Thanks guys 🙂 copied ideas of others (mostly...).
The power supply is made of two 40VA 12Vac potted lighting transformers. The primaries of both and an additional earth wire are connected to the mains plug, and the secondaries and earth wire connect to the amp via a 3 pin XLR (earth plus one end of each secondary on pin 1, other ends of two secondaries on pins 2 & 3). The transformers were heading for the bin at work, and I thought I'd make use of them rather than see them wasted (I actually got three, and used the two with closest Vac on the seconadries).
The ebay fet buffer is discussed here: http://www.diyaudio.com/forums/solid-state/126334-stereo-fet-buffer-ebay.html
The big elna caps supply +/-17.5V to the LM3875 chips, which each have 2x 35V 470uF sikorel caps on the pins. The buffer gets about +/-17.2V from the four 220uF silmic II caps, that are supplied from the big elnas via a 22ohm resistor (each rail of each buffer channel is fed from it's own R & C).
The speaker terminals are from Maplin. I usually use speakons, but this amp is for test/play at work so screw terminals are handy.
The power supply is made of two 40VA 12Vac potted lighting transformers. The primaries of both and an additional earth wire are connected to the mains plug, and the secondaries and earth wire connect to the amp via a 3 pin XLR (earth plus one end of each secondary on pin 1, other ends of two secondaries on pins 2 & 3). The transformers were heading for the bin at work, and I thought I'd make use of them rather than see them wasted (I actually got three, and used the two with closest Vac on the seconadries).
The ebay fet buffer is discussed here: http://www.diyaudio.com/forums/solid-state/126334-stereo-fet-buffer-ebay.html
The big elna caps supply +/-17.5V to the LM3875 chips, which each have 2x 35V 470uF sikorel caps on the pins. The buffer gets about +/-17.2V from the four 220uF silmic II caps, that are supplied from the big elnas via a 22ohm resistor (each rail of each buffer channel is fed from it's own R & C).
The speaker terminals are from Maplin. I usually use speakons, but this amp is for test/play at work so screw terminals are handy.
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It appears that you have input transformers AND DC input blocking caps..
(edit) That would be trafo and dc caps on the signal input path...
Is there a reason for both?
(edit) That would be trafo and dc caps on the signal input path...
Is there a reason for both?
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The input transformers are there to isolate the amp from sources with noisy ground (laptops etc.). The output of the FET buffer has a small amount of dc offset, so the coupling caps prevent this reaching the LM3875 chips.
Not the last word in audiophile minimalism, but surprisingly good. I've built several chipamps and this one sounds most full and solid (the unbuffered ones sound thinner in comparison). The additional coupling cap is a small price to pay for having the buffer.
Not the last word in audiophile minimalism, but surprisingly good. I've built several chipamps and this one sounds most full and solid (the unbuffered ones sound thinner in comparison). The additional coupling cap is a small price to pay for having the buffer.
Gotcha.
I would have expected a DC servo or offset adjust on the buffer to compensate but yes a cap is just as effective.
And I like the compactness.
Mini Gain Clone LM4765
I got 2 LM4765 from NS 3 years ago. I destroyed one when I tried to
hardwire and stop it for a long time. I has been built this amp again
but used PCB instead of hardwire and succesfully to build 25Wx2 amp
from this IC.
I prefer its sound than LM4780 (60Wx2). Even if its power lower than
LM4780 but its sound is more smooth and clearly.
I got 2 LM4765 from NS 3 years ago. I destroyed one when I tried to
hardwire and stop it for a long time. I has been built this amp again
but used PCB instead of hardwire and succesfully to build 25Wx2 amp
from this IC.
I prefer its sound than LM4780 (60Wx2). Even if its power lower than
LM4780 but its sound is more smooth and clearly.
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I'll go better than "nice".
Beautiful. But then I'm not married.
Would any ladies care to comment?
Beautiful. But then I'm not married.
Would any ladies care to comment?
That one was my favourite design also.
I liked it so much i based mine on it. Still not close too as cool as that one though.
http://sphotos.ak.fbcdn.net/photos-ak-sf2p/v149/114/74/607902362/n607902362_478216_6842.jpg
http://sphotos.ak.fbcdn.net/photos-ak-sf2p/v155/114/74/607902362/n607902362_478226_3200.jpg
http://sphotos.ak.fbcdn.net/photos-ak-sf2p/v155/114/74/607902362/n607902362_478228_3955.jpg
I liked it so much i based mine on it. Still not close too as cool as that one though.
http://sphotos.ak.fbcdn.net/photos-ak-sf2p/v149/114/74/607902362/n607902362_478216_6842.jpg
http://sphotos.ak.fbcdn.net/photos-ak-sf2p/v155/114/74/607902362/n607902362_478226_3200.jpg
http://sphotos.ak.fbcdn.net/photos-ak-sf2p/v155/114/74/607902362/n607902362_478228_3955.jpg
if you see the black thing on the bottom of the RCA input, that is the speaker terminal.( I do not like them at all).I would use "normal" nicer speaker terminals for sure.😀
lanchile-
I think he was referring to tangmonsters units here:
http://sphotos.ak.fbcdn.net/photos-ak-sf2p/v155/114/74/607902362/n607902362_478226_3200.jpg
They appear to have 2 RCA inputs for signal and an XLR for pwr... No spkr out.
Red RCA is speaker terminal
Black RCA is low level input.
It is not good for commercial design where people will tend to swap them easily. But for my design they work perfectly.
Black RCA is low level input.
It is not good for commercial design where people will tend to swap them easily. But for my design they work perfectly.
hey - thanks for the kind feedback. You may have now noticed that my pics have been delinked. My brothers website/server has been attacked by malware. We have not had the chance to search through all the code and find the offending lines. I hope we can resolve it soon and get the pics back up. Sorry for the inconvenience.
That looks lethal. I hope you don't have the shakes when operating the on/off switch 😱 🙂