Simple scalable mic preamp
Simple scalable mic preamp
I'm realizing with my current recording setup, a console is rather unnecessary. I have an old 24 track Soundcraft 500, and I'm using 8 channels of it, just as mic preamps, I'm doing everything else in the box.
Rather than have the giant console, I'm wondering if I should just get a mic preamp unit, one of those 8 way affairs. I just need something that takes 8 XLR's in and outputs 8 1/4" TS with a gain or level on each channel. No phantom power, phase reversal or anything.
Coming from the less is more school, I want to build something super simple, like a couple of FET's or a single op-amp per channel. Any suggestions, already available kits or whatever?
Rather than have the giant console, I'm wondering if I should just get a mic preamp unit, one of those 8 way affairs. I just need something that takes 8 XLR's in and outputs 8 1/4" TS with a gain or level on each channel. No phantom power, phase reversal or anything.
Coming from the less is more school, I want to build something super simple, like a couple of FET's or a single op-amp per channel. Any suggestions, already available kits or whatever?
The previous statement is from a guy who records his own, and other projects for fun. No money is made.
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- mixes from purgatory
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The THAT 1510/1512 are probably the best bang for the buck, low parts count preamp chips around. Add a 1646 if you need a balanced output.
You could always wire a 5534 as a diff amp with gain...or build out the front end with more opamps (instrumentation amp config) or transistors (which is very close to your 500's pres).
Most fully discrete designs use a transformer on the front end - see the Hamptone JFET design. Transformers are great for low parts count, but not so great for low cost.
Maybe I should revive my doorbell transformer preamp...
You could always wire a 5534 as a diff amp with gain...or build out the front end with more opamps (instrumentation amp config) or transistors (which is very close to your 500's pres).
Most fully discrete designs use a transformer on the front end - see the Hamptone JFET design. Transformers are great for low parts count, but not so great for low cost.
Maybe I should revive my doorbell transformer preamp...
"What fer?"
"Cat fur, to make kitten britches."
"Cat fur, to make kitten britches."
I have an old Tapco 6200B, that has transformers on each input. It's too noisy and scratchy to use, but I imagine the xfmrs are usable.
I had been looking at a wchematic with the 5332, which is just a pair of 5334's right?
I had been looking at a wchematic with the 5332, which is just a pair of 5334's right?
The previous statement is from a guy who records his own, and other projects for fun. No money is made.
Dunno, google images.
It looks like a differential amp, so they'd be gain setting, or at least R6 in ratio with R3 would be.
Hmm R5 would have to equal R6 to equal the balance on both sides.
Don't know how large you could make them for gain, guess it would depend on the device.
It looks like a differential amp, so they'd be gain setting, or at least R6 in ratio with R3 would be.
Hmm R5 would have to equal R6 to equal the balance on both sides.
Don't know how large you could make them for gain, guess it would depend on the device.
The previous statement is from a guy who records his own, and other projects for fun. No money is made.
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- tinnitus
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If you layout for those mic preamp chips you can also use the Audio Upgrades PIP module. That is a hybrid/discrete mic preamp fitted on a 7/8" square pcb that plugs into the SSM2017/2019/INA217 and THAT 1510 layouts.The Scum wrote:The THAT 1510/1512 are probably the best bang for the buck, low parts count preamp chips around. Add a 1646 if you need a balanced output.
It features a super low -133 db EIN at 50 ohms source impedance, a 60v us slew rate, 50 ma output current and .0005% THD, .00015% IMD. None of the current mic pre chips can approach those specs.
If you want higher performance I also have the High Speed mic preamp cards for $175. It is by far the world's fastest mic preamp with a 7000V/us slew rate, 110 ma output current (drives 150 ohm loads easily) -133 db EIN and .00012% IMD. Bandwidth is 30 mhz and bandwidth is maintained up to +60 db gain. It is an all current feedback design.
Sonically it sounds much more like my tube designs than anything solid state. The current feedback design features low odd harmonic partials and soft clips unlike any transistor designs. The clipping produces mostly 2nd harmonics and the waveforms have rounded edges, sort of like tubes.
