Behringer ADA8000 modifications..

[synthi]

Thanks for the info saxtim, but in my own case, I need the DAs more than the ADs, I just want to use the ada8k line ins just if I need aditional inputs, but my main interest is the DAs: I use them for buss summing using a external box.
I read the topic about that lovely lundhal transformer base output buffer, I wonder if a similar mod would be possible for the ADA8k

About the digi001, there is a clear sonic diference between the B_ada8k and the 001 converters, thankfully the b*r*ng*r converters sound much better by far, those 001 are one of the worst sounding converters, lot of people with 001s use even the old fostex converter box (vc-8?)because they sound better than the 001`s

Best Regards,

Synthi.[/quote]

 

[bradzatitagain]

[quote author="synthi"]

About the digi001, there is a clear sonic diference between the B_ada8k and the 001 converters, thankfully the b*r*ng*r converters sound much better by far, those 001 are one of the worst sounding converters, lot of people with 001s use even the old fostex converter box (vc-8?)because they sound better than the 001`s

Best Regards,

Synthi.[/quote][/quote]

Well gosh darnit, that's great news! I'm firin' up the credit card...

 

[rafafredd]

[quote="bradzatitagain]I'd toss 8 Ampex MX35 EF86/PF86 cathode follower pre's in there and have a dynamite box.
[/quote]

Do you mean this one?

http://hps.infolink.com.br/rafafredd/mx35_ef86_CF.gif

 

[bradzatitagain]

[quote author="rafafredd"][quote="bradzatitagain]I'd toss 8 Ampex MX35 EF86/PF86 cathode follower pre's in there and have a dynamite box.
[/quote]

Do you mean this one?

http://hps.infolink.com.br/rafafredd/mx35_ef86_CF.gif[/quote]

Yeah Fred, nearly, go here for a complete manual and read Theroy of Operation. Gosh, my friend John is just going to love me after his bandwidth gets stomped while everybody's downloading this...

http://ampex.hughescatalog.com/mx-35/mx-35%20manual.html

Include the mic pre circuit before the rotary switch, so you'd have 3 tubes. Keep in mind that the output is at 100K, intended to load tape recorder heads. You need an xfrmr at the end of this circuit, if you get one with +db you'll get the xfrmr's rated gain plus 65dB from the mic pre circuit. Good for ribbons. Should probably need a -26db pad in the present world.

 

[rafafredd]

The mic pre isn´t a cathode follower.

Also, I think it´s impossible to fit eight channels of all the three stages with transformers and the AD board in a 1U rackspace. :shock:

 

[bradzatitagain]

[quote author="rafafredd"]

Also, I think it´s impossible to fit eight channels of all the three stages with transformers and the AD board in a 1U rackspace. :shock:[/quote]

That's probably true. If you use one ECC85/6AQ8 in place of two of the triode strapped EF86s that gets you down to 16 tubes from 20. I've got 8 of the Beyers that were in the MX10/35 stock, they're very very small. Then output xfrmrs, even with OEPs/Lundahls thats a lot of real estate. & you'd definitely need horizantal pcb mount sockets. Hmmm, I dunno, *maybe* everything could squeeze in there w/an outboard psu for the tubes. There are certainly easier solid state ways to get everything to fit in the 1U case. Maybe AM-10 pre's? 75db gain:

http://ftp.ampex.com/ampex/manuals/audio/am10man/

I know you guys are big Neve fans, I bet somebody's got a good notion cooking.

The mic pre isn´t a cathode follower.

Right, but all three tubes, both circuits, give the 65 db gain in the mixer. So you've got the first triode strapped EF86 that's controlled by a 100K pot that feeds the third grid of the EF86 that sits on top of the 12AU7, the cathode of which feeds the outputs through a 25K master gain pot. The only thing I'm not certain of is, if the mic pre pot is at maximum setting, will the master gain pot then control the full range of gain, from the mics input gain (if its got one, but a new condensor would have about 25db of gain in the head amp, right?) to the full 65 db of gain from the pre-amp circuit. Then you could get away with one pot, & pro'ly reuse the ADA8000 pot if it were an appropriate value, or simply replace it.

