Scrap the Lynx, what about a digi 003?

[tv]

No. Now it takes only 15min to mix a song, before it took 4hrs.

 

[TheGuitarist]

They've just recently raised their prices and it looks like it will be above 1200 for me just to get the basic mod....to me... its not worth it. Thats a good chunk of a way to a better upgrade down the road.

 

[Morning_Star]

...-does that mean that it can now record a 3-minute tune in 2:43, or something?

;D

Keef

Yeah, but when I finish there are all these pieces missing.....  ???

 

[living sounds]

Can someone please elaborate more on the bridging transistor mod, in general terms, not in regards to a specific device? Pictures would be great, too. Does this mean you need an output transformer, or can it be left out?

As for the Aurora, I switched the OPA2227 for OPA2211A in the DAC, which made a big difference. Sounds a lot clearer, less compromised now.

I don't think I would do things like soldering pins directly to the converter chip in my Aurora (it's a 16 channel unit anyway), but it would be great to know more about mods like the aforementioned to do to other, cheaper devices.

 

[Tubemooley]

Disclaimer - Modify your own gear at your own risk. General terms - The bridging transformer completely replaces the opamp output amplifier circuit. You need one bridging transformer for each DAC output. That's it. The bridging transformer is doing the job of an output transformer in this case. It is the output transformer. More specific terms - Open your converter box. Locate one of the DAC's (or codec's). Read the number off the top and go to the manufacturer's website and get the datasheet for that device. I believe the Aurora uses Cirrus converters but that's a guess. With the datasheet you can identify the DAC output pins on the DAC IC. Again, somewhat guessing, the aurora uses voltage output DAC's which are differential and not single-ended. So there are two output pins per DAC. Remember..... most of these DAC's are stereo devices so there are two channels coming out of that one IC. The output pins will be labelled something like Vout L+, Vout L-, Vout R+ and Vout R-. Open up your aurora and tell me what the DAC's are and I can pull that datasheet and tell you exactly which pins are the output pins. OK. Now..... Get your digital multimeter out and put it in resistance mode or continuity mode. You want to probe around (gently) to find the first resistor connected to each of those pins. It could be a capacitor too but I'm guessing it's a resistor. So you want to measure zero ohms (or 0.5 ohms with meter lead resistance) or continuity between one of those pins and this resistor/capacitor you're identifying. Do that for all four output pins (two channels, remember?) and write all that down. Draw a little schematic picture. OK..... When you have that, remove that resistor on both pins of one channel. The aurora is probably SMT in there so you can easily remove resistors or caps. Well, I can anyways. You can save those resistors to put them back in later if necessary. Replacement 1206 or 0805 SMT resistors are less than $0.10 each in cut-tape quantities at Digi-Key. So don't worry about destroying a resistor. OK. After you remove those two resistors, grab your multimeter again and re-confirm that each output pin from the DAC goes directly to this one SMT resistor pad. OK. I have used Jensen JT-11P-1 input transformers to do this. You can buy them for 60 to 70 dollars a pair used on the bay. Any decent 10k:10k input transformer will work but they will all sound a little different. Not hugely different but a little different. But the transformers connected to your DAC's will sound HUGELY different from the opamp circuit in there now. HUGE I say. Huge and better. Sick and huge and better. OK. So identify the leads (or pins) on your transformer. One side is the primary and the other side the secondary. If you have the Jensen's, go by their datasheet. Connect the + (or start) lead of the primary to the Vout + DAC pin but go to that resistor pad. You can solder the transformer lead directly to that resistor pad. Yes, this is a little delicate. But if yer in this far, ya' better be ready to keep going. Let me back up for a minute. Before you solder these wires, figure out how to mount the transformer inside the box, even temporarily if necessary. Hold it in place with sticky tape or velcro. Whatever you need to do to keep it from rolling around and shorting out to anything on the circuit board. Or do this on a table where the converter box and transformer can sit while you do this. The transformer can just sit on the flat top of it's can if the wires will reach all the way to the DAC IC. OK. So solder that first wire as described. Then solder the - (or finish) lead of the primary to the Vout - DAC pin. Now, solder an XLR connector or a 1/4" balanced connector to the secondary or output wires. For 1/4", Tx Out + goes to tip, Tx Out - goes to ring. And then on the Jensen trannie, there's a white wire and a black wire too. One of those is the core lead and the other is the shield lead. Both of those go to the sleeve on the 1/4" connector. And you may have to connect circuit COM (or ground) from the converter box to that same connection if you get a ground loop. You'll know if you have a ground loop. It's obvious.

