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SOHA II Builders Thread - Page 101

post #1501 of 1665

Startup

Finally, some descent sound.

 

Unfortenatly I have som problems with it.

From time to time, the e12 turns off, but turns back on after a few secounds.

The problem is worse when it is cold, and gradualy fades away.

After aprox 30minutes of playing music, and the amp is getting warm, the e12 almost never fails.

The right channel is also slightly less volume than left.

Any one got any good tips where the problem may be?

post #1502 of 1665

not sure, it sounds like multiple problems.

 

1) swap tubes left to right to see if the problem follows the tubes.  if so, replace tubes.

2) when the e12 trips, measure the DC offset before the e12 with a DMM, to see if you can isolate the channel and by how much is the offset.

3) remove the tubes and see if the e12 trips without the tubes.  make sure your DC blocking caps are actually working.

 

post #1503 of 1665

I removed the tubes, and it does not trip.

plugged them back in, no trip yet?

and the difference in L & R channel is gone..

The only way I can make it trip for now, is when i put a screwdriver on the trimpot of P1P?

I think it might be a ground issue?

 

I will keep it playing for a while to see if the e12 trips again.

Fingers crossed

 

 

edit: still trips :(


Edited by egotrip - 1/11/11 at 11:22am
post #1504 of 1665

After almost 2 years of lying on the shelf my SOHA II is now completed (well... almost - just waiting for some 0,22/1000V Caps:). I hope this weekend I will finish this great amp and listen to it:).

For now all measurment are ok. Tubes are EH 12AU7, trans are Toshiba 2SC4793, C1 will be Jantzen Z-Silver Caps. Thanks Alex!

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post #1505 of 1665

How will you finish the front and rear...?

Otherwise it is looking good... very clean build!

post #1506 of 1665

Its standard Fischer combination case (KO HL profile series - http://www.fischerelektronik.de/fischer/uploadfischerfcase/Fischer/M.1.2.pdf) so there will be a standard faceplates supplied with case, just drilled/milled for pot and sockets. In the rear panel I'm going to istall small Sunon 12V fan powered by a little lower voltage. For the front I have a really huge alu knob:) Now I must to think about protecting the tubes somehow...

post #1507 of 1665

I don't like tube cages... I always leave my tubes unprotected and never had an issue with it (and I do have children...). The tubes in a SOHA don't get really hot anyway wink.gif

post #1508 of 1665

 

Just finished my SOHA II.

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This is basically a kit from Glass Jar (thanks, Jeff). I used my own tube sockets, tubes (JAN Phillips 6922), RCA jacks,

switch, electrolytic cap's (FC, FM, UPW), and Vitamin Q's for C1. Output devices are BD137's. Wiring is some cryo'd

Vampire I had. Tube bushings are from ACE Hardware.

 

Although it works with both my HD600's, and Denon 7000's, I think it's really much better suited to high impedence

'phones. The right channel tube behaves fine with the 600's, but goes terminally microphonic when I plug in my

7000's.

 

 

 

post #1509 of 1665

@funch, try different tubes.  that's primarily a tube issue.  I use mine with low impedance and high impedance just fine, including the D2000, M50, Q40, etc.

 

nice drilling job, it looks painful to do.

post #1510 of 1665
Funch,

Awesome drill job on the top cover!

Did you use a pattern or was it more-or-less free form? After seeing some of your previous work, it is a legitimate question, as you are the consement perfectionist!

BTW, Ace hardware is a treasure trove of goodness. All kinds of great and wonderful stuff buried in various trays and cabinets. First stop for stainless #4 hardware.
post #1511 of 1665
Quote:
Originally Posted by jdkJake View Post

AFunch, Awesome drill job on the top cover! Did you use a pattern or was it more-or-less free form? After seeing some of your previous work, it is a legitimate question, as you are the consement perfectionist! BTW, Ace hardware is a treasure trove of goodness. All kinds of great and wonderful stuff buried in various trays and cabinets. First stop for stainless #4 hardware.

Thanks for the nice remarks Jake.


I first lay out a pattern on the FPE software. I set all the holes to 1.5mm, the panel to 'clear', and print it out. Then I tape it to the panel and use a

center punch to dimple the panel. I leave the paper on and use a pin vise to start each hole, using three sizes of bits. Once that's all done, I remove

the paper and fire up the drill press. I start with a small bit, working my way up to the desired size. I finish up each hole with a hand held countersink

tool I got at Harbor Freight. The real pain doing anodized panels are what I call 'spinners'; the shavings that can scratch circles in the finish. The process

is painstaking enough as it is, but having to stop each 'plunge' 4 or 5 times to clear them is really a pain in the patootie. BTW, the pattern on this amp

started out as concentric circles, and, uh, got a little out of hand. :-)

 

Amen to your Ace endorsment. I also use the stainless #4 stuff. I also like to use M4 screws for the Hammond panels, as the #6 stuff, to me, is too

easy to strip.


 

Quote:
Originally Posted by holland View Post

@funch, try different tubes.  that's primarily a tube issue.  I use mine with low impedance and high impedance just fine, including the D2000, M50, Q40, etc.

 

nice drilling job, it looks painful to do.



 Yes, you're right. I'm noticing it with the HD600's as well, just way more noticeable with the D7000's. Of course, it's only when I'm touching the amp, so it's

not a major deal. I'm thinking of ordering a couple of 8416's, so that would fix the problem (I hope). BTW, does anyone here know of a good source for them?

I see Tube Depot has them. Just wondering if there might be a better, read cheaper source.

post #1512 of 1665
Quote:
Originally Posted by funch View Post

Yes, you're right. I'm noticing it with the HD600's as well, just way more noticeable with the D7000's. Of course, it's only when I'm touching the amp, so it's

not a major deal. I'm thinking of ordering a couple of 8416's, so that would fix the problem (I hope). BTW, does anyone here know of a good source for them?

I see Tube Depot has them. Just wondering if there might be a better, read cheaper source.



LOL.  It's a crap shoot with tubes.  I have lots of used and NOS tubes.  Some work at the operating point I have for my SOHA II, some don't.  I have some new tubes which didn't hiss at the stock SOHA II operating points, but after modifying my SOHA II, it hissed like mad in one tube, but not the other.  tubes....it's a love/hate thing.

post #1513 of 1665

 

O' course, there's always opamps. eek.gif

post #1514 of 1665

 

I think I'm going to revise my earlier impressions of this amp. It seems to work equally well with high or low impedence 'phones.

My D7000's are sounding very nice through it. I have to say that, for the money (especially with the Glassjar kit), it's got to be one of the best hybrids around.

It seems to be very revealing of the source, or source material. Easy to build, compact, and great sounding. Another triumph Lord Cavalli.

post #1515 of 1665

Hello,

 

I got my kit from Jeff this week and started installing the power supply diodes, and so it starts!!

 

I have a few simple questions, I havent dont this in awhile, but have a lot of experience in building stuff...

 

1. What gauge hookup wire do you guys use? 20 or 24 ?

2. Do you use shielded wirr from the isolated RCA input connectors to the amp board.

2. Do yoy only ground this on one end, if so which end, and does it really matter?

 

Going to use the Avil Y236203 to allow for 600ma and 12volt heater for the 12 v tubes etc...

 

Thanks

Alex

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