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SOHA II Builders Thread - Page 48

post #706 of 1687
That should be fine. You can use the UF4004_Q

and you can use uf4005, uf4006, and uf4007 as well.
post #707 of 1687
Thread Starter 
No probs on the diodes.

TI is the only supplier for the reg.

C3E can be bipolar. There should be pads on the board for the larger size.

I see that Holland has already answered the diode question.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #708 of 1687
Quote:
Originally Posted by runeight View Post

But there are a few things you should check. Are the rails +/-15V?? Are all of the resistors in buffers the correct values? Are you using the stock BD transistors or something else?

210mV is enough for almost anything that you'll want to do. I'd just like to see you have more range on the high side of the setting.
+15V and -15V is correct. I have checked all resistors few times, and have not found any errors. I use BD139.

And, If You say, that 210mV is enough... I use Sennheiser 515. What do You think? Is it enough?
post #709 of 1687
Quote:
Originally Posted by TimJo View Post
I'm about to order parts for my build and have a couple of questions.

Mouser is backordered on a couple of parts.

One is the high voltage regulator. I took a quick look through the catalog and it looks like TI is the only one making this part - is that right Alex, or does Mouser have an alternative selection that I missed? I may need to order it from Digikey I guess. It will be my only Digikey part.
I ended up having to get that part from Digi-Key too. At least they got rid of that minimum order policy they used to have (or was that Mouser? lol). I just price compared the parts they both carried and ordered the cheaper ones from Digi-Key and took them off the Mouser order. The Hammond case is cheaper at Digi-Key, just make sure you get the right part #. I order silver on accident
post #710 of 1687
Thread Starter 
OK. I guess this one is on the far edge of the curves. Try running it for a while to see if the current increases.

95mA is plenty for 300R headphones. You won't have any problems nor will you bump into any limits on the buffers.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #711 of 1687
I just finished building my SOHA, took more time than it should have ...

Well - just as I expected and the same time hoped the opposite it does not work.
In the very first step of the setup I'm stuck.

TB+ Reading is only ~23Volts - not over a hundred as it should be.

Normally this woulnd't bother me that much, I'm used to startup- problems with my DIY projects.
But this special one is a birthday gift for my father - tomorrow ...

post #712 of 1687
Quote:
Originally Posted by Sathimas View Post
I just finished building my SOHA, took more time than it should have ...

Well - just as I expected and the same time hoped the opposite it does not work.
In the very first step of the setup I'm stuck.

TB+ Reading is only ~23Volts - not over a hundred as it should be.

Normally this woulnd't bother me that much, I'm used to startup- problems with my DIY projects.
But this special one is a birthday gift for my father - tomorrow ...

Have you checked to see that the transformer wires are going to their proper terminals?
post #713 of 1687
Well - this is the schematic on the transformer:

Black - 0V
RED - 15V
Orange - 0V
Yellow - 15V

Black and orange are connected to the middle binding post - the 0V one
Red is on the left side, yellow on the left side - should be correct this way - or not?

What I forgot - the other readings of that step show correct values. (15, 15 and 12,6V)
post #714 of 1687
Thread Starter 
Sathimas, the correct way to wire the transformer would be:

Black to one outside post
Yellow to the other outside post
Orange/Red to the middle post

Try this and see what happens.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #715 of 1687
What do you read for an input voltage? (From the input connector on the board)
What's voltage at TL+/- and TB?

[edit] Never mind, I lack reading comprehension skills. Looks like Runeight cleared it up.
post #716 of 1687
thank you very much runeinght - I misunderstood the transformer wiring somehow.

Could someone explain it to me so that I won't make that mistake again?

Now all readings are ok for the moment, I'll go on testing in a minute and keep you up to date
post #717 of 1687
Thread Starter 
The transformer must be wired so that it give 30V center tapped. The two "outside" wires must be out of phase to get this arrangement.

Now the transformer leads are marked with their phase relationships. This means that the two 0V leads are in phase with each other and the two 15V leads are in phase with each other. Using two 15V leads for the outside connections makes them both in phase and this is not what is needed for 30V center tapped.

To get out of phase "outside" leads you must use one 0V lead and one 15V lead. Then the two remaining leads are connected together to make the "center tap."

It actually doesn't matter how you form the outside leads. You can do it the way I did or you can do it this way:

Red - outside
Orange -outside
Black/Yellow - middle

They are both 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.
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post #718 of 1687
Its alive now.

Only thing I still have to change are the LED-resistors.
The LEDs should be much brighter, at the moment you hardly notice them.
post #719 of 1687
I started looking at the parts from my kit tonight in preparation for starting tomorrow. I discovered one disadvantage of using a kit. When I order from mouser, everything comes in nice labeled bags. The print on the Dale resistors is very hard for my old eyes to read. I realize I need to measure each resistor anyway, but it would be nice to be able to pick out the proper resistor easily.

This is going to accelerate me getting bifocals
post #720 of 1687
Are there any Australians who've built this baby?
I'm looking to find out a rough price of importing the needed items.

Even if someone could give me a rough price of all the needed items, it'd be much appreciated.
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