Which JLM Preamp Kit Is For Me?

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ciscan.81
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Joined: Sat May 26, 2012 8:33 am

Which JLM Preamp Kit Is For Me?

Post by ciscan.81 »

Hi DIYers

Having read the majority of the massive JLM Baby Animal thread over at GroupDIY and loads of others on JLM pre's I understand that some of what I am asking has been, in part, covered elsewhere but I thought a fresh take might help other newcomers.

I have been spending a lot of time researching JLM pres lately as I am hoping to up my studio’s ante and make my first preamp purchase.

I have only a little electronics experience having built a beautiful pair of 3 way tower listening speakers, in-line pads, in-line Z patches and the odd lead.

I have been looking at 4 build options:

1. The two channel Dual 99v Rack kit with the JLM14 input trans and the JLM111 out.

2. The 2 channel 1290 Rack kit

3. Building 2 of each - Dual 99V on a BAD PCB and 1290 macro kit and housing them in one unit on a shared power supply (to save a little money)

4. A BA2 or BA4 Kit using the 99v opamps with transformer setups similar to the pres above. (ie one with a JLM14 and the other with an OEP262A3C on the inputs and JLM111's on the outs) (also toying with the idea of one matched stereo pair and 2 other BA opamp/trans combos to give me 3 different flavours - thats the problem with BA's too many options!!!)

I want to have DI, variable Z and the small round VU meters from JLM (on a buffer) on each channel. (got to have all the options!)

Initially I intend to use the pres mostly for: DI bass, Guitar Cabs, snare, kick and maybe overheads. Something that covers vocals, acoustic guitar, uke, harmonica and percussion is a bonus but not my main focus at this stage. I understand that I'll need quite a few pres to cover all of these instruments in a variety of situations, but that'll come later.

Although I'd love to NOT trot out the usual clichés, I don't know how else to put this so: Sonically I am looking for something vintage, big, fat, warm and punchy (as I'm sure everyone is; never heard of anyone chasing a small, thin, cold-wet-sock sound). Given I want this pre to cover mostly DI bass, guitar and drums a bit of colour is not a bad thing.

The only pre I have used before is a friends Golden Age pre 73 on DI Bass; I liked the sound, but felt it sounded a bit cheap and could be easily bettered. Also, I didn't like the way it broke up when driven hard. I understand Joe's 1290 Macro kit is also a loose take on the N*EVE 1073 but is head and shoulders above the Golden Age...Any thoughts on whether the JLM dual 99v is better again for this application?

My humble mic collection (kind of a starters kit in need of upgrading) currently consists of a Rode NT1A, 2x NT5, Audix i5, Sm57’s and a sennheiser e620. My interface is a Digi002r.

So that's where I'm at.

To aid me with my decision on which pre kit to purchase could anyone with the time and inclination to help out a beginner please advise on the following queries:

1. Given my brief and vague description of what I am after sonically, which of the Dual99v or 1290 (or 4 x single stage BA variants described above) would you recommend as a first preamp purchase?

2. Is it possible to put some sort of output trim pot/fader on a BA without adversely affecting the sound? (as on the 1290 and Dual99v) if so how?

3. What advantages (both sonically and features wise) do the dual stage pres have over their single stage BA build counterparts?

4. Is it possible to run 2 of each Dual 99V on a BAD PCB and 1290 macro kits (with TREX2) with all features on a single 48v 40w 840mA SMPS? If not, which JLM supply should I use in this instance?

5. Does the 1290 macro kit come with or is it possible to add variable input Z?

Many thanks for your time and assistance to help me begin my JLM DIY Preamp journey . I can’t wait to get started! :)

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Joe Malone
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Re: Which JLM Preamp Kit Is For Me?

Post by Joe Malone »

ciscan.81 wrote:Hi DIYers

To aid me with my decision on which pre kit to purchase could anyone with the time and inclination to help out a beginner please advise on the following queries:

1. Given my brief and vague description of what I am after sonically, which of the Dual99v or 1290 (or 4 x single stage BA variants described above) would you recommend as a first preamp purchase?
From your list I would be starting with a BA4 with 2 x OEP/VTX and 2 x JLM14 and 4 x 99v it is by far the most popular and useful pairs. JLM14 is great to add fatness to drums and bass mic and using the DI input. OEP is great on vocals and all acoustic instruments, overheads. Since you will always need these pres even when you add extra new pres to fill out the number of channels you listed that you want to get to.
2. Is it possible to put some sort of output trim pot/fader on a BA without adversely affecting the sound? (as on the 1290 and Dual99v) if so how?
You can run a 1k pot on the output of the BA but turning down the output will reduce headroom and increases output impedance. In reality you do not need it as with the pad on and minimum gain the BA is unity gain.
3. What advantages (both sonically and features wise) do the dual stage pres have over their single stage BA build counterparts?
More gain 75dB instead of 60dB and the fact you can overdrive the first opamp and turn down the output so you can get more colour range our of the pre. But variable impedance also gives you large preamp colour variation range.
4. Is it possible to run 2 of each Dual 99V on a BAD PCB and 1290 macro kits (with TREX2) with all features on a single 48v 40w 840mA SMPS?
Yes but if you are buying full rack kits they already come with power supplies in the kit. BA2, Dual99v and 1290 come with 48v 25w and BA4 comes with 48v 40w.
5. Does the 1290 macro kit come with or is it possible to add variable input Z?
No not without a huge amount of changes but the ratio jumper can be brought out easily to a switch for 150/600 switching.
Many thanks for your time and assistance to help me begin my JLM DIY Preamp journey . I can’t wait to get started! :)
8) :D
Joe :-)
JLM Audio
Capturing Audio without Injury

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Joe Malone
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Posts: 2069
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
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Re: Which JLM Preamp Kit Is For Me?

