MONO Ver2 Mic pre kit BUILD THREAD

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lordofgrug
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by lordofgrug »

Hey Joe,

So I'm hoping to add one of your fet DI kits to the Mono.

My question is, my Mono doesn't seem to handle unbalanced outs, is this normal?
If so can it be modded to handle unbalanced outs?

Is there any other reason why i shouldn't go down this route?
I'd need to mod the fet DI to 10meg input resistance if that makes a difference. I'd do that by changing the two 2M2* resistors to 20meg correct?

Cheers mate

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by Joe Malone »

lordofgrug wrote:Hey Joe,

So I'm hoping to add one of your fet DI kits to the Mono.

My question is, my Mono doesn't seem to handle unbalanced outs, is this normal?
If so can it be modded to handle unbalanced outs?
It will work with unbalanced outputs fine as long as phantom power is turned off and cable has unbalanced in on pin 2 of the XLR and pin 2 & 3 are shorted together. But the input impedance is low so will only work well with synths and active guitars. Passive pickups and guitars would need a a high impedance input like our FetDI
Is there any other reason why i shouldn't go down this route?
I'd need to mod the fet DI to 10meg input resistance if that makes a difference. I'd do that by changing the two 2M2* resistors to 20meg correct?

Cheers mate
yes changing the input 2m2* resistors to 20Meg would give you 10Meg input impedance. For this make a real difference the cable going to the input of the DI should be kept as short as possible otherwise the cable capacitance will make the impedance at high frequencies less than 10Meg.
Joe :-)
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jsaunders9
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by jsaunders9 »

Gday Joe,

Just a question about Rload for the JLM14 (normal version). The build instructions specify a 2k2 but my kit doesn't include one of these, is the 2k7 in the parts list supposed to be for the same purpose?

Cheers!
Jarrah

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by Joe Malone »

jsaunders9 wrote:
Mon Oct 04, 2021 7:20 pm
Gday Joe,

Just a question about Rload for the JLM14 (normal version). The build instructions specify a 2k2 but my kit doesn't include one of these, is the 2k7 in the parts list supposed to be for the same purpose?

Cheers!
Jarrah
HI Yes in Mono kit we have found 2k7 works better fitted as Rload and wired to 50k log pot (link front and back legs of Z pot together to make 50k)

If this is your first build get the mono working with NE5532A opamp first and then convert it to JLM99v.
Joe :-)
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caoimhin
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by caoimhin »

I'm considering using a Mono as an on-stage preamp for gigs. I'm trying to figure whether the output would be protected against phantom power inadvertently being sent to it. Would 'accidental' phantom coming in through the output XLR potentially fry the opamps?

If so, I'm guessing either blocking caps or an output transformer are two possible solutions?

I think C3 and C4 are for removing the DC offset from the opamps, right, and any additional blocking caps would need to be the opposite polarity to those?

(If a transformer is the preferred way to go, then I'll go with a BA kit rather than the Mono.)

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by Joe Malone »

caoimhin wrote:
Mon Jan 29, 2024 9:27 am
I'm considering using a Mono as an on-stage preamp for gigs. I'm trying to figure whether the output would be protected against phantom power inadvertently being sent to it. Would 'accidental' phantom coming in through the output XLR potentially fry the opamps?

If so, I'm guessing either blocking caps or an output transformer are two possible solutions?

I think C3 and C4 are for removing the DC offset from the opamps, right, and any additional blocking caps would need to be the opposite polarity to those?

(If a transformer is the preferred way to go, then I'll go with a BA kit rather than the Mono.)
Yes changing R15 & R16 to 6k8 & C3 & C4 to 470uF 25v Non Polar. Will protect against phantom power and allow the pre to work perfectly with phantom power on. R15 & R16 work as voltage dividers so the max phantom volts on the output will be 24v so 25v NON Polars can be used.

If I know which opamps you plan to use I can advise the best setup for live.
Joe :-)
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caoimhin
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by caoimhin »

oh super stuff, Joe, that is great. thank you!

re the opamps, I was thinking of going the DIY route with either a pair of garOA10's or a pair of Pier Paolo's APP992's, if you think they'd work o.k.? I'm planning on ending up with a LOT of your JLM99v's in other equipment in the studio (I've already built a pair of LA500's, a BA500v2, and I'm planning to get a pair of PEQ500 kits from you plus a few BA/BAD/BAN kits), but thought maybe I could save a few quid by going the DIY route for the Mono opamps.

Planning to go with the VTX input transformer.

