Now that my darling bride is out of town, I've been hard at work. The first of my Alephs is up and running. I let a little magic smoke out before I bought a variac. I must admit, I was worried that I sunk $700 into a project that may never get finished. I replaced 5 shorted fets (yes they failed shorting drain to source) and a few source resistors and powered up slowly.
First was some 60 hrz hum , then sound. I inched it up and it became clearer and the line on the scope sharpened.
I worked the voltages up to +- 40 then cranked the bias to 5 amps total and the line on the scope became razor sharp and dead straight. And the sound! Beautiful clear and focused.
Thanks to everyone
Hardvarian and BrianGT for the boards
Damon for the new soldering station
Mark for the insperation
And the countless other posters (I've read them all over and over)
First was some 60 hrz hum , then sound. I inched it up and it became clearer and the line on the scope sharpened.
I worked the voltages up to +- 40 then cranked the bias to 5 amps total and the line on the scope became razor sharp and dead straight. And the sound! Beautiful clear and focused.
Thanks to everyone
Hardvarian and BrianGT for the boards
Damon for the new soldering station
Mark for the insperation
And the countless other posters (I've read them all over and over)
Attachments
Now for hard numbers
Source resistors are .8 ohm x 8 fets @ .5 volts
Total bias 5A
Supply is running (humming along) +- 40 V
Total dissapation 400W
Heat sink temp 156 Degrees F
Sound to die for
There'll be no sleep in here tonight
I've got to get to work on the other channel
Source resistors are .8 ohm x 8 fets @ .5 volts
Total bias 5A
Supply is running (humming along) +- 40 V
Total dissapation 400W
Heat sink temp 156 Degrees F
Sound to die for
There'll be no sleep in here tonight
I've got to get to work on the other channel
I have .2v of ripple on the supplies and you can see the music signal superimposed on it. I thing I'll add inductors between the banks of caps and bypass the second bank with some film caps.
And Shame on me
I neglected to give the biggest thanks of all to the man that made this all posible... Nelson Pass, My hero!
And Shame on me
I neglected to give the biggest thanks of all to the man that made this all posible... Nelson Pass, My hero!
Brian,
So you added 2 more fets to the Gain and CC boards? Seeing
that the Aleph 2 needs about 45 volts on the rails, i would think
your amp would need close to 50 volt rails (??) Or can you get
away with 40 volts because you upped the bias?
was just wondering - in no way am i any kind of expert!, just
trying to soak everything in.
very nice what you've done here.
m.
So you added 2 more fets to the Gain and CC boards? Seeing
that the Aleph 2 needs about 45 volts on the rails, i would think
your amp would need close to 50 volt rails (??) Or can you get
away with 40 volts because you upped the bias?
was just wondering - in no way am i any kind of expert!, just
trying to soak everything in.
very nice what you've done here.
m.
Well the 40 volt rails was an accident. The surplus transformers I bought were 60Vct 20 A. I decided I could live with slightly less voltage because my speakers are 4 ohm. So I've upped the bias so I still have over 100 watts rms at 4 ohms. I also bought a 22 amp variac (pictured) on Ebay for $40 that I'm thinking about installing in a power conditioner for the amps so I can juice it on up for louder listening or turn it down to save elecrticity for background. It's not the electric bill that I'm concerned over, My A/C is undersized and overworked and one extra kw of heat will make it run almost continuously on a hot Houston summer day.
I've noticed that to bias decreases as the voltage increases. I think I want to put a pot for r19 and a bias meter on the front panel. I like knobs an buttons and meters.
I've noticed that to bias decreases as the voltage increases. I think I want to put a pot for r19 and a bias meter on the front panel. I like knobs an buttons and meters.
Nice job!
Your front panel would also be great if you polish it mirror like!
congratulations on you work!
Your front panel would also be great if you polish it mirror like!
congratulations on you work!
This forum has been lacking photos of innards lately, so I'll show you what I've been up to. The big ugly IE's hummed and buzzed and didn't give high enough rail voltages, so there out. There was also a lot more supply ripple than I want ( 2.5V ). I called Avel Lindberg and orderd a pair of 1000 va 50+50v toroids. The price was right, but they're made in China. (Not to knock our Chinese members. They They know that they keep the good stuff and send us the trinkets and crap.) Yuck. The wires seem a bit small for 10A but they will only see 5A load.
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This layout will give a much cleaner looking inside. I may put a slab of steal under the driver board if I hear any noise from the tramsformer. I'm also going to put air core chokes on the front corners of the Al subfloor the toroid is mounted on.
Sweet home made ground bar, eay.
Sweet home made ground bar, eay.
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PSU has fred rectifiers, 68000 uf 100v monster caps, air core chokes around 6mh 1ohm then 34000 uf 74 v caps (per rail). Should get the ripple down where I want it.
Those are not the chokes. and they will mount flat with nylon bolts the the holes near the corners seen in the other post.
Those are not the chokes. and they will mount flat with nylon bolts the the holes near the corners seen in the other post.
Attachments
My wife leaves town and I can barely keep myself fed and in clean clothes...
When I fantasize how my amps will look when I someday build them...
When I fantasize how my amps will look when I someday build them...
Hi Brian,
I want to ask you something to do for me. Please call my wife to visit you. This is the only way to catch some extra time to finish my Aleph. (he, he, he)
Nice work and good luck to listening your amps.
Greetings from Belgrade.
I want to ask you something to do for me. Please call my wife to visit you. This is the only way to catch some extra time to finish my Aleph. (he, he, he)
Nice work and good luck to listening your amps.
Greetings from Belgrade.
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