Solid State Class A Amplifier

[James D]

Agree about Class D! Horrible rf everywhere...

The Tripath or Class T amps are different - they don't just chop pulses out in well defined pulse trains that squirt out several peaks of rf energy at certain frequencies (and associated harmonic distortion and intermod products). Tripath use adaptive algorytms from the communication industry to produce a result more akin to spread spectrum outputs. In this way they avoid the peaks of rf energy in favour of a more constant increase in the rf noise background... so they appear cleaner than Class D amps.

They still put out rf and it still can be a problem to deal with but I have found them to be easier to live with both electronically and sound wise.

James

[John Caswell]

Hi James,
Guess which make of Class D amps I have had trouble with.

John aka Dr John

[James D]

Tripath

Sods Law is going to get you!

[leo:)]

I've had no rf problems with the Hypex modules although I've read some worrying reports with some other classD modules.
The Tripath chips are not bad regarding the sound if you feed them a very good quality psu,using those crappy wallwart supplies will give poor results, Tripath classT also claim to use a variable switching frequency instead of a constant one

Hi Greg,

Pavels Doz, Mosfet power follower was not a bad amp really, very smooth and nice sound, the things run very hot though so you need good heatsinks.
It sounded very similar to the JLH classA amp, the output is not very high though and then theres that big coupling cap on the output but if you already have suitable transformers and heatsinks its fairly cheap to build up, some people must love it seeing as though it has quite a big following
You want classA I'd stick with valves

[Black Stuart]

Leo,
when are you going to post on the Hyex modules?

Black Stuart

[leo:)]

Originally Posted by Black Stuart

Leo,
when are you going to post on the Hyex modules?

Black Stuart

As soon as I believe I'm getting the best out of them

The main thing I'm working on is its input stage, I first brought the standard UCD180ST with the NE5532 input section, I've since replaced this op-amp to the AD8620 which is used in Hypex's more expensive version, there was a big difference to the sound fitting these AD8620's but also there was too much of an artificial sound which I did not like, because the AD8620 has a very low DC offset and coupling caps sound better with a dc bias I linked the coupling caps out, the sound improved again but still had this artificial character so I added smd current regulator diodes on the AD8620 output to -12v supply (theres pads on the modules for this )
The sound improved some more but I'm still not 100% happy, it seems the input section has a huge effect on these modules, btw the input op-amps gain are set to around x5 I think.
Ideally I'd like to scrap the input section and build something else, possibly disrete.
I tried running the output stage of my external dac straight into the UCD's modulator so bypassing the op-amp etc and the sound was unfornately the gain was too low
I also need 4 x good quality 10,000uf 63v PSU caps, the ones I'm currently using are not that great to be honest

[colin.hepburn]

Originally Posted by Martin213

Hi Richard,
Haven't you got supplement number 10,october '94? Andy Groves designed 36 wpc s/s class A monoblocks. Can scan and send to you if you haven't got it.

Regards

Martin

Wanted
I’m interested in this 36 watt Class an amp if anyone still has a copy of this article
Andy Groves designed 36 wpc s/s class A monoblocks in supplement number 10,october '94 if anyone Can help
Thank you

[BOONDI]

Originally Posted by colin.hepburn

Wanted
I’m interested in this 36 watt Class an amp if anyone still has a copy of this article
Andy Groves designed 36 wpc s/s class A monoblocks in supplement number 10,october '94 if anyone Can help
Thank you

I will send it to you Colin......FOC......I already have your snail mail.....

[colin.hepburn]

Originally Posted by BOONDI

I will send it to you Colin......FOC......I already have your snail mail.....

Hi BOONDI
Nice one
Thank you
Colin

[Grog]

i'm part way through building a PLH, got all the hard bits sorted case heatsinks fets etc.
just lacking the motivation to wire it all up!

I think a kit of something along these lines would be good, it's the hardware people struggle with.
hardwiring it all up is fairly straight forward or even a PCB as there are only a handful of components.

i've gone the old fashioned route with big heatsinks, but if i were to do ahigher power one or even this 10W monster again i'd use computer CPU heatsinks with fan. There are a number of very fancy silent (or near silent) CPU heatsink solutions which are incredabily cheap due to the huge number sold.
even the ones with fans (sold as very quiet) make less noise than a lot of torroidial transformers!
something like this £15 and 15dBA (which you'd really struggle to hear even up close)
http://www.quietpc.com/gb-en-gbp/pro...im-silence-am2