Archive for the ‘electronics’ Category

Microphone Mod: Carvin’s CTM100 via

Sunday, June 16th, 2013

Carvin CTM100 Tube Mic

“Like butter in a black silk cocktail dress.”

I have been interested in microphone modification for years and I went so far as to purchase a Oktava-Mod mic and modification a few years back. While Michael Joly’s mod did sound great, I wasn’t satisfied because I hadn’t done the work myself. I have been short a tube microphone so I decided to get a cheap Chinese mic and put some time and effort into improving the sound.

I ended up getting a Carvin CTM100 tube microphone which is actually the same mic as the Apex 460. At the time of this post the mic is selling for $179 + $12 shipping, which is quite a bargain. The package comes with a large plastic foam lined case, a mic bag, a decent shock mount, a multipin XLR and a power supply. Out of the box the mic didn’t sound bad actually. Certainly better than I was expected for $200. Some high frequency boost made the mic sound sibilant and too bright. While the high frequency boost