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-   -   Is This a good Amplier? (http://www.diyaudio.com/forums/tubes-valves/228377-good-amplier.html)

Mariusmssj 22nd January 2013 06:11 AM

Is This a good Amplier?
 
Hey guys I am planning to buy this amp:
Pictures:
http://image.hotsalekey.com/usa-on-s...MP-kit-60W.jpg


Schematic:
http://img43.imageshack.us/img43/5193/capture1n.png

Few specs:
Chips -
Valve Tube 6N11
Texas Instrument LM4780

Components -
C1, C2 = 100V 33uF
C3 = 100V 220uF
C5 = 50V 10uF
C6, C7 = 50V 3300uF
C9, C12, C14 = 16V 100uF
C10 = 50V 47uF
C11 = 16V 2200uF
C13 = 4.7uF

So I wanted to ask if this would be a good little amp???
Thank you

ErikdeBest 22nd January 2013 06:50 AM

Why did you choose for this one? Because of the tube? It is configures as a cathode follower (CF), with a very low load (only the 1k) which will probably introduce lots of distortion, ie, wrong use of this topology. A CF doesn't have any voltage gain either, so all gain has to come from the op amp.

It appears to use a very specific transformer, with dual 24V, dual 18V secondaries and a 6,3V. Do you have a source for this transformer? For the LM chip only the 24V (at high A) are needed, the 18V and 6,3V are only for the tube buffer. With other words, if there is no off the shelf transformer for this amp, you will need a custom job or combine different transformers.

I wouldn't go with it.

Mariusmssj 22nd January 2013 07:06 AM

Quote:

Originally Posted by ErikdeBest (Post 3336909)
Why did you choose for this one? Because of the tube? It is configures as a cathode follower (CF), with a very low load (only the 1k) which will probably introduce lots of distortion, ie, wrong use of this topology. A CF doesn't have any voltage gain either, so all gain has to come from the op amp.

It appears to use a very specific transformer, with dual 24V, dual 18V secondaries and a 6,3V. Do you have a source for this transformer? For the LM chip only the 24V (at high A) are needed, the 18V and 6,3V are only for the tube buffer. With other words, if there is no off the shelf transformer for this amp, you will need a custom job or combine different transformers.

I wouldn't go with it.

Why I chose this is because it's a build your own amp kit:

http://img.alibaba.com/img/pb/034/73...736034_750.jpg

http://www.hifidiy.net/jhwz/200806/W...4266255981.jpg

http://www.hifidiy.net/jhwz/200806/W...4271254272.jpg

http://www.hifidiy.net/jhwz/200806/W...4268757002.jpg

And this is a finished one by some guy:
http://www.hifidiy.net/up/135/31.jpg


So you think it wouldn't sound great?

ErikdeBest 22nd January 2013 07:27 AM

I see that I missed that the filament is fed with 6VDC, not that it matters much.

It is hard to say if it will sound great. It is just that this use of a cathode follower is far from being the ideal application of this circuit, I think it is only there to introduce some distortion, the 'tube sound' (and I don't like tubes being applied that way).

Best regards, Erik

enzoastro 22nd January 2013 07:31 AM

Looks like they have added a tube where it would be better off without to add value. Awful !

Enzo

balerit 22nd January 2013 08:54 AM

I don't like the way the volume pot is mounted, might have a loose joint from vibration after a while.

Mariusmssj 22nd January 2013 08:57 AM

Would you be able to advice a good Build your own amp kit?

cotdt 22nd January 2013 09:03 AM

This is just a classic tube buffered Gainclone amp using LM4780. Looks fine to me. No, the tube buffer is not needed. Yes, people prefer the sound with the tube buffer in there.

I'd say try it, and tell us how you like it (or not).

Mariusmssj 22nd January 2013 09:10 AM

Quote:

Originally Posted by cotdt (Post 3337036)
This is just a classic tube buffered Gainclone amp using LM4780. Looks fine to me. No, the tube buffer is not needed. Yes, people prefer the sound with the tube buffer in there.

I'd say try it, and tell us how you like it (or not).

Well the kit seems high quality using Nichicon Muse and Gold Tune caps. The pot also looks like a Original Alps 50KAX2. This why this caught my interest.

But I got absolutely no idea what king of transformer I would need to power this amp. Any suggestions?

cotdt 22nd January 2013 09:16 AM

It says 24VAC transformer right on the page. You want around ~35VDC rectified. I would rather use an SMPS, though.


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