Tubes amp

[Kippei 0]

The buzz goes away when i touch the input RCA. So whats the deal

 

So whats the next big thing you gonna make?

Edited January 11, 2006 by Kippei

[squalle 0]

I think you might have a ground loop problem there

 

you touched the ground part ?

 

try resolder that part or errm change the ground wire to the star ground

I cant test it out myself as I'm not using any RCA sockets yet

[huangyong 0]

mind you diode will get hot!!

[1bit 0]

wow guys you really do talk a lot haha

i mean it's page 11 already haha i feel like i'm far behind

 

i just got the sijosae MHHA kit from neutralzz today

 

there seems to be a lot of discussions about the power supply here

how do you guys apply the power?

can i use wallwart type of dc supply?

or is a diy transformer and regulator a real necessity?

[squalle 0]

SOHA's supply and MHHA or millet are different

 

MHHA and millet use relatively low voltage (24 volt only rite?)

 

SOHA needs 60v then 40v at plate, so we're using 15-0-15 trafo, then by using voltage doubler we can get 60v or thereabout.

then just use RC network to filter off the ripples.

 

for ur MHHA, it's simple aint it?

if u can, just get some trafo with 28volt secondary, either 14-0-14 or just 0-28

then use LM317 regulate it down to 24 volt.

and u're done with PS

 

of course PS layout and scheme is as usual, which if not sure, you can chk with tangent's TREAD. either follow that, or you can choose to omit some things from there

oh, you need to recalculate small things like resistors' values..

[1bit 0]

mm i guess so

 

why SOHA needs more voltage? is it because of the selection of tubes?

[squalle 0]

errrmm not really

 

I did try running the exact same tube at 20+ volt

but as you might've known, tubes are not for low voltage run

if u read the specs of tubes, all starting at 100v and above

 

it will sound nicer at higher voltage as the designers believe

[kross 0]

I think you might have a ground loop problem there

 

you touched the ground part ?

 

try resolder that part or errm change the ground wire to the star ground

I cant test it out myself as I'm not using any RCA sockets yet

i seem to have to same problem. When i touch the psu ground the buzz is gone. how do you make a star ground? right now, all grounds share the same ground plane, including the input, output, volume pot ground.

[squalle 0]

for me, somehow erm, the ground is placed at a spot where from all "modules" are about of equidistant

modules here are like, 12v PSU, then ground for tube,ground for signals

 

nothing much special...

gotta see ur amp man... hard to play guessing work

[kross 0]

so it is better to first separate the signal ground, (input socket and output socket) from the tube ground and then join both of these ground to the main filter cap ground? am i right to say that?

[squalle 0]

Is your ground a real ground or just a floating virtual ground?

 

mine comes from the centre tap of the trafo

 

and I dont do exactly a star ground

 

I made 2 units, 1st one using a ground "lane" (not even a plane, LOL)

2nd one somehow a star ground, per module basis like I've elaborated above.

both are OK

maybe it's the AC signal that's interfering

and also have you check for loose connection.

 

the buzz comes from both sides?

ADD: the buzz happens when the input is there, but of course no song's playing

or with no input. if no input then it buzz, it's somehow normal especially when you dont put volume pot

Edited January 12, 2006 by squalle

[kross 0]

ok, i get wat u mean by virtual ground. my ground is the ground from my psu, which is actually the ground from the output of a lm317, similar to that in the TREAD, not a real mains ground.

 

i am currently redoing my connections to eliminate any lousy connections.

 

the buzz is from both sides, even when there is input. and the peculiar thing is that there is no buzz when the vol pot is turned on to near max but the buzz gets louder when i start to turn the vol pot towards minimum.

[squalle 0]

then try checking ur ground on the volume pot

 

yeah, go check all connections.

use old toothbrush and brush over hard enuff to break a loose connection

 

that's what I did and managed to get my protection diode loose then cause oscillation on my output op-amp

[squalle 0]

that blooze guy in this page having similar problem with you guys

 

http://headwize.com/ubb/showpage.php?fnum=...5896&fpage=9999

 

wonder why...

 

any of you have access to oscilloscope?

[kross 0]

i spent hours today redoing all the connections, and made two different grounds before connecting them together. well, the buzzing has reduced significantly, although at certain positions of the vol pot, the buzzing is still there, but much much softer and better. therefore, i think grounding is quite important here. i think i should have made a single pcb board in the beginning. and i think when i have the time again I'll change to a better pot. my current one has terrible imbalance on L and R when near min position.

 

I have access to oscilloscope but how to check?