DINGO PCB and kit BUILD THREAD

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conleycd
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Re: DINGO PCB and kit Now Available

Postby conleycd » Sat Apr 24, 2010 12:50 pm

Hey Chrisp,

Yes and No. You're right... if you want things to be absolutely correct you could use a dINgO in front of each channel to unbalance (among other things) before hitting the Virtual Summing Amplifier. This could get pretty expensive. My thought is just to run unbalanced into it.

My modification of the dINgO circuit was to build a virtual summing mixer on the dINgO circuit board. This would essentially be a replication of the circuit listed at Figure 3. This takes the unbalanced inputs. An input potentiometer could be set out first on each channel to control the volume into the summing mixer.

Image

One advantage of doing this on the dINgO is the additional gain (not that you really need it in all likelihood) at the end of the virtual summing amplifier. The other advantage with a dual opamp in the second opamp stage or transformer at the end of it all is polarity correction.

Coming out of the virtual summing amplifier (as built on the dINgO) the polarity reversed. With an electronically balanced output stage you could swap the outputs. With a single opamp in the output stage with a transformer the polarity can be corrected along with a floating output.

CC

chrisp
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Re: DINGO PCB and kit Now Available

Postby chrisp » Sat Apr 24, 2010 9:53 pm

Yes, Fig 3 is what my comments were aimed at as well. Just watch out where you are putting the gain control. You can't use the DINGO's normal gain, because that is structured as a non-inverting buffer, not as a virtual summing point. If you want gain in the virtual summing, its controlled by the resistor in the feedback loop in parallel with the pf cap. That's where I've got a 5K trimpot in series with a larger resistor, so that I can adjust the gain for unity through the summing network. Apart from that, by all means give it a shot, you're certainly on the right track.
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

conleycd
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Re: DINGO PCB and kit Now Available

Postby conleycd » Sun Apr 25, 2010 3:13 am

Yup, I think the plans I posted account for it all.

You enter into the negative input of the balanced input only and the replacements I noted would be the gain that is added by the first opamp based on how many 100k resistor channel inputs you have. Unused channels would be need to be shunted to ground. R6 is replaced with a 100k resistor which creates the makeup gain in the virtual summing amplifier. So the signal is attenuated by the input resistors (100k - although as you mentioned it can be anything as long as R6 matches whatever the input resistors are). In fact, 10k might be better given it would likely be accepting line inputs. So the first opamp is definitely adding gain in the virtual summing makeup.

The output of the whole thing comes out of the unbalanced output of the DINGO. The unbalanced output would then feed the unbalanced input of the DINGO. This where any additional gain is applied and the signal is balanced. You definitely don't need the the whole gain that that the second opamp can provide. It might be nice to be able to add 6db or so if needed. There would have to be some changes there for that level to be controlled with the normally 20k pot. Electronically the signal coming out of the unbalanced output is still polarity reversed so swap the output connections on the balanced output (if electronically balanced or transformer balanced).

CC

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Re: DINGO PCB and kit Now Available

Postby Joe Malone » Fri May 07, 2010 4:00 pm

Yes the dingo first stage opamp can indeed be used as a unbalanced virtual summing amp or balanced in summing amp with the unbalanced out going to a volume/level pot or fader back into the unbalanced in and use the second amp stage with a set gain as a master output stage. Use pair for stereo. Very easy one to do. Use 20k resistors instead of the 100k ones shown in the API doc. and change the 47uF cap to 220uF or 470uF.
Joe :-)
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awguitars
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Re: DINGO PCB and kit Now Available

Postby awguitars » Sun May 23, 2010 10:01 pm

Correct me if i am wrong. I'm just starting to learn all this stuff.

But when using output transformers and Discrete op amps is there need to put R17, R18, R20, C13, And C11 on the dingo PCB?

Also i noticed the previous versions of the dingo did not have zener diodes next to IC 1 do i need to put them in when using the dingo for the MAC project?

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Re: DINGO PCB and kit Now Available

Postby Joe Malone » Sun May 23, 2010 10:15 pm

awguitars wrote:Correct me if i am wrong. I'm just starting to learn all this stuff.

But when using output transformers and Discrete op amps is there need to put R17, R18, R20, C13, And C11 on the dingo PCB?

Yes those parts can be left off in that setup.

Also i noticed the previous versions of the dingo did not have zener diodes next to IC 1 do i need to put them in when using the dingo for the MAC project?

The zeners only need to be fitted if running the dingo from our 48v 520mA SMPS as it makes the +/-24v. If running from a bipolar +/-15v to +/-24v power supply the zeners are not needed.
Joe :-)

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awguitars
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Re: DINGO PCB and kit Now Available

Postby awguitars » Sun May 23, 2010 10:54 pm

Joe Malone wrote:
awguitars wrote:Correct me if i am wrong. I'm just starting to learn all this stuff.

But when using output transformers and Discrete op amps is there need to put R17, R18, R20, C13, And C11 on the dingo PCB?

Yes those parts can be left off in that setup.

Also i noticed the previous versions of the dingo did not have zener diodes next to IC 1 do i need to put them in when using the dingo for the MAC project?

The zeners only need to be fitted if running the dingo from our 48v 520mA SMPS as it makes the +/-24v. If running from a bipolar +/-15v to +/-24v power supply the zeners are not needed.



Firstly, wow amazing, you replied on Sunday at 10pm. within 5 minutes of my question.
ok, fault finding time. I have looked over the board and am trying to figure out what is wrong.

I put the zener's in and removed those components.

With the zeners in i read 0V(could they have died?)
without i read -30.5V and +17.5V

I am using the 48v SMPS, the 48v is in the +Vs and the 0V is in the -Vs. Is this correct?

