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The A400 GTE gives up its secrets!

mmterror

pfm Member
Okay as I was staying over at my parents this week I though as it was 20 years ago this month I bought the old A400 it was time to give it a clean.

I also had it GTE'd and it was one of the first A400's done.

So out into the utility room we go and get to work.

There is 20 years of dust -

CIMG0035.jpg


Scratchy pots and switches apparently so I got to work with my camera lens blower and a can of switch cleaner.

So we got to this -

CIMG0048.jpg


Pots were a lot smoother but couldn't find any evidence of GTE tinkering. So we opened up the bottom. We found these wires -

CIMG0043.jpg


Ahhh where do they go -

CIMG0038.jpg


And there it is! A small board with a op-amp on it. Judging buy the soldering points its bypassing this -

CIMG0039.jpg


The chip on the GTE mod was rubbed (as I kind of expected) but it did still have the numbers ***241 visible. So I reckon its maybe a OPA241/OPA2241 (?) op-amp. These cost today around £2.40 each. The op-amp on the main board is a C4570C which cost around 25p!

So there we go. That's the GTE mod exposed. We put it all back together -

CIMG0049.jpg


It sounded fine. No scratching or problems. Back to normal and probably good for another 10 years.

Sorry about the pics. Phone was all I had.
 
Prices of standard A400 to set increase :)

I had wondered about this mod and had considered asking about it as the A400 looked like a good candidate for a DIY project.

Not much modding though it seems! Has anyone a standard A400 to compare to see if there was anything else done?
 
That's interesting, thanks.

I had a 400x, never liked it. A second hand Quad 33/303 blew it away, I never looked back. On that basis I can't say I'd hand over a large sum for a '400 when a Quad is so cheap and so much better.
 
I have one - been meaning to try to sort out a noisy volume control - or at least thats what i think it might be.

I'd be happy to use this thread as an excuse to get off my ar$e and open it up at the weekend and take a look.
 
What might be quite interesting is to remove the original op-amp and solder in a socket so one could try alternative (but within spec) op-amps in it.

Op-amp rolling with a A400!
 
So, was that it - a tiny circuit board with £4.00 of components!

Well a lot of far more expensive amps run off 25p op-amps if truth be known.

So putting in one costing £2.40 could well warrant a £100 upgrade in terms of SQ.

Folks have paid more for less I'm sure. All those little add-on boxes......;)
 
£4 worth of bits and bobs sounds about right, I've seen it before with this stuff. After all, the original boards aren't worth much, as ever the costly bits are the case, controls and power supply. Board components are loose change.
 
It is a DC servo, bypassing two AC coupling caps in the signal path. The original opamp is still in the signal path.

This is not a secret. A 1991 issue of Audiophile revealed this, with pretty similar pictures, but less dust.

One would question the wisdom of attempting so with all these long flying wires.

The opamp is probably a dual version of the LF441, if such a thing existed.



Not surprised with the Quad 33/303 performance. Years ago when shopping for the next step (over my Cyrus One) I bought a 34/306 on the spot when I heard it demolish many of the UK magazine-approved contenders. Not subtle.
 
Yes Tom Evans.

When I called up asking about the upgrade he was a bit cagey, then when I said I wasn't working for the hi-fi press he was a really nice chap. We chatted for about 45 minutes.
 
That's Lee and Brent's outfit. Nice website. I wouldn't hand over £175 plus the cost of a '400 (£50-80?), you can do a lot better pound for pound.
 
Well some folks get attached to their old gear. If I was still using the GTE as my main amp then I would think about it.

Well I wouldn't as I just don't care about hi-fi so much anymore but say I was still in my younger (read late 20's early 30's) frame of mind. Then yeah why not.

After all some folks still restore shitheaps like MGs!
 
Indeed they do!

My last resto was a 2CV. It wasn't really a resto, it was a low-budget get-it-back-on-the-road exercise, and it was great fun. I had to sell it when I came back to the UK, a mate still has it in his parents' back garden, apparently these days in a sorry state after he lent it to a distant cousin and they trashed it, either by collision or just abuse and neglect, I'm not sure. I've offered to go and inspect it, if possible get it running again, then he can get it home for further attention but I'm not sure he is that bothered. Shame.

MGs never really did it for me, I've helped a mate with one. That sill construction is a hell of a thing, you take a deep breath before you start cutting out the panels on that one. Fortunately we only had the outers to patch, the inners were OK. Having done all that work you still end up with a cart-sprung Morris Oxford in drag that tries to slide off the road at modest cornering speeds. Fun though as you say.
 
Well I was given a 2003 spec Athlon PC from a customer a few weeks ago. It was typically filthy, dusty and generally unpleasant.

However, I spent a very pleasant Saturday afternoon totally stripping it out. Cleaning and dusting every internal component and even put the case in the shower to clean it all out (much to my other halfs disgust when she found it sitting there).

Put it all back together and installed a lovely clean XP SP3 build on it with Open Office.

Looked better than new to be honest. Junk really but was fun to do but the charity I gave it to as a web browser loved it.
 
...even put the case in the shower to clean it all out (much to my other halfs disgust when she found it sitting there).

So you haven't put a cylinder head through the dishwasher yet? It works rather well.

Allegedly.

Junk really but was fun to do but the charity I gave it to as a web browser loved it.
Good for you :)
 

I had a 400x, never liked it. A second hand Quad 33/303 blew it away, I never looked back. On that basis I can't say I'd hand over a large sum for a '400 when a Quad is so cheap and so much better.[/QUOTE]


Don't equate an A400 with the bland A400X.
 
I have one - been meaning to try to sort out a noisy volume control - or at least thats what i think it might be.

I'd be happy to use this thread as an excuse to get off my ar$e and open it up at the weekend and take a look.

So did you?:D
 


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