IO board support thread

ppa · Oct 29, 2011

This is the official support thread for the IO board,

these are the related documents:

schematic:
http://home.teletu.it/APPSI/IO_board_eq2.pdf

components list:
http://home.teletu.it/APPSI/IO%20BOARD%20BOM.pdf

All your questions are welcome

radiance · Oct 30, 2011

The holes for the mil max pins are to small. I have to drill them out and by doing so I break continuity between both pcb planes.
It's not a very big deal since I can solder the pins at both sides but still....

ppa · Oct 30, 2011

radiance said:
The holes for the mil max pins are to small. I have to drill them out and by doing so I break continuity between both pcb planes.
It's not a very big deal since I can solder the pins at both sides but still....

there are no real problems to drill them out because is not necessary any electrical continuity between both pcb planes there.
I have designed the pin receptors' holes for the 2520 socket to permit to drill these ones.

The matter is that there are several pin receptors for the 2520 socket so I tried to make larger holes as well as possible but I cannot them too large to permit to solder the narrow
ones too.

radiance · Oct 30, 2011

Good,
... thanks!

radiance · Dec 20, 2011

Working slowly on a Solid State Pultec here....

One thing I would like to verify:
When using an input transformer (Hs56V) it's best to put it between the input buffer/de balancing opamp (DOA 1) from the IO board, and the Filter stage right?
This way the DOA 1 drives the Hs56V and there will be no impedance issues with other gear not able to drive the Hs56V directly...
Also, when building it like this I should use the 620R resistor (situated after the Hs56V input transformer) as well (see pic attached.
I think this resistor is not needed when driving the filter stage directly with DOA1 right?

ppa · Dec 21, 2011

radiance said:
Working slowly on a Solid State Pultec here....

One thing I would like to verify:
When using an input transformer (Hs56V) it's best to put it between the input buffer/de balancing opamp (DOA 1) from the IO board, and the Filter stage right?
This way the DOA 1 drives the Hs56V and there will be no impedance issues with other gear not able to drive the Hs56V directly...
Also, when building it like this I should use the 620R resistor (situated after the Hs56V input transformer) as well (see pic attached.
I think this resistor is not needed when driving the filter stage directly with DOA1 right?

Since you're using the Hs56V on input stage you should not use the input buffer/de balancing stage. At this point to you should use the 620R resistor after the Hs56V, and after this resistor the filter stage.

After the filter stage you should use the IO board's buffer stage and the makeup/output stage.

ppa · Dec 21, 2011

just to be precise, you should not populate the right part of the PCB with the label "IN" that the input stage.

radiance · Dec 21, 2011

Thanks Paolo.

But just to get this straight, it's possible to have it like this right?

Opamp > Hs65V > filter stage

This way, you don't get impedance issues with gear that's unable to drive the 620R load the Hs56V presents cause the opamp is driving the Hs56v. Or am I missing something?

ppa · Dec 21, 2011

radiance said:
Thanks Paolo.

But just to get this straight, it's possible to have it like this right?

Opamp > Hs65V > filter stage

This way, you don't get impedance issues with gear that's unable to drive the 620R load the Hs56V presents cause the opamp is driving the Hs56v. Or am I missing something?

yes this is possible having this configuration

Opamp > Hs65V > filter stage

but as the Hs65V than IO board's input stage do the work to debalance the input signal
so if you want having a > 10k impedance at the input stage, instead of the 600 ohm gives by Hs65V with the 620ohm resistor, you could use the IO board's input stage only without the Hs65V with the 620ohm resistor.

But if you want listening the Hs65V sound than the Opamp > Hs65V > filter stage configurtion is possible.

radiance · Dec 21, 2011

I'll try all scenarios and will post the results here..
Thanks again!

radiance · Mar 16, 2012

Here a pic of my Solid state Pultec...

http://www.groupdiy.com/index.php?topic=48070.0

ppa · Mar 16, 2012

cool , very cool !

Cormacrestrike · Sep 5, 2012

Hi
I'm looking for some transformer recommendations to use on the io boards output. Any thoughts/suggestions greatly appreciated.
Cheers
Cormac

dubwarrior · Sep 18, 2012

I guess you can use the Transformer wich you prefer..

Something from Edcore, Lundahl or what ever, the guy above has used the original from pultec.

But some recommendations from the designer would be great stil..

Regards

ppa · Sep 20, 2012

dubwarrior said:
I guess you can use the Transformer wich you prefer..

Something from Edcore, Lundahl or what ever, the guy above has used the original from pultec.

