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SOHA II Builders Thread - Page 103

post #1531 of 1688

I have my c1s air wired after swapping a few caps to see which one I liked.  doesn't seem to affect the sound at all..

post #1532 of 1688
let us know if some caps are really better than others and where smily_headphones1.gif
post #1533 of 1688

I tested vitaminq pio, obliggato golds, and russian ft-3s  I ended up with the russian ft-3s  but the vitaminqs were also quite nice...

post #1534 of 1688
And where are you using them?

How do you find the soundstage and subbass on your soha II and what about internal DC filter effectiveness?

I have humming with mine cause by too much DC on my line and also placement of the toroidal transformer ( not sure but ground might be picking hum from toroidal since the ground bolt is near the transformer)

Also it might be my source and or headphones but my soundstage is too wide and very 2D in the head.. Also very mid centric but again might be my source. I will have to test it on another dac to be sure..

I would really appreciate if SOHA II owners could tell me how their soha built sound.. I need to know if it was wrongly built or if its by design by cavalli.
Edited by sinae - 8/28/11 at 6:35pm
post #1535 of 1688



check your wiring scheme and transformer placement.  I get no excessive dc offset or hum in my build.  soundstage is nice and wide, esp with some HD800s.  the trick to this guy is the tube rolling capability.  you can swap in tons of different tubes to find your flavor....

post #1536 of 1688
Thanks Particleman, do you have some kind of contraption to allow easy cap rolling?
post #1537 of 1688

I soldered alligator clips to my wires:)

post #1538 of 1688
Originally Posted by particleman14 View Post



check your wiring scheme and transformer placement.  I get no excessive dc offset or hum in my build.  soundstage is nice and wide, esp with some HD800s.  the trick to this guy is the tube rolling capability.  you can swap in tons of different tubes to find your flavor....

What tube do you prefer with yours? Mines are 12AU7A

How about subbass quantity?

what do you mean by wiring scheme?

How have you positioned your transformer.. mine is at the far left near power plug..
Its currently unmounted.. do you think this could be the cause

I opened the box and positioned the transformer outside the box ( should not do any interference there) even then still same humm problems..

also if i have nothing plug but AC power, volume to max. The 2 cables that are connected to the RCA jacks to the front volume on the board are picking a lot of noise by just moving my hand over them.. They are twisted together could this be the cause...

actually at volume to max you hear a lot of garbage even when not moving my hand over them but when moving my hand over its even more garbarges..

also on cavalli web page he says
The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation.

what should it be 12.6v or 6.3v mine is currently 12.6v

Anybody have an high res zoom pic of all the parts of their SOHA II amp so that i can compare to make sure the dude did it right

that humm is killing me the guy sold me a defect amp..

I think i found something..

The C16P capacitor has melted a lot because the Q1P transistor was touching it or something... What is the use of those 2? anybody can tell me
and if the melted C16P capacitor could have an effect on all this ****..
Edited by sinae - 8/29/11 at 12:28pm
post #1539 of 1688

I have some 6922 JAN and they are pretty nice.  you have a damaged cap on c16p? replacing it might help.


  are the input wires shielded?  they could be picking up noise...   12au7s are 12.6V tubes so your jumpers are right..  post pics of your case and layout...

post #1540 of 1688
Yep i will replace both the caps and the transistor.

they are small wires with small plastic cover.. dont think they are shielded..

Do you recommend other cable in the box to be shielded?

did you compare 6922 JAN with 12au7 in the soha II
Edited by sinae - 8/29/11 at 4:26pm
post #1541 of 1688

never ran any 12au7s..  usually shielded input wires are recommended to prevent noise pickups.  replace the caps and see if that fixes your problems...

post #1542 of 1688
I will change the cable and the cap thx for your help
post #1543 of 1688
anybody can tell me what effect could be created by a melted 0.1uf Metalized Polyester/Polypropylene Film Capacitor 100n 100V place at position C16p based on this shemantic
power supply shemantic

as for the shielded cable.. what AWG would you recommend
would this do
Cardas twinaxial

im sorry with all those questions im a new DIYer..
Edited by sinae - 8/30/11 at 2:56pm
post #1544 of 1688

I'm pretty sure that's a bypass cap.  As I understand its meant to "smooth" out the ripple current by providing a little store of charge to fill in dips in the voltage.  definitely get that part replaced...it's suposed to make your psu less noisy


I like navships wire on ebay , it's cheap and solid.  or some belden cables are cheap and good as well.  that cardas wire won't be too bad either as you'll only need a foot or 2...

post #1545 of 1688

Hi all!I m building a SOHA ii but got some problems for the buffer DC offset.Please advise.


I used

1.5M for R15,

Q6,Q7=2SC2238 from TOSHIBA,

OPA627au for both opamps

Ibias =100mA(Voltage accross R10(2R2) is around 220mV)

V+ = 15V

V- = -14.95V

and no tube is installed for below measurement for both channels.


For Left channel ,everything is just fine.DC offset is nearly 0~3mV constantly which is reasonably low as what i expected.



For Right channel,DC offset is around -7.68V for the output and it will slowly decrease to -0.5V in 4 mins after the transistors was getting hotter and hotter(around 40C for the heatsink)

After around 5mins,the offset is around -3-5mV for awhile but will soon increase to -30mV forever.


After 10mins,offset =-30mV,Relay never close or toggle.


So i tried to re-solder all the solder points again and check the direction of transistors and check any mismatch or wrongly assigned components.

Also,i swapped or changed opamps for both channels but in vain.


I was told that around 20-30s,the relay will toggle and music will be heard.

I am now wondering some components may be broken but it would be very unhappy to solder off the old parts and replace them but new parts again.

Please state some suggestions for me.Thanks.


Edited by KWS - 1/12/12 at 8:09am
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