That's it. The 10k transformer provides the correct load on the voltage output of the DAC. Most DAC's want to see a load of about 3k or 4k ohms. So 10k is higher than that and works great. Less than 3k or 4k would be too large a load and would load down the DAC and sound like shit or destroy the DAC itself. So a $35. dollar transformer ($70. if new) is replacing about $3. worth of IC's and SMT components (if that). You will never know how this sounds until you try it. I have done this mod several times on at least two completely different DAC boxes. It's awesome. But ya' gotta' be prepared to do this work without damaging anything inside yer box. I do this stuff for a living so it's second nature for me. I don't have any photos of this stuff handy or I would post them. DW.

 

[kambo]

Tubemooley
this is really great info, my aurora's ch1-2 was blown while ago, and never had time to replace the opamps, but will sure create some time for installing the output trx

i suppose some treatment should be able to made for the inputs too !!! help on that appreciated  too

 

[boji]

So you are using Jensen Input trannies on the output of the Aurora?

In thru the out door?

 

[living sounds]

Thanks alot Tubemooley! I somehow misread the first post mentioning the mod as "transistor" instead of "transformer", even though UTCs were mentioned later...

I think even if I were a total noob I could follow your explanation. This is really straight forward.

Now I'm wondering what all the op amps do in the Aurora. There are three in the line, two of those three are there double per channel (still duals), probably for +4/-10db operation.

I just see one potential problem with the output transformer: Would destruction of the converter chip in studio use be more likely, e.g. by shorting the outputs or even accidentally applying voltage to it (by mixing up input and output on a patchbay for example)?

Would it work the other way around for the ADC, too?

Anyway, thanks again! Will definetely try it, although maybe not with the Aurora right away. ;-)

 

[Tubemooley]

1. I suppose some treatment should be able to made for the inputs too !!! help on that appreciated too.
1a. The ADC's are a whole other story. let's save that for another day.
2. So you are using Jensen Input trannies on the output of the Aurora? In thru the out door?
2a. Correct. These input trannie's are functioning as an output trannie in this case. Input and output trannie's are pretty similar. Sometimes they can be used interchangeably. Sometimes.
3. Now I'm wondering what all the op amps do in the Aurora. There are three in the line, two of those three are there double per channel (still duals), probably for +4/-10db operation.
3a. We would have to talk to the designer of the Aurora. All those opamps are used to take the raw signal from the DAC and prepare it to shoot out an output jack. There is gain in there, filtering in there, output drive capability, any number of things. What the designer decided to end up at that circuit is difficult to know.
4. I just see one potential problem with the output transformer: Would destruction of the converter chip in studio use be more likely, e.g. by shorting the outputs or even accidentally applying voltage to it (by mixing up input and output on a patchbay for example)?
4a. Anything is possible in the studio. But I don't feel that this mod unnecessarily exposes the DAC to possible damage. Shorting the output should not do anything to the DAC. The DAC will see a much larger load all of a sudden. But that load is reflected back thru the trannie itself and is not an actual short as seen by the DAC. There is still galvanic isolation between the DAC and the short. A similar situation occurs if you accidentally connect another output to this output. The DAC should still be OK. I've been running DAC's like this in our studio for coming up on 5 years. My engineer is pretty good at screwing up connections and he hasn't fried one of these DAC's yet.
5. Would it work the other way around for the ADC, too?
5a. No. That can be done but it's a completely different situation. Go look at the Burl Audio B2 Bomber ADC. That's a trannie input ADC. It can be done and it's been discussed on this forum. And I think I know how to do it. But I ain't gonna' get into that discussion now. Maybe another day. DW.

