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Old 22nd June 2007, 09:15 AM   #31
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sandyK could you send me the schematic please.

I was given one of these amps years ago and told the mosfets were blown up. I have never turned it on so is there some way of testing the mosfets in circuit?
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Old 18th July 2007, 02:16 AM   #32
feyef is offline feyef  Australia
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Default ETI 5000 amp for evaluation

suziej,

Please let me know if you are still interested in listening to/measuring sandyK's ETI 5000 amp. From memory, sandK's modifications made it sound quite a bit better than the standard version.
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Old 21st July 2007, 06:14 AM   #33
suzyj is offline suzyj  Australia-Aboriginal
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Firstly, feyef, many thanks for the amp. It's a pity you weren't about when I dropped by. I'll have to find another excuse to come over though, as those speakers of yours look pretty amazing. I'll bet they sound wonderful.

I've surprised myself though. I didn't think I'd be able to tell the difference between my AEM6000 clone and the ETI5000. I figured that they'd both be reasonably similar, but so far they're actually audibly different.

After doing a quick DC check with a multimeter, and applying a wet finger to the HF shunt resistors to ensure there's no enormous oscillations, I hooked it up to my little study monitors (no Infinitys yet, until I've played through some slightly more easily replaced drivers for a bit), and played some music.

My selection: Old Dire Straits stuff, some nice noisy Led Zepp, Redgum, Crowded House, and Mike Oldfield.

For starters, the transformers in the ETI5000 give a lovely reassuring hum when it's powered up. Make you really appreciate all that wattage My AEM6000 amps only hum for a second or three, until the field stabilises.

Also, I note the noise floor on the ETI5000 is somewhat higher than that of the AEM6000. The AEM6000 is really quiet - in between tracks it's as though there's no power on. The ETI5000 has some audible hiss, at least at good healthy power levels (yes, my husband is cowering in the corner - I think it was Smoke on the Water that was the final straw).

But even aside from this, it does have an audibly different character to the AEM amp. It's more raw, less clean. The AEM amp is just totally transparent, but this amp makes its presence known. I'd hazard a guess that it may even be breaking into oscillations a tad.

I must confess it's not actually a displeasing sound though. The sound is evocative of the smoky pubs that I was often to be found in as a teen Or maybe that's just the music I'm playing through it?

Anyway, I'll sneak it into work through the week and bung the distortion analyser on it and see if I can't extract some numbers.
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Old 21st July 2007, 06:27 AM   #34
sandyK is offline sandyK  Australia
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Default ETI 477 article

suzy
I'm surprised to see that it is still working after all these years.
The 6,000 was much better !
SandyK
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Old 21st July 2007, 04:56 PM   #35
VHF man is offline VHF man  Australia
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Quote:
Originally posted by suzyj

But even aside from this, it does have an audibly different character to the AEM amp. It's more raw, less clean. The AEM amp is just totally transparent, but this amp makes its presence known. I'd hazard a guess that it may even be breaking into oscillations a tad.

I must confess it's not actually a displeasing sound though. The sound is evocative of the smoky pubs that I was often to be found in as a teen Or maybe that's just the music I'm playing through it?

Anyway, I'll sneak it into work through the week and bung the distortion analyser on it and see if I can't extract some numbers.
I've also heard both of these amps and still have an original AEM6000 is full working condition. Your appraisal of the sound quality difference is almost exactly the way I would have worded it. The 5000 seemed to exhibit a slight grainy quality in the treble and it highlights how smooth and silky the treble is in the 6000.

FTR I no longer use my 6000 because I've replaced it with my own derivation of the SC100W ULD class AB amplifier. I still use the 6000 as a reference amp because I'm so familiar with the sound but my new amp is better than the 6000 by about the same magnitude that the 6000 was better than the 5000 and in the same areas plus a few others.
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Old 21st July 2007, 10:26 PM   #36
sandyK is offline sandyK  Australia
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Default ETI477

Suzyj
I can vouch for the claims of VHF man.
Current technology,and circuit techniques, has left the AEM6000,
and I am referring to this highly bleprinted version of the AEM6000 here, more suited for biamping at the low end.
VHF Man and myself both built "tweaked" AEM6000 amplifiers, which were much better sounding than most amplifiers of that time.
Valve Audio fanatics would probably love them ,though.
BTW, we are talking about the 240W RMS versions here.

SandyK
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Old 25th July 2007, 08:26 PM   #37
amp_guy is offline amp_guy  United States
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Default eti 477

the references to the eti 477 caught my interest.
while I lived in Queensland 1980-1982 I picked up PCBs
and built them up when I returned to the U.S.later in 1982.

IMHO you could do better, to me they were a little on the harsh side they measured well on my sound technology 1700b.
mine is still running in a relatives H.T setup.
so they are stable.
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Old 25th July 2007, 11:50 PM   #38
suzyj is offline suzyj  Australia-Aboriginal
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There's good news and bad news...

I fired the ETI5000 up this morning before work on an 8 Ohm load, using a Tektronix SG505 oscillator to drive the input, and monitoring the output with an AA501A distortion analyser.

Quick first readings (I'll do more extensive tests at lunch time) indicate that the left channel does 0.0062% THD (50W, 1KHz). Not too shabby for a pretty old design. Sandy, did you have access to distortion mesauring gear when you built it?

The right channel, however, is a basket case. 0.35% THD (50W, 1KHz). The distortion doesn't drop as I vary the input level, either. It's so bad that it's actually visible on my cro (a 1GHz high zoot factor Lecroy).

No wonder it sounded interesting

Neither channel is oscillating though. I wonder what's causing the distortion? I presume capacitors have dried out. It is, after all, some thirty years old.
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Old 26th July 2007, 12:01 AM   #39
feyef is offline feyef  Australia
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Default right channel distortion

Hi suzij,

Any chance of poking around to determine which stage of the right channel is causing the distortion? I would like to bring it back to spec if I can.

Many Thanks
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Old 26th July 2007, 12:05 AM   #40
sandyK is offline sandyK  Australia
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Default ETI477 article

Suzy
No , I didn't have access to such equipment. I am sure that the other channel would have been pretty similar to the other in performance originally, as the amp was far better than the Jaycar Gore Hill amplifier during a demo. Actually, I am quite chuffed that it is even working at all after all this time. Funny you should mention heat problems, as you will have noticed the extra scraps of aluminium added to try and overcome such problems.It's a pity we didn't have some of those nice screw on heatsinks back then.
SandyK
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