Jim Williams
Audio Upgrades
Audio Upgrades
Really what I'm doing is spitballing ideas, and seeing if anyone says, oh there's this super simple circuit you can try, or hey the FLAPDAP1865 is a perfect chip for this
I'm just looking to reclaims some space, I might just get something like one of those Nady boxes, but I figured for the same price, or less, it might be easier to get 8 XLRs, 8 1/.4"s, 8 pots and 8 FET's or op-amps or whatever and build something nice and clean, no extra bells or whistles. Then I can put the console back in it's roadcase, until my setup expands enough to require it
Not set on anything except simplicity, I mean with the transformers I can get say 8 x 12AU7 and go tube, long as I can source a transformer that will supply that kind of heater current.
Just looking for peoples favourite ideas really.
**EDIT Sorry Jim, I was writing this post while you posted yours, this was not a response to that, I will check it out.**
I'm just looking to reclaims some space, I might just get something like one of those Nady boxes, but I figured for the same price, or less, it might be easier to get 8 XLRs, 8 1/.4"s, 8 pots and 8 FET's or op-amps or whatever and build something nice and clean, no extra bells or whistles. Then I can put the console back in it's roadcase, until my setup expands enough to require it
Not set on anything except simplicity, I mean with the transformers I can get say 8 x 12AU7 and go tube, long as I can source a transformer that will supply that kind of heater current.
Just looking for peoples favourite ideas really.
**EDIT Sorry Jim, I was writing this post while you posted yours, this was not a response to that, I will check it out.**
The previous statement is from a guy who records his own, and other projects for fun. No money is made.
- Nick Sevilla
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I would recommend getting some DIY 500 series preamps.
There is a whole thread here that has most if not all the 500 series manufacturers.
Getting some of those, you alleviate a lot of self build issues, and you get a lot of support from the builders as well as many people here who have built them.
And you can scale it up as you need to.
Cheers
There is a whole thread here that has most if not all the 500 series manufacturers.
Getting some of those, you alleviate a lot of self build issues, and you get a lot of support from the builders as well as many people here who have built them.
And you can scale it up as you need to.
Cheers
Howling at the neighbors. Hoping they have more mic cables.
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if you like lo-fi, get some transformers from edcor, use a couple common drain jfets or common emitter bjts as the gain elements (or just one if you don't need a lot of gain), stick an emitter follower after it, and impedance balance the output. cheap, easy & fun. i built one of these the other day (with p48, an input pad & transformer balanced output) and it sounds good:
if you want hi-fi the THAT chips are simple to implement and won't cost you more than what, $10 per channel.
if you want hi-fi the THAT chips are simple to implement and won't cost you more than what, $10 per channel.
I'm not atall sure how-fi I am
I think I'm more of a DIY 4-tracker soul, with a pawn store budget, which is where I got my 1010-LT which is my sole interface. The Soundcraft was from when I had thoughts of making a real studio, until I realized that was a lot of work and I probably didn't have the social skills
Nowadays, I keep the cover on the Soundcraft, and just turn it on, unless I'm moving mics around. In which case I'll solo each channel and then ignore it again. I have cats, they shed, a lot.
So the THAT sounds like a possibility, how sane would a tube version be? I'm thinking maybe a 12DW7, using the AX side for the gain stage, and the AU side for the output? Those little Fender reverb clone transformers have 3A of heater, which is more than enough for 8 tubes, not sure if the plate current will be super high? Use the Tapco transformers on the input.
I'm a lot better at scavenging and tweaking other designs from cookbooks and stuff as I am from doing something from scratch.
What were the Edcor transformers? According to the Service Manual these Tapco ones are 150ohm:600ohm
I think I'm more of a DIY 4-tracker soul, with a pawn store budget, which is where I got my 1010-LT which is my sole interface. The Soundcraft was from when I had thoughts of making a real studio, until I realized that was a lot of work and I probably didn't have the social skills
Nowadays, I keep the cover on the Soundcraft, and just turn it on, unless I'm moving mics around. In which case I'll solo each channel and then ignore it again. I have cats, they shed, a lot.
So the THAT sounds like a possibility, how sane would a tube version be? I'm thinking maybe a 12DW7, using the AX side for the gain stage, and the AU side for the output? Those little Fender reverb clone transformers have 3A of heater, which is more than enough for 8 tubes, not sure if the plate current will be super high? Use the Tapco transformers on the input.
I'm a lot better at scavenging and tweaking other designs from cookbooks and stuff as I am from doing something from scratch.
What were the Edcor transformers? According to the Service Manual these Tapco ones are 150ohm:600ohm
The previous statement is from a guy who records his own, and other projects for fun. No money is made.
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