low budget cheapskate recording tips

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low budget cheapskate recording tips

Postby dai h. » Fri Jul 30, 2010 12:12 pm

This isn't a clip, but related (to accomplishing them) so I'm putting this here (Brian, please go ahead and move this if not well placed).

Anyway thought I would begin a thread for any sorts of tips on recording for the budget minded. I suppose they don't absolutely have to be cheapskate-oriented but things with good price to performance, price to value, etc.

To start, something I discovered with the classic, ubiquitous, highly destruct-proof classic Shure SM57 and 58 (well I suppose the 58 is more abuse-proof but I'm grouping them since the tip applies to both AFAIK). Simply put, there apparently needs to be an awareness with the load that these mics are plugged into, since the load the outputs see can affect the frequency response in a negative way since the 57/58 contains a transformer. The easy way to adjust the load is to use a resistor. Another way is to use a transformer. Say if you have a 10k (input impedance) mic input, use a 150 ohm to 10k input transformer (I don't think there needs to be exact matching but relative matching within a range).
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One thing I suspect that could be happening (reading threads here and there) is that people buy an SM57, then use it with a preamp that has an excessively high load impedance for the SM57/58 (say, 2.5k, 3k...10k, etc. from a cursory search looking up specs on Mackie, Behringer, Yamaha mixers, etc. has told me), then get a poor result, concluding that somehow the SM57 is a crappy mic. Then, they buy a condenser (maybe they think they need to spend more money, or perhaps from word of mouth recommendations) which wants to see that higher input impedance (and works better that way) and get a better result reinforcing the conclusion that (despite being used on countless recordings of which they may own many) somehow the SM57 is a crappy mic or just isn't working for them. And also, typically that condenser mic is going to have a greater output (and be louder for the same gain setting), and a louder signal (when comparing two) can cue the brain into thinking the louder one is better (could be another factor as well).
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For more reading:

"Mic Loading Confusion" thread at prodigy pro bbs:
http://www.prodigy-pro.com/diy/index.ph ... #msg317995

"Tube Mic Pre Input Impedance" thread@Group DIY (formerly prodigy pro bbs) :
http://www.groupdiy.com/drawing-board/t ... impedance/

(I'm getting a "this site may harm your computer" message when I plug this link into google, so I've copy/pasted the article below until whatever is going on with the Recordingmag.com site is sorted. Update: looks like the site is fixed so I've deleted the article.)
"Shure SM57 Impedance Modification" article at Recording Magazine:
http://www.recordingmag.com/resources/r ... l/330.html

Jensen AN-005 Theory and Construction of Mic "Splitters"(112KB PDF) by Bill Whitlock(see page 2)
http://www.jensen-transformers.com/an/an005.pdf

Impedance matching of mics with pres? thread at rec.audio.pro
http://groups.google.com/group/rec.audi ... scoring=d&

edit:

and also, check the SM57 datasheet (courtesy of David B.) here:

http://music-electronics-forum.com/t11561/

adding more links:

What is "nominal" or "rated" impedance? See "Microphones" section of wiki article:

http://en.wikipedia.org/wiki/Nominal_impedance
------------------
(check out pp.601-603.)
http://books.google.com/books?id=y0d9VA ... &q&f=false
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diassembly and some tech. specs for the transformer (which seem to agree with the data in the google books link:

http://www.prodigy-pro.com/diy/index.php?topic=14541.80

Pri- DCR - 1.50 ohms L = 386 mH Leakage - 150 uH
Sec- DCR - 24.18 Ohms L = 7.95 H Leakage - 4.26 mH

Impedance Ratio: 1:20.6
Turns Ratio: 1:4.53


so overall internal impedance = ((capsule DCR+pri.winding DCR)*impedance ratio)+sec.DCR=302.1ohms which appears to agree with "300ohms +6mH" from the book and "310 ohms actual" figure from Shure, so I guess on the higher end of a "150 ohm rated impedance"(75-300ohms).

reference (Sorry. This is in Japanese) :

http://www2.famille.ne.jp/~teddy/pre/pre3e.htm

---------------------------------------------

http://www.jensen-transformers.com/an/A ... hapter.pdf (page 11)

--------------------------------------------

http://recording.org/tech-talk/43821-de ... c-pre.html

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http://recording.org/tech-talk/44493-te ... post343373

Neumann definition:

Rated impedance - The rated impedance is the complex output resistance of the microphone. The input impedance of the following microphone pre-amplifier should be at least three times higher.

Rated load impedance - The rated load impedance is the smallest recommended impedance of the following microphone pre-amplifier to ensure the nominal values of the microphone. The rated load impedance should always be at least three times higher than the rated impedance of the microphone.


