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SOHA II Builders Thread - Page 89

post #1321 of 1686
Hello everyone.

first of all, I haven't seen any "introduce yourself" thread on the forum, so if I just missed it, feel free to let me know.

Having spent a lot of time to read this forum and to learn by heart the Cavalli Audio site I decided to jump the step and to start the construction of a SOHA II. I already received the PCB from Glass Jar Audio and I should receive the components from mouser by the end of the week. I feel like a kid on Christmas Eve...

Well, I have a question about the enclosure : I plan to build the same one (well, at least I'll try...) zkool448 did, but on Alex Cavalli's website, I can read this :
Quote:
Warning: The SOHA II dissipates a lot of heat. The top plate must be opened so that there is a high amount of ventilation. More than 50% of the area of the top plate over the entire board must be opened for ventilation.
Is zkool448's enclosure ventilated enough?

Thank you very much for your answer.
post #1322 of 1686
Quote:
Originally Posted by runeight View Post
Well then, we'll have to be a bit more exhaustive in our debugging. I hate to ask, but if you would kindly measure with respect to ground:

1. All pins on both tubes.
2. All test points
3. All opamp pins

I will transfer these to a paper schematic and see if I can figure out what gives.
I see Alcaudon's been busy with his amp while my internet's been down. I took some measurements and overall they seem to be fairly similar to his measurements.

TB+ = 107.8 V
TL- = -15.05 V
TL+ = 14.92 V
TH = -12.88 V

R10L = 210 mV
R10R = 211 mV
TPL = 60.4 V
TPR = 59.1 V
TB+L = 60.7 V
TB+R = 58.4 V

TBL to TB+L, 295 mV
TBR to TB+R, 247 mV

Tube pins - Right, Left
1, 40.5, 39.6
2, 0, 0
3, 2.02, 2.07
4, -12.87, -12.87
5, 0, 0
6, 59.1, 60.4
7, 0,0
8, 2.02 , 2.07
9, 6.35, 6.48

opamp pins.. right and left opamps are identical, all except pin 6.
1, 14.54
2, 0
3, 0
4, -15.08
5, 0
6, Right=3.28, Left=3.88
7, 14.92
8, 14.55

I'm using EH 12AU7 tubes with the heater set at 12.6v. Q1L, Q1R and Q2L,Q2R has been replaced twice.
post #1323 of 1686

Part question

Quick q: In the SOHAII part list it specifies R5P as 1W but the Mouser part number in the .xls spreadsheet points to is 1/2W. Looks like I ordered the 1/2W one. Will this be an issue?

Thanks
post #1324 of 1686
Quote:
Originally Posted by stringgz301 View Post
Quick q: In the SOHAII part list it specifies R5P as 1W but the Mouser part number in the .xls spreadsheet points to is 1/2W. Looks like I ordered the 1/2W one. Will this be an issue?

Thanks
Damn, you're right. I ordered the 1/2W too...
post #1325 of 1686
the datasheet is kind of confusing.. It lists the ccf60 as being rated for "1/2w, 3/4w, 1w" at 70 C
I interpret it as being rated to 1w given a lower lifespan tolerance.. I'm usually wrong though :P
post #1326 of 1686

Confused about part values

I've started to build mine, and unfortunately I now notice that the parts list on the Cavalli website does not match the schematic nor the excel spreadsheet. It appears the schematic and excel spreadsheet are correct...which means I need to unsolder R1P,R2P,C6P, and C7P since I sourced the parts from the other parts list...
post #1327 of 1686
I'm about to start my build today, and I noticed that some resistances I ordered (from the BoM mouser references) don't match the descriptions. For example, R9L and R9P are supposed to be 820 Ohms but the mouser and digikey references are 825 Ohms.

Just so I know : do the 5 Ohms make a big difference?
post #1328 of 1686
Quote:
Originally Posted by Nevohteeb View Post
Hello everyone.

first of all, I haven't seen any "introduce yourself" thread on the forum, so if I just missed it, feel free to let me know.

Having spent a lot of time to read this forum and to learn by heart the Cavalli Audio site:) I decided to jump the step and to start the construction of a SOHA II. I already received the PCB from Glass Jar Audio and I should receive the components from mouser by the end of the week. I feel like a kid on Christmas Eve...

Well, I have a question about the enclosure : I plan to build the same one (well, at least I'll try...) zkool448 did, but on Alex Cavalli's website, I can read this :


Is zkool448's enclosure ventilated enough?

Thank you very much for your answer.
Do you have a picture of zkool448's enclosure? Most of us with the standard enclosure are using perforated aluminum or copper sheet that can be bought at McMaster Carr or I think even Amazon now. I have P-I-O caps under the board so I driled a few holes around them to keep them cool.
post #1329 of 1686
Quote:
Originally Posted by regal View Post
Do you have a picture of zkool448's enclosure?
Here it is : http://www.head-fi.org/forums/f6/cas...0/#post5646690
post #1330 of 1686
Can't say, certainly doesn't meet Alex's criteria on his website, but it may work only someone with experience with that enclosure would be able to make that call.
post #1331 of 1686
Hello, I have a question about the linear regulators.
Mouser does not have any in stock of the three I need, but there are alternative except they put out 1.5 Amp instead of the nominal 1 Amp.
Are these okay to get or should I look elsewhere.
post #1332 of 1686
Thread Starter 
They are ok so long as the pinouts are the same.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
post #1333 of 1686
Hi everyone,

my SOHA II is alive!



The tubes are Telefunken 12at7 (I got them for free so...)

I currently have a buzz noise, but I guess this is a ground/earth problem. I'll check that once my enclosure is finished.

EDIT : I wired the board ground to the power inlet ground. Result : no more buzz
post #1334 of 1686
Quote:
Originally Posted by runeight View Post
They are ok so long as the pinouts are the same.
Thanks a lot!
post #1335 of 1686

Another SOHA lives!  Just got it up and running and (no surprise) it sounds great.

 

Quick question.  I built it incorporating Regal's mod from the start.  B+ is set to 85v and the tail current set to 2.75 mA per tube section.  However, the difference between TB+L and TPL is 22.6V (not 19V per the design website).  Is this correct?

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