DINGO PCB and kit Now Available

[Joe Malone]

The JLM Universal IO PCB currently known as dINgO shown below can be used as a balanced in to unbalanced out and unbalanced in to balanced out with gain at the same time. It takes a 218* VCA IC direct on the PCB for a VCA comp and runs it of the +/-24v to 34v rails so no other power rails are needed. Can have terminals for in and out or Neutrik Series A PCB connectors direct to the PCB. Also has a hard bypass relay and terminals so you can just use it to balance any unbalanced equipment in and out.



Full final circuit fo JLM dINgO here
http://www.jlmaudio.com/JLM%20dINgO%20complete%20schematic.pdf

The I/O 10 pin IDC on the dINgO can plug into and power our
JLM PEQ1 passive EQ PCB (as shown below)
and soon
JLM T filter EQ PCB (Sontec/GML type eq)
JLM VCA Comp side chain front panel PCB
JLM Opto comp PCB.
JLM Volume Controller PCB.

[Joe Malone]

dINgO PCB's are due to arrive here on the 16th of March.

[Holger]

Joe, is this the initial launch of a complete modular mixer system? If so, well, ...

[Bear]

Hmm. What kind of gain can you get out of the Dingo - are the opamps giving more oomph than just balancing? Strikes me if they have enough gain to spare, this might be a cool back-end to a passive mix bus.

Bear

[Joe Malone]

Joe, is this the initial launch of a complete modular mixer system? If so, well, ...

Well kind of

Hmm. What kind of gain can you get out of the Dingo - are the opamps giving more oomph than just balancing? Strikes me if they have enough gain to spare, this might be a cool back-end to a passive mix bus.

Bear

The dINgO input balance to unbalance amp is set to unity but can add gain by changing 2 resistors. The output amp can add as much gain as the opamp type will allow so there is heaps of gain available.

[conleycd]

Is it possible or appropriate (more accurately) to use the dINgO as a REAMP device? So this would be taking a balanced line level signal and running it unbalanced into a guitar amp? I know that this would not provide floating ground without a transformer. That could be a disadvantage. Also would there be a simple way to change the impedance to look more like a "guitar" to the amplifier?

Any thoughts?

CC

[Joe Malone]

The dingo will do this fine and by lifting the ground to the 1/4 insulated jack ground loops can be avoided to guitar amps as well. The balanced in signal would need to be dropped 20 or more dB at the unbalanced output. with a 2 resistor divider or 1k pot and then sent to the 1/4 jack tip with a 47k resistor in seires to emulate a fender guitar pickup impedance. The 47k resistor could be a pot to vary the output impedance.

The unbalanced input would need to be made 1Meg input like most valve amps to load the guitar pickup properly. This can be done by changing R25 to 1Meg and leaving out C8. Leave out RV2 and wire up a external 10k rev log pot so the DI can have a gain pot so no mic pre would be needed to get the guitar signal to good balanced recording level.

[conleycd]

That is great! You should definately include said information in your description of the dINgO. Assuming access to a power supply this still comes in cheaper than transformer reamp designs and I imagine sonically better.

CC

[mylesgm]

Hi,

Just wondering about creating a spring reverb unit with the dingo. I'd like to make a stereo version and I'd like to be able to switch the length and density of reverb by switching in series multiple spring units (for length) or switching them into parallel (for density). Accutronics have variable length decay times and they also have variable in/out impedances. I'm not sure which impedance to select though to suit the dingo. any ideas? http://www.accutronicsreverb.com/Type9.htm

M

[Joe Malone]

Hi,

Just wondering about creating a spring reverb unit with the dingo. I'd like to make a stereo version and I'd like to be able to switch the length and density of reverb by switching in series multiple spring units (for length) or switching them into parallel (for density). Accutronics have variable length decay times and they also have variable in/out impedances. I'm not sure which impedance to select though to suit the dingo. any ideas? http://www.accutronicsreverb.com/Type9.htm

M

Yes we have several DIY guys running reverb springs with 1 x dingo or 2 x BA mic pres or 1 x BAD mic pre. In the dingo with a normal OPA2604AP or NE4432AP you can drive 240ohms or higher (using a 99v or Hybird you could go down to 190ohm or 10ohm with a series resistor of 51R and the input to the dingo makeup amp is 20k so will work with any output spring impedance lower than that.

[reddwarf]

Hi to all,
Is it possible to run the input opamp at+/- 24V (opa2604) and the output opamp (jlm99V) at +/-34V? in the same time?
Thanks

[chrisp]

Anything is possible. It would be a bit of kludge, though. You would need to mount the 99V off board and run connections for the in+, in-, 0V and out pins, using the 24V supply for the DINGO and a separate 34V supply just for the 99V. You'd also need to upgrade the electro caps across the output to a suitable voltage rating (100V or so). Begs the question of why would you bother. The additional headroom is what, 3db or less, but +/-24V is still giving you something like +27dbu, so your'e talking the difference between +27 and under +30dbu. I'm not sure that sort of difference is worth the noise risk the connecting wires would introduce.

What equipment are you running that needs an input signal of +30dbu? Unless you have a good answer to that question, my advice would be to just go with the DINGO's design at +/- 24V.

[Joe Malone]

Hi to all,
Is it possible to run the input opamp at+/- 24V (opa2604) and the output opamp (jlm99V) at +/-34V? in the same time?
Thanks

No. The +/- power rails are shared by both opamps so you can only have both opamps on +/-24v or +/-34v. Unless you want to start cutting tracks.

Everything Chris mentions above is correct except that the caps will not need to be changed as they are correct for up to +/-34v operation already.

The 99v dc offset is only a couple of volts so the output cap could be as low as a 10v type.
The cap only needs to be rated for any DC as for any AC it is technically short circuit so no voltage drop appears across the cap.

But be careful when running a 99v at +/-34v as this is its limit and any error or oscillation could end in smoke
Out of several thousand 99v only about 20 have been blown that we know off and most of those were incorrect +/-34v setups.
Always mention when ordering our 99v if you are thinking of using the full +/-34v so we can help you get it working correctly.

[conleycd]

Hey folks and Joe,

I am always interested in not reinventing the wheel. I am (eventually) planning to do an active combining mixer and I was thinking the dINgO might be the perfect start. Correct me if I'm wrong...

Here's the thought (based a lot on the 2520 datasheet applications). Load the first Opamp with JLM's 99v 16volt version and the second opamp with say the good old NE5532. Run the whole thing at 16v. Of course there's lots of options here for opamps and even more with transformers on the output.

Use the default polarity input settings. Leave out R1, C1, R3, C3, and replace R4 with a jumper.

Leave out R2, replace R5 with a jumper and replace R6 with 100k resistor and a C4 with a 10pf (I base this on the 2520 datasheet - does this reduce RF in the gain?). Replace C2 with a 47uf/10v (based on 2520 application sheet).

Individuals channels could run to a 10k audio pot first (unbalanced), then a 100k summing input resistor. All 100k resistors would combine into the "-" balanced input. Maybe a little project board would do well here for the 100k input channels.

I've seen mixer schematics like this use caps 1uf with each channel instead just one cap (47uf) like the one in 2520 sheet

Ok... now I think the polarity is reversed on the balanced output from the first stage opamp. So an electronically (polarity correct) output needs to be reversed. So, "+" will be "-" and "-" will be "+". A transformer of course would do too if a single opamp was used in the second portion..

I think I need to think less and build more!

CC

[chrisp]

Hi CC

Interesting project idea. How many channels are you thinking? I've built a summing box using transformers rathers than DINGO's so I've done the virtual earth summing thing - its easy enough and works well.

My initial though is that you should, for each input channel, stick with the full parts build on the DINGO through to (and including) R9 on the schematic. That will give you a solid, DC offset corrected high impedance input for each channel. You then need to bring each signal through a mixing resistor (I used 10K, but its not a critical value). If you look at the schematic, you could use R10 as the position for this, and then use a PCB Pin at Pin 1 of the 2181 socket as your offtake to the summing opamp. Insert channel gain control here if you wish, but unless you are building the thing with slider pots, I would use the DAW or other source to control channel input levels.

You now need to sum the inputs, and the balance the summed output. The second is easier - you simply use the second half of one of you DINGO inputs, either a 99V type opamp and transformer or else a 5532 by itself (the 5532 option provides electrical balancing so you do not need a transformer).

As I understand your intent, you then want to use the second half of another of the DINGOs to do the virtual earth summing? You'd need to do something along the following lines -
* omit C8, C9, C11, C13, R13, R14, R15, R17, R18, R20
* keep C10, C12, R19
* bridge R25 (ties opamp + to ground)
* bring your channels all together at pin 8 of the 2181 socket.
* bridge C7

The transformer or jumper for sig + will then be the summed signal, which you then take to another DINGO for output balancing as above. That should work. With 99V's as the input and summing stages, and 5532 as the outputs, I would think you'd get a nice amount of presence without too much colour. I used Hybrids in my summing stage 'cause the transformers provide enough niceness by themselves - you might think about using a Hybrid in Class A/B as the summing stage - its fast transient response does work nicely in summing applications.

Hope this all helps. Let me know if I've got the big picture wrong.
* replace R16 with a 5 or 10K log pot (adjust for unity gain or as desired)