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Old 6th July 2003, 06:36 AM   #1
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Default At last, My Aleph 2+

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)
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Old 6th July 2003, 06:43 AM   #2
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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
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Old 6th July 2003, 07:06 AM   #3
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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!
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Old 6th July 2003, 11:02 AM   #4
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congrats!!! Brian

DIRT®
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Old 6th July 2003, 11:42 AM   #5
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Now that's what we like to see ....... really serious hardware

cheers
mark
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Old 6th July 2003, 11:23 PM   #6
moe29 is offline moe29  United States
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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.
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Old 7th July 2003, 02:01 AM   #7
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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.
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Old 7th July 2003, 03:56 AM   #8
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Her's some more pics

This is semi complete chasis. I still need to anodise front, top and back. I'll leave the bottom raw. All but the heat sink is surplus 1/4" aluminum cut with a skill saw
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Old 7th July 2003, 03:58 AM   #9
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The feet in previous pic are 2.25" x 1.25" solid bar stock (surplus)
It'll also make nice knobs for apox.
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Old 7th July 2003, 04:02 AM   #10
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I know, it's a MESS now, but I want to run it before I pretty it all up inside. Plus I'm going to do some of the tweaks in the ultimate Aleph thread.
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Old 7th July 2003, 04:05 AM   #11
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Starting the next one
The row of holes down the middle is exaust for the fan in the back of the chasis. I shouldn't be needed, but it would be nice to keep the caps inside cool.
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Old 7th July 2003, 04:08 AM   #12
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The extra holes and grease spots were from r theta test. I wanted to be sure these things would keep cool.
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Old 7th July 2003, 11:21 AM   #13
PedroPO is offline PedroPO  Portugal
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Nice job!

Your front panel would also be great if you polish it mirror like!

congratulations on you work!
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Old 5th October 2003, 12:48 PM   #14
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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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Old 5th October 2003, 12:52 PM   #15
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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.
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Old 5th October 2003, 12:56 PM   #16
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The peice of l on the back is clamp mount for relays for soft start. Freds will be mounted on the bottom. I have mosfets there now for layout.
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Old 5th October 2003, 01:00 PM   #17
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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.
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Old 5th October 2003, 01:10 PM   #18
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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...
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Old 5th October 2003, 01:36 PM   #19
Djomil is offline Djomil  Serbia
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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.
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Old 5th October 2003, 03:43 PM   #20
Netlist is offline Netlist  Belgium
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Thumbs up Ceci n'est pas une pipe

Quote:
Originally posted by Brian Donaldson

Those are not the chokes.
Very nice and robust looking amp.
You remind me of Magritte, or is it a tipo?

/Hugo
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Old 5th October 2003, 04:22 PM   #21
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I was refering to the homemade coils on the smaller caps. They have too low R and H. I need to dump around 6 v to bring the rails down a bit.
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Old 11th October 2003, 06:50 PM   #22
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Nice Job! My 2's are running with about +- 42 volts due to availability of surplus toroids. First thing I did was pull the bias resistor completely out and man what a difference..... Now to add a couple more devices and make the changes to go to 5 amps.....Thats gotta sound great and will greatly reduce my GAS bill costs this winter. My 2's will be one year old this xmas!
Mark
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Old 11th October 2003, 09:39 PM   #23
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Default Re: At last, My Aleph 2+

Quote:
Originally posted by Brian Donaldson
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)
Looks great. I wish my projects looked near as nice. My wife and children are leaving Wednesday for a month. There are several projects I hope to finish with that much time.
Also, we have that same table and chairs from World Market. But my wife does not let me work on it.
I could not live here in Houston with the Aleph 2's. My Zen V4 generates just about all I can handle. But it gives up a lot in bass and punch to those power hungry 2's.
I guess you have been there, but Ace Electronics has the chokes you need. Big muthers for 15.00 to 25.00 each. You should find 6 mH 15 amps ones that have 0.2 - 0.3 ohm DCR.

George

George
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Old 11th October 2003, 10:25 PM   #24
jam is offline jam  United States
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Mark,

When you say you pulled out the bias resistor what do you mean,
and what improvements in sound quality did you get?

Regards,
Jam
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Old 11th October 2003, 11:43 PM   #25
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Thats easy, just pull R-19 the 56k resistir and the amp goes wide open... as based on other preset component values.

The soundstage went much deeper and wider. Distortion also goes down lower although they sounded really nice with R-19 in circuit...things just got even better. I also had to increase the line fuse to 5 amps. The specified fuse would blow after a week and a half.
Mark
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Old 12th October 2003, 01:36 AM   #26
jam is offline jam  United States
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Mark,

Have you tried pulling R21 thusbdefeating the dynamic current source?

Regards,
Jam
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Old 12th October 2003, 04:21 AM   #27
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Nope, Haven't tried that as of yet. Does anyting else have to be changed to be able to do that and what is the overall effect of doing it?
Thanks!
Mark
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Old 22nd October 2003, 07:44 PM   #28
Eric is offline Eric  United States
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Brian, Great looking work! I'm a little confused about your power supply configuration, would you be able to describe it in a little more detail for me?

It looks like you are building a stereo Aleph 2 using a single transformer (with a single secondary) feeding your two large caps, and then tap individual + and - rails for each channel (the four smaller caps) from the two large caps. This would mean that the toroid and two large caps are shared by both channels. Is this correct?
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Old 22nd October 2003, 08:50 PM   #29
jleaman is offline jleaman  Belgium
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Congrats another aleph 2.. Mine to come soon now..

One thing you shuold do is make sure you have no metal shaveing near or in the amp. would hate to see you power it up and see a nice spark or clowd of smoke..!
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Old 22nd October 2003, 09:38 PM   #30
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Eric
Actually this is only one channel. I added 2 extra output fets to each rail and decreased source resistor to .89ohm to raise bias.
The toriod feeds fred diodes to 2 huge caps (68000uf100v) to 6mh air inductors to 2 pairs of 17000uf75v caps. Sims showed .05v ripple(if I remember right) at 5A load.
I haven't got it all back together, but I'm expecting 50v at 5A bias.
I'm going to include a pot and bias meter so I can turn it down for non-critical listening. I'm also including a temp meter and output meter and variable speed fan so I can keep an eye on everything and try to not burn down the house.
Before I tore back in to it, I was running both channels from a 22A variac at around 180v in to get 50V rails and it sounded great. But it ran at 170 deg without the fan. I'm hoping the fan can keep it down around 155 without making niose. I wish I had 20 hours to finish tham instead of only sneaking a few minutes here and there to talk and dream.
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