that 1512 or similar preamp
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Tony Ramone
Member
Ha Ha, I was just about to do the same thing 
Well, I built myself a test version of the very basic circuit shown in the datasheet on perfboard, and was amazed that I actually managed to get it to work.
Granted there's a bit of noise on the output signal, which could be coming from just about anywhere - when I tested it, I had the board sitting on the table next to my laptop, with the open power supply right next to it (the most likely source, I'm guessing), and I didn't bother coupling the output, just took the signal directly from the output pin on the chip.
But, hey, at least it's a starting point. Now I just need to figure out how to tweak the design for best results.
First thing I know I need are proper gain pots - the one I used was off a guitar, so it was 500k instead of 10k, so there's almost no gain change until the last millimeter or so of a turn (even with a 10k resistor strapped on in parallel *cringe*), at which point you jump into insane distortion
Btw I used a +/- 12V supply I found at work so I suppose there's slightly less headroom. Now that I know it works though, I can look into getting a proper +/- 15V supply of my own, preferably one with a cage
Well, I built myself a test version of the very basic circuit shown in the datasheet on perfboard, and was amazed that I actually managed to get it to work.
Granted there's a bit of noise on the output signal, which could be coming from just about anywhere - when I tested it, I had the board sitting on the table next to my laptop, with the open power supply right next to it (the most likely source, I'm guessing), and I didn't bother coupling the output, just took the signal directly from the output pin on the chip.
But, hey, at least it's a starting point. Now I just need to figure out how to tweak the design for best results.
First thing I know I need are proper gain pots - the one I used was off a guitar, so it was 500k instead of 10k, so there's almost no gain change until the last millimeter or so of a turn (even with a 10k resistor strapped on in parallel *cringe*), at which point you jump into insane distortion
Btw I used a +/- 12V supply I found at work so I suppose there's slightly less headroom. Now that I know it works though, I can look into getting a proper +/- 15V supply of my own, preferably one with a cage
gemini86
Well-known member
quick question to those who would know...
After looking at all the literature for the 1510/12 ICs, I see it states that the 1512 has a 0dB output at 10Kohm RG, between pins 1 and 8, (and the IC's minimum output is -6dB with pins 1 and 8 open) the demo board schematic shows 60dB at 4R99 Ohms RG, so am I right to think I could use a 4r99 resistor in series with a 10kohm pot, and if I felt it would be of any use, add a switch to set RG to open (or infinity) to have a -6dB gain reduction?
(noob alert, guys...please be gentle!)
I got to talking to the THAT corp guys at the AES convention in SF.... really knowledgeable reps...
After looking at all the literature for the 1510/12 ICs, I see it states that the 1512 has a 0dB output at 10Kohm RG, between pins 1 and 8, (and the IC's minimum output is -6dB with pins 1 and 8 open) the demo board schematic shows 60dB at 4R99 Ohms RG, so am I right to think I could use a 4r99 resistor in series with a 10kohm pot, and if I felt it would be of any use, add a switch to set RG to open (or infinity) to have a -6dB gain reduction?
(noob alert, guys...please be gentle!
)I got to talking to the THAT corp guys at the AES convention in SF.... really knowledgeable reps...
When I built mine I tested several configurations, and the most useful was a 500-ohm linear taper pot in series with a 5-ohm fixed resistor (unless you really think you'll need less than 20 dB of gain).
You want a 47-ohm metal film resistor in series with the output. You also want the phantom-power protection circuitry of Figure 4 of the data sheet, even if yours doesn't provide phantom power (I use external phantom power supplies with mine). At minimum you should use the four diodes from Figure 4 as well as R3 and R4. I power mine with a pair of 9-volt batteries to avoid power supply issues and to make it portable.
You also want to build it on a circuit board with a ground plane, such as the Twin Industries 8100-45. Mine had a very, very low-level 60 Hz hum in it, and it was recommended to me to use the Twin Industries board.
I love mine. It has served me well and sounds great -- quite impartial.
You want a 47-ohm metal film resistor in series with the output. You also want the phantom-power protection circuitry of Figure 4 of the data sheet, even if yours doesn't provide phantom power (I use external phantom power supplies with mine). At minimum you should use the four diodes from Figure 4 as well as R3 and R4. I power mine with a pair of 9-volt batteries to avoid power supply issues and to make it portable.
You also want to build it on a circuit board with a ground plane, such as the Twin Industries 8100-45. Mine had a very, very low-level 60 Hz hum in it, and it was recommended to me to use the Twin Industries board.
I love mine. It has served me well and sounds great -- quite impartial.
Wayne Kirkwood, beloved former member here, has his own forum.
There many schematics over there, but no "official" circuit boards for the 1510/1512.