But you're totally right, Fred, it would be a challenge to jam all of that in the 1U box. It would want a couple of rack Us for breathing room, that's for sure and you'd want to perforate the lid and the bottom to get some ventilation. The thing about the MX35 is it handles tube wear with grace, plus it sounds great. I'd think a parallel psu, one xfrmer per 8 tubes, would pro'ly be a good idea, less expensive xfmrs than one that could run 16-20 tubes. From the pics in the manual it looks like there might be enough space between the IEC and the TOSC linc on the back panel to squeeze a din or canon psu connector. Anyway, it's a daydream until I buy one, so...

 

[gyraf]

An update:

We now have people working on this. Stay tuned..

Jakob E.

Edit: Synthi, Rafa, TestPoint - I edited out some of your comments. Best that way, I think :wink:

 

[synthi]

Good news!
Synthi

 

[tony dB]

Synthi,

To what topconvertors did you compare? I'm interested as well and get the b**rùùùùs VERY cheap if bought in multiples of 6.

Cheers,

Tony

 

[synthi]

I was comparing the B`s vs Swissonic (DA24, DA96) and RME ADI 8, all of them running at 44.1Khz.
I also compared them Vs a yamaha 03D in a friend studio, now he have another ada8k and he is bypassing the yamaha mixer

I noticed a subjetive sound quality increase when the ADA8k is Wordclock slaved to the Swissonic but not when slaved to RME, may be swissonic have better clock than the rest...?

I bought my B`s very cheap in Germany, brand new for 200 Euros each.
Best Regards,

Synthi.

 

[rafafredd]

[quote author="gyraf"]We now have people working on this. Stay tuned...[/quote]

Nice!

 

[Bauman]

I'd be very happy with a copy of ADA8000 schemo also...

cheers!
Fabio

 

[rafafredd]

Yeah. I would want to take a look at this.

 

[gyraf]

Sorry guys - no factory schematics.

B* simply does not give these away.

But we're working on a rev-eng stunt - after all, there's not much in this box that's not specified by the chipset dtasheet..

Stay tuned..

Jakob E.

 

[synthi]

Good news, Thank gyraf!

Synthi

 

[gyraf]

Here it is - for now only the analouge sections including the converters. Optical in/out, clock generation and powersupplies are all by-the-book.

http://www.gyraf.dk/schematics/schematics.html (at the bottom)

Data sheets for the used "Wavefront" (Alesis) chipsets are available at ProFusionPLC:

http://www.profusionplc.com/cgi-bin/gex/pcatlst?ipartno=all&imanuf=wavefront&itypes=all

Preliminary modification suggestions:

D/A - replace SMD TL074's with ditto MC33079's.

A/D - It seems that the line inputs on this one is made simply by attenuating the line input signals and then gaining them back up through the mic pre. Not pretty, if you don't always use the mic inputs. We could scrap the mic input stage and connect directly to the balancing stage that drives the converter. Change the TL074 here to MC33079 as well. Metering would be easy to extend. An interesting experiment would be to drive the differential inputs on the converter directly with an input transformer - bypassing ALL the A/D analouge parts..

Ideas?

Jakob E.

 

[rafafredd]

Would you use a step down transformer for this purpose? Maybe a 4:1, 10k/600, because the converter is only 5v... less headroom.

 

[DrFrankencopter]

Here's some suggestions:

Remove the mic preamp stage, and build a small daughter board input buffer that ties into the A/D lines and D/A ouput lines. The buffer can use a nice FET input op-amp (2604, 4132/4134, or opa627), and a DC servo, or perhaps nice big non-polar coupling caps. The output driver can use a similar arrangement.

Cheers,

Kris

 

[synthi]

wow! Thanks gyraf!

I agree with a new input/output stages, either transformer or fet, also would be possible to switch the meter for input or output monitoring?

Synthi

 

[Bauman]

THANKS JAKOB!!!