 

[kambo]

documentation is available at
http://www.cirrus.com/en/
D/A CS4398
A/D CS5381

and the usage of opamps as follows;

 

[living sounds]

I know Joe from JLMAUDIO has modded an AD converter using their JLM14 input transformer and a few resisors. No idea about the specifics though. Would the JLM14 work in the DAC as well? It's a very nice sounding but inexpensive 1:4 input transformer (600:9,6kOhm). I'm not sure it will do the balancing, here's a schematic of it in use (no proper documentation availible, it seems): http://jlmaudio.com/Baby%20Animal%20Mic%20Pre%20with%20JLM14%20&%20OPA2604.pdf

 

[kambo]

input buffer,

 

[Tubemooley]

That won't work as well or not at all. You would have to connect the 9.6k side to the DAC. So then you have a 9.6k:600 trannie so it's a step-down at that point so you're attenuating your signal. Hard to say if this one will work connected to the DAC. My guess is that it won't.

 

[living sounds]

That won't work as well or not at all. You would have to connect the 9.6k side to the DAC. So then you have a 9.6k:600 trannie so it's a step-down at that point so you're attenuating your signal. Hard to say if this one will work connected to the DAC. My guess is that it won't.

Thanks! I'll if I can find some Jensen trafos then. Sowter makes fitting ones, too, but the Jensen specs look better. Lundahl LL1544A looks good, too. Will a 600 : 10k 1:1 transformer work as well?

 

[skipwave]

That won't work as well or not at all.

Sure it will.

In a transformer stepping down voltage is stepping UP current. The aforementioned UTC A-24 has a similar turns ratio to the JLM14, spec'd for 15k ohm (tube anode) to the pri, and a 600 ohm line at the sec.

This would also provide the benefit of bridging a 10k load presented by the following input, as opposed to the high-Z transformer connected to a high-Z load.

The step-down transformer offers several benefits in this application with the only sacrifice being some voltage gain, which is easy to recover - gridcurrent referred to his selection of lineamps for makeup gain.

 

[living sounds]

Sure it will.

In a transformer stepping down voltage is stepping UP current. The aforementioned UTC A-24 has a similar turns ratio to the JLM14, spec'd for 15k ohm (tube anode) to the pri, and a 600 ohm line at the sec.

This would also provide the benefit of bridging a 10k load presented by the following input, as opposed to the high-Z transformer connected to a high-Z load.

The step-down transformer offers several benefits in this application with the only sacrifice being some voltage gain, which is easy to recover - gridcurrent referred to his selection of lineamps for makeup gain.

Thank you very much! Would there be a drop in amplitude compared to using either the op amps or the 10k : 10k transformer?

Now the UTC transformers look to be even pricier, and also harder to find.  Unfortunately there is not much documentation to find about the JLM trafos. I guess they won't reach the fantastic specs of the Jensens though. On the cheap side there's Edcor, probably good enough for mixing but not something I'd like to monitor through if it can be avoided...

 

[Tubemooley]

Veddy interesting. I may have to try a step-down such as UTC A-24. I didn't think that would work. DW.

 

[skipwave]

There will be a drop on voltage amplitude, but power is nearly constant less core losses.

Negative voltage gain, positive current gain.

Jensen undoubtedly has a model with the desired turns ratio. It may be presented as a "consumer to professional" line interface. That's a typical application for a transformer meant to allow a wimpy output stage intended for 10k to drive 600 ohm "pro" loads.

You could even use a multi-600ohm-winding xfrmr like the JT-MB-D, and run the windings in series for the hi-Z side. I think that jensen only has three windings on the "split" side. Four would be better. That points out the difference between turns ratio and impedance ratio, which is the square of the turns.

 

[s2udio]

The mic pres are "hyper-modded" and they are very clean pre's with TONS of gain.  Also very fast, which seems to be their goal. 

Should'nt that read "Hype Modded "
;D

 

[Mark Slocombe]

The mic pres are "hyper-modded" and they are very clean pre's with TONS of gain.  Also very fast, which seems to be their goal. 

Should'nt that read "Hype Modded "
;D

LMAO

I don't think mods to most commercial digital products are worthwhile. Mods typically void the warranty and the original manufacturer probably will no longer accept the unit for repair (at all) even if its out of warranty, they just don't have time to figure out what has been modded.

If the basic unit has any proprietary parts in it and you have a problem with it after it has been modded it's probably changed into a boat anchor. Motu is this way, modded units can not be sent back to the factory for service.

IMHO sell the piece and buy something better if you're unhappy with the performance.

Best of luck to you