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A Very Compact Hybrid Amp - Page 123

post #1831 of 2213
Thread Starter 
Well, either the D10 is introducing hum or it is causing a ground problem by introducing ground noise into the CTH. Does the D10 float?
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 #1832 of 2213
my little baby is finally running again and here with me

Sadly, for whatever reason, there is a huge amount of hum when using the 6f8g tube now. No idea why but it's generating a lot of hum that none of the other tubes do. Touchy buggers!
post #1833 of 2213
Ok, so demonstrating my newbiness, what do you mean by float?
post #1834 of 2213
Thread Starter 
Is the D10 grounded in any way separately from the other pieces of equipment?
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 #1835 of 2213
Not that I'm aware of. The D10 is only connected to the CTH via mini-to-mini and the macbook via optical.

Could it be the input jack? I used the one from the Spruce Canyon kit and didn't do anything special to insulate it from the case.
post #1836 of 2213
Thread Starter 
It's possible that the input jack is causing problems. I don't think so, but possible.

The input jack should be insulated from the case and grounded through its connections to the volume pot which is in turn grounded to the board.

You could try just disconnecting the input jack from the box just to see what happens.

Other than that I have to defer to others who listen from a computer. Perhaps they can help diagnose the problem.
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 #1837 of 2213
Tried pulling the input jack away from the case. No change. Also tried the CTH with my iPhone as source via LOD and zero hum. Although I still get the whole soundstage "leaning left" so that the center is around 11 o'clock. I'm guessing these are 2 different problems. Somehow the right channel is a little weak?

EDIT: More tests.

1 - CTH volume @ 100%, connected to D10. Some hum
2 - CTH volume @ 100%, connected to D10, touching CTH volume pot, less hum than (1)
3 - CTH volume @ 100%, cable removed from D10 (so no source), hum stronger than (1)
post #1838 of 2213
Don't know if this helps in the debugging process, but if I use the same setup (Macbbok -> D10 -> amp -> headphones) but substitute a cmoybb for the CTH there is no hum, unless I touch the cmoybb in which case it is there.

Could it be the cable?
post #1839 of 2213
Thread Starter 
Could be, but my guess is no.

You have the SG connected to the case? I think you said that earlier.

Is anyone else out there reading this who has experience running a CTH from a computer?
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 #1840 of 2213
Quote:
Originally Posted by stringgz301 View Post
Tried pulling the input jack away from the case. No change. Also tried the CTH with my iPhone as source via LOD and zero hum. Although I still get the whole soundstage "leaning left" so that the center is around 11 o'clock. I'm guessing these are 2 different problems. Somehow the right channel is a little weak?

EDIT: More tests.

1 - CTH volume @ 100%, connected to D10. Some hum
2 - CTH volume @ 100%, connected to D10, touching CTH volume pot, less hum than (1)
3 - CTH volume @ 100%, cable removed from D10 (so no source), hum stronger than (1)
It shouldn't be the jacks - both are insulated. If there's a change when you touch the pot, I'd suggest grounding the pot. Unless you have and I've missed it as I haven't been following the thread closely. Sorry.

The soundstage could be the tube as well. Did I sen you an extra tube? Does the behavior remain the same with both?
post #1841 of 2213

Solved

Ok. Not sure where the smiley is for "blushing" and "really embarrassed", but I solved the issue. When I wired up the input and output jacks I swapped L and G (R was correct) on both. Somehow, despite this, the CTH still produced music, albeit with some hum. After looking at the wiring diagram for the 1000th time and then looking up the specs for the jacks I discovered my error.

My CTH is now making sweet music and is ready to be cased up again. Thanks to Runeight and Wiatrob for your patient support.
post #1842 of 2213
Thread Starter 


Happy listening. Please let us know how you like it.
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 #1843 of 2213
Indeed. Sorry for being a @ss and making you post here - but your travails will help all future builders.

As we say:

BTW, it's:
post #1844 of 2213

CTH as preamp

I'm pleased to report all the qualities that make CTH a very nice headamp make it a very nice preamp as well



That's a std CTH feeding my FW F1 clone powering Hornshoppe horns. I've had my share of SS & tube preamps & this puppy competes well.
BTW, CTH having offset protection & muting delay make this possible, with the F1 being a DC amp, I'd not try this unless it did. Used a mellow Mullard to complement F1/HSH serious presentation, so CTH's tube rolling is a must as well.

Use std 100R R18s & a better-than-std pot if building a CTH for headamp/preamp duty. I know we'll be seeing such a CTH around these parts in the next month or two
post #1845 of 2213

A thank you to Bill for his support of this project w/kits

Got a nice, small package from wiatrob yesterday.

I was reminded how compact this feature-packed baby really is


Had Bill omit some parts for me as I'll be using a few that are bigger (pot, case, etc.) than std for this next build.


Putting kits like this together is certainly not trivial & must really be a labor of love... Thanks again Bill!
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