ETI 5000 MOSFET Power amp

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#161
Re: Sound Quality

nsaidor said:
Have anyone else build this design?

Did you get the same measurements as Suzy got?

How's the sound quality compared to Krell clone KSA50 or Leach amp? 😎

Cheers
-Navin
Click to expand...

There are a few people in Romania building them. See http://www.elforum.ro/viewtopic.php?p=136428&sid=85bd391ad4d7943ec5b049af70919a6f#136428

Feedback that I've had has been very positive, though I haven't seen any other objective tests.

If you're considering building some, make sure you can get the SST404 dual JFETs before you commit to getting boards. Siliconix have stopped doing JFETs all together. Mouser used to sell the Siliconix ones, but no longer stocks them, which is a real pity. Calogic and Linear Systems (who may be the same people) appear to be the ones who actually make them, but my attempts to get small quantities (50) have so far been completely fruitless.
 
#164
poweramp theramal compensation

Hi,
I also want to buid Suzy's power amplifier. I looked at the schematic and I don't see any thermal compensation of the output power MOSFETs .
Did anyone build this amp and used for a longer period of time driving it close to max power?
How does it behave when hot?
What do you think about adding a thermal compensation ciruit?
 
#165
It is the best amplifier that I did!
And there were many🙂🙂
The sound is perfect!
And the bass ... superb!
After hours of working is very stable.
I am very pleased with this amplifier, I had 6 channels home-cinema.

Suzy ,thanks for your effort to projects are the amp!!
 
#166
Aem6000

Some pictures🙂🙂
 

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#167
I still could not get all components as they seem not available here in Sri Lanka. 😡 I tried Farnel, esp. SST404 dual JFETs could not be found. Is there any suggestion for a replacement. Not sure how good the 2n3958 is?

vitalica said:
Some pictures🙂🙂
Click to expand...

vitalica,
Did you compare this with one of Krell clone KSA50 or Leach amp, if you have already built one of them?
 
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#168
AKSA said:
Suzy,

You come out very strongly in favour of zero measured distortion and justify this with purist, engineering notions of correctness (and convention). It is difficult to argue against this, but how do you explain the huge popularity of the SET, with its horrific measured distortion? I don't want to challenge you or be rude about this, but you might ponder that an amp is not just a scientific apparatus but also a musical instrument, and that the two purposes should be complementary......

Cheers,

Hugh
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The same reason people like tone controls and loudness switches.

Does it make it correct just because they are popular ?? NO !!

And since when was it the role of an amplifier to color the signal ?? Surely that is the job of the mastering engineers and the musicians and not the reproduction equipment which is supposed to faithfully reproduce what is fed into it.

regards
Trevor
 
#169
vitalica said:
Suzy ,thanks for your effort to projects are the amp!!
Click to expand...

Thanks for the compliments. It makes me really happy that people are getting enjoyment out of my work.

I've got a couple of different variants at home - the main 140W/channel ones in the loungeroom, as well as a smaller 50W/channel one that I did for my study. Both have performed flawlessly in the few years they've been running. The one in my study especially occasionally cops a hiding, when I'm in the mood to play my guitar really loud (via a pod DSP guitar amp emulator), but it's never missed a beat.

polcad said:
I looked at the schematic and I don't see any thermal compensation of the output power MOSFETs .
Did anyone build this amp and used for a longer period of time driving it close to max power?
How does it behave when hot?
What do you think about adding a thermal compensation ciruit?
Click to expand...

Lateral MOSFETs have a negative temperature coefficient, so they don't go into thermal runaway. That's one of the really neat things about them, and one of the reasons (along with lower Cgs and Cgd) they're so popular despite their really low Rds.

So no, no thermal compensation. This amp runs reasonably warm anyway due to fairly high bias currents. Even after I give it a thorough hiding it drops back to idle temperature quite quickly.
 
#170
nsaidor said:
I still could not get all components as they seem not available here in Sri Lanka. 😡 I tried Farnel, esp. SST404 dual JFETs could not be found. Is there any suggestion for a replacement. Not sure how good the 2n3958 is?



vitalica,
Did you compare this with one of Krell clone KSA50 or Leach amp, if you have already built one of them?
Click to expand...

Hi Nsaidor,

The Krell does not, but I compared Aleph5 and Leach, Holton.
Suzy's amplifier is my favorite🙂🙂
And my friends, they have made, are of the same opinion.
Every time you listen to are very surprised by the quality and transparency of sound!
 
#174
nsaidor said:
That's sounds great! 🙂
could someone please help me getting SST404 dual JFETs or any other suggestion as an alternative one?

Cheers
-Navin.
Click to expand...

Hi Navin,

Have you been successful on locating dual JFETs? SST404 is a low gm device and 2N3954~8, LS843~5 and 2SK30 (single) fall into the same group (2~3 mS @ 1 mA, something like that). Gluing together two 2SK30 whould be the cheapest solution but the DC drift can be a nuisance.

Good luck!
Satoru
 
#175
eti 5000 rebuild with exicon`s

i have the amps running with exicon fets ..only the 125 watt ones yet to try the 250 watt ones yet if you want the detailed mods i did to the amp to rebuild it please email me and i would be glad to help you with everthing {i was the manager of the kit dept from 1983-1987...sparkey@hotkey.net.au
 
#177
from sparkeey ,,i have looked at your amp pic`s very nice i must say ..on the otherhand i have been building the eti 477 amps mow for 27 years ..i can do it blindfolded... although i have made quite a few with exicons now and was wondering if the 470 pf by pas caps on the drain sorce need to be alterd in capacitance i also changed the gate resistors to 680 ohm and have made a few other mods with the help of ian ...regards brian ..sparkey@hotkey.net.au
 
#180
I thought it was obvious, so didn't explain in the text.

They allow you to run the input stages off a different power supply to the output stages. The latfets have ~10-12V Vgs, which means that in order for the output to pull hard to the rail, the gates have to be pulled beyond the rail.

The idea was that you could run the output stage off +/- 56V @ 200+ W, and the input stages off +/- 65V @ 5 odd W. That way you'd get a little more than the usual 140W into an 8 Ohm load.

In practice I just bridge T7-T8, and T9-T10, and leave T11 unconnected.
 
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