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Old 25th November 2003, 12:00 PM   #21
protos is offline protos  Greece
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Congratulations! Some questions :
What is the total ma or power consumption of the amp?Is there a possibility to get the pcb from you? Are the regulators on the same board?
By the way I did once connect my headphones to my aleph 5 monos but the hum levels were way too high for headphone listening.
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Old 25th November 2003, 01:22 PM   #22
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Thumbs up Too cool for school

One of the nicest jobs I have seen on the forum. The design looks great and is only overkill from the attention to design details and not for parts count. For the penny pinchers I would say that one could use J202 fets for current regulators in place of the jfet two terminal current source. I would try the Zetex ZVP3310 for the current sources for the J109 jfet pairs. Zener protection for the mosfet gates is generally a good idea too. I wish I had one. When are circuit boards available?
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Old 25th November 2003, 02:10 PM   #23
jam is offline jam  United States
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Thumbs up ....Is Fred getting soft?

jwb,

Great effort. Has to be up there, since you got praise from Fred, no mean task I might add.

How did your experiment with bypassing the Aleph circuit turn out?

Regards,
Jam
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Old 25th November 2003, 02:28 PM   #24
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Default Yes that what I am saying

JWB,

According to your schematics, you have a non-inverting input and only one input. The output is single ended and not balanced. A balanced amp always has two inputs that are non inverting and a inverting. That’s the only way you can get right of a common mode signal like 60Hz on at the outputs.

Audio amp don't have balanced input they have diff amps but that in it's self does not make it balanced. The Aleph is a diff amp with balanced input but not in the purest form.

Having said that, I think you done a nice job with the circuit and construction.

Regards
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Old 25th November 2003, 03:28 PM   #25
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Default Basic balanced amp

JWB,

This is the basic balanced amp design, but there are many way to implement a balance diff amp. So as I was trying to say, is if you do not have balanced input it easier to pickup 60 Hz common mode signals.
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Old 25th November 2003, 04:31 PM   #26
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Default Re: Too cool for school

Quote:
Originally posted by Fred Dieckmann
I wish I had one. When are circuit boards available?
I have pcb's ready for sale. I have started with 10000 boards. I think I can sell them in a week. Are you interested?
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Old 25th November 2003, 04:40 PM   #27
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Why does the peranders cross the road! Answer there a circuit design he want to copy.
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Old 25th November 2003, 05:19 PM   #28
jam is offline jam  United States
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Talking Copycat!

Nice one Jim!
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Old 25th November 2003, 05:37 PM   #29
grataku is offline grataku  United States
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Jbw,
remember I contacted you about purchasing the board BEFORE I even knew how it sounded...that shows remakable faith in your abilities from my part
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Old 25th November 2003, 06:22 PM   #30
jwb is offline jwb  United States
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Default Re: Too cool for school

Quote:
Originally posted by Fred Dieckmann
One of the nicest jobs I have seen on the forum. The design looks great and is only overkill from the attention to design details and not for parts count. For the penny pinchers I would say that one could use J202 fets for current regulators in place of the jfet two terminal current source. I would try the Zetex ZVP3310 for the current sources for the J109 jfet pairs. Zener protection for the mosfet gates is generally a good idea too. I wish I had one. When are circuit boards available?
Knock me over with a feather! I think Fred and I have exchanged three or four cordial messages. Consecutively even. Peace and prosperity

As grataku vigorously points out, he has first claim on my one and only extra printed circuit board. The rest of you should consider your luck. If my Design for Manufacturability instructor saw this, he would fail me retroactively. There are power transistors mounted under the middle of the board, surface mount components in impossible-to-rework positions, no component references on the silkscreen, and so forth. Also the mounting and cooling is specific to the Sun 411 SCSI disk chassis. Only the most intrepid will be happy trying to build it. I'll happily post my CAD files if someone wants to use this design as a starting point.

To the other question, the design dissipates 16W, and it's capable of over 700mW into 32Ω cans. I'm thinking of lowering the power ability to something like 300mW to only produce 9W, for a little less toasty running.

Jam: I've only been listening to it in Aleph mode so far. Will report on Zen performance later. The other jumper, which shorts the DC feedback cap, is very useful for quickly adjusting the DC offset. With a 12-turn pot I can get the offset below 100µV.
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