Recently, I started a thread over there, about a "simple" 1510 or 1512 mic pre circuit. I will be building it point-to-point, on perfboard.
Here is the link...
http://www.ka-electronics.com/forum/php/viewtopic.php?f=7&t=222&start=0&sid=ec81b9de2d644e6f44af1ea125350e72
=FB=
There many schematics over there, but no "official" circuit boards for the 1510/1512.
Recently, I started a thread over there, about a "simple" 1510 or 1512 mic pre circuit. I will be building it point-to-point, on perfboard.
Here is the link...
http://www.ka-electronics.com/forum/php/viewtopic.php?f=7&t=222&start=0&sid=ec81b9de2d644e6f44af1ea125350e72
=FB=
bxt403
Well-known member
Since this place is all about DIY, there ought to be plenty-o-ppl who might be comfortable with SMT soldering: the Rane MS-1B can accept the THAT 1512 (although I had to reverse the signal LED for my Rane).
I've modded my MS1-B...however I should note that the signal LED (that turns green with a signal present and turns red when clipping with the BB INA163) changed to only lighting green when the signal is clipping. I reversed the LED and it lights red when clipping (still nothing otherwise). I think it has to do with the fact the BB's have a "sense" pin which is unused on the THAT 151x.
My Rane:
From what I've read from the tech notes from THAT, the 1512 can directly replace an BB INA163 and the 1510 is meant to replace the BB INA217.
Personally I would reccommend a pre that also incorporates the THAT 1646 since it's suppose to emulate certain properties of an audio transformer, as well:
The Five Fish Sc-1mk2 with the trafo option is a definite sleeper and is the reason I decided to return the Daking Mic Pre One I had special ordered. BOTH incorporate mic input trafos, and 1646's. I dunno, the SC1 was just less harsh (even after I took out the trafo) than the Daking (which I can best describe as sounding annoying to my ears). I was testing with a guitar through a wah pedal, still; I wasn't as impressed with the Daking as I was with the Five Fish kit. Price wise, it's a no-brainer. What I found most shocking was the SC-1 (even without the transformer) was more pleasant to my ears than the Daking. I've heard that Daking is one of those pieces that you either like or hate..I think it's obvious what I think of the Daking...
As for the Five Fish Studios' pre. I like it better than the Seventh Circle Audio T15, since the Five Fish allows for a transformer to be installed. I think the T15 is a much better deal if you're not concerned about having the option to install a transformer at the input. I built and sold some T15's last year...I'll try to find the sample file for it, and share some files of the SC-1mk2 (without trafo), and the modded Rane- so y'all can get an idea of what I mean about the added benefit of having the 1646 with the 1510/1512.
I guess THAT's all I have to share about THAT. :-\
I've modded my MS1-B...however I should note that the signal LED (that turns green with a signal present and turns red when clipping with the BB INA163) changed to only lighting green when the signal is clipping. I reversed the LED and it lights red when clipping (still nothing otherwise). I think it has to do with the fact the BB's have a "sense" pin which is unused on the THAT 151x.
My Rane:
From what I've read from the tech notes from THAT, the 1512 can directly replace an BB INA163 and the 1510 is meant to replace the BB INA217.
Personally I would reccommend a pre that also incorporates the THAT 1646 since it's suppose to emulate certain properties of an audio transformer, as well:
The Five Fish Sc-1mk2 with the trafo option is a definite sleeper and is the reason I decided to return the Daking Mic Pre One I had special ordered. BOTH incorporate mic input trafos, and 1646's. I dunno, the SC1 was just less harsh (even after I took out the trafo) than the Daking (which I can best describe as sounding annoying to my ears). I was testing with a guitar through a wah pedal, still; I wasn't as impressed with the Daking as I was with the Five Fish kit. Price wise, it's a no-brainer. What I found most shocking was the SC-1 (even without the transformer) was more pleasant to my ears than the Daking. I've heard that Daking is one of those pieces that you either like or hate..I think it's obvious what I think of the Daking...
As for the Five Fish Studios' pre. I like it better than the Seventh Circle Audio T15, since the Five Fish allows for a transformer to be installed. I think the T15 is a much better deal if you're not concerned about having the option to install a transformer at the input. I built and sold some T15's last year...I'll try to find the sample file for it, and share some files of the SC-1mk2 (without trafo), and the modded Rane- so y'all can get an idea of what I mean about the added benefit of having the 1646 with the 1510/1512.
I guess THAT's all I have to share about THAT. :-\
Hi, I'm thinking about building 8 channels of these, so I wanted to bump with a few questions.
First of all thanks for the tip of building on a ground-planed perf board for noise performance.
