Author Topic: How to integrate a DI inside a v-guitar box?  (Read 861 times)

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Offline MusicOverGear

How to integrate a DI inside a v-guitar box?
« on: October 13, 2015, 10:10:01 AM »
I am working specifically on a GP-10 but I assume this could be interesting to anyone doing DIY v-guitar stuff.

I am waiting for delivery of a Jensen JT-DB-E transformer to mount inside my GP-10. I want to have an integrated DI because I'm retooling to carry my rig on my bicycle and every bit of space and weight counts. A lot of the gigs I play have a real janky sound system and there is no full-time tech to patch me in, do a proper soundcheck, etc. I often cover bass or keys with this rig, so i need a no BS, legit DI. So far I have figured out everything except 1) how to ride my bicycle when there is snow on the ground, and 2) precisely how to wire this internal DI haha

Here is the schemo for a generic DI: http://www.jensen-transformers.com/wp-content/uploads/2014/08/as066.pdf

So here are my assumptions:
XLR jack on front of GP-10
signal is present on XLR jack regardless of what is plugged into the stock audio jacks (phones, L, R)
DI circuit may saturate but not distort if i soundcheck with GP-10 vol at noon and progressively turn up to full volume
there will be no jacks - just directly wired to the audio source (so no parallel output)
ground lift will definitely be mandatory sometimes, but not necessarily all the time
overall my wish is to build this circuit once and never have to touch or think about it again.

And here are my questions:
is the audio signal always present on L/Mono, even if nothing is plugged in?
or put it this way - where is a good place on the GP-10 PCB to get the audio from?
do i really need the input caps? i assume the output of the GP-10 is already has extreme frequencies filtered out?
what would happen if my DI circuit was feeding the PA and the stock L/Mono jack was also feeding a powered monitor in front of me?
will i need the pad circuit at all? maybe build it with a trimpot as suggested in the inset and just set it to a static value?
can i just build it permanently wired for ground lift? what is the risk doing it that way?
what am i failing to consider/anticipate? what is wrong with this idea in general? (i'm generally smart and i've built a lot of stuff but i really don't know electronics like i  should)
when will kansas city have public transportation good enough that i can get rid of my car?

Online admsustainiac

Re: How to integrate a DI inside a v-guitar box?
« Reply #1 on: October 13, 2015, 10:19:06 AM »
I suspect the GP-10's "Smart Jack Switching might present a  hurdle with implementing a built in DI

I just feed a 1/4" cable from GP-10 Left Mono Output


 to a Palmer PDI -09 and I'm happy


http://www.vguitarforums.com/smf/index.php?topic=9887.msg70941#msg70941
« Last Edit: October 13, 2015, 10:21:24 AM by admsustainiac »

Offline sixeight

Re: How to integrate a DI inside a v-guitar box?
« Reply #2 on: October 13, 2015, 11:55:13 PM »
I suspect the GP-10's "Smart Jack Switching might present a  hurdle with implementing a built in DI

You could always leave dummy plugs in the outputs of the GP10. The adapter plugs that come with headphones will do the job as they are small.

Offline MusicOverGear

Re: How to integrate a DI inside a v-guitar box?
« Reply #3 on: October 14, 2015, 08:14:19 AM »
Very cool  - yeah I could totally live with that. GREAT IDEA - Thanks!

Offline Elantric

Re: How to integrate a DI inside a v-guitar box?
« Reply #4 on: October 14, 2015, 08:20:12 AM »


referring to your schematic - the GP-10 Main Output is already buffered and driving at 150 ohms

no need for the pad and RC networks   - Just tie the primary side of the Jensen transformer in Parallel with the existing GP-10 1/4" Left Mono output, and connect an XLR Male connector pins #2 & # 3 to the Jensen transformer secondary side. 

but this works too and no cutting required
I advise try this one before you go modifying your GP-10  - zero gain loss. ($26 at Amazon) its dual audio transformers - and works decent. if you must have Jensen Transformers consider a Radial DI Box
Pyle PCD22 Stereo DI box  -
I like this box because its durable, low cost and provides "Feed thru" 1/4 jacks to send signals to stage monitor amps while also feeding balanced audio out to FOH PA via the XLR outs

http://www.amazon.com/gp/product/B00356J8KE/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

« Last Edit: October 14, 2015, 11:24:00 AM by admsustainiac »

Offline MusicOverGear

Re: How to integrate a DI inside a v-guitar box?
« Reply #5 on: October 14, 2015, 11:10:43 AM »
Cool thanks for info. Yeah that will be super easy to build then.

One more question, though: Is there anything wrong with wiring it for permanent ground lift?

I want the good transformer because bass seems to lose some muscle with anything less. Also synthy leads and atmospheric pads with high end seem to lose air. The latter isn't a big deal in crappy clubs but the bass MUST be there, and these are really bad situations where nobody else has any skills to solve these problems.

Even on big productions I get stuck with [what's the cheap blue DI that everyone uses now?] - my guess is that they see guitar and think I will only be sending midrange audio down the line?

The internal mount makes sense to me because I am already at capacity for what I can carry on my bicycle without adding more bulk and weight. I'm jamming everything into a Baby Taylor gig bag (Steinberger body with homemade neck).

Online admsustainiac

Re: How to integrate a DI inside a v-guitar box?
« Reply #6 on: October 14, 2015, 11:26:09 AM »
Quote
One more question, though: Is there anything wrong with wiring it for permanent ground lift?

the could work - but if you perform at lots of different venues, you might find the odd stage where Ground tied to the XLR Pin #1 is necessary for lowest noise. 

Offline MusicOverGear

Re: How to integrate a DI inside a v-guitar box?
« Reply #7 on: October 16, 2015, 12:19:41 PM »
Just did the mod. No problems testing it at home.

Had to make my own mounting bracket for the xformer - the one supplied I think assumes you can mount it to a surface perpendicular to one the top of the can is resting against.

FWIW there is audio on L/Mono and Phones with nothing plugged in.

Offline AshHeeger

Re: How to integrate a DI inside a v-guitar box?
« Reply #8 on: December 18, 2015, 11:39:39 AM »
As per my experience no need for the pad and RC networks just tie the primary side of the Jensen transformer in Parallel with the existing GP-10 1/4" Left Mono output
Also connect an XLR Male connector pins #2 & # 3 to the Jensen transformer secondary side.
You must try this one before you go modifying your GP-10 zero gain loss.

pcb manufacturer
« Last Edit: December 23, 2015, 03:46:17 PM by AshHeeger »

 

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