First channel is working. I ended up using a Radio Shack dual gang 100K pot to get things going. Once I have my chassis built, I'll look at upgrading the volume control.
Just to be sure, the signal input ground runs to the board (SG) and the potentiometer ground also runs to the board (SG). Is this correct?
I have 1/4" aluminum bar stock on order from McMaster Carr. Hope to have a chassis built in the next couple of weeks.
widman
Just to be sure, the signal input ground runs to the board (SG) and the potentiometer ground also runs to the board (SG). Is this correct?
I have 1/4" aluminum bar stock on order from McMaster Carr. Hope to have a chassis built in the next couple of weeks.
widman
Attachments
Photos from Oregon
As promised, here is my "closet amp", all ready to be put away forever with an old HP Pavilion to play music in the kitchen. It sounds really good, given the low level of quality connectors and all wiring, case components and transformer are scrounged. Cost was about $15 in addition to Brian's kit. Also, you will note the input is a mini-jack (see next post), which mates with the computer of course. Rather disgusting but simple and I think somewhat elegant. I like the overall result and hope you do to!!!
-Robert
As promised, here is my "closet amp", all ready to be put away forever with an old HP Pavilion to play music in the kitchen. It sounds really good, given the low level of quality connectors and all wiring, case components and transformer are scrounged. Cost was about $15 in addition to Brian's kit. Also, you will note the input is a mini-jack (see next post), which mates with the computer of course. Rather disgusting but simple and I think somewhat elegant. I like the overall result and hope you do to!!!
-Robert
Attachments
Wow - what a difference!
I got 2 channels of the four that I purchased working last night. The sound is just lovely!
I had been experimenting with chip amps up until now, but had only ever used cheap metal film resistor, and easy to buy capacitors. Although the sound I had achieved was OK, it was a little too harsh, and quite tiring to listen to. Nuuk suggested building a buffer but I didin't really achieve much there, laziness being the main problem !
I had a quick panic
when I first powered up one channel, when it would read no output on my 'scope....In end the amp was fine, but my scope was set between two sensitivity ranges...which doesn't work..
After disconnecting my 8ohm resistor, and connecting the JVC mini speakers that I stole form the wife's kitchen mini system (replaced them with some old PC speaker with amp ripped out), I achieved music.
Within seconds I knew that my previious efforts had been a waste of time! This was the real thing. I don't know if it's the better Panasonic FC capacitors, the Black Gate snubber caps, the combination of exotic resistors the diodes or even the PCB, but the sound is MUCH better than my previous efforts. All the harshness I had before is gone. The music is much more involving now & even the wife was impressed (she normally can't tell the difference).
Next I need to buy another transformer (I'm using 300VA 18V), and find a suitable case to stuff it all in. The project will be finished when it's a working 6 channel amp. I'm going to experiment with a small home theatre setup, and if I get bored of that, I may just build an active crossover, and tri-amp my speakers.....
To Brian & Meredith, thankyou for all your work. You've restored my faith in Hi Fi. -- I'll be buy ing another 'Premium' kitwhen Wiki 2 is at the order stage
Steve
I got 2 channels of the four that I purchased working last night. The sound is just lovely!
I had been experimenting with chip amps up until now, but had only ever used cheap metal film resistor, and easy to buy capacitors. Although the sound I had achieved was OK, it was a little too harsh, and quite tiring to listen to. Nuuk suggested building a buffer but I didin't really achieve much there, laziness being the main problem !
I had a quick panic
when I first powered up one channel, when it would read no output on my 'scope....In end the amp was fine, but my scope was set between two sensitivity ranges...which doesn't work.. After disconnecting my 8ohm resistor, and connecting the JVC mini speakers that I stole form the wife's kitchen mini system (replaced them with some old PC speaker with amp ripped out), I achieved music.
Within seconds I knew that my previious efforts had been a waste of time! This was the real thing. I don't know if it's the better Panasonic FC capacitors, the Black Gate snubber caps, the combination of exotic resistors the diodes or even the PCB, but the sound is MUCH better than my previous efforts. All the harshness I had before is gone. The music is much more involving now & even the wife was impressed (she normally can't tell the difference).
Next I need to buy another transformer (I'm using 300VA 18V), and find a suitable case to stuff it all in. The project will be finished when it's a working 6 channel amp. I'm going to experiment with a small home theatre setup, and if I get bored of that, I may just build an active crossover, and tri-amp my speakers.....