I was wondering what modification would be need to made to this circuit in order to add an input transformer like the CMMI-10PCA, JT-115K-E, EA 2622, etc. And which was it that the Five Fish uses standard? I saw in the build .pdf of the SC-1 to add a single resistor to somehow allow phantom power past the input transformer (I would need a drawing to help me out with understanding this). I guess I could just copy the old 3124 schematic, regarding phantom power. Also would the input section of the circuit need to be changed at all due to different impedance and such? Zobel networks need to be added?
I can't decide whether this is my super-budget utility preamp, or to spruce it half way up to fancy with nice input transformers and maybe want to use them more.. has anyone made this comparison? I think I'll just do half and half, for different sound options.
Has anyone gotten picky about capacitor choices in these?
My last question is which power supply is recommended? I've looked at JLM's AC/DC and the Five Fish 1U high PSU, I'm also open to stripboard, perfboard, or otherwise DIY options. How much current do these THAT channels draw?
pretty excited about this project! I'll be doubling my channel count, wow.
First of all thanks for the tip of building on a ground-planed perf board for noise performance.
I was wondering what modification would be need to made to this circuit in order to add an input transformer like the CMMI-10PCA, JT-115K-E, EA 2622, etc. And which was it that the Five Fish uses standard? I saw in the build .pdf of the SC-1 to add a single resistor to somehow allow phantom power past the input transformer (I would need a drawing to help me out with understanding this). I guess I could just copy the old 3124 schematic, regarding phantom power. Also would the input section of the circuit need to be changed at all due to different impedance and such? Zobel networks need to be added?
I can't decide whether this is my super-budget utility preamp, or to spruce it half way up to fancy with nice input transformers and maybe want to use them more.. has anyone made this comparison? I think I'll just do half and half, for different sound options.
Has anyone gotten picky about capacitor choices in these?
My last question is which power supply is recommended? I've looked at JLM's AC/DC and the Five Fish 1U high PSU, I'm also open to stripboard, perfboard, or otherwise DIY options. How much current do these THAT channels draw?
pretty excited about this project! I'll be doubling my channel count, wow.
Meathands
Well-known member
I built a unit with 8 of these a couple years ago--now my go-to mobile rig (http://www.petersongoodwyn.com/category/diyer/).
The 1512 includes a differential receiver circuit, which makes an input transformer a bit redundant. The output of the 1512, however, is single-ended so you could use a nice 1:1 or 1:2 transformer to balance it. I used the THAT1646 line drivers.
Regarding the PSU, check out the 1512 datasheet (http://www.thatcorp.com/datashts/THAT_1510-1512_Datasheet.pdf), current draw should be below 10mA each. Most power supply kits will be overkill for 8 of these, which is fine and dandy.
THATcorp has done most of the hard work for you with these chips and their app notes / datasheets. Where you're skills and patience are going to be put to the test (at least mine were) is implementing the proper grounding scheme.
Best of luck!
The 1512 includes a differential receiver circuit, which makes an input transformer a bit redundant. The output of the 1512, however, is single-ended so you could use a nice 1:1 or 1:2 transformer to balance it. I used the THAT1646 line drivers.
Regarding the PSU, check out the 1512 datasheet (http://www.thatcorp.com/datashts/THAT_1510-1512_Datasheet.pdf), current draw should be below 10mA each. Most power supply kits will be overkill for 8 of these, which is fine and dandy.
THATcorp has done most of the hard work for you with these chips and their app notes / datasheets. Where you're skills and patience are going to be put to the test (at least mine were) is implementing the proper grounding scheme.
Best of luck!
Any tips on the best grounding schemes you've devised? That would be very helpful.
I like your wood panel!
Regarding input transformers, I'm mainly wanting to do half with those for sonic variation, more than technical advantage. From first hand experience with and without them, and from reviews from other users, I am interested in the coloration an input transformer will provide as a variation from the transformerless channels. I am considering a Jensen just because I've never used those. I have had great luck with Cinemag, also. What modifications would I need to make to the THAT or SCA T15 schematic to add an input transformer? If anyone's feeling especially charitable and has a graphics editing program, the T15 schematic is the one I'd like to most closely follow. I'm guessing you could get rid of the inductors at the input with the addition of a transformer?
I feel like I'm getting close to a final design, how exciting!
I like your wood panel!
Regarding input transformers, I'm mainly wanting to do half with those for sonic variation, more than technical advantage. From first hand experience with and without them, and from reviews from other users, I am interested in the coloration an input transformer will provide as a variation from the transformerless channels. I am considering a Jensen just because I've never used those. I have had great luck with Cinemag, also. What modifications would I need to make to the THAT or SCA T15 schematic to add an input transformer? If anyone's feeling especially charitable and has a graphics editing program, the T15 schematic is the one I'd like to most closely follow. I'm guessing you could get rid of the inductors at the input with the addition of a transformer?
