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Old 6th September 2013, 12:34 AM   #1301
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Default Beefy ps for ACA

I finally finished my linear ps for my ACA's. I apologize for the poor pictures but my camera broke; so we get iphone pictures. My goal was to build it with the left over parts I had on hand. A second goal was to see if I could learn anything before I build the bigger ps for the Aleph J that I already started.
I used CLC with 60k uF before the choke, and 60k uF after. The last 10,000uF is connected to the amp end of the cable. I used a cheaper choke with higher resistance, but if I had to do over, I would use the lower resistance chokes from Madisound like I am on my Aleph J. The capacitors and LED's are held in with hot glue (my friend). For sheathing I used bright colored paracord and pulled out the middle. I do not have a shop, so I bought an NOS radio case from Surplus of Nebraska. It required a “drawer” insert, sliding in from the front, so I had a friend with a table saw cut up the drawer with scrap wood. For the connectors I heard that Buzzforb was using Nuetrik Speakon and I tried them. They are great and low cost. I will use them everywhere I can.
My first round using my Antek 50VA, 15V secondary only produced 17.8VDC. So I broke down and had to buy two Antec 100VA, 15V which gives me about 19VDC. My mains voltage varies, so at night I get 19.2VDC. At night it sounds a little better. I realized I did not need a CL60 on the input and took them out. I do not need the bridge rectifier for the chassis ground. A lone CL60 there will do. After they warmed up I checked the ACA adjustment and it still said 10.00VDC, so I left good enough alone. The first thing I noticed over the bricks was that I could no longer hear the slight buzz and hiss when I put my ear to the speaker. It is dead quiet now. Overall the change in sound is subtle. In the evening I can hear a little more low level detail. I am very happy. On one CD that I have heard over 50 times, I suddenly could make out a couple of words the female singer was singing. Is it worth the trouble for most people? Probably not. Should a person first build the ACA using the bricks? Definitely!
As I said in a post several months ago, these are driving a pair of Madisound speaker kits, ZRT. The 7” Scan-spec driver is only 87db, yet these are loud enough for me 98% of the time in my medium small living room. The sound is so sweet. The main reason I am building an Aleph J is for the other 2% of the time (and I like to build a good amp).
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Old 6th September 2013, 03:12 AM   #1302
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With that many uF's on the rail the turn off thump should be ruduced. Can you still hear it or see the woofers move?
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Old 6th September 2013, 02:28 PM   #1303
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Quote:
Originally Posted by Loudthud View Post
With that many uF's on the rail the turn off thump should be ruduced. Can you still hear it or see the woofers move?
There is no turn-off thump. If the thump is a problem for someone using the bricks, notice there is no thump when you unplug them from the AC outlet. The switch on the ACA disconnects the DC out, not the AC in. The thump was not a big problem to me with the bricks, but I usually left mine on or unplugged them if gone. Maybe someone could try an outlet that uses a light switch and see if turning off the switch has no thump. At the moment I am not sure if you would need to disconnect both the AC hot and neutral (ground) or just the AC hot to get rid of the thump.
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Old 7th September 2013, 08:25 PM   #1304
Bones13 is offline Bones13  United States
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Quote:
Originally Posted by Lerg View Post
Are you sure that you have your meter reading DC voltage, and you are on the center pin of Q1?
Newbie mistake for sure. I had another go at it, and I did indeed have the meter on resistance, not voltage.

Works fine now. That pot is fickle though, lots of up and down to get about 10.6v.

Wiring up the other side now.
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Old 7th September 2013, 10:16 PM   #1305
Bones13 is offline Bones13  United States
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Default ACA in action

Finished my ACA monoblocks. Playing them now with a set of Zu Audio Essence speakers (newly upgraded main driver and crossover). Sound very nice, takes more power from the pre-amp than the 35 watt tube amp they are sitting on. They sound really good, the bass is improving slightly over the afternoon. They will end up on smaller speakers in a nearfield setup.

Thanks for the great amp/kit!
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Old 8th September 2013, 02:36 AM   #1306
Lerg is offline Lerg  Canada
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I am glad that you sorted out the issue. I found that adjustments of the pot to get 10.0 volts required a very fine touch.
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Old 8th September 2013, 06:13 AM   #1307
zany is offline zany  Australia
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same here, back and forth with tiny adjustments... my brother thought I was obsessive...
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Old 9th September 2013, 06:21 AM   #1308
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Just finished my first one, and I can't seem to get the voltage between the center pin of Q1 and GND above 5.5v, even with the trim pot maxed out. Any ideas what could be wrong?
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Old 9th September 2013, 02:05 PM   #1309
Zen Mod is offline Zen Mod  Serbia
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not clear enough ......
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Old 9th September 2013, 06:34 PM   #1310
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Quote:
Originally Posted by flohmann View Post
Just finished my first one, and I can't seem to get the voltage between the center pin of Q1 and GND above 5.5v, even with the trim pot maxed out. Any ideas what could be wrong?
Do Q1 and Q2 get hot?

Is Q3 installed correctly with the flat side away from C2?

Did you verify by color code or resistance check the value of the resistors you installed? Did you observe the polarity of capacitors you installed?

Take voltage readings at each transistor pin as indicated in the diagram below.
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Last edited by Loudthud; 9th September 2013 at 07:00 PM.
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