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Old 22nd January 2013, 06:11 AM   #1
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Default Is This a good Amplier?

Hey guys I am planning to buy this amp:
Pictures:
Click the image to open in full size.


Schematic:
Click the image to open in full size.

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
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Old 22nd January 2013, 06:50 AM   #2
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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.
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Old 22nd January 2013, 07:06 AM   #3
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Quote:
Originally Posted by ErikdeBest View Post
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:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

And this is a finished one by some guy:
Click the image to open in full size.


So you think it wouldn't sound great?
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Old 22nd January 2013, 07:27 AM   #4
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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
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Old 22nd January 2013, 07:31 AM   #5
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Looks like they have added a tube where it would be better off without to add value. Awful !

Enzo
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Old 22nd January 2013, 08:54 AM   #6
balerit is offline balerit  South Africa
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I don't like the way the volume pot is mounted, might have a loose joint from vibration after a while.
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Old 22nd January 2013, 08:57 AM   #7
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Would you be able to advice a good Build your own amp kit?
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Old 22nd January 2013, 09:03 AM   #8
cotdt is offline cotdt  United States
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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).
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Old 22nd January 2013, 09:10 AM   #9
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Originally Posted by cotdt View Post
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?
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Old 22nd January 2013, 09:16 AM   #10
cotdt is offline cotdt  United States
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It says 24VAC transformer right on the page. You want around ~35VDC rectified. I would rather use an SMPS, though.
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