If you have specific questions, maybe someone would be able to reply.
As a comment to the criticisms raised before, regarding the preamplifier and other features, it was assumed that the product was only available as a complete amplifier kit. It has been available for six years in module form too, for anyone not wanting to build the project but just wants the PCBs and parts. The amplifier modules are still $49.95 AU each at the Altronics website. The other modules are the PSU, remote controlled preamp and universal output relay.
This is class A and needs 2 big heatsinks of <0.4 deg/W rating, even in our climate. The transformer also must be selected to give DC rails of +/- 22V @ 2.5A continuous to get the full 20W rated output. That means a non-standard AC rating of 16-17V, but 15V @ 160VA may be OK with a small penalty.
As a comment to the criticisms raised before, regarding the preamplifier and other features, it was assumed that the product was only available as a complete amplifier kit. It has been available for six years in module form too, for anyone not wanting to build the project but just wants the PCBs and parts. The amplifier modules are still $49.95 AU each at the Altronics website. The other modules are the PSU, remote controlled preamp and universal output relay.
This is class A and needs 2 big heatsinks of <0.4 deg/W rating, even in our climate. The transformer also must be selected to give DC rails of +/- 22V @ 2.5A continuous to get the full 20W rated output. That means a non-standard AC rating of 16-17V, but 15V @ 160VA may be OK with a small penalty.
silicon chip 20W Class A
w c
I didn't want to buy modules.
I have handmade PCB as usual.
These are etched today.
I have a large transformer 2x15v from a damaged UPS.
As for large heat sink........a smaller with blower ....just for try.
I'll post pictures from first steps tomorrow.
w c
Thanks for reply Ian Finch.
I didn't want to buy modules.
I have handmade PCB as usual.
These are etched today.
I have a large transformer 2x15v from a damaged UPS.
As for large heat sink........a smaller with blower ....just for try.
I'll post pictures from first steps tomorrow.
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Thimios, check you email.
Fairly good Class-A amplifier (essentially a Douglas Self design), but I would change a few things.
First, I would use independently biased current sources for the input stage (transadmittance stage or TAS) and the the second stage (transimpedance stage or TIS): each of those current sources would be an amplified negative feedback (ANF) current source.
Secondly, the amplifier has no Safe Operating Area (SOA) protection; I would use the double-slope arrangement discussed in my paper here:
Michael Kiwanuka: SOA Protection for Audio Power Amplifiers
and discussed further here:
http://www.diyaudio.com/forums/solid-state/235841-michael-kiwanukas-soa-paper.html
Fairly good Class-A amplifier (essentially a Douglas Self design), but I would change a few things.
First, I would use independently biased current sources for the input stage (transadmittance stage or TAS) and the the second stage (transimpedance stage or TIS): each of those current sources would be an amplified negative feedback (ANF) current source.
Secondly, the amplifier has no Safe Operating Area (SOA) protection; I would use the double-slope arrangement discussed in my paper here:
Michael Kiwanuka: SOA Protection for Audio Power Amplifiers
and discussed further here:
http://www.diyaudio.com/forums/solid-state/235841-michael-kiwanukas-soa-paper.html
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silicon chip 20W Class A
Thanks Sir for reply.
This is a theoritical examine of SOA.
I must read it carefully .
Practical speaking this kind of protector has friends and enemies.
Enemies say that this protector is good...... if it is absent because of clipping results.
Many of diy amplifiers out there are without this stage.
My opinion is (for diy) ...anytime we must protect the speakers .
Best regards.
Thimios.
Thanks Sir for reply.
This is a theoritical examine of SOA.
I must read it carefully .
Practical speaking this kind of protector has friends and enemies.
Enemies say that this protector is good...... if it is absent because of clipping results.
Many of diy amplifiers out there are without this stage.
My opinion is (for diy) ...anytime we must protect the speakers .
Best regards.
Thimios.
silicon chip 20W Class A
Some photos from first fire.
Keep in mint that power supply isn't so good.
Two separates adjustable power supplies just for first try.
+/-22V
1.2A idle current
-11mv offset
R dummy= 8R
20W RMS Just before clipping.
Some photos from first fire.
Keep in mint that power supply isn't so good.
Two separates adjustable power supplies just for first try.
+/-22V
1.2A idle current
-11mv offset
R dummy= 8R
20W RMS Just before clipping.
Attachments
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silicon chip 20W Class A
I know but this is a test board not a complete amplifier.
Thanks for reply sandyk
I know but this is a test board not a complete amplifier.
They are fine amplifiers and leagues ahead of the various other Altronics amps I've had (ETI-5000 anyone? Although I do think I had some PS problems)
I have one sitting in my lounge.
Next to the vintage JLH which is the amplifier I actually listen to.
This is most likely a side effect of the speakers I have (Ariels) which are not known for being silicon friendly.
<HUNCH> - I suspect that reducing rectifier switching noise in the power supply would result in improvement </HUNCH>
Hey guys, a bit OT here but has anyone had any issues with those Lelon caps Altronics sells? (as above) I've used them on my SKA PSU and they're fine, but I know that is one of the so called badcaps brands from a few years ago. I'm quite comfortable they seem to be good quality nowadays, but wondered if there have been failures.
silicon chip 20W Class A
Board is for test only so it's ok.
These caps is that i found here in Agrinion(Greece).
Board is for test only so it's ok.
These caps is that i found here in Agrinion(Greece).
Board is for test only so it's ok.
Have you put a CRO on the capacitor bank while under load? I found a lot of noise/ringing when putting lots of capacitors in parallel (this being many years ago when all caps were bad caps!)
Funny, I've seen them in goodcaps lists too. I think, that given the long association between Altronics and Lelon, they are no better or worse than similarly specced products for the price. They seem consistent, and I would rate them with other Taiwanese cap manufacturers (good).
IMHO, the perceived quality of a brand is from the range stocked by the supplier. If your supplier is small, he'll likely only stock cheaper grades, whether premium brand or otherwise.
silicon chip 20W Class A
Amplifier with this power supply is silent death even you put your ear close to the speaker.
You hear nothing ,absolutely nothing.
I can't say nothing about capacitors durable life as this is a test power supply and not a continually function power supply.
Thanks and sorry for my bad English.
Thimios.
Amplifier with this power supply is silent death even you put your ear close to the speaker.
You hear nothing ,absolutely nothing.
I can't say nothing about capacitors durable life as this is a test power supply and not a continually function power supply.
Thanks and sorry for my bad English.
Thimios.