Upgrade a basic Delta 200

[g fin]

Hi,

I'd like to upgrade my delta 200 myself, and don't know how to do it.

It seems very hard to find expainations on the web...

What about new caps (which ones should/shouldn't I change and why?), sowter transformers, new op amps?

And how can I upgrade the master section?

Thanks for answering!

[polyal]

is there something wrong with the desks performance?i should have thought all the components were selected with the circuit designs in mind..esp the passive components..i suppose you could upgrade the ics' but would it be worth the trouble
transformers can be optional on the inputs though ..i think
regards
polyal

[Jim Williams]

It's a crapshoot without the skills and background to redesign it. It's an incomplete design that was "allowed" by the stable low bandwidth 072 opamps. Increasing the opamp bandwidth will cause major oscillations if band limiting is not applied.

If one examines an input modified here you will see around 25 extra components added to the rear of the pcb. Once redesigned, the console is stable with just about any opamp up to about 300 mhz gain bandwidth. Sockets allow the user to "plug and play" all day with various opamps. The TI THS4012 dual opamp is a real winner, if you can make them work. At 16 ma idle current, you will need a BIG power supply and those chips also require heatsinking, but that's an example of getting a very high test 300 mhz opamp to work in a console designed with 2 mhz opamps.

Don't let the smoke out!

[polyal]

so now you know...you'd be better off upgrading the whole desk to a better spec mixer
if thats what you're after...stick to what you've got for now ..and save your energy
for running repairs
polyal

[Jim Williams]

The Delta design is very advanced for an analog console. The 90 db stereo crosstalk spec at 10k hz is due to routing and the discrete balanced summing amp design, it's top dog as measured on my Audio Precision rig. In fact, those basic building blocks like the balanced line input, fader amps, pan buffers and summing stages are identical to the top-o-line 3200 console.

Similar circuit designs are found in the 24 buss 6000 as well. The lack of psu bypassing, feedback phase compensation caps, scores of 072 opamps and poor quality EQ and coupling caps is what limits it's performance, THD and noise specs.

There are far easier platforms for mods than the Delta, but once treated, it's very hard to beat for transparency, if you like that sort of thing. Mine is direct coupled to the summing amps, only 2 capacitors in the entire console signal path. Remove a few hundred electrolytic caps and things really begin to open up nicely. Use under 1 nv noise opamps and you get a 120+ db dynamic range.

[g fin]

Thank you Jim,

It seems I'm not skilled enough yet, and the need of heatsinking and beter power supply is definitely reluctant, so I won't try to change for 300MHz bandwith op-amps... I read evrywhere you work well on it, but I'm french and can't easily come to you to have it modded.

Are the defaults 072's under 1nv noise? What about replacing them by NE5532?

You mentioned the lack of PSU bypassing, I thought it was an easy thing to do (with a bypassing cap...), isn't it?

What about the optional sowter tranformer on balanced inputs?

What about adding low value caps in parallel with high value caps, which is known to improve response to impulisve signals?

Finally, what about changing actual caps with audiophile caps like the Elna one?

[Jim Williams]

Thank you Jim,

It seems I'm not skilled enough yet, and the need of heatsinking and beter power supply is definitely reluctant, so I won't try to change for 300MHz bandwith op-amps... I read evrywhere you work well on it, but I'm french and can't easily come to you to have it modded.

Are the defaults 072's under 1nv noise? What about replacing them by NE5532?

072's are 22 nv noise, pretty high. 5532's are 6 nv noise but require extra part to work.

You mentioned the lack of PSU bypassing, I thought it was an easy thing to do (with a bypassing cap...), isn't it?

Yes, but I add a pair of .1 uf mono ceramic for each opamp.

What about the optional sowter tranformer on balanced inputs?

You can add any transformer as it's fitted to mount one. A 150/600 ohm 1/2 ratio is best like the Jensen JT-16. It will degrade the EIN spec a couple of db if you do that.

What about adding low value caps in parallel with high value caps, which is known to improve response to impulisve signals?

Something that is done of the remaining caps here. Wima makes good low cost stuff, look to InfiniCap, MIT and Mundorf for the better parts.

Finally, what about changing actual caps with audiophile caps like the Elna one?

Total waste of time and money. "Audio" grade el caps are nothing more than generic 85 degree rated caps with a fancy label, the exception being the Rubycon Black Gates. Use tantalum replacements like Panasonic FM, Rubycon Z and Nichicon HE series.

[g fin]

072's are 22 nv noise, pretty high. 5532's are 6 nv noise but require extra part to work

I'm interested, what do I have to add (resistance?) and where to make them work? I thought I just had to place them on on the DIL8 socket.

Yes, but I add a pair of .1 uf mono ceramic for each opamp.

From both power rails to the ground, is this it?

And what caps should I use for the PSU? Should I place them between +17 to ground, and -17 to ground?

Thanks!

[g fin]

It will degrade the EIN spec a couple of db if you do that.

Sorry, what does EIN stand for?

[Jim Williams]

EIN or Equivalent Input Noise is a sum of the total gain + the unweighted signal to noise ratio. It is a standard spec for noise in mic preamps. PSU bypass caps connect from pin's 4 and 8 to ground. 5532's will not work without extra parts added, they will oscillate. If you want to try and swap opamps around, this is not the platform for it. Better to choose a product with the psu bypass caps and the feedback phase compensation caps already installed.