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Post by wiz on Jul 29, 2013 19:07:31 GMT -6
I am designing and building a mic preamp.  Its based on the Texas Instruments INA217. Here is a zip file containing 4 tracks. dl.dropboxusercontent.com/u/13120658/Archive.zip Acoustic Guitar Track ( Maton Messiah, KM84 mic, JLM NV500 preamp.) and three tracks of the same vocal take. There are 3 SM57s set up next to each other , a pop screen about 4 inches out from them, then my cakehole. The aif files are labelled as to what they are, you can play hide the name yourself if you like. You can listen to them pre judged. I aint your momma!!! 8) The preamps were matched, Peak Level, as well as I could humanly possibly do. You can set the RMS level to what you like, how do I do that? I do it by picking a word in the first line, and then using VU meters and my ears. Why? because, each preamp behaves differently, and it will vary, depending on how close you want these things, that can matter or not depending on your anal retentativity. I suggest import all into your DAW of choice, and you can mute and solo, and compress and add reverb to your hearts content. The only thing I ask is this... dont write about how the test is flawed. Its the best I can do. I dont care if your uncle worked for NASA's department of anal retentive shoot out test knocking dunderheads. You want a better controlled test done.. you do it. 8) My preamp, vs two commercially available ones thru SM57s , into RME UCX. Thats what this test is for. I am slowly making changes to my preamp design, to see how well I can make it. Its for my own enjoyment and interest I have no interest in doing this commercially. why did I use SM57s? Cause they are the only mics I have that I have more than two of the same model. cheers Wiz |
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Post by jimwilliams on Jul 30, 2013 10:11:15 GMT -6
You can check self noise by wiring a 150 ohm metal film resistor inside an XLR connector from pin 2 to pin 3. That eliminates mic noise, acoustic noise, etc.
There are also several variants to those chips that are pin compatible. There is the original discontinued SSM2017, the improved replacement, the Analog Devices SSM2019 (my fav of the chips) and the that Corp. 1510. Get that one from Mouser. You can sign up at Anlog device web site and get free samples of the SSM2019. Same with TI and BurrBrown.
The low cost kit from SCA also has balanced output drivers and some DC servos to eliminate some electrolytic blocking caps, a good platform to 'experiment'.
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Post by wiz on Jul 30, 2013 14:55:25 GMT -6
Hi Jim
I did in fact measure the noise how you have suggested with the 150 ohm resistor and was very very impressed.
I will look into every one of your suggestions, thank you.
Is your PiIP available?
I am about to start substituting out the few discrete components I have , with quality versions and seeing what difference it makes to the sound.
I also have a OEP tranny coming for the input to try.
I am taking it slow, with the object being fun and learning.
Thanks again.
Cheers
Wiz
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Post by Johnkenn on Jul 30, 2013 16:05:46 GMT -6
You're talking to a total dummy here...but isn't this similar to preamps in the stuff like the Apollo and MR816? I though the pres in both of those units were actually pretty damn good.
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Post by wiz on Jul 30, 2013 16:13:15 GMT -6
Hey John
in some ways, I guess.
What this is, is a IC that is basically a preamp inside it. In the older days, there would have been quite a few discrete components, things like transistors and resistors and capacitors, that are now all inside that chip.
You build a power supply and put a few components around the chip, and you have a microphone preamplifier.
The chip I have used, INA217, is used in quite a few commercially available preamps.
Its not like I am breaking any new ground here ... 8)
But, I am interested (and I have some down time from playing due to post shoulder surgery issues) and its been quite revealing, putting up something that has cost me peanuts, against preamps I have that are worth thousands of dollars.
I suggest loading those files I provided into a daw and having a listen. 8)
I can see, that I might, if I sonically get where I want to go, construct these to replace all my other preamps. Or at the very least replace a number of them and keep a couple of specific ones for specific tasks.
But, as I said, its more about enjoyment and learning.
hope that cleared some of it up.
cheers
Wiz
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Post by jimwilliams on Jul 31, 2013 9:45:35 GMT -6
The first version of these IC mic preamp chips was the SSM2015 made by Dan Parks of SSM audio back in the early 1980's. That was used in the Symetrix SX202 and many others. It was replaced by the SSM2016, used by AMEK in the 2520 console. SSM was bought by PMI and later sold to Analog Devices. Dan has long since left but his SSM brand lives on with the SSM2017 and the newer SSM2019.
