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A Very Compact Hybrid Amp - Page 61

post #901 of 2201
4/24/09 at 4:43pm
Quote:
Originally Posted by tacitapproval View Post
Bump on this. Anybody?
This sounds like a servo problem in the buffer. IC1 is supposed to compensate for any DC offset, to keep it as close to zero as possible. What if you try swapping IC1L and IC1R and see if the problem changes channels.
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post #902 of 2201
4/24/09 at 4:47pm
Quote:
Originally Posted by zkool448 View Post
tacitapproval, sorry to hear about you're ongoing issue with your build. I really hope you get it sorted out soon. I brought mine up and with a bit of luck on my side lately my CTH came to life without any issues.

adamus, that's quite a nice build you got there - congrats!

The only changes I made is I socketed the LED pads, I want to route wires for the E12 LED to go somewhere on the panel. I must've lost the three 100R resistors (R18L, R18R, R9S), so I picked some up from my local electonics shop and used 1/4W metal films instead of 1/8W (it's all they had).

Sadly I'm no expert in giving impressions and pardon my french but, this little guy has some major f*** balls! IMO it holds its own alongside my SOHA II and like the fact that I (no audiophile experience whatsoever) can actually hear the subtle difference in sound as I swap the tubes. Anyway I'll let adamus and other experts share their own comments and impressions.

...time to enjoy and listen to some tunes

Nice job Z. So.. since you have a SS and the CTH, you can give us a nice, objective comparison between them.. Something that has been discussed before.
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post #903 of 2201
4/24/09 at 5:30pm
oh geez... as I mentioned I don't really have what you experts call "trained ears" not too mention a total hp noob ...but If you'll insists, i'll do my best and give an objective comparison of the two once I get the CTH fully burned in (just like my MSSH).

I also have to build me this A/B box by danobeavis first since it's probably that only way I can distincttively identify their similarities and/or differences.
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post #904 of 2201
4/24/09 at 6:38pm
Quote:
Originally Posted by MrSlim View Post
This sounds like a servo problem in the buffer. IC1 is supposed to compensate for any DC offset, to keep it as close to zero as possible. What if you try swapping IC1L and IC1R and see if the problem changes channels.
Thanks for the suggestion, I am not sure I understand though. IC1 is a dual opamp. And, as I mentioned, I have checked this part and it is not the tl082 that is at fault. I have also swapped ICR and this is not the problem. What else could account for sporadic offset on the right side?
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post #905 of 2201
4/24/09 at 7:58pm
Quote:
Originally Posted by zkool448 View Post
I also have to build me this A/B box by danobeavis first since it's probably that only way I can distincttively identify their similarities and/or differences.
That's the next thing I want to build too! That way I can better compare between different tubes using two CTH's.
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post #906 of 2201
4/24/09 at 8:06pm
Fixed mine. Switched the caps around and its working beautifully now thanks guys!
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post #907 of 2201
4/24/09 at 8:36pm
Quote:
Originally Posted by nux View Post
That's the next thing I want to build too! That way I can better compare between different tubes using two CTH's.
I recommend you listen using one tube with your favorite tracks for a week or two and then roll in a new tube. Flipping back and fourth will just confuse matters. Just a suggestion.
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post #908 of 2201
4/24/09 at 9:38pm
Quote:
Originally Posted by Coreyk78 View Post
Fixed mine. Switched the caps around and its working beautifully now thanks guys!
nice!!..
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post #909 of 2201
4/24/09 at 10:29pm
Quote:
Originally Posted by adamus View Post
heres my build so far. just waiting on the bushing, wiring + smoke test!
Looking good, and it will be so much more so with the bushing, which is on the way!
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post #910 of 2201
4/24/09 at 10:36pm
Quote:
Originally Posted by wiatrob View Post
Looking good, and it will be so much more so with the bushing, which is on the way!
Bill, he has C5P and C10P swapped..he needs to set that right before turning on
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post #911 of 2201
4/24/09 at 11:21pm
Quote:
Originally Posted by zkool448 View Post
I also have to build me this A/B box by danobeavis first since it's probably that only way I can distinctively identify their similarities and/or differences.
I take it from that that these two amps are very close in performance and sound?

Quote:
Originally Posted by Coreyk78 View Post
Fixed mine. Switched the caps around and its working beautifully now thanks guys!
Congratulations

Quote:
Originally Posted by olblueyez View Post
I recommend you listen using one tube with your favorite tracks for a week or two and then roll in a new tube. Flipping back and fourth will just confuse matters. Just a suggestion.
x2 Excellent advise. I started out swapping tubes and headphones constantly and started to think all tubes sounded pretty much the same with only a slight variation. Its only after listening to a variety of music that you can really appreciate what a particular tube has to offer.
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post #912 of 2201
4/25/09 at 12:13am
Quote:
Originally Posted by sachu View Post
Bill, he has C5P and C10P swapped..he needs to set that right before turning on
Except for that! Those devilish zeros...
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post #913 of 2201
4/25/09 at 12:58am
Quote:
Originally Posted by sachu View Post
Bill, he has C5P and C10P swapped..he needs to set that right before turning on
haha, it's quite easy to make that mistake, I almost did it too -- perhaps need to make one of the caps Nichicon

Quote:
Originally Posted by Forte View Post
I take it from that that these two amps are very close in performance and sound?
nope, sorry didn't mean to leave that impression. I wanted to say was i first need to build a true A/B device that allows to switch amps 'on-the-fly' easily before I can subjectively hear their differences. My initial impression though is that the CTH and SS millett do not sound alike to my ears. The SS has warm, tubey like sound and much deeper bass while the CTH sounds more detailed, accurate and good channel separation with very sharp mids/highs (but not bright).. am very happy with it.

I'm currently using a Russian 61NP NOS tube which I'm going to let burnin for a bit.


.
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post #914 of 2201
4/25/09 at 1:24am
Quote:
Originally Posted by tacitapproval View Post
Thanks for the suggestion, I am not sure I understand though. IC1 is a dual opamp. And, as I mentioned, I have checked this part and it is not the tl082 that is at fault. I have also swapped ICR and this is not the problem. What else could account for sporadic offset on the right side?
Oops, my mistake, I looked at the schematic and didn't check the parts layout...
It might be worthwhile measuring the voltage on the input and output of C4L and R, the interstage coupling cap and compare the two channels. That might help determining if the input stage is at fault or it's something in the buffer.

Runeight would have to comment on this, but I'm wondering if a bad D2(R) might cause this? It is supposed to provide a constant current source for the upper half of the buffer, and the servo opamp is used to adjust the lower current source to compensate for variations between the parameters of the upper and lower transistors, to end up with close to zero DC offset at the output.

Also, have another look at all your solder joints, in case you have a cold/bad one that is causing you issues.
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post #915 of 2201
4/25/09 at 1:32am
Hey Bill, I wanted to let you know my package arrived this week, and I installed the perf top on my proto.. It looks great and runs much cooler too. I probably won't be doing the second CTH for a while though. I have a couple of SOHA+Jisbos to get done, and some major studying for a CISSP exam coming up in June..
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