Summit Audio mic pre 2BA-221 (which has a variable impedance knob which appears to be a variable resistance) manual gives recommendation that "(l)oading impedance should be approximately four times the microphone output impedance listed below") in a manual:

http://www.summitaudio.com/manual.php?m=2ba-221

(The listed impedance for the SM57/58 is the rated impedance of 150ohms.)

Summit expounds on this a bit more in their FAQ section re: the 2BA-221:

http://pub40.bravenet.com/faq/show.php? ... id=9432#q6

2BA-221 Basic Set Up and User Guide

Choosing the right mic input impedance: Inside the manual is a basic list of microphones and their corresponding output impedance. Generally, mics are looking for AT LEAST four times their output impedance value. In general, turn the impedance control all the way up to 10k Ohms to start with and turn the impedance down to get the sound you desire or for an effect. You can get a lot of different tones with some microphones this way. Some microphones are impervious to the preamp's impedance; check their manual for details.


According to this source (which I think makes sense), 1x or 2x the impedance (not clear if he is talking about rated or actual) should give the most neutral response. Then, as the terminating impedance goes higher, the highs should become more lively. Then, beyond that at some point the negative sonic effects of the sort described in the Recording Mag article should come into play. (I think I should note though that from an artistic standpoint, even if something sounds conventionally "bad", this may be exactly what someone wants in a situation, so from the standpoint of art, I don't think "staying within x3 or x4 the impedance, etc." has to be an absolute ironclad rule. And also, notice that in one of the Prodigy Pro threads, there is someone who disagrees.)

reference (in Japanese) :

http://www.geocities.jp/brabecaudio/amp/techinf4.htm

When choosing to terminate with not a particularly high value/multiple range, there could be a problem with noise (hiss), since the heavier the load (that is, the lower the value of the load), the less signal you get out of the mic. This may not present any problem with a loud source (loud guitar amp cab, drums, etc.) but perhaps say, for vocals you might want more noise free gain. That can be where a transformer comes in, since one with a high step up ratio will allow you to obtain a higher signal voltage out of the mic, and this means the mic preamp gain won't need to be set as high and that should help overcome hiss. But again, the problem of cost could be an issue, and since you'll need to stick it in an enclosure this could be an obstacle too.

(As far as noise, modern mixers (even inexpensive ones) seem to have very low noise figures, so adding the load R may not be a problem as far as noise if gain loss can be compensated for by simply increasing the mic preamp gain (and no extra noise in particular is added).)
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related links:

loading, ringing, intermodulation distortion consequences:

Damping transformer ringing (Zobel network question)

a lower impedance driving the primary (of a transformer) should improve low frequency response:

http://www.diystompboxes.com/smfforum/i ... ic=82878.0

Michael Wagener (famous engineer, producer guy) remarks that, "(the) higher impedance settings on any of the preamps (in his mic pre collection) seem to result in a thinner tone with every mic I have tried":

http://www.3daudioinc.com/3db/archive/i ... -5045.html
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Doing some reading on inexpensive modern condenser mics, I've found that apparently a number of them are basically copies of a Neumann U87. The MXL V67 is one, and apparently can be made a bit more similar by tweaking (the different) values around the front end:

The front end of (the V67) circuit is basically a copy of the U87

discussion on the area to be tweaked (feedback around the capsule) :

http://www.prodigy-pro.com/diy/index.php?topic=20652.0

(MXL2001 is the same circuit) :

http://www.xaudia.com/xaudia/Schematics ... xl2001.jpg

(V67 schematic) :

http://www.gearslutz.com/board/attachme ... xl-v67.gif

V67 guts pics (appears the capsule in this one may be damaged) :

http://s711.photobucket.com/albums/ww11 ... 0Projects/

(Now if I could just find an inexpensive used one to play with.)
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I managed to find a used not particularly expensive one that has the MXL2001, V67G, Behringer B1, joemeek JM(47?), etc. type circuit (managed to find a PCB pic first to get a degree of confirmation that it was the type I wanted). Mine is a "Seide" brand which has the same type of PCB layout, an internal low cut switch (some have them, some don't, but many typically seem to have a spot for the switch on the PCB). Also mine has a 2SK30A(Y) and not a 2SK170(GR). Only tried it for a bit, but subjectively it seemed sort of a bit grungy sounding (might be good for emulating the sound of older bootlegs?) and somewhat noisy (nothing particularly bad like obvious hum and buzz but more in the background). I like that it's different to my Rode NT2 (the Rode seems to have more clarity), so I'm thinking any changes I make should try to stay with the dark-ish orientation and not make it too bright and clear sounding). Found info regarding getting a more correct bias for the transistors:

(one of the posts above is from this gearslutz thread)

http://www.gearslutz.com/board/geekslut ... -mods.html

(the suggested mod only adds a resistor, so it looks easy to do/try)

http://www.wavebourn.com/forum/viewtopic.php?f=7&t=1151

so I think I will try things bit by bit.
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some suggestions/analysis/tweaks that look good for mellowing out the highs for the Schoeps circuit:

(check out the "ChinaMicModU87hybrid.doc" by Ricardo Lee)

http://tech.groups.yahoo.com/group/micb ... sage/15398

http://www.prodigy-pro.com/diy/index.php?topic=42836.0

(the suggestions look far easier and less costly than sending a mic to a modder to have the capsule changed, circuit tweaked, etc. i.e. they have the Good Cheapskating Seal of Approval! :mrgreen: )

Jul 22, 2011
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dai h.
 
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Re: low budget cheapskate recording tips

Postby dai h. » Thu Mar 03, 2011 12:31 pm

Another little thing that came to mind (with the transformers and loading business) is that (loading effecting freq. response) is something that should generally apply to every transfomer (though some seem to have more complicated designs to reduce this(forming of a CL tank circuit??)), and thinking back I remembered getting (subjectively better) results from the 1/4" unbal. out (10k output impedance) of my Palmer PDI-03 (spk. emulator) to the insert of my Tascam 488mkII (10k input Z), rather than the bal. out (600ohms) to the bal. in of the Tascam (2.8k input Z). *Maybe*, what I needed to do to get a more satisfactory result was load the output of the bal. XLR out of my Palmer was load down the XLR bal out a bit (both 1/4" and XLR outs of the Palmer are transformer coupled).

Also, maybe the same with those cheap 600 ohms to 10k in-line impedance converters. Probably (since those are typically not expensive) they don't contain a particulary high quality transformer, but tweaking the load might help the sound when going into a higher Z input (50k or whatever).
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Re: low budget cheapskate recording tips

Postby dai h. » Sun Jul 24, 2011 6:42 pm

some good stuff on a Dutch site here:

http://www.nvrecording.nl/nhc/AudioTech ... o_tech.htm

(the main site: http://www.nvrecording.nl/nhc/pa0nhc.htm )

for improving Schoeps circuit mics (improving common mode rejection, widening frequency response, explanations of which tweaks affect which frequency ranges).

adding another link (DEC 3 2011) :

more on Schoeps circuit plus another possible mod which apparently could help to reduce distortion (small impedance (a resistance) added in series to RF shunting caps by "mshilarious" (Naiant Microphones)) :

http://taperssection.com/index.php?topic=127204.165

more links (DEC 7 2011) :

link regarding disassembly of MXL 990 (note that the MXL 770 loooks to be pretty much the same thing but with a longer body) :

http://www.rickshawrecords.com/mxl/

info on how the HPF (low cut) switching in MXL 990/770 is accomplished:

http://www.groupdiy.com/index.php?topic=17753.20

(Reply #30) (Apparently the 220nFs are in series with 15nFs. When the HPF switch is off, the 15nFs are shorted out. When the switch is on, they are unshorted, putting them in series with the 220nFs.)
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Re: low budget cheapskate recording tips

Postby dai h. » Sat Sep 03, 2011 11:50 pm

couple more links related to MXL V67/2001, etc. type mic rebiasing of the FET (I would be careful to read through before attempting anything) :

http://www.diystompboxes.com/smfforum/i ... 416.0;wap2

http://www.aronnelson.com/gallery/main. ... pictorial/

http://www.prodigy-pro.com/diy/index.ph ... ic=14003.0

http://www.prodigy-pro.com/diy/index.php?topic=11325.0

http://www.prodigy-pro.com/diy/index.php?topic=21266.0

more links on biasing the FET:
(DEC 3 2011)

http://recforums.prosoundweb.com/index. ... msg_435425

(article with segment on FET biasing--the article FET preamp project looks nifty as well) :

http://www.hawestv.com/amp_projects/fet ... reamp4.htm
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Re: low budget cheapskate recording tips

Postby dai h. » Sat Dec 03, 2011 10:19 am

info on capsule cleaning (Neumann factory instructions available for download plus an idea to use easy-to-source cigarette rolling paper (with the adhesive portion removed) as blotting paper to soak excess water while cleaning) :

http://www.gearslutz.com/board/geekslut ... psule.html
---
(DEC 20, 2011)

More on capsule cleaning, plus warning about info from said doc plus specific ways on how liquid could work its way behind the capsule diaphragm:

http://recforums.prosoundweb.com/index. ... 44/0/16/0/
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Re: low budget cheapskate recording tips