To Brian & Meredith, thankyou for all your work. You've restored my faith in Hi Fi. -- I'll be buy ing another 'Premium' kitwhen Wiki 2 is at the order stage
Steve
Some questions for you guys...
- My trafo is rated 2x22V but the the DC from the power source is +/- 32V; I know the DC is higher usually, but this high?
- The DC offset is ~60mV for a channel and ~70mV for the other. It doesn't get better without a source. Isn't this too high? Is there something I could to to lower it?
One thing I love about this amp is it's power requirements: going with the volume to the highest I usually listen, it takes only 8W, and idle at ~4W. Now this is what I call an environment friendly amp(boo the class A monsters).
These are the best values I ever saw!
- My trafo is rated 2x22V but the the DC from the power source is +/- 32V; I know the DC is higher usually, but this high?
- The DC offset is ~60mV for a channel and ~70mV for the other. It doesn't get better without a source. Isn't this too high? Is there something I could to to lower it?
One thing I love about this amp is it's power requirements: going with the volume to the highest I usually listen, it takes only 8W, and idle at ~4W. Now this is what I call an environment friendly amp(boo the class A monsters).
These are the best values I ever saw!
Bas Horneman said:
The biggest improvement was caused by properly chosen resistor types in particular places, as well as the PS caps (adding those small BGs is beneficial when using Panasonics).
It took me almost a year to come to this point (in GC design). Also, it seems like the insulated chip sounds better (smoother with less harshness).
I hope MUR860 were used in both amps
Peter, got a question... I've seen that you use 35V black gate ps caps? What type are these? If so, are they significantly better than the 50V Std's (which I'm currently using)?
btw, I personally wouldn't put that output cap in, hence ... last resort... I wasn't thinking as it was early (for me)
btw, I personally wouldn't put that output cap in, hence ... last resort... I wasn't thinking as it was early (for me)
I used those 35V caps as I got them really cheap from Indonesian seller. Unfortunately they are not available anymore.
I compared them to STD grade and thet look exactly the same and sound similar. Maybe that F is slightly more open in the highs, but this was unsignificant really. It is also pretty old production run, that's why I was hesitant to buy more of them (at the time). But 1000/50 STD is pretty good and as I mentioned previously some people actually preferred them to N type (same value). I also have some Nichicons Muse (1000/50) and will be checking them out soon.
I compared them to STD grade and thet look exactly the same and sound similar. Maybe that F is slightly more open in the highs, but this was unsignificant really. It is also pretty old production run, that's why I was hesitant to buy more of them (at the time). But 1000/50 STD is pretty good and as I mentioned previously some people actually preferred them to N type (same value). I also have some Nichicons Muse (1000/50) and will be checking them out soon.
What sounds superiror PSU board closest to AMP or to Transormer
Perhaps I am to lazy to search all through the history written here.
In making final choices in the design of the housing:
I will build seperate housing for PSU (transformer, fuse e.a.) and the CLONE's.
Is there, from sound quality perspective, a preference to have the PSU board close to the LM 3875 board or to the transformer???
My limited electricity/elctronics know-how would say from cable interference do DC through the cable from tranformer box to amp. From "resistance" perspective AC would be better.
I do love the tiny design that Peter made.
But still with both options I would remain within the size of the original 4717, that's my target.
Sofar I have not seen any reply to my earlier question on linear displacement pot. Does anyone have a clue what they are using?
apathic:
Brian, you did a beautifull job. Thanks to you and Meredith. Amp One is now soldered, will start wiring up and listening tonight (I hope)
Perhaps I am to lazy to search all through the history written here.
In making final choices in the design of the housing:
I will build seperate housing for PSU (transformer, fuse e.a.) and the CLONE's.
Is there, from sound quality perspective, a preference to have the PSU board close to the LM 3875 board or to the transformer???
My limited electricity/elctronics know-how would say from cable interference do DC through the cable from tranformer box to amp. From "resistance" perspective AC would be better.
I do love the tiny design that Peter made.
But still with both options I would remain within the size of the original 4717, that's my target.
Sofar I have not seen any reply to my earlier question on linear displacement pot. Does anyone have a clue what they are using?
apathic:
Brian, you did a beautifull job. Thanks to you and Meredith. Amp One is now soldered, will start wiring up and listening tonight (I hope)
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