FET DI QUESTIONS

Support for JLM Audio Kits

Moderator: Joe Malone

martthie_08
Posts: 12
Joined: Wed Jun 06, 2007 7:31 pm
Location: Stuttgart, Germany

FET DI QUESTIONS

Post by martthie_08 »

is there any pic of the "naked" pcb or a wiring hookup? I installed the wiring posts and did not take notes on the connection scheme :roll: I find myself going to the "old website" for this kind of info, but nothing there unfortunately, Joe could you be of help? Thanks and best regards, Marten

User avatar
Joe Malone
Site Admin
Posts: 2103
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: quick Q - FET DI hookup?

Post by Joe Malone »

martthie_08 wrote:is there any pic of the "naked" pcb or a wiring hookup? I installed the wiring posts and did not take notes on the connection scheme :roll: I find myself going to the "old website" for this kind of info, but nothing there unfortunately, Joe could you be of help? Thanks and best regards, Marten
Image
Joe :-)
JLM Audio
Capturing Audio without Injury

martthie_08
Posts: 12
Joined: Wed Jun 06, 2007 7:31 pm
Location: Stuttgart, Germany

Re: quick Q - FET DI hookup?

Post by martthie_08 »

wow, that was quick, perfect!

thanks, Marten

martthie_08
Posts: 12
Joined: Wed Jun 06, 2007 7:31 pm
Location: Stuttgart, Germany

Re: quick Q - FET DI hookup?

Post by martthie_08 »

another short question - I am hooking this up in front of a preamp, will the FET DI have a problem with phantom power appearing at its output? And will it pass the 48V through to a mic connected to the input posts?

thanks, Marten

User avatar
Joe Malone
Site Admin
Posts: 2103
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: quick Q - FET DI hookup?

Post by Joe Malone »

martthie_08 wrote:another short question - I am hooking this up in front of a preamp, will the FET DI have a problem with phantom power appearing at its output? And will it pass the 48V through to a mic connected to the input posts?
The Fet DI will pass the 48v phantom on but will make a pop when changing over from DI to MIC if a phantom power mic is plugged in so make sure the mic pre output level is turned down during change over.

So if possible it is best to apply the 2 x 6k8 phantom power resistors direct to the input XLR so they are before the DI. If using our Go Between kit or GO between plus this there will be no pop as the phantom is applied before the DI.
Joe :-)
JLM Audio
Capturing Audio without Injury

martthie_08
Posts: 12
Joined: Wed Jun 06, 2007 7:31 pm
Location: Stuttgart, Germany

Re: quick Q - FET DI hookup?

Post by martthie_08 »

thanks, that clears it up! The preamp has a "mute output" switch, so I'll probably leave it as is and pass the phantom power through the DI.

mb_berlin
Posts: 4
Joined: Sun Jan 22, 2012 3:12 am

Which DI, opamp or FET?

Post by mb_berlin »

Hi everybody,

I'm currently planning the racking of a TAB V372/1 amp module as mic pre, which is my first DIY project. I would like to add a DI, but I am not sure which one to choose, opamp or FET DI? I have an idea about the technical difference, but how about the difference soundwise? Can anybody tell me? I would also be happy about recommandations for my specific case.

Thanks!

User avatar
Joe Malone
Site Admin
Posts: 2103
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Which DI, opamp or FET?

Post by Joe Malone »

mb_berlin wrote:Hi everybody,

I'm currently planning the racking of a TAB V372/1 amp module as mic pre, which is my first DIY project. I would like to add a DI, but I am not sure which one to choose, opamp or FET DI? I have an idea about the technical difference, but how about the difference soundwise? Can anybody tell me? I would also be happy about recommendations for my specific case.

Thanks!
Circuit wise they are very different but sound wise they are pure and clean so they only take on the tone of the mic pre they are in front of. Main difference is mounting of the sockets. The old Opamp DI will only just bolt to a 3mm thick front panel and if you over tighten the nut it can strip. Where as the New Fet DI has a Cliff S4 socket which can bolt to 1mm to 5mm thick front panels and is very strong. I recommend the Fet DI for all new builds.

The Fet DI draw about 20mA idle and the Old Opamp DI about 10 to 15mA idle from a 48v power rail.
Joe :-)
JLM Audio
Capturing Audio without Injury

mb_berlin
Posts: 4
Joined: Sun Jan 22, 2012 3:12 am

Re: Which DI, opamp or FET?

Post by mb_berlin »

Hi Joe,

The ordered kits arrived to Germany very quickly. Thanks! Now I started building the DI and the only thing that I am wondering about is in which direction to put in the three 100uF caps. I found a + mark on the PCB close to one of them. Is that the indication of the direction? If yes, do I have to mount the other two in the same direction?

Sorry if this is a stupid question, but as I said I am new to this and I don't want to blow any of the parts.

Thank you!

User avatar
Joe Malone
Site Admin
Posts: 2103
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Which DI, opamp or FET?

Post by Joe Malone »

mb_berlin wrote:Hi Joe,

The ordered kits arrived to Germany very quickly. Thanks! Now I started building the DI and the only thing that I am wondering about is in which direction to put in the three 100uF caps. I found a + mark on the PCB close to one of them. Is that the indication of the direction? If yes, do I have to mount the other two in the same direction?

Sorry if this is a stupid question, but as I said I am new to this and I don't want to blow any of the parts.

Thank you!
The 3 x 100uF caps we use in the DI kit are NP (NON polar) types so can go in either way around. The latest batch of NP 100uF has a gold negative stripe for some unknown reason but ignore it.
Joe :-)
JLM Audio
Capturing Audio without Injury

mb_berlin
Posts: 4
Joined: Sun Jan 22, 2012 3:12 am

Re: Which DI, opamp or FET?

Post by mb_berlin »

Ok, great! It's exactly the negative stripe that made me wonder. Thank you!

ilikeit
Posts: 2
Joined: Fri Apr 13, 2012 8:32 pm

JLM AUDIO FET DI

Post by ilikeit »

Hello

I have a little problem with my fet di
everything are ok
but i would like to add a link under the input jack
i'm wiring another TRS but any sound go out? :o
what is the problem?
how i can make a parallel input?

thx

Greg

User avatar
Joe Malone
Site Admin
Posts: 2103
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: JLM AUDIO FET DI

Post by Joe Malone »

Yes you can connect a TS jack across the PCB jack for link just fine by connecting to the PCB pads marled T and S.

Or if you want a amp driven link out connect the T S jack to the +out and 0v.

Image
Joe :-)
JLM Audio
Capturing Audio without Injury

ilikeit
Posts: 2
Joined: Fri Apr 13, 2012 8:32 pm

Re: JLM AUDIO FET DI

Post by ilikeit »

It s OK

Thanks a lot Joe!!
And many thanks for your product!!!!

best Regards


Greg

Audiobatik
Posts: 2
Joined: Sat Aug 25, 2012 5:19 am

FET DI ... Is there a build thread?

Post by Audiobatik »

I just can't seem to find one.
-Thanks.

-Ab

Post Reply