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leo
13-07-2009, 16:50
Ok, I'm wondering what diy amp to try next, I've heard good things about Circlotron output stage (mosfet not valves) and was thinking this may be the next thing to try, anybody else tried it or any other idea's whats decent and would be worth a go?
I want something which will drive the average speaker

These are the diy based amps I've tried so far (ready made commercial not included)

WAD KIT88, did various upgrades to this including upgrading the output transformers to some nice Sowters
Avondale NCC200 with cap6
Aspen Aksa 50+
Various chip amps like Gainclones
Modified 15w classA from Silicon chip magazine
Hypex UCD classD modules

Covenant
13-07-2009, 18:46
Leo-its got to be that Class D thats not Class D. Was it lateral mosfet?
Anyway reading the various comments it seems the equal of Hypex at much lower cost.

alb
13-07-2009, 18:49
Well i know someone who made a good stab at a Circlotron last autumn.
Caused him a few headaches and i'm not sure if it ever made a public appearance in working order.
By all accounts it was a good incendiary device though.:)
Seemed like a lot of hard work and a bit of a challenge. Should be right up your street.
Good luck.

leo
13-07-2009, 18:52
Leo-its got to be that Class D thats not Class D. Was it lateral mosfet?
Anyway reading the various comments it seems the equal of Hypex at much lower cost.


I was considering it but would rather want something which is going to be a noticeable upgrade to what I already have rather than something similar
Its a shame theres no schematic for that amp

Just not sure which way to go, if I can't find anything I may give those a bash, dunno :confused:

leo
13-07-2009, 18:54
Well i know someone who made a good stab at a Circlotron last autumn.
Caused him a few headaches and i'm not sure if it ever made a public appearance in working order.
By all accounts it was a good incendiary device though.:)
Seemed like a lot of hard work and a bit of a challenge. Should be right up your street.
Good luck.

Thanks Al, sounds like it should be fun:lol:

jonners
13-07-2009, 19:19
How about the Nelson Pass amps? Plenty of info, lots of followers. Never tried them myself though (yet).

aquapiranha
13-07-2009, 19:57
Leo, how did you get on with the UCD amps? I am looking for two as I need to have 2 stereo amps for my active set up when it is ready.....?

Thanks!

Puffin
13-07-2009, 20:49
How about the Nelson Pass amps? Plenty of info, lots of followers. Never tried them myself though (yet).

As Meatloaf sang "you took the words right out of my mouth"

I have had great success with P2P single chip and bridged Gainclones (both LM3886 and LM3875 chips) using the NatSemi schematics.

I have just ordered some boards on diyaudio in the group buys section. Pass F2 and F5 amps.

F2 is 5W per channel Class A, the F5 25W per channel. I will be taking my time to build and source all parts so I won't know what they sound like for some time.

aquapiranha
13-07-2009, 20:55
Or how about these...

http://www.classd.ltd.uk/Datasheets/Specifications%20for%20the%20CD%20NX%27s.pdf

Not sure if these are the NX200's I have been hearing VERY good thingsabout.

:)

FireFly
13-07-2009, 21:24
Leo, try this: http://bas.elitesecurity.org/mojiprojekti1.html

You will need Java to display page & menu on the left. Search under "Pojacala" for "CALOR-Gold" amplifier shematic.
Original input op-amp is 5534, but can be changed.

leo
13-07-2009, 21:52
Thanks guys, a few choices to be looking at :)
Soon as its decided I'll be sure to take pics, write up etc
Any more idea's feel free to post:eyebrows:

alb
13-07-2009, 22:12
Always fancied trying one of the Jean Hiraga amps.
Cheap enough to build, except for the heatsinks.
Plenty of power for me, but maybe not for you.


http://www.tcaas.btinternet.co.uk/hiraga.htm

SPS
14-07-2009, 08:21
As Meatloaf sang "you took the words right out of my mouth"

I have had great success with P2P single chip and bridged Gainclones (both LM3886 and LM3875 chips) using the NatSemi schematics.

I have just ordered some boards on diyaudio in the group buys section. Pass F2 and F5 amps.

F2 is 5W per channel Class A, the F5 25W per channel. I will be taking my time to build and source all parts so I won't know what they sound like for some time.

ed swift built one of these and couple of other variants..
they sounded very very nice in isolation..
but played next to a good SE valve amp....
i've heard a few wd 88 amps, and they have all been replaced with various diy singles ended.. but you need matching speakers of course
steve

Alex Nikitin
14-07-2009, 11:07
I would recommend this little thing:

http://www.s-audio.com/

http://www.diyaudio.com/forums/showthread.php?s=&threadid=127374&highlight=

http://www.diyaudio.com/forums/showthread.php?s=&threadid=142747&highlight=

LM3886 based composite opamp with extremely low distortion (-120 dB @ 10 kHz) and a fairly simple and straightforward circuit. A good PCB is essential thought to get this kind of results.

Alex

leo
14-07-2009, 15:56
Thanks again chaps!