But some recommendations from the designer would be great stil..

Regards

yes, you can use a lot of trasformers made by Edcore, Lundahl , Cinemag, Jensen, Classicapi, OEP, Haufe, Sowter, JLM and others, but regarding out trasformers to put inside the IO board's hole
done for the out trasformer, the trasformers compatible are the following:

BIFILAR TYPES

for 1:1 config.

Jensen JT11-DMCF
CINEMAG CMOB-2H
CINEMAG CMOB-2L
CINEMAG CMOB-2S

I have used the CINEMAG CMOB-2L and I like it very much, good quality at low price , I have not tried the others. It is a clear trasformer with good trasparency, if you want the highest trasparency the CMOB-2H and the Jensen should (should) be to suggest.

Quadfilar output transformers:

for 1:2 or 1:1 configuration

– CLASSICAPI EA2503
– CINEMAG CMOQ-2S
– CINEMAG CMOQ-2L
– CINEMAG CMOQ-2H
– JENSEN TRASFORMERS JT-11SS-DLCF
– JENSEN TRASFORMERS JT-123-ALCF

I have used CLASSICAPI EA2503 and it is very good one as 1:2 config for making sound.
CINEMAG CMOQ-2S is very good also for making sound at 1:2 ratio.

for clear sound with 1:2 ratio JENSEN TRASFORMERS JT-11SS-DLCF is very very good.
The sound is clear but amazing at the same time.

synchroman · Jan 17, 2013

Dear Pier Paolo:

Can I use this board to go from RCA -10 signal to a balanced + 4 signal... with absolute transparency.

Which op amp would you recommend?

Please let me know... I have some DACs that sound really good.. buy the are prosummer level -10 and the need to be used in a mastering studio where every thing is +4

What part of the board would I populate...

Thank you for your help

Kindest Regards,

Eric

ppa · Jan 17, 2013

synchroman said:
Dear Pier Paolo:

Can I use this board to go from RCA -10 signal to a balanced + 4 signal... with absolute transparency.

Which op amp would you recommend?

Please let me know... I have some DACs that sound really good.. buy the are prosummer level -10 and the need to be used in a mastering studio where every thing is +4

What part of the board would I populate...

Thank you for your help

Kindest Regards,

Eric

thanks for inquiry,
yes, io board can be used for this, just using only the out stage, it has no cap on the signal path but it uses
a servo DC for max trasparency.
The DOA's indicated for this application are the APP992 and the APP2055.
The out stage has a trasformerless out (and a trasformer balaced out too).

Kindest Regards

tzman · Feb 23, 2013

Hi,

I've got a couple of questions and I hope any of you can help me out...
I'd like to use this board's gain makeup section together with ruffrecords Helios69 type passive EQ. I can't really figure out if this is possible and which parts of the PCB I would have to use (I'm guessing only the make-up gain and not the FET buffer?).
I'm planning on using the EQ after the 9K pre-amp as a channelstrip, so I wouldn't need the IO boards input stage then, right?
I'd like to be able to patch the output of the IO board into a mixer input channel. Are there things I would have to be aware of (impedance?).

I hope you can help me out, because I'm a little stuck at the moment...

ppa · Feb 23, 2013

yes, you can use the io board with helios eq, just the make-up stage, fet buffer and input stage are not needed for your application. for the helios input you can use only the positive out of 9K pre-amp.
You can use the io board out for mixers. The min. impedance load that the make-up stage can drive depends by the opamp used in this stage, if you use a DOA of mine you can drive even loads of 600 ohm without problem, the same thing with 2520 , je990, melcor and others, using IC opamps the things are a bit different but since generally the typical in impedance is bigger than 10kohm very often there are not problems with IC opamps.
If you have other question tell me please.

Pier Paolo

tzman · Feb 24, 2013

Thanks!
This is a great help. I've got a slight change of plans though... I'm planning on building a channelstrip consisting of the following: SSL9k->LA4->Helios69->IOboard. So I've added the LA4. All DIY projects found on the forum.
Maybe it's the wrong place to ask, but here it goes: the LA4 has a 600:600 transformer out. Could I connect the transformer directly to the Helios input (so I would use it as an interstage transformer). Or would it be better to skip the transformer (and sacrifice it's "sound").

Another question: Can I use your new APP992 as the output DOA? I would like to use a Cinemag transformer going to the XLR out. Have you got any recommandations on which type to use keeping the above described channelstrip in mind? I'm planning on using the CMOB-2H.

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