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Stereo XLR Mic preamps For MD ( I am building some)

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I will post some pics , here , and Audio samples of my Mic preamps .

These will be XLR input x 2 -> 1/8 stereo output , for MD / DAT/ Flash Recorders etc .

These preamps will be about 150 US .

Without Phantom , you can use any Self powered Condenser Mic ( Has its OWN battery in it ) IE: AKG C1000 , Sony ECM series , Sennheiser stereo mics that are self powered . All Dynamic mics , Shure SM 57, 58 ......... Beyer Dynamics (I Love Beyer mics) A pair of M201 's would sound awesome with this preamp .

( For the moment I am removing the Phantom power option , The chip I need isnt available here in Japan for it , I have to find a different circuit )

The Caveat is , at the Moment until I can figure out why , When using a Remote with the RH1 , there is a fair amount of process noise from the Remote . Without the Remote the recording is quite clean

Samples ( you can really hear the difference between the RH1 and the Tascam , the RH1 is soo much more airy )

RH1 sample without Remote , sitting outside on the back , with two Sony ECM23F3 mics , at about 3 feet distance from me .

The RH1 files were uploaded as WAV , then to Final Vinyl , to trim the end off only no noise reduction at all , then To Switch MP3 Converter to 192( 160 for the ambient so it would fit the upload size) kbs MP3

Tascam DR-07 Mic input Test

same file Normalized in Audacity

post-101758-0-71564000-1297522368_thumb.

The Tascam was uploaded straight from the recorder , not edits

Specifications

Gain= 26 db fixed setting

S/N = -88 db ( very very quiet )

Power =1 x 9 Volt battery

input = XLR balanced , converted internal Balanced to Unbalanced for better shielding and noise rejection

Output = 1/4 inch stereo connector, use Headphone adapter (Supplied)for 1/8 inch

Impedance set for a weak mic input on a recorder , Home Multi Track , or Low Mic Gain on MD , Or Low Mic Gain on Flash Recorder such as Tascam DR-01 , DR-07 etc ) Sharp MD Recorders will benefit greatly from this preamp because I have always found the Sharps to a little noisy , this will clean it right up.

Pro Mics ........... With your MD !!

I can take Paypal , and will ship wherever from Japan , you pay shipping .

Shipping will be by EMS , insured and with tracking number

Edited by Guitarfxr
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Even with the remote's backlighting off?

Yeah sad to say , the remote was a bust , even tried the 11elk , noise was way less , but still there ( learned that I can adjust the record level from the 11elk !!!!)

What I think is , that I may need to use coupling capacitors on the output stage, because the residual voltage from the RH1 mic input . I will experiment with that . I will take it apart , and change a couple things on the circuit .

But it sounds really good as it is setup now . The Tascam doesnt quite record at accurate DB levels , so I could actually run a little Hotter on the Tascam , I will try that today .

The R50 is what I tested with first ( reasoning , not everyone is using the RH1 ) so an Older MD was first , and actually was a Very good union the first test was about 25 minutes of this and that , and I was really liking what I was hearing .

I am not quite done with the design , a couple improvements . but it is quite likable at this stage .

Edited by Guitarfxr
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Guitarfxr,

just wondering if there's any possibility of getting a unit like this to run off (lots of) AAs (perhaps with an external 'power pack')? Reason I ask is it's very hard to find 9V rechargeables (and I'm a 'reduce waste' freak who hates throwing out disposables, even if it's once a year).

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Guitarfxr,

just wondering if there's any possibility of getting a unit like this to run off (lots of) AAs (perhaps with an external 'power pack')? Reason I ask is it's very hard to find 9V rechargeables (and I'm a 'reduce waste' freak who hates throwing out disposables, even if it's once a year).

If you dont mind the Weight that would introduce ,The box would of course be sized to accept the AA's , but yeah I can build one that way .

Rechargeable AA's are 1.2 volts , so your looking at an 8 pack( 9.6 volts) ( 6 pack is only 7.2 volts ) and your battery life would be ........... um how should I say this ..................... About 1 galactic year or so ( provided the AA's dont self discharge before then )

Or I could MOD a standard one with a switchable DC Jack , so you can use an external pack , so when you plug in it shuts off the internal battery .

Edited by Guitarfxr
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250 views , and ..............

Wiz , I will continue working on the Remote issue , and If I fix that , I will email you .

Anyone with a 4 track recorder , You really need one of these . The improvement is substantial .

Edited by Guitarfxr
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Guitarfxr,

just wondering if there's any possibility of getting a unit like this to run off (lots of) AAs (perhaps with an external 'power pack')? Reason I ask is it's very hard to find 9V rechargeables (and I'm a 'reduce waste' freak who hates throwing out disposables, even if it's once a year).

Hey Tekdroid , I went to the shop where I buy the goods for these preamps , and They have a box and TWO , poptop AA holders which I can embed in the back of the case nicely

Case is 180 MM wide , vs the 150 of the design above , so it isnt that much bigger . But most definately doable . Just let me know

The case and Batt packs are a little extra , so I would have to include that in the budget

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I Did a test this morning , of the preamp I put together vs. the Presonus Stereo Blue Tube Preamp .

Sony MD4X 4 track , inputs 1 & 2 First from the Presonus , Using my Sony ECM23F3 condenser mic . I had just changed the Tube in the preamp and wanted to make sure it was working , I put a lesser gain tube in it , a 12AT7 , instead of the 12 AX7 , With the AX7 the Presonus is know to be a little noisy when you add the drive into the signal .

With the 12 AT7 noise was noticably less , output was better , and gain was smoother . But still some noise . I thought " Hmmm I wonder what this Homebuilt will sound like in comparison ( At this point I had not tried it with the Sony 4 track ) So I switched the cables , and Mic to My Preamp .

WOW , what a difference , the Noise level was NO WHERE NEAR the Presonus , way quieter , and good clean solid gain .

I will try to post some sample after the weekend , My Family is here so the house is noisy . tuesday I might have some time .

But seriously , if you have a 4 track , you need this preamp .

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Well I tested with the Yamaha Md4 track , and was pleasantly surprised by what I got out of it , Two mics to th preamp , direct from my guitar , so three channels .

The guitar was ALSO going thru a Mono version of these same preamps . Mic left , Guitar Center , Mic Right .

I was in audio heaven , Fat studio sound on a Budget . And very Clean .

I am also buggin for a Tivoli Model One Radio , if anyone wants to do some trading , ( The Japanese Version , the frequencies are different , the FM band is WAY narrower only goes up to a little over 90 mhz , the US version goes to 108 .

4121CAS45ML._AA280_.jpg

Edited by Guitarfxr
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768 views , ........ not one nibble .

Ok I will break it down this way

Here is my cost on these

1300 yen per channel for the preamp circuit . 2 channels = 2600 yen circuit parts alone

another 1350 yen for the Case , we are up to 3950 yen

Then the XLR connectors are 1250 yen each = 2500 yen

6450 yen so far

Output Jack is no cheapo garbage . 780 yen

Power switch = 800 yen

Battery popout 1850 yen ( From Yamaha Guitar distribution )

9880 yen Parts alone = then My time and tool work and I am only asking 150 and shipping .............?!?!

Interesting ...........

Edited by Guitarfxr
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