Pending MO for Millet Hydrid boards

[squalle 0]

standing

 

but errm no solid support beneath

just my lead wires

 

do U think that's the cause?

[Kippei 0]

I try my last tube hunt in echoloft... Apparently the 7-pin socket can be found in martin electronics. Will update soon

 

Last resort wil lbe importing the main component from USA... which might not be a good thing for some.

Edited January 1, 2006 by Kippei

[neutralzz 0]

standing

 

but errm no solid support beneath

just my lead wires

 

do U think that's the cause?

this problem very hard to catch..

 

last time i know one fella who diyed a 100+ watt tube amp using 8 kt88s.. couldnt solve the hum problem.. sold the $1k+ diy project for $200 to another person who managed to troubleshoot by relocating the switch to the back of the casing instead of the front..

 

 

i too cope with some hp amp hum as well, i put a resistor to the output.. for the convenience of it.. lazy to troubleshoot.. and so far the hum's inaudible with higher resistance headphones

 

values of resistances you can try range from 50 ohm, to 300+ ohm if you like. according to digi01, its recommended at 10% of headphone impedance.

 

well i ignore that and tried various resistances + did listening tests, i felt 250 ohm to be good for me. insanely high.. its like putting 2 x 120ohm adaptor plugs.. but.. hehe my mileage may vary

[Kippei 0]

Which amp are you all specially building on. Coz I also blur liao.

 

Kross you using which circuit type. A or B?

[Kippei 0]

squalle mind taking a photoshoot of your amp...

 

I think i am tired of the rare tubes...

 

btw u using 12au7 for the soho?

Edited January 1, 2006 by Kippei

[squalle 0]

kippei: i did this one: http://home.swbell.net/acavalli//images/Ca...Heater_1.07.gif

 

using Jfets as CCS as shown there. all parts are obtainable easily. but of course, you've gotta solder point to point

 

project discussion: http://headwize.com/ubb/showpage.php?fnum=3&tid=5896&fpage=1

 

the good thing is that, according to the 3 guys designing SOHA, all parts are cheap generics yet give stoopidly good sound

(stoopid word borrowed off wat they declare anyway, SOHA = stoopid op-amp hybrid amp)

 

take a look, then tell me wat u think. if u want, i can help u. no worries

 

neutralzz: I've moved back the trafo and the switch like 5inch from the tube, but rather close to the PSU part of the amp, around 2 inches

however as I've mentioned, I've tried putting alu foil around the trafo + switch + fuse. still can hear hum

I've put 300ohm at output. still can hear hum. my headphone is hd497 32ohm

 

[Kippei 0]

What is the input voltage of this soha?

 

The tube koba selling.. i notice they got a list. I forget everything about it.

 

the transformer koba also selling?

[squalle 0]

yup

 

both I got it from them

 

but for tubes, alternatively u can get it from well audio in burlington

for 80c cheaper

and different brand

mine is Rohren von Weltruf

not sure if it means anything

trafo, ermm I think I got both of wat they have for 15-0-15.

farnell selling it for around 10 bux, checked that out

 

so wanna build SOHA instead?

[Kippei 0]

yea......... the reason y i wanted to do millet is because of the transformerless design. If it is possible with a wallwart anything goes. But the tube for millet are rare.........

[kross 0]

i am doing the constant ccs design of the sijoase hybrid amp. the hum is very background and is not very noticeable when the music is playing but becomes more obvious when there is no music.

 

my output already has a 120ohm resistance so i think need to troubleshoot elsewhere. my dad says that the power line might be too close to the ground line. so tomorrow i might try shifting them away, see if it helps.

 

i have read about the soha also but haven't seen the schematics yet. when i complete this project i might be doing the soha, that is if i have the time.

[Kippei 0]

Maybe i have a go in Koba later

 

squella wat your damage?

Edited January 2, 2006 by Kippei

[huangyong 0]

ok. squalle.. let's try this, removed the tube and short the input to the buffer using crocodile clip. this is to convert it to normal buffer . test it out, this is to ensure that hum not coming from buffer or power line.

 

if everything ok, then the problem lies in the tube amplification section.

 

you can try measure the current throught the anode by taking out the 1k5 resistor. see what's the current, and compare that with the curve in the tube's datasheet.

 

alternatively can try the trial and error method, put in a trim pot to replace 1k5 and vary the current.

 

ans squalle, pls tell us more what kind of hum you heard, left louder or right louder, because different kind of "hum", might caused by different thing.

 

ahh..and one experience is to share with you all, my first tube encounter is also with hum..lots of it.. later realized my grounding not correct.

 

 

 

 

[huangyong 0]

btw, adding in resistor can't reallt cure the root problem. some just caused by EMI, try to use shielded cable whenever possible.

 

kross, how's your sijosae hybrid grounding like? to main ground or to PSU ground? if to PSU ground, try to capacitively couple to the main ground using low capacitance poly caps, sometimes it helps.

[squalle 0]

I've posted in headwize for help

 

look here for my posts: http://headwize.com/ubb/showpost.php?fnum=...=47187&fpage=20

 

and this: http://headwize.com/ubb/showpost.php?fnum=...=47193&fpage=20

 

I've recorded down the hum, and analyzed the spectrum. turns out to be 50Hz, which means from the mains, am I correct to say so?

 

grounding, I use the big copper line at the bottom

wat do you guys reckon causing the hum?I've tried to shield away the signal lines as you've seen with all those small wires twisted around the signal wires then ground one side of it.

only the lead wires to the tube that is not shielded

[squalle 0]

Maybe i have a go in Koba later

 

squella wat your damage?

not sure how much as some of the parts I've already had them, but shd be less than 100

a lot less I'd say