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-   -   Little dot and direct coupled amps...... (http://www.diyaudio.com/forums/everything-else/209728-little-dot-direct-coupled-amps.html)

JoeDJ 28th March 2012 08:24 PM

Little dot and direct coupled amps......
 
Little dot pre amps are not to be use with direct coupled amps and I do understand why. Exactly how is one to know exactly which amps are direct coupled?

I have been told that most amps these day are direct coupled but, I do no know how true this is. Yes, I'm a bit confused over this born of my ignorance.

I ask this as I may get a Little Dot MKIII for headphone use.
However, I was wondering if I can also feed the LD output into an intergrated amp to boost low output sources such as an mp3 player.

What about T class amps? Are they considerd DC?

JoeDJ 28th March 2012 11:30 PM

I have to assume that others are about as confused about this as I am.
Even on the LD forums, others can not get an answer to questions about DC amps.

godfrey 28th March 2012 11:46 PM

Quote:

Originally Posted by JoeDJ (http://www.diyaudio.com/forums/everything-else/209728-little-dot-direct-coupled-amps-post2963872.html#post2963872)
Little dot pre amps are not to be use with direct coupled amps and I do understand why.

Why? :confused:
Quote:

Originally Posted by JoeDJ (http://www.diyaudio.com/forums/everything-else/209728-little-dot-direct-coupled-amps-post2963872.html#post2963872)
Exactly how is one to know exactly which amps are direct coupled?

Open it up and look inside, study the schematic, or ask the manufacturer.

JoeDJ 29th March 2012 12:35 AM

Quote:

Originally Posted by godfrey (http://www.diyaudio.com/forums/showthread.php?p=2964128#post2964128)
Why? :confused:

Open it up and look inside, study the schematic, or ask the manufacturer.

I've been told that with a DC amp, if a valve fails on the LD, it can send high dc current to the speakers.

To be honest I thought that here, among the "experts" someone would know about the T amps. :)

BTW, if I was competent in reading schematics, I would already know the answer .;)

Simon B 29th March 2012 08:41 AM

I guess we must all just be too stupid Joe......:D

"Class-T" isn't a class at all, it's a trademark for a now bankrupt company's class D amp chips.

If you want to know if an amp you've got is dc coupled, you could always try putting some dc into it - not too much mind, and watching what happens at the output with a meter.


godfrey 29th March 2012 09:38 AM

If in doubt, you can always do the AC coupling yourself; just put a suitable capacitor between the Little Dot's output and the power amp's input.

DF96 29th March 2012 09:56 AM

I thought the Little Dot was a headphone amp? Surely it has to include a DC blocker at the output? I realise the LD is strange: I believe one version of it is simply a solid-state amp with a variable-mu cathode follower to add some distortion.

godfrey 29th March 2012 10:33 AM

Quote:

Originally Posted by DF96 (http://www.diyaudio.com/forums/showthread.php?p=2964597#post2964597)
I believe one version of it is simply a solid-state amp with a variable-mu cathode follower to add some distortion.

Aha! That's what I was suspecting. I guess they could leave out the output cap and use a DC servo or some other feedback arrangement to get rid of DC offset at the output, but I wouldn't want to own something like that.

If the valve fails the wrong way, you're screwed; there will be 100V or so on the output, and the feedback won't help. It's not just DC current through the speakers either; that kind of abuse would probably fry the input stage of a number of amps as well. (and an input coupling cap rated at 16V or so won't help either)

DF96 29th March 2012 10:52 AM

I understand that the different versions of the LD had quite different circuits, although details are hard to find. I saw on one website that someone had bypassed the CF and found that measured distortion roughly halved! (and it sounded better?)

JoeDJ 29th March 2012 04:26 PM

As I said, even on the LD fourm there is confsion about the compatability of the LD amps when used as a preamp citing not to use them with a direct coupled amp. Even the moderators say "check with the amp's maufacture for compatabilty" to everyone who needs an answer..... never really adressing the issue.

BTW, I'm aware that T amps are a trade mark for amps using a Tripath chip but, they are a class of amps none the less with a certain architecture. My question was are they generally considered direct coupled designs.

I am interested in the LD MKIII.


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