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A Very Compact Hybrid Amp - Page 59

post #871 of 2203
4/22/09 at 6:22pm
Hmm, may have to go the millet starving student hybrid rout then, 150 is just a bit much
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post #872 of 2203
4/22/09 at 6:30pm
Quote:
Originally Posted by cms5423 View Post
For those who have built this--About how much did this amp cost to build? And What case did you use for it? Thanks very much
Don't think you can do much better than the link you see atop of the CTH board page

@ sachu That proto board was working fine at one time, if I remember correctly... Didn't some tinkering precede the problems on it?
It's quite tempting to see what can be done with & to a CTH, but confines are very tight on the board. And its quite a complex amp in that 3" x 5" space.

My hats off to nux for seeming to have built 5 that work right off the bat, even tho he did have quite a bit of elect experience. I think he went std BoM on them & that helped.

Edit: Hmm, may have to go the millet starving student hybrid rout then, 150 is just a bit much
For your budget maybe, but not for what this amp is Perhaps we'll see ya building one a bit further down the road....
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post #873 of 2203
4/22/09 at 6:34pm
Quote:
Originally Posted by cfcubed View Post
Don't think you can do much better than the link you see atop of the CTH board page

@ sachu That proto board was working fine at one time, if I remember correctly... Didn't some tinkering precede the problems on it?
It's quite tempting to see what can be done with & to a CTH, but confines are very tight on the board. And its quite a complex amp in that 3" x 5" space.

My hats off to nux for seeming to have built 5 that work right off the bat, even tho he did have quite a bit of elect experience. I think he went std BoM on them & that helped.
I went standard BOM too..a misplaced diode first started smoking, replacing that worked for a bit. After 2 mins of music more burning smell. Possible problem with the splitter, but could be the buffer as well.
edit:waiting for parts to arrive before I can debug further

My third build,uses Jantzen audio caps, and a production board is working fine and that is making its way to Smeggy tomorrow.
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post #874 of 2203
4/22/09 at 10:28pm
Quote:
Originally Posted by holland View Post
tacitapproval. My 2nd build is having some issues as well, and I'll be looking at it. Can you measure the DC offset, and keep an eye on it. What I mean is power it on, measure the DC offset (before the e12 if you can). Watch both channels or find the one that is tripping the e12.

What I am finding with mine is that the DC offset climbs with time, on the right channel. It bounces around, albeit slowly, but it is significantly higher than the left. The left is at a few mv at most.

I was just wondering if your problem is similar.
I got the switching reg from digikey today and that was the problem with the heater. Unfortunately, the e12 trips remain--although, I am listening to it as I type this and the relay has gone off only once in about 15 to 20 minutes. It is tantalizingly close to being fully stable. Drats.

I guess I will procede with swapping the output and splitter transistors next.

Holland - I measured the offset on both channels, but I don't see any steady increase. Of course, I didn't have the meter on it when the last relay throw happened, to see what the reading was--see above. The numbers jump around some, but are pretty low; single mVs. It does occur to me that I have heard some popping on, I think, the right side before the e12 kicks in, which I guess maybe caused by offset? Of course, it is not doing it now--damn confounding problems that are not even problematic when they are supposed to be!
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post #875 of 2203
4/22/09 at 11:18pm
Single mVs is normal (really god actually). It doesn't sound like you have the same symptom as Holland.

Was the 'pop' you heard similar in intensity to the one heard when you power off the amp with 'phones plugged in? Maybe try replacing the right channel buffer Q's first...
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post #876 of 2203
4/22/09 at 11:58pm
The pops are like that, but somewhat softer. I will try the right side first--fingers crossed.
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post #877 of 2203
4/23/09 at 1:41am
Is the consensus that we don't need a standoff under the tube for this board?
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post #878 of 2203
4/23/09 at 10:11am
@ tacitapproval - Sorry if this was mentioned, but what tube(s) have you tried? It's not beyond possibility that a questionable tube could be causing this...

@rds - No standoff is necessary, but as with all electronics best to get heat out of the case if it is easy to do so. I like my projects < 60C, preferably < 55C internally.

Not having a socket saver handy (or even knowing they existed , in my 2nd CTH I made my own:
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post #879 of 2203
4/23/09 at 2:23pm
cfcubed - I have tried a variety of tubes--it is not tube dependent. Although, different tubes seem to trigger it more or less.

Speaking of which, I was able to watch the offset numbers on a 12bh7, which seems to trigger the problem more than some. It is definitely on the right side. The left is pretty consistently between 2-5mV. The right will swing between positive and negative DC, generally staying low, but sometimes jumping up to as much as 75mV in my brief observation and triggering the e12. This must also confirm the distorted/popping noises I hear in the right side at times. Unfortunately, I changed out Qs4-9R and this has not affected the problem. Any thoughts out there on what to try next?
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post #880 of 2203
4/23/09 at 4:18pm
Do you have a spare TL082 you might swap out?
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post #881 of 2203
4/23/09 at 4:57pm
It's not that opamp, I tried that earlier on.
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post #882 of 2203
4/24/09 at 12:25am
Quote:
Originally Posted by cfcubed View Post
Perhaps, but we're really waiting to see what kind of casework his CTH gets
Quote:
Originally Posted by smeggy View Post
zk will eat my build for lunch
nice... not to put any pressure eh?

BTW, this might be a dumb question. In the assembly notes, it says "Do not install D5H." Maybe I didn't look hard enough can't seem to find any reference on why, and/or when I should install D5H?


.
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post #883 of 2203
4/24/09 at 12:47am
I believe you install d5h after putting all the flat parts so you can easily turn the board upside down and not have d5h protrude out.
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post #884 of 2203
4/24/09 at 1:08am
Yep, you need D5H. The instructions should maybe say "Do not install D5H yet". If you read on it says to install it in step 5.
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post #885 of 2203
4/24/09 at 1:26am
Ahhhh... thanks. I'm bad at always trying to read too much into things

I've got most of the board populated and now I have to squeeze in D5H <sigh>
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