I make the PIP here, the "Plug in Preamp". It's a small pcb with 20+ discrete parts made to sub those chip preamps. It does have superior noise, THD and bandwidth specs and slew rate is much higher. These are much lower noise than a 150 ohm resistor residing at -132 db EIN at 50 ohms.
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Post by wiz on Jul 31, 2013 15:52:47 GMT -6
Thanks Jim
Expect a phone call from someone with a weird Aussie accent 8)
Cheers
Wiz
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Post by dandeurloo on Aug 2, 2013 10:17:39 GMT -6
Jim, I want to hear your pre amp. Have you ever heard a Buzz MA 2.2? It's a great mic pre and I would love to hear yours compared to it. I think they probably are aiming in the same direction. Thoughts!
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Post by wiz on Aug 2, 2013 16:17:02 GMT -6
I have one Jims PIP on the way, I can't wait to give it a try.
I have incorporateded a transformer on the input of my preamp and I am liking it...
Cheers
Wiz
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Post by wiz on Aug 8, 2013 19:10:34 GMT -6
I had a sample of the SSM2019 arrive this morning.
I plugged it an and did a quick vocal and then redid the vocal with the INA217. So its not exactly scientific.
But I hear a difference. I like the sound sound of the SSM2019. it would end up being source dependant I think.
I was surprised actually by the difference in sonics, I dont know why I was surprised, but I was 8)
I am still waiting on Jims PIP, and cant wait to give it a try.
Can we move this thread to the DIY section?
cheers
Wiz
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Post by tonycamphd on Aug 8, 2013 19:14:31 GMT -6
good idea wiz, i'll pm JK
T
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Post by svart on Aug 9, 2013 7:44:21 GMT -6
I've tried all of those IC preamps. Pretty good workhorse preamps. Not a lot of mojo or much else. Just clean audio.
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Post by wiz on Aug 9, 2013 16:09:32 GMT -6
I ain't done yet.. 8)
I will say this, I have been really, really surprised at how good these things can sound , when in a minimalist state with a good power supply. I got a ways to go yet, but it's been very revealing.....particularly when you start blind testing 8)
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Post by dandeurloo on Aug 10, 2013 3:23:30 GMT -6
What are you hoping for out of the pre? Cheap an clean? General purpose or single application in mind?
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Post by wiz on Aug 10, 2013 4:01:12 GMT -6
What are you hoping for out of the pre? Cheap an clean? General purpose or single application in mind? Really I am kind of just passing time. i had surgery on my shouder in April. I then developed what they call frozen shoulder. I haven't played since Jan. So I am doing this in an effort to stay kind of sane and put my enforced time off to some good use.... 8). It's more about interest and seeing how close I can get to my PRO preamps... What effects things like tranny's have etc. I am thinking ATM that its not that far fetched that I might end up building some of hese for specific tasks. i am also going to be doing the same sort of things with mics. |
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Post by dandeurloo on Aug 10, 2013 4:20:40 GMT -6
My guess is you will find a preamp sound you will really like for a specific task. Which is great. I have a few things that I have built with one thing in mind and found out that it wasn't great at that, but ended up being great for something else. So in the end, well worth the effort.
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Post by category5 on Aug 26, 2013 0:10:30 GMT -6
Hey Wiz, give the THAT 1510 a try. It's pin compatible with the other chips you're messing with and possibly the best of the bunch. The 1512 has improved noise specs over all of them but requires slightly different gain resistor values. It's amazing how good these ICs are getting. Pres like the Grace and DAV BG1 enjoy reputations alongside much more prestigious mic amps, and they're really just simple circuits based around these chips masquerading as innovative designs.
For clean gain feeding an AD converter they are super! Heck, I'm a bog fan of the PGA2500 used in the UFX and Apollo as well.
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Post by wiz on Aug 26, 2013 3:49:56 GMT -6
Hi Cat
I actually have a 1510 on order 8)
Jim Williams PIP is a real winner.
Cheers
Wiz
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Post by dandeurloo on Aug 26, 2013 9:15:16 GMT -6
Jim knows his stuff. Not many do affordable & clean better then Jim!
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