I feel like I'm getting close to a final design, how exciting!
Meathands
Well-known member
monkeyxx said:
The major things I learned about grounding from this project were to attach the sleeve pins of ins and outs to the case at their point of entry, and connecting the signal commons and chassis ground wires in one place only near the mains power entrance (star grounding).
monkeyxx said:
I totally understand the desire for transformers, but why not kill two birds with one stone and use an output transformer in lieu of the line driver?
The inductors on the input are ferrite beads to suppress high-frequency noise. I'm not if an input transformer would perform the same duties? I guess perhaps if the primary or secondary inductance was similar to the ferrites?
Have you considered the Eden preamp? its got all the basics of a Burr Brown ina163 preamp and a balanced line driver. It comes assembled and tested on one pcb. Theres plenty of opportunity to mod your own front end too...
I'm clearly biased (i'm part of expat audio, and i work for ti/bb by day). - but youe request really seems like a simple home run in this case.
Cheers
/R
I'm clearly biased (i'm part of expat audio, and i work for ti/bb by day). - but youe request really seems like a simple home run in this case.
Cheers
/R
monkeyxx said:
How many channels do you need? I think you'll be very pleased with the results on a 4ch setup. (and the price per channel drops quickly!)
In addition, don't forget that the board comes assembled and tested. That's an instant bonus on a complete diy
(thats why it costs more than the sum of individual components!)
I'm kind of looking forward to building this thing from scratch. I want to see if I can pull off a high end hi fi build on stripboard or perfboard, that would really amuse me. I need 8 channels.
regarding the Uber power supply can it go as high as 18 or 20 V or is 15V the limit on the + and - rails? the price on this PCB and mouser parts is very attractive
regarding the Uber power supply can it go as high as 18 or 20 V or is 15V the limit on the + and - rails? the price on this PCB and mouser parts is very attractive
hazel
Well-known member
Hi monkeyxx!!!
i've just finished my 1u 8 channel 1512 preamp and sounds great!!!!
my main goal was to have perfect stereo matching due to nature of my recordings (mainly jazz and classical stuff), so i put 12 step switches for selecting gain (from 0 to 60dB) and added this for balance signal and output level control: http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=118
PSU i use this: http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=12
and got PCB's from Dantimax, great guy and great products!!!
http://electronics.dantimax.dk/Kits/Preamps_-_poweramps/index.html
sounds transparent and neutral, no color at all, only room and microphone!
Hope it helps!!!!
i've just finished my 1u 8 channel 1512 preamp and sounds great!!!!
my main goal was to have perfect stereo matching due to nature of my recordings (mainly jazz and classical stuff), so i put 12 step switches for selecting gain (from 0 to 60dB) and added this for balance signal and output level control: http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=118
PSU i use this: http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=12
and got PCB's from Dantimax, great guy and great products!!!
http://electronics.dantimax.dk/Kits/Preamps_-_poweramps/index.html
sounds transparent and neutral, no color at all, only room and microphone!
Hope it helps!!!!
The uber PSU takes its output from whatever fixed voltage regulators you use.
The +15V is generated by a 7815, +18V can be generated by a 7818. Not sure if there are higher ones.
/R
The +15V is generated by a 7815, +18V can be generated by a 7818. Not sure if there are higher ones.
/R
monkeyxx said:
Adding a transformer to a transformerless preamp involves removing the "less" 8)
But seriously why? A lot of effort has gone into optimizing noise (both input noise voltage and noise current) for the direct connection to low impedance microphones. Transformer input preamps OTOH, use the transformer to "transform" that source impedance up higher to get decent S/N with noisier active electronics.
In general you can't have too little noise voltage, but that lower voltage often comes with higher noise current, which multiplies times the increased source impedance due to transformer action and may no longer be optimal.
If you just want the transformer for a distortion effect the noise is not a big deal deal, but if you are trying for superior performance you are fixing the same problem twice, which slightly un-fixes it.
JR
Meathands
Well-known member
monkeyxx said:
To echo JR, to add an input transformer is redundant before a 1512. I understand that FiveFish does this, I'd be interested in seeing how/why.
But to return to my previous suggestion, why not try an output transformer is you are looking for some of that sound? This has the added benefit of serving a purpose in the circuit that is not addressed by the 1512.
Meathands said:
This is a great suggestion! The oitput of the that ic, and the ti equivelent is single ended... It'll need conversion to balanced - a tranformer is a fine way. I prefer an ic... But then, i'm biased.
