Which one to build please.

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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.
Alan
 
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
 
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.
 
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6L6

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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. :D

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.
 
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Alibear,

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. :D

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. :D

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... :cool:
 
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:D:D:D
 
Hi, thanks to all for the recommendations, much appreciated.
The f5 looks favourite or the Aleph J . I could not find out too much about the J, perhaps I have not looked in the right place. What are the differences between them [ does the J dissipate the same heat as the F5].
I have two 18 -0 -18V 250Va transformers and eight 47,000uF 40V Epcos screw terminal capacitors, I presume they will be OK for a separate supply for each channel. I believe I have enough heat sink for both channels, I will post a picture of the heatsinks for any comments.
I don't know if it is correct to ask this question, but here goes. Jim's Audio is advertising an F5 kit with matched input FET's and Fairchild output devices and a good quality PCB'S. Does anyone know anything about these?
Thanks for your help
Alan.
 
Jim's Audio is advertising an F5 kit with matched input FET's and Fairchild output devices and a good quality PCB'S. Does anyone know anything about these?

No, I never heard of these kits. It surprises me that it comes with Fairchild fets; in the original article of Nelson on the F5 he suggested Fairchild fets, but these were pretty quickly out of production. I'm not aware of anyone offering them at the moment.

However, most simply use the popular IRFP instead.

Personally, I would recommend the F5 as well, as it's the more universal amp. The Alephs favour high impedance speakers (with high efficiency ideally). Most speakers, today, are however rather low impedance types (the typical 2.5 way D'Appolito ones for example).

Any case - enjoy!
 

6L6

Moderator
Joined 2010
Paid Member
Alibear - The components you list for the PSU will be perfect for the job! :)

The Jim's audio PCB are not done with the permission of Nelson and you won't find many people here on the boards to assist you if you use them.

Approved F5 PCB can be bought from Peter Daniel or the DIY audio store. (Peter also has Aleph J PCB as well)

Contact Peter here - DIY Chip Amplifier Kits, PCB's, Components and Information. (The F5 and Aleph PCB are not listed on his site, just ask, he will tell you what you need to know.)

Or the DIY audio store - First Watt Clones - Power Amplifiers - PCBs

The store should have an Aleph J PCB in a month or two. '

Can you provide information on your heatsinks?


h_a said:
It surprises me that it comes with Fairchild fets; in the original article of Nelson on the F5 he suggested Fairchild fets, but these were pretty quickly out of production. I'm not aware of anyone offering them at the moment.

Member ' buzzforb' has Fairchild Fets for sale. They are great! The IRFP are wonderful as well.
 
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Hi all, here are some pictures of the heatsinks I hope to use. I have eight of them, each one measures 150mm high x 70mm wide x 90mm deep. They can be mounted side by side. I think they are rated at 1CW each.
For test purposes I mounted three side by side on a 10mm aluminium plate, then mounted two pairs of MJL21193 / 94 TO3 transistors and biased them to 1.4A (total ) with a Krell KSA clone board modified to run with 24V rails. This gives between 60 and 70 W of heat. Ambient temperature was 24C and after about five hours the sinks were at about 52C and the cases of the transistors were about 60C, measurments were with a probe and digital thermometer.
I hope to make monoblocks with four of the sinks mounted at the rear ( or front ) of the chassis. I think this should provide enough cooling for an F5.
Any views or suggestions please.
thanks
Alan

Sorry, have tried to upload pictures, DIY Audio not accepting them, will try again later.
 
tried again
 

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