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post #1366 of 1686

ok. I'll have a look. thanks

post #1367 of 1686

here is regal's current mod..

 

Here's how to get the most of your tubes on the SOHA II. The issue I was hearing on some of the 12AU7s and 6DJ8's was a slight weakness or thinness. So here is how you can safely get more current thru the tube:

1. Set B+ to 85V
2. Add another 18k ohm resistor on top (parallel) of R4L&R (makes it 9k ohm)
3. Add another 200 ohm resistor on top (parallel) of R6L&R (makes it 100 ohm)

Adjust P1L&R to give .550 V across R6L&R

Check to make sure you have at least a 19V drop across the top CCS (adjust P1 until you do)

This gives 2.75 mA thru each tube section.

 

 

 

also I am using the heatsinks in the excel bom, but they are fricken hot too.. but if they are enough then I guess I'll just heatsink HV and be done..

 

post #1368 of 1686

yeah found it in the tubes thread, thanks anyway. its very easy to do and easy to turn back to original. will definately try this..

 

got some components delivered today. I forgot to add one of each pair of trimpots.

 

post #1369 of 1686



In some homes you have to lower B+ to 75-80V depending on your wall outlet stability.   If your heatsinks are hot,  are you following Alex's rule for ventilation?

Quote:
Originally Posted by particleman14 View Post

here is regal's current mod..

 

Here's how to get the most of your tubes on the SOHA II. The issue I was hearing on some of the 12AU7s and 6DJ8's was a slight weakness or thinness. So here is how you can safely get more current thru the tube:

1. Set B+ to 85V
2. Add another 18k ohm resistor on top (parallel) of R4L&R (makes it 9k ohm)
3. Add another 200 ohm resistor on top (parallel) of R6L&R (makes it 100 ohm)

Adjust P1L&R to give .550 V across R6L&R

Check to make sure you have at least a 19V drop across the top CCS (adjust P1 until you do)

This gives 2.75 mA thru each tube section.

 

 

 

also I am using the heatsinks in the excel bom, but they are fricken hot too.. but if they are enough then I guess I'll just heatsink HV and be done..

 

post #1370 of 1686

I am currently running 80V, I'll try 75 or so.  I am unfamiliar with alex's guidelines..I am using the 1" tall heatsinks.  will this be ok?  or should I grab some 1.5"s or something?

right now the soha has no cover or anything and there is a fan right next to me. here are some pics  it will be in this box for a while until I case it up..

IMG_2874.JPG

I have taped up some caps to test which ones I like best.  FT-3 teflon (big ones), sprague vitaminQ, and obbligato premiums.  getting ready to put in a good listening session this weekend..

IMG_2876.JPG

I am starting to think my alps pot is hurting my sound so I'm switching it up with this stepped atten from ebay.. we'll see how it works i'm about to solder it up after this post:)


Edited by particleman14 - 6/19/10 at 12:07am
post #1371 of 1686


The guidelines for heat are when you case it to use a perforated aluminum cover and some holes in the case under the heatsinks,  you will be fine if you do that.


For caps my favorites were the vitQ's and AmpOhm C-I-F,  let us know what you prefer.  80V may be fine for your house,  to test plug in an electric heater to the same wall socket,  if it trips the E12 you will have to lower the B+.

Quote:
Originally Posted by particleman14 View Post

I am currently running 80V, I'll try 75 or so.  I am unfamiliar with alex's guidelines..I am using the 1" tall heatsinks.  will this be ok?  or should I grab some 1.5"s or something?

right now the soha has no cover or anything and there is a fan right next to me. here are some pics  it will be in this box for a while until I case it up..

I have taped up some caps to test which ones I like best.  FT-3 teflon (big ones), sprague vitaminQ, and obbligato premiums.  getting ready to put in a good listening session this weekend..

I am starting to think my alps pot is hurting my sound so I'm switching it up with this stepped atten from ebay.. we'll see how it works i'm about to solder it up after this post:)

post #1372 of 1686

 Hi everyone ! As the topic seams to be heat ect... I have a Triad-Magnetics transformer # VPT30 -830 that I would like to use. It is rated 30Vct @ 0.83A  or 15 + 15 @ 1.66A, what mods would be needed to implement using this ? Would the output transistors half to be changed as I believe the Toshiba's are rated for 1.5A ? If so can someone point me in some kind of direction and/or what mods I should do ect...    Thank's

post #1373 of 1686

nothg you can use it as it is.

post #1374 of 1686

Tamu, Thank-you thats good news as I had picked 3 of them up for $ 25.00 usd at a local supply no longer selling Triad ect...

post #1375 of 1686

no problem:) enjoy the build!

post #1376 of 1686

Hey so i am finally finding a use for my temperature tip that came w/ my dmm.  I am reading about 55-60C on all my heatsinks after running for about 8 hours constantly..

this is actually not too bad when I look in the transistor datasheets which give like 125C-150C as their max rating.... hopefully my numbers won't go up much higher when I case it up.

 

Also some initial listening tests have narrowed down my capacitor choice to the vitaminQ's and the FT3's.  both have their signature, I am still deciding what I like best with the music I intend to listen to.

 

I plan on using a1Galaxy Maggiorato GX283 230 x 230 mm

The case only has a small row of slits in the back so I'm not sure if this will be sufficient or not?  

also my voltage difference between my tpr/tpl and tb+ is 25V instead of the suggested 19V.  will this extra 6V give me trouble down the road? or is it within an acceptable range?  

gunna do some more listening tests; building amps are fun yay!:)

post #1377 of 1686

25v is fine. 19v is a minimum amount of drop.

post #1378 of 1686

well did a little building and listening this weekend, but now I have a problem.. I am paying the price for having an open top box sitting all on the same project table..

apparently a clipped lead managed to get into the soha between the pin 4 and C1 lead on the right side of the board. 

I started to see smoke coming from the tb+r area (looed like it was coming from the caps, but not sure)  the right side now doesn't work. I coudln't see any visible burn or char on the boards so i'm not sure what component is damaged.

the tpr measures 80V which is my Hv setting.  so what have I blown? lol.  just when I was ordering a case for it and all too! 

post #1379 of 1686



Pin 4 is the heater,  check that the tube is getting proper heater voltage first.

Quote:
Originally Posted by particleman14 View Post

well did a little building and listening this weekend, but now I have a problem.. I am paying the price for having an open top box sitting all on the same project table..

apparently a clipped lead managed to get into the soha between the pin 4 and C1 lead on the right side of the board. 

I started to see smoke coming from the tb+r area (looed like it was coming from the caps, but not sure)  the right side now doesn't work. I coudln't see any visible burn or char on the boards so i'm not sure what component is damaged.

the tpr measures 80V which is my Hv setting.  so what have I blown? lol.  just when I was ordering a case for it and all too! 

post #1380 of 1686

hmm ok so checking the test points, I am finding that the pin 4 on the right tube is about 10V vs about 5v for the left tube.  also pin 1 gives me about 58v on the right vs about 54v on the left. pin 6 is reading about 79V on the right vs 55V on the left. 

kind of stumped at this point, damn you clipped leads!


Edited by particleman14 - 6/23/10 at 8:50am
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