Peter Daniel said:Front end board mounted in the amp, awaiting connection.Point to point is the way to go on all Alephs.
Note how output Caddock resistors are connected. The flat pieces of copper (Goertz speaker wire) are used for output buses and Caddocks solder directly to them. The short pieces of the wire coming from Dales connect directly to binding posts.
Gorgeous
Peter, are those inrush current limiters at the bottom of the board mounted on a PCB. Can you pl put up a picture of the underside.
Underside of what? The front end board is mounted on aluminum plate so underside is plain metal. Better views are in Aleph X thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=3748&perpage=15&pagenumber=63
Check this thread too, because everything I did so far is documented with pics.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=3748&perpage=15&pagenumber=63
Check this thread too, because everything I did so far is documented with pics.
Well it's seems like the amp is working fine, at least on a bench. No listening impressions yet.
I am really surprised that everything came out so nicely. Most of the resistors values I guessed or took whatever I had on hand. You might not believe it, but I don't even have to do any adjustements.
Right from the beginning the offset was 2mV with fluctuation up to 5mV. The absolute offset was 1.2V but now it's going down and currently after half an hour is around 0.6V. I used 0.56ohm source resistors (that's what I had from A75) and adjust the trimmer for47kohm before starting an amp and I was right on the mark. The voltage drop on source resistors is 0.48V and it's about right for my heatsinks. I'm runnung the amp with 15V rails. Without the load the rails were 20V. with the load they dropped down to 16V, minus 1V drop on thermistors (2 x CL60 in parallel) they came down to 15V. I can believe it's working that smoothly, or should I say, like Jake.
I am really surprised that everything came out so nicely. Most of the resistors values I guessed or took whatever I had on hand. You might not believe it, but I don't even have to do any adjustements.
Right from the beginning the offset was 2mV with fluctuation up to 5mV. The absolute offset was 1.2V but now it's going down and currently after half an hour is around 0.6V. I used 0.56ohm source resistors (that's what I had from A75) and adjust the trimmer for47kohm before starting an amp and I was right on the mark. The voltage drop on source resistors is 0.48V and it's about right for my heatsinks. I'm runnung the amp with 15V rails. Without the load the rails were 20V. with the load they dropped down to 16V, minus 1V drop on thermistors (2 x CL60 in parallel) they came down to 15V. I can believe it's working that smoothly, or should I say, like Jake.
Attachments
The absolut offset is 150mV now and there is 6mV between outputs. Wile heatsinks are pretty warm the transformer keeps its cool. I'm running the amp with 7A total current (3.5A per side). Offset comp resistor is 4k7 and ouput to ground resistors are 100 ohm.
Still, I didn't do any adjustments on the amp.
I'm running the amp with 7A total current (3.5A per side). Offset comp resistor is 4k7 and ouput to ground resistors are 100 ohm.Still, I didn't do any adjustments on the amp.
why Fred was trying to scare everybody off from building that amp?
Not everybody...... You have built several amps and are being careful to go slow and measure everything and test the amp on the bench before hooking up speakers. I fear that most people will not do this. Don't forget to test 10kHz square waves into a capacitive load. Looks very nice so far.
Fred
Not everybody...... You have built several amps and are being careful to go slow and measure everything and test the amp on the bench before hooking up speakers. I fear that most people will not do this. Don't forget to test 10kHz square waves into a capacitive load. Looks very nice so far.
Fred
Good point Fred, I didn't realize that some people might rush things and forget about being careful. I've checked everything few times before powering the beast. What surprises me, is how well the amp behaves on a bench. Not taking in account all the heat and high currents, it's much simpler that my first amp I built 20 years ago, and that thing was smoking before I had it running.
What surprises me, is how well the amp behaves on a bench. Not taking in account all the heat and high currents, it's much simpler that my first amp I built 20 years ago, and that thing was smoking before I had it running.
Another thing I noticed is that the pot I'm using to adjust the current feeding differential pair has big influence on the absolute DC offset. While I'm turning it and it doesn't change the voltage drop on drain resistors (392 ohm) by more than 2mV it still changes the absolute offset by more than 1V or so. Very easy to adjust that value.
All in all this amp is much easier to adjust than A75.
All in all this amp is much easier to adjust than A75.
Well, some of my first impressions listenng to one channel of the X amp, comparing to Aleph 5. The new amp seems to be more relaxed with much better sounding vocal. Although it's only one channel I think I can perceive much more deph. The highs are more silky and bass is less flabby, seems like more control there (overall, it's almost like a curtain was removed ).
It's hard to estimate how much these improvements are related to better parts and much more bias. I'm also getting a bit of hum, which I didn't have with A75 in the same chassis and similar arrangement. I'm also not sure if I terminated the inputs properly. Positive goes through series 2u cap, shield goes directly to ground as well as the amp's input is connected to ground through 2u cap.
).It's hard to estimate how much these improvements are related to better parts and much more bias. I'm also getting a bit of hum, which I didn't have with A75 in the same chassis and similar arrangement. I'm also not sure if I terminated the inputs properly. Positive goes through series 2u cap, shield goes directly to ground as well as the amp's input is connected to ground through 2u cap.
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