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by Joe Malone »

caoimhin wrote:
Mon Jan 29, 2024 11:04 am
oh super stuff, Joe, that is great. thank you!

re the opamps, I was thinking of going the DIY route with either a pair of garOA10's or a pair of Pier Paolo's APP992's, if you think they'd work o.k.? I'm planning on ending up with a LOT of your JLM99v's in other equipment in the studio (I've already built a pair of LA500's, a BA500v2, and I'm planning to get a pair of PEQ500 kits from you plus a few BA/BAD/BAN kits), but thought maybe I could save a few quid by going the DIY route for the Mono opamps.

Planning to go with the VTX input transformer.
I would for live actually go the NE5532A or if you can find a real OPA2604A as with the VTX that would give you basically a Neve V or Focusrite Red mic pre. And you can use batteries if needed. If you use DOA you can only run on 48v plug pack which is good if you need 48v phantom but most modern mics will run on 12v to 48v for phantom power.
Joe :-)
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caoimhin
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by caoimhin »

o.k., super Joe, I really appreciate your wisdom on this, thank you!

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by caoimhin »

If I'm building this, I'm thinking I might as well take the chance to customise it to my needs, and I'm wondering can I annoy you with a few more questions?

I'd like to add a mute switch (with LED lit while muted), an extra Balanced TRS output, and an extra unbalanced TS out for using a tuner (only while output is muted). Is the below sketch way too simplistic, or am I barking up the right tree?

(I guess I'd be doing this with a BA kit in another enclosure, rather than making sh*t of the Mono!)


I had noticed you had added an extra TRS output on this: http://www.jlmaudio.com/BA1%20Back%20400.jpg. Is it o.k. to just parallel the connections like I've sketched, or is it more complicated than that? (My XLR output would be going to FOH, while my TRS would be going into my computer audio interface XLR/TRS combo input for live audio processing, in case that's useful to know)

Is it a bad idea to run the phantom through a 4PDT footswitch for the 'Mute' LED, should I be thinking of using a relay?


thanks for any help you can offer, Joe, and please feel free to tell me to take my questions elsewhere - if there's a more appropriate place for me to be trying to learn these basic things, just point me there.
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by Joe Malone »

caoimhin wrote:
Tue Jan 30, 2024 9:28 am
If I'm building this, I'm thinking I might as well take the chance to customise it to my needs, and I'm wondering can I annoy you with a few more questions?

I'd like to add a mute switch (with LED lit while muted), an extra Balanced TRS output, and an extra unbalanced TS out for using a tuner (only while output is muted). Is the below sketch way too simplistic, or am I barking up the right tree?

(I guess I'd be doing this with a BA kit in another enclosure, rather than making sh*t of the Mono!)


I had noticed you had added an extra TRS output on this: http://www.jlmaudio.com/BA1%20Back%20400.jpg. Is it o.k. to just parallel the connections like I've sketched, or is it more complicated than that? (My XLR output would be going to FOH, while my TRS would be going into my computer audio interface XLR/TRS combo input for live audio processing, in case that's useful to know)

Is it a bad idea to run the phantom through a 4PDT footswitch for the 'Mute' LED, should I be thinking of using a relay?


thanks for any help you can offer, Joe, and please feel free to tell me to take my questions elsewhere - if there's a more appropriate place for me to be trying to learn these basic things, just point me there.
That will work fine but if there is phantom on the output it will make a huge bang when switching. If you change R13 & R14 to 100 to 270ohm each depending on opamp you use, you could just short XLR pin 2 and 3 together and take the TS jack from the opamp output with its own 100ohm 470uF 25v cap and 10k resistor to ground that you switch to the TS jack. That way you can use a normal 3-way stomp footswitch.
Joe :-)
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caoimhin
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by caoimhin »

super, Joe, thank you! just to make sure I understand correctly, is the below roughly what you mean? And is there a way for me to understand how to calculate the value for R13/R14 correctly? If it's too complicated to explain, let's just say I'll stick with the NE5532A :)
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Post by Joe Malone »

caoimhin wrote:
Tue Jan 30, 2024 10:51 am
super, Joe, thank you! just to make sure I understand correctly, is the below roughly what you mean? And is there a way for me to understand how to calculate the value for R13/R14 correctly? If it's too complicated to explain, let's just say I'll stick with the NE5532A :)
Yes that is correct. NE5532A can run a 500ohm load balanced. So shorted load is best to be about that. So 500 / 2 = 250ohms. So 220 or 270ohms will be fine. The cap going to the TS output can be a normal 25v polarised type and probably smaller like 100uF as it should be a higher impedance load and 6k8 could be 22k etc.
Joe :-)
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