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Old 12th January 2015, 09:31 AM   #1
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Default Which Pass amp?!

Last month I built ACA mono blocks, only to feed my curiosity! Then I built original B1. I love the sound of these little mono blocks. Right now I'm using boxed Philips alnico full range speakers. Not sure about sensitivity. I also tried B1 with SX-939 power amp. More powerful of course, solid bass, but details are lost, not like ACA. So this led me to think about building bigger pass amp. There is lots of variations, these kind of variations easily confuses a newbie like me.

Got a spare 35-0-35V approximately 500VA center tapped transformer. And I'm thinking about using Powermac G5 aluminium case for a chassis.

So my question is, Which Pass amp should I build? I want to use B1 as a source selector and a buffer ofc, which has no gain at all.

Thanks!

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Old 12th January 2015, 10:32 AM   #2
Zen Mod is offline Zen Mod  Serbia
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heatsinks ?

count on hefty ones - plenty of pics around

"normal" FW amps are cruising at 60-100W of heat/channel
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Old 12th January 2015, 11:01 AM   #3
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Zen Mod, I'll mount hefty heatsinks to mac g5 chassis. First I need to decide amp to build
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Old 12th January 2015, 11:08 AM   #4
Zen Mod is offline Zen Mod  Serbia
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Aleph J or J2 (if Papa reveal it's schm - see few newest threads around)

are those spks 8 or 12" ?

I had bigger ones for years .....
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Old 12th January 2015, 11:25 AM   #5
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Those are 10" AD4000M. Nice drivers. For closed box, I didn't expect much bottom end, but final response was shocking. Much better than I expected, not boomy, sharp slammy bass. Total 140 liter cabinets..

Do you know the transformer requirements for J or J2?

What about F5? Do I need to play with gain settings if I want to build? Or is it adjustable?
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Old 12th January 2015, 11:31 AM   #6
ColinA is offline ColinA  United Kingdom
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Well I am a newby, still collecting parts (for an F5.)
But from what I have found out it breaks down cost wise to getting
The best & biggest heatsink case that you can.
Then a big transformer and capacitor bank power supply.

After that which model, Jfets and Mosfets is "just" a detail!
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Last edited by ColinA; 12th January 2015 at 11:45 AM.
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Old 12th January 2015, 11:35 AM   #7
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plenty of user/service manuals at FW site , same as threads here ....... so all you need for proper prepare is to read , acclimatising your self for actual producing of amp

however - almost all FW amps are using 2x18Vac/300VA xformers , common PSU for both channels

you can build from that , or use 2 of 250VA , if willing to go dual mono route (each channel having own dedicated PSU)
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Old 12th January 2015, 11:38 AM   #8
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a single 35-0-35V 500VA transformer is not suited for 2ch class A. You can wind down the transformer to 25-0-25V and build a F5turbo V1 or V2. Or you can go for a high bias class A/B amp. Or you can get one more of those transformers if that is possible.
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Old 12th January 2015, 12:05 PM   #9
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Quote:
Originally Posted by ColinA View Post
Well I am a newby, still collecting parts (for an F5.)
But from what I have found out it breaks down cost wise to getting
The best & biggest heatsink case that you can.
Then a big transformer and capacitor bank power supply.

After that which model, Jfets and Mosfets is "just" a detail!
Colin, I agree, case must be big enough for proper sized heatsinks and it must be able to dissipate heat properly. These G5 chassis is quite big and pure aluminium. I think it is suitable for this kind of task.

Which F5 are you building?
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Old 12th January 2015, 12:05 PM   #10
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Does your transformer have 2 primaries. That is sometimes a transformer is made to be able to run from either 110v or 220v. If this is the case with your transformer you could rewire it for 220v and now have a 17 0 17 volt transformer when run from 110V. Or you could use a full wave rectifier ( full wave not full wave bridge ) and get about 45VDC which might be ok for one of the ZEN amps at Passdiy.com
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