Postby David B » Mon Apr 02, 2012 3:21 pm

Dai,

I would like to be able to record some clips using my old Tascam Porta One however I have no idea how to get the sound onto my laptop which has a goofy soundcard with no mic input!
I would assume I‘d need some sort of USB interface for the task and if I’m barking up the right tree what would be a good gadget for this :?:

Thanks,
David
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Re: low budget cheapskate recording tips

Postby dai h. » Mon Apr 02, 2012 8:00 pm

Hey David, (being no computer expert, I'm probably the last guy you would want to ask... :lol: ), but FWIW I bought an Edirol UA-1EX (used), which sounds like the sort of thing you could use (it's a physically small "bare-bones"-ish USB connecting audio interface). I only tried it once (after I bought it to make sure it worked), and indeed it did. There are probably comparable (maybe a cheaper Behringer copy?) as well as nicer (more features and such), so I would probably try to look at a number of them to find the most suitable (features, portability, price, etc.).

(p.s. you have a Porta One that still works? :shock: )
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Re: low budget cheapskate recording tips

Postby David B » Mon Apr 02, 2012 8:17 pm

Dai,

Yeah something like that, outta production though but looks promising..

http://www.sixstardj.com/eduausbauin1.html

Yeah P1 is still going , few things have needed repair and I’m sure the caps & rubber bands should be replaced :lol: but I like it, just slap a 57 into there and go. Think the 424 has some better features like faster speed and some other stuff but for a scratch pad its good enough..

ah maybe this?

http://www.sweetwater.com/store/compare ... 222|UCA202)

David
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Re: low budget cheapskate recording tips

Postby dai h. » Tue Apr 03, 2012 12:20 am

The Sweetwater link isn't showing anything for me, but they do have a number of the same sort (some by Behringer) which look pretty similar. One thing to think about though is the number of inputs. (Not sure exactly how you're going to output the Porta One, but) you may need something with four inputs if the four individual tape outs are planned to be accessed (I vaguely recall the Porta 1&2 having indiv. tape outs via RCA connectors). You know I wonder how good the sound could be on those now, since condenser mics these days are much easier to access (read:cheaper), plus you could bounce tracks digitally to reduce the loss.
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Re: low budget cheapskate recording tips

Postby David B » Tue Apr 03, 2012 9:48 am

Yep I was looking at the Behringer; looks like it will meet my cheapskate needs :lol: two outs is fine to mix down to the laptop...



http://www.sweetwater.com/store/detail/ ... nQodFFWfLw
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Re: low budget cheapskate recording tips

Postby dai h. » Thu Apr 05, 2012 6:07 pm

the price is right and looks adequate where nothing super sophisticated is required (hopefully...knock on wood, cross fingers, throw baby lamb into fiery volcano for good measure--yes I am not serious... :mrgreen: ).

p.s. my 488mkII finally died (the tape section) a while back unfortunately. The mixer section seems fine and I've been goofing around with that to try to decrease noise, reduce crosstalk and such (basic audio improvements).
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Re: low budget cheapskate recording tips

Postby David B » Fri Apr 06, 2012 10:15 am

Well if it gets too complicated I'd just throw the gadget in the volcano after a while :twisted:

Mechanical issue with the 488mkII ? that things got a lot of knobs!
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Re: low budget cheapskate recording tips

Postby dai h. » Fri Apr 06, 2012 6:48 pm

lol (maybe... if it'll stop another earthquake).

the 488mkii tape section won't play (but did RW/FW IIRC).
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Re: low budget cheapskate recording tips

Postby David B » Sat Apr 07, 2012 10:32 am

Motor still work? oh yeah you got motion,I had mine get jammed at times & usually a cleaning of the gears etc would help but if it's stuck you might have to help it along...big hammer.

I only have one screw holding the bottom on,easy access when something else fails...
Ah maybe it's getting too beat & needs to get tossed into the firey chasm :twisted:


still getting the shake rattle & roll ?
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Re: low budget cheapskate recording tips

Postby dai h. » Sat Apr 07, 2012 6:47 pm

it was left disassembled for a while so I wonder if perhaps that contributed to the rubber belt deteriorating.

the quaking has settled (LOTS of aftershocks immediately after but over time tapering down) but lots of talk in the media about "the big one" (more of a "direct hit") that will probably hit the capitol (Tokyo/Yokohama) area within the next few decades (I think a couple of tectonic plates meet nearby). IIRC a 70% likelihood in the next 30 years, so hopefully 30 years from now instead of tomorrow. :lol:
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