Post by Joe Malone »

ciscan.81 wrote:Hi DIYers

To aid me with my decision on which pre kit to purchase could anyone with the time and inclination to help out a beginner please advise on the following queries:

1. Given my brief and vague description of what I am after sonically, which of the Dual99v or 1290 (or 4 x single stage BA variants described above) would you recommend as a first preamp purchase?
From your list I would be starting with a BA4 with 2 x OEP/VTX and 2 x JLM14 and 4 x 99v it is by far the most popular and useful pairs. JLM14 is great to add fatness to drums and bass mic and using the DI input. OEP is great on vocals and all acoustic instruments, overheads. Since you will always need these pres even when you add extra new pres to fill out the number of channels you listed that you want to get to.
2. Is it possible to put some sort of output trim pot/fader on a BA without adversely affecting the sound? (as on the 1290 and Dual99v) if so how?
You can run a 1k pot on the output of the BA but turning down the output will reduce headroom and increases output impedance. In reality you do not need it as with the pad on and minimum gain the BA is unity gain.
3. What advantages (both sonically and features wise) do the dual stage pres have over their single stage BA build counterparts?
More gain 75dB instead of 60dB and the fact you can overdrive the first opamp and turn down the output so you can get more colour range our of the pre. But variable impedance also gives you large preamp colour variation range.
4. Is it possible to run 2 of each Dual 99V on a BAD PCB and 1290 macro kits (with TREX2) with all features on a single 48v 40w 840mA SMPS?
Yes but if you are buying full rack kits they already come with power supplies in the kit. BA2, Dual99v and 1290 come with 48v 25w and BA4 comes with 48v 40w.
5. Does the 1290 macro kit come with or is it possible to add variable input Z?
No not without a huge amount of changes but the ratio jumper can be brought out easily to a switch for 150/600 switching.
Many thanks for your time and assistance to help me begin my JLM DIY Preamp journey . I can’t wait to get started! :)
8) :D
Joe :-)
JLM Audio
Capturing Audio without Injury

ciscan.81
Posts: 24
Joined: Sat May 26, 2012 8:33 am

Re: Which JLM Preamp Kit Is For Me?

Post by ciscan.81 »

Hi Joe

Many thanks for your reply.
2. Is it possible to put some sort of output trim pot/fader on a BA without adversely affecting the sound? (as on the 1290 and Dual99v) if so how?

You can run a 1k pot on the output of the BA but turning down the output will reduce headroom and increases output impedance. In reality you do not need it as with the pad on and minimum gain the BA is unity gain.
I was thinking that adding an output trim pot to dial down the output level would allow the opamp to be overdriven without clipping my interface's input...so basically driving the input hard to get a dirty sound and then dropping the output level down just before the XLR...or is that not achievable without a dual stage setup?

I was thinking something like this really nice BA build:

http://www.groupdiy.com/index.php?topic=33839.0

a quote from a PM from this GroupDIY user:
The output trim I used is just a standard log taper volume pot wired as a straight attenuator. It works much like a fader in a console. The only trick is that I wired the pot after the output transformer to keep the load consistent from the preamp to the transformer, and that means the output pot has to be a dual ganged pot to take both leads from the output transformer. And that's it really.
will a setup like that still encounter the problems you mentioned?

also from same user:
I think I used 25k dual ganged pots. It doesn't affect the sound quality other than attenuate the volume level. If you have the trim pot all the way full up, it goes completely out of circuit and leaves hte output signal unaffected.
so would something like this work (maybe different value?) or am I way off track?:

http://classicapi.com/catalog/product_i ... cts_id=254

Many thanks for your time and patience with all these questions!

With some luck I hope to be settled on an order this coming week....just wanting to explore my options fully before I dive in!

Thanks again

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Joe Malone
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Joined: Wed Jan 24, 2007 11:35 pm
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Re: Which JLM Preamp Kit Is For Me?

Post by Joe Malone »

I was thinking that adding an output trim pot to dial down the output level would allow the opamp to be overdriven without clipping my interface's input...so basically driving the input hard to get a dirty sound and then dropping the output level down just before the XLR...or is that not achievable without a dual stage setup?
A single 500ohm or 1k log output pot after the output transformer (if one is used) will work as long as you are aware of headroom and don't turn it down to far and that is will change the output impedance which will only show on vintage 600ohm input gear. Modern 10k input gear the impedance change will do very little. A single pot floating across the balanced output works fine or you can use a dual pot to make it all look fully symmetrical. Our variable impedance kit can be wired to do this and limit the range to say -20dB or -10dB. You do not need the true impedance 3 pot arrangement like in apiclassic.
With some luck I hope to be settled on an order this coming week....just wanting to explore my options fully before I dive in!
8) :D
Joe :-)
JLM Audio
Capturing Audio without Injury

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