I don't really need monster watts, infact the diy solid state classA I have is only rated at 15w and is fine for normal listening
Just nice though to try and improve on what I have :eyebrows:

SPS
14-07-2009, 19:55
I would recommend this little thing:

http://www.s-audio.com/

http://www.diyaudio.com/forums/showthread.php?s=&threadid=127374&highlight=

http://www.diyaudio.com/forums/showthread.php?s=&threadid=142747&highlight=

LM3886 based composite opamp with extremely low distortion (-120 dB @ 10 kHz) and a fairly simple and straightforward circuit. A good PCB is essential thought to get this kind of results.

Alex

70db + of feedback to ensure low distortion?
to get a 'really' clean sound, surely feedback is the last thing you want going in an amp?..

cheers
steve

Alex Nikitin
14-07-2009, 20:55
70db + of feedback to ensure low distortion?
to get a 'really' clean sound, surely feedback is the last thing you want going in an amp?..

cheers
steve

Hi Steve,

Design approach is important, however the implementation is more so.

There are some very good amplifiers with lots of feedback. And there are some below average amps with a "zero feedback" approach . And the other way around too ;) . Problem with the feedback is that you either use as little as possible (and that usually requires a lot of attention to detail) or use as much as you can - to get the distortion very very low. At the moment I use as my main amplifier a 50W class AB very high feedback design (below -110 dB distortion at low and mid -frequencies) and I am quite happy with it. I do prefer low or "zero" feedback approach for my phono stages, preamps and headphone amplifiers, however it is possible to produce a decent sound with high levels of NFB even in these applications, thought it may be more difficult than in a "zero" NFB design.

Alex

Barry
14-07-2009, 21:31
Hello Leo,

Regarding the Circlotron amplifier, the following might be of interest to you:

http://en.wikipedia.org/wiki/Circlotron
http://circlotron.tripod.com/
http://www.tubecad.com/articles_2003/Cars_Planes_Circlotrons/Index_files/page0002.htm
http://www.angelfire.com/electronic/funwithtubes/Amp-Circlotron.html
http://www.glass-ware.com/programs/TCJ_Programs_files/page0015.htm
http://circlotron.tripod.com/a50.pdf

Apologies if you are already aware of these articles. The Circlotron design has fascinated me. I am especially interested in OTL designs. I would need at least 20W and would want it to be a solid-state design. I don’t think the Circlotron is very efficient; it requires massive heat sinks. I think Nelson Pass has had a go at them.

Regards

SPS
14-07-2009, 22:11
Hi Steve,

Design approach is important, however the implementation is more so.

There are some very good amplifiers with lots of feedback. And there are some below average amps with a "zero feedback" approach . And the other way around too ;) . Problem with the feedback is that you either use as little as possible (and that usually requires a lot of attention to detail) or use as much as you can - to get the distortion very very low. At the moment I use as my main amplifier a 50W class AB very high feedback design (below -110 dB distortion at low and mid -frequencies) and I am quite happy with it. I do prefer low or "zero" feedback approach for my phono stages, preamps and headphone amplifiers, however it is possible to produce a decent sound with high levels of NFB even in these applications, thought it may be more difficult than in a "zero" NFB design.

Alex

yea.. i can see what you mean... there are 'good' amps that use feedback

but all that back emf from the speakers is going back in the mix too..
Just put a volt meter to a driver and vibrate the cone as fast as you can...
and that's nothing to what real world back emf is creating... and adding to the music signal through the feedback loop,

clean sound... mmmm
..it also removes the acuracy of the original signal, as that second back emf is directly related to the actual speaker movement which is not following the signal as accurately as some may believe it is...

i know my views on how hifi works, are not the norm.. but i'm talking about getting the best sound.. or at least an improvement on a wd88

steve

Alex Nikitin
14-07-2009, 22:20
yea.. i can see what you mean... there are 'good' amps that use feedback

but all that back emf from the speakers is going back in the mix too..


Steve, I know about "that back emf" ;) . There are different ways to deal with it. A proper high-NFB design is one of these ways. The worst case scenario is when the amp is relying almost exclusively on NFB to provide a low output impedance. In this situation the load variations (including back emf) essentially modulate the open-loop gain. However if the open-loop output impedance is sufficiently low it helps do deal with that problem.

Cheers

Alex

Yomanze
19-07-2009, 21:30
Hi Leo,

There's a FET Circlotron amplifier + build guide on the homepage at http://www.passdiy.com/

Cheers,

Neil

Covenant
19-07-2009, 21:32
Have a look at this Leo:
http://www.coldamp.com/opencms/opencms/coldamp/en/index.html
Havent heard of them before but there website is good.

leo
19-07-2009, 22:52
Decisions decisions :)

Was listening to the UCD's today using the balanced out of the ES9018 based dac, got to admit it sounded bloody good:smoking:

Then tried the classA , this one doesn't have balanced in but it also sounded very good

Then tried one of the chip amps I have left using LM3886, design is this one http://3.bp.blogspot.com/_ZVgJtItVgnk/Scr-8REpEmI/AAAAAAAAAhY/-iusJkNs8e0/s1600-h/MyRefC-LM3886-chipamp-schematic.png

Pretty good but certainly not in the same league as the classA or UCD's imo