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Old 21st May 2013, 01:13 PM   #1
alibear is offline alibear  United Kingdom
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Default Which one to build please.

Hi all, this is my first post to the Pass forum, hope this is not a daft question. Can someone guide me through what appears to be a maze of Pass amplifiers.
I want something in the region of 25W per channel that I can use passive heatsinks to keep cool.
Do I look at F4, F5, F5turbo, Zen, Aleph3 etc. What are the merits of each?
My loudspeakers are 8 Ohm.
Thanks for your help.
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Old 21st May 2013, 01:32 PM   #2
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I have just built the F5, so many people thnk it the best, it was a clear choice. I have almost no experience in building audio, but found ( with some help ) I was able to complete with only minor hiccups.

I am AMAZED that an amp can make SO much difference it's awesome!

I would advise you to discover the sensitivity of your speakers, this is not the same as the ohms. The F5 needs sensitive speakers to show true magic!

Best wishes - LB
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Old 21st May 2013, 01:32 PM   #3
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Well it looks like you have built class A amps before (or delved into that area from your previous posts), so you aren't new to all this.

I see that the most popular Pass amp is still the F5 and it's many variants (EVUL, Turbo, C, and plain old). Why not take a look at those? The Turbo looks interesting to me because it will probably drive almost anything out there without a problem, but the availability of boards is an issue if you want it right now. Otherwise, the F5 is the next best with respect to information here and the number of builds.

I haven't built anything big Pass class A, but have lurked around for a while here and am starting off with a B1 (have the boards and FETs and 90% of the parts) and an ACA (need the time to so start and finish it) to dip my feet in so to speak. After that, probably the F5 will be my first big build.

Last edited by overtheairbroadcast; 21st May 2013 at 01:33 PM. Reason: Changing caps S to lower case
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Old 21st May 2013, 01:49 PM   #4
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F5turbo Boards are in the store now. so boards are no problem.
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Old 21st May 2013, 02:16 PM   #5
6L6 is offline 6L6  United States
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All the Firstwatt amps are wonderful. They all have a wonderful quality that is not found in many other amps, and if you haven't experienced it, you will be amazed and very pleased.

Comparing the different amps is similar to going to the most wonderful ice cream store, where everything is wonderful, and trying to choose the 'best' flavor... It can't be done, they are all great.

Reading your post I would suggest a F5 or Aleph J. - Both are in the power range you want, keeping the chassis cost under control. (eliminating the F5Turbo.)

PCB are available for the F5 and (soon) the Aleph J. (eliminating the Zen)

Both the F5 and AJ have voltage gain, so you can use it with your current preamp/source. The F4 has no voltage gain, usually requiring a specific preamp to drive it, so it essentially requires another project. (Fantastic amp, however...)

My specific suggestion - Get a DIYaudio "Jack of all Chassis", a 400-500VA transformer and PSU, and start with the F5.

When that is complete, you can swap in and out Aleph J, F4, F5C amp boards easily, leaving the big expensive part (the chassis and PSU) alone, enabling you to try all the different flavors of amp.

Last edited by 6L6; 21st May 2013 at 02:23 PM.
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Old 21st May 2013, 04:15 PM   #6
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That's a pretty wide-open-ended question, something along the lines of Bill Cosby's "Why is there air?"...

Mr. Pass has certainly been prolific in offering a broad, rich range of his power-amplifier designs to the DIY community.

The Zen projects are an exploration into the potential performance of very simple amplifiers. The Zen projects provide audible insight into the advantages of minimalist circuit topologies, but they tend to be rather compromised from the standpoint of daily usability and eco-friendliness... The Zen projects assume that you can fabricate the projects from the ground-up, including chassis fabrication, PC-board design/implementation, etc.; very hands-on DIY.

The Aleph designs are practical implementations of high-bias, pure-Class-A design topologies; these designs provided the technology foundation for the first-generation of products from Pass Labs, Mr. Nelson's commercial venture that followed Threshold Audio, Inc. Mr. Pass has been kind enough to permit non-commercial, personal implementations, but like the Zen projects, the Aleph designs assume that you can fabricate the projects from the ground-up, including chassis fabrication, PC-board design/implementation, etc.; very hands-on DIY.

The First Watt power-amplifiers are the result of Mr. Nelson's kitchen-table company which enables him to experimentally produce some of his cutting-edge designs on a small scale. Mr. Pass has granted the DIY Forum store permission to offer PC boards, power-supplies, etc. for most of the First Watt designs. So, you can order a suitable chassis, First Watt PC boards, power supplies and be most of the way there. The F5 variants offer an amplifier with nominal power-amplifier characteristcs (gain, power output, etc.) with exceptional sonic characteristics. I would recommend that you look into building one of the First Watt F5 variants...
Mullard EL34
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Old 21st May 2013, 10:13 PM   #7
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If i have only the possibility to build only -one- amp
than i would everytime take the Aleph J again.
There is a alephwiki where you can get some layouts and partslist.
The only problem could be the 2sj74.

If you can have 2 amps than the F5 and the aleph J

The J for the magic and the F5 if you want it really clear and direct

Also some people says the Aleph 3 or better 30 would be really good and should have more bass than the J and you haven`t the problem with the 2sj74

What a dilemma...
...to many amps to less time, space & money
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Old 21st May 2013, 10:30 PM   #8
6L6 is offline 6L6  United States
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Spencer (fetaudio.com) has the 2SJ74 - Problem solved.

With a pre-drilled case from DIYaudio, you could build one powersupply, and then swap just the amp boards of Aleph J, F5, F5C, F4 and even tea-bag's F6 PCB as you see fit.
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Old 22nd May 2013, 01:18 AM   #9
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Have you purchased from spencer recently? He has not responded to multiple requests sent to his primary email at fetaudio and is not accepting PMs here.
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Old 22nd May 2013, 01:34 AM   #10
6L6 is offline 6L6  United States
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I haven't recently... I think buzzforb has, drop him a line and ask.
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