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SIMPLE SE amp design wanted
SIMPLE SE amp design wanted
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Old 24th August 2003, 09:00 AM   #1
DrewP is offline DrewP
diyAudio Member
Join Date: Jan 2002
Location: Canberra, Australia
Default SIMPLE SE amp design wanted

About 3 years ago I began to be interested in building a Passlabs Zen amp.

To this end, I purchased a very nice 500VA C core tranny with twin 10 amp 0-25V AC output windings.

At the same time I got 4 nice low ESR 2200uf caps for use as output couplers and 8 80v 15,000uf electros for the PSU.

I've also got a couple of VERY substantial heatsinks to go with it, each about a foot long and 5 inches high with 2 inch long fins all along. Perfect for a class A amp.

My first attempt at breadboarding the Zen produced flames from the packages of the mosfets (not quite well enough secured to the heatsink) and since then Nelson has changed the scematics alot and many other folks ahve stepped up to pooh pooh the Zen design as well.

This leaves me with all the bits to make a great 30v rail PSU but no killer amp project to go with it.

Should I cut my losses, write off the C core and electros to the spares bin or can anyone help me out with a SIMPLE but stunning sounding SE amp that will use these bits. Or should I just track down an old schematic and build the Zen again?

I'm very much set on class A and the 30 seconds of music that emerged from the Zen prototype sounded stunning. I'd like to stay SE as well.

I have a preamp in the works that will happily feed more than 5V rms into a 5k load so the input impedance of the amp isn't too much of a drama. My speakers are single driver Fostex FE168sigmas with around 95dB/W and the room i'm listening in is only 12 x 18ft with 8 ft ceilings so I doubt much more than 10 watts would be necessary.

Help me (PLEASE)

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Old 24th August 2003, 09:17 AM   #2
mikelm is offline mikelm  England
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Join Date: May 2003
Location: England
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right now I'm listening to my own balanced wkg version of the john linsley hood's SE 'simple class A amplifier' and everything sounds more musically 'right' than I have ever enjoyed before.

a balanced version would not be the simplest but for discussion and diagrams of the original and improved versions look here.


I have heard that TimA's version is VERY good.


sometime I would like to get to listen to it

hope this helps

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Old 25th August 2003, 03:59 AM   #3
Jay is offline Jay  Indonesia
Join Date: Feb 2003
Location: Jakarta
I have gone through Zen1 to Zen4 (and also JLH), and also Aleph3 and Aleph5 (and Aleph4.7, Aleph4.9, etc). I'm now using Aleph3 with no "Aleph" current feedback. I'm very tired of looking for better sounding amp. What I will do in your situation is exactly what I have done and partly what I'm going to do.

The 25V tranies are suitable for the Aleph3. With massive heatsink you can build a tower amplifier like a speaker stand, and hence a short speaker wire (I haven't seen such amp structure from pictures in this forum). You can bias the amplifier higher and get better result. You already have sensitive speaker. The 2200s are not useless, there are many possible/valuable tweaks in the CDP.

IMO, if you want a low power amp, you should not use too many gain stages from the source to the final amplifier. Use as minimum as gain stages as possible, and compensate the drawbacks with premium components and stabilization. CDP - SE AMP - Sensitive speaker (acceptable crossover), that's what I want to build with premium components and careful tweaks.

Remember, I'm not going to reccommend this setup (and the Aleph3 tweak) because people have "preference". If you are looking for highly dynamics system or better bass or sparkle highs or low distortion or sweet sound or better image or accurate sound, you may never found what you are looking for. Look for system that fills your listening sessions with joys. And trust me, you cannot achieve that by simply building "high end" systems.
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Old 25th August 2003, 04:59 AM   #4
DrewP is offline DrewP
diyAudio Member
Join Date: Jan 2002
Location: Canberra, Australia
Thanks for input foks.

I'm planning to run MC cartridge into single stage mc phonoamp, from there into a preamp based around a triode connected EL84 with choke plate load and thence onto a power amp.

Speakers have no crossovers at all, just the single fostex driver.

I was contemplating using the fet follower design that shows up from time to time as my pre will swing the 9v required to give me 10W out with no hassles.

At present the prototype of the phono stage is up and running but needs to be rebuilt with boutique parts (caddocks, AD797 and auricaps). Already sounds pretty good with cheap metalfilms, MKY p/esters and NE5534's so i can't wait till the next gen is built.

In theory, the follower would give me a total of one AD797, one triode EL84 and one mosfet in the signal path.

I have no intentions of going back to PFIYI (pay for it yourself), DIY is definitely the path for me since i found out in 1995 what it would cost me for the next hit (Sugden A21ap) to cure upgradeitis.

Keep the ideas coming,

...Enjoying the music

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