, 12:37 AM   #297
Shamron is offline Shamron  Norway
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e_fortier: Thanks for swift reply. :-)

We've been trying different configs, trying to get rid of hum. Right now, i'm running bd139/140 and 2sc5200's. Psu consists of a 2x18V AC, 400VA transformer, both rails smoothed with 10KuF caps before 0V is joined. Then additional smoothing on the pcb's.

signal gnd, speaker gnd and 0V connected at star gnd, but tried different solutions here.

Just can't get rid of the hum. Not so much prob for me as i got 87db speakers, but friend enjoys louder hum :-P

Even tried with 100K uF caps.
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Old 17th December 2016, 12:48 AM   #298
e_fortier is offline e_fortier  Canada
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★★ Free PCB for JLH 2005 Class-A Amplifier
Mine is a lower power version at +/- 14Vdc which is basically like the JLH69 that works at 27Vdc but this one is a bipolar version, same output, i.e. 10Wrms. My bias is 1A.

10KuF per rail is not much for this amp, what is your bias ?

If I were you I would try the typical CRC filter; 33000uF, 0.2ohm, 33000uF per rail which is basically what's being use for a typical 25W F5 amp.

BR,
Eric
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Old 17th December 2016, 02:48 AM   #299
Shamron is offline Shamron  Norway
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e_fortier:

Ive tried from 450mV to 650mV across R10(?), but i am now running at 600mV/0.33ohm=1,8A bias.

Was a bit unclear in last post. I am NOW running 10K/rail (plus the onboard 5-10K, but i've tried with 2x Evox Eifa 100.000uF caps in there as well.

I think my main issue, is proper grounding. Grounding of signal gnd, speaker gnd, DC 0V and routing of the cables from mains, transformer, rectifiers, and to the pcb.

Am i correct if i am connecting signal gnd, speaker gnd and DC 0V, together at a star, as soon as they enter the chassis?

I did this once, but with some noise. Which got further reduced if i also connected a cable to the signal gnd input on the pcb, to the same star gnd. (hints of pcb traces with too much resistance in them?)

I'll upload a few pics and illustrations. unclear explanation this. :-)
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Old 17th December 2016, 05:40 AM   #300
nautibuoy is online now nautibuoy  United Kingdom
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Quote:
Originally Posted by e_fortier View Post
If I were you I would try the typical CRC filter; 33000uF, 0.2ohm, 33000uF per rail which is basically what's being use for a typical 25W F5 amp.
or perhaps a cap multiplier power supply.
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