Replacement OpAmps for Allen & Heath GL Series console

[Nick Sevilla]

Hi,

I just got 6 opamps to test on my console's channels : OPA1642AID from Texas Instruments.

They are TINY. I hope they sound good (just kidding...)

I am going to modify only two channels with these, and when I get the other set of 6 of a different make, I'll mod the other two channels.

Then it will be OPAMP SHOOTOUT TIME!!!

Oh my, what have I gotten myself into?

[The Scum]

Oh my, what have I gotten myself into?

RF oscillator hell?

[Peterson Goodwyn]

Oh my, what have I gotten myself into?

Audiophilia?

[Jim Williams]

Got scope?

[Nick Sevilla]

Got scope?

Yes, a Tektronix old school one, but really useful.

I am going to install some 8 pin sockets, so I can compare the two OpAmps to the normal channels.

What should I be looking for?

Should I be concerned about RF oscillation, as the other poster suggested I might?

Thanks Jim,

Spock

[Nick Sevilla]

Oh my, what have I gotten myself into?

Audiophilia?

Crappy Audiophobia?

[Nick Sevilla]

Oh my, what have I gotten myself into?

RF oscillator hell?

Maybe , maybe not... the two channels I am adapting for now will be my test bed, so I can change other components if need be, and then after I decide what sounds best, go and do the rest of the board. Once the two are working properly.

I might try to get long ribbon cable to hook up the two channels without having to install them continuously... but I really don't know where to get these.

They might be to crappy anyways... so I may as well just do it the hard way.

Cheers

[alf]

Yes, a Tektronix old school one, but really useful.

Off topic, but just out of curiosity, what model Tektronix do you have?

I have an old 321-A I got off Ebay for 70$ I love it. I think it was their first "portable" unit.

[Nick Sevilla]

Yes, a Tektronix old school one, but really useful.

Off topic, but just out of curiosity, what model Tektronix do you have?

I have an old 321-A I got off Ebay for 70$ I love it. I think it was their first "portable" unit.

Hi,

I thought I have a Tektronix... but nooooo, it's a Tenma old school one.

Still very useful and accurate.

BTW I got all the missing testing parts, so after AES, I will be tearing a new one into my console, and starting the replacing / testing phase.

Cheers

[Jim Williams]

I just finished a older model Saber master section. I was able to remove all the electrolytic caps in the main mix path with only a pair on the balanced outputs.
The monitor module was done with no caps. Combined with modern precision opamps, the sonics are about as clear as clear can be.

[Nick Sevilla]

Cool Jim.

Good Job.

I bet it sounds a lot better now.

When I get back fro AES, I'll be breaking my console (open, that is...)

Cheers

[jcaudio]

Have you gotten anywhere with the mods. yet? I'm most curious what your results are. I have a Mizwizard that I wouldn't mind experimenting with some mods. I'm satisfied with the board but if I can get more out of it why not try.

[Nick Sevilla]

As soon as I am over this throat infection... I'll get with it.

Oh how I love my children, even when they bring unwanted guests into our home...

[Nick Sevilla]

Hi,

So I started to do the mod to two channels of my console today.

1.- My ancient soldering iron DIED. Since it was it's third death, I am retiring it. Good ole Weller TCP 201. It gave me and it's previous owner about 20 good years of service. RIP, you will be missed.

2.- On to Fry's electronics, where I picked a nice HAKKO 936 model with a 907 iron. It states it has a 2 year warranty. I'll be the judge of that claim.

3.- While I was there I bought more 8 pin sockets. Why? Because I decided if I am going through all this trouble, I would go ahead and install the sockets, so I can change the OpAmps back, if there is negligible difference in sound quality.

4.- So, tomorrow I finish outfitting 4 mono channels with 5 sockets each, one per OpAmp, adn then start the insanity.

I have bought three different OpAmps to test with :

a.- OPA2134PA-ND from Texas Instruments.

b.- LME49720NA-ND from National Semiconductor

c.- OPA1642AID from Texas Instruments. These fuckers were only available in the pain in the arse surface mount type, so I also bought some adaptor sockets to get them to the correct size and form. FUCK, this I will do tomorrow after my second coffee.

5.- Not to be aging gracefully, I also bought a loupe, with it's own stand, so I can see what the hell I am burning...errr...soldering.

6.- Let's hope I do not have to replace any channels from burning the stuff. I kid, I have extensive soldering experience, just not in the last 4 years or so.

7.- Removing the channels is actually quite easy with the right tools of course. Once you take out all the top knob plastic knobby thingies, and then remove all the circular dohickeys from the shafts, there are only three screws, appropriately done in lovely torx no.10, to get the channel off the chassis. ALso, there is a ground bar (yes, a ground bar, but with no booze in it), which has to be removed from the whole right side of the channels, in order to get the channel out. Why do manufacturers put gooey semi-gooby stuff on their connectors? I see this stuff all over every connector. It must be fear of having them be disconnected... or tampering. WELL I'M TAMPERING, OK?

I will report back, post pictures, etc... tomorrow.

Cheers

[Nick Sevilla]

So I put in two different opamps, the OPA2134 and the LME4972.

So far the channels pass signal.

They all sound different from each other, being the original 5532 as well.

I'm doing some program material recording in MONO for now.

Calibrated the channels to within 0.1 dB.

Warming up the old scope now... and calibrating it before more hijinks tomorrow.

Let's find this "RF" stuff... if it is there. Or anything else untowards.

So far, I have to say these are a close match in operation, they bot work replacing only the three 5532s in the mono channel circuit.

Now I'll find out if I need to "fine tune" some other components to make these operate at their best.

Cheers