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Re: DINGO PCB and kit Now Available

Postby Joe Malone » Sun May 23, 2010 11:16 pm

Firstly, wow amazing, you replied on Sunday at 10pm. within 5 minutes of my question.
ok, fault finding time. I have looked over the board and am trying to figure out what is wrong.

I put the zener's in and removed those components.

Usually best not to remove parts that make no difference as it can damage plate holes on the PCB causing problems.

With the zeners in i read 0V(could they have died?)
without i read -30.5V and +17.5V

If you get 0v and the zeners have gone short then the 10R resistors should have burnt? Always check you have the voltages right at the opamp sockets before plugging in any opamps.

I am using the 48v SMPS, the 48v is in the +Vs and the 0V is in the -Vs. Is this correct?

That is correct but the DC connector used for the 48v SMPS must be a plastic insulated type so the 48v smps 0v is not connected to the chassis or PCB 0v ground. The 0v on the dingo PCB can be connected to the chassis.
Joe :-)

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awguitars
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Re: DINGO PCB and kit Now Available

Postby awguitars » Sun May 23, 2010 11:30 pm

Joe Malone wrote:
Firstly, wow amazing, you replied on Sunday at 10pm. within 5 minutes of my question.
ok, fault finding time. I have looked over the board and am trying to figure out what is wrong.

I put the zener's in and removed those components.

Usually best not to remove parts that make no difference as it can damage plate holes on the PCB causing problems.

With the zeners in i read 0V(could they have died?)
without i read -30.5V and +17.5V

If you get 0v and the zeners have gone short then the 10R resistors should have burnt? Always check you have the voltages right at the opamp sockets before plugging in any opamps.

I am using the 48v SMPS, the 48v is in the +Vs and the 0V is in the -Vs. Is this correct?

That is correct but the DC connector used for the 48v SMPS must be a plastic insulated type so the 48v smps 0v is not connected to the chassis or PCB 0v ground. The 0v on the dingo PCB can be connected to the chassis.


Problem found. non-insulated type connector. zeners gone, but 10R just fine... onto some power supply questions (i'll put them in the other thread though)

mylesgm
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Re: DINGO PCB and kit Now Available

Postby mylesgm » Fri Jun 25, 2010 8:58 am

Hi Joe,

Wondering about using the dingo as a buffer for a buffered monitor controller. Not sure if this is the best thing for the job though. I guess what I really need is a balanced i/o buffer or preamp to drive the cables to the monitors after all the input switching, mono etc...

If the dingo wouldnt suit what would?

M

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Re: DINGO PCB and kit Now Available

Postby Joe Malone » Fri Jun 25, 2010 10:12 am

mylesgm wrote:Hi Joe,

Wondering about using the dingo as a buffer for a buffered monitor controller. Not sure if this is the best thing for the job though. I guess what I really need is a balanced i/o buffer or preamp to drive the cables to the monitors after all the input switching, mono etc...

If the dingo wouldnt suit what would?

M


We use the dingo or dingo pup for a active monitor controller all the time. By wiring a 10k dual volume pot to the unbalanced in and out with 2 x 1k resistors in series with the top of the pots to add mono switch and 2 x 100R from the top of the pot switched to 0v for dim.

I am actually going to make a tiny PCB for just this so the JLMIO port ribbon cable can be used with no other wiring needed once the micro headphone amp for the JLMIO port I am working on is finished as it will all work together with auto mute when the headphones are plugged in.
Joe :-)

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jreakee
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Re: DINGO PCB and kit Now Available

Postby jreakee » Fri Jun 25, 2010 8:51 pm

Hi Joe,

I just ordered the dingo for a solidstate pultec I have, the siemens line amp module in it does not working good, so I saw this and thought it was a good opportunity to add some new flavor (DOA :) )

small questions!

- I guess I need to use the unbalanced input and output for insert point of the passive filter?
- for starter I've only ordered the Dingo with 5532, are they fine @ 24V maybe they could live better @,18V or something?
- I have a bunch of output tranny laying around (Utc, Tamura, etc...), what is the primary / secondary impedance needed?

thanks.
Jr.

mylesgm
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Re: DINGO PCB and kit Now Available

Postby mylesgm » Sat Jun 26, 2010 6:36 pm

Which form of 10k pot? log or linear and why 10k? wouldn't a greater resistance give wider volume control? Could you draw schematic for what you mean with the 1k resistors for mono?

M

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Joe Malone
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Re: DINGO PCB and kit Now Available

Postby Joe Malone » Tue Jun 29, 2010 10:13 pm

jreakee wrote:small questions!

- I guess I need to use the unbalanced input and output for insert point of the passive filter?

Yes

- for starter I've only ordered the Dingo with 5532, are they fine @ 24V maybe they could live better @,18V or something?

The NE5532A can only run on +/-18v. (+/-24v will kill them)

- I have a bunch of output tranny laying around (Utc, Tamura, etc...), what is the primary / secondary impedance needed?

The NE5532A provide electronic balanced out and are not recommended for driving any transformers. If you use a DOA like out 99v or Hybrid then any output transformer of 1:2 to 1:3 that can handle +24dBM out the high ratio can be used.
Joe :-)

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Re: DINGO PCB and kit Now Available

Postby Joe Malone » Tue Jun 29, 2010 10:18 pm

mylesgm wrote:Which form of 10k pot? log or linear and why 10k?

You can use a 10k log or 10k lin with extra resistor to make it kind of log

wouldn't a greater resistance give wider volume control?

It is a volume control so goes from about -90 to 0dB attenuation. Using a 1k or 10k or 100k makes no difference except for noise.

Could you draw schematic for what you mean with the 1k resistors for mono?

M

Yes I will draw up a circuit of what I am making the small volume control PCB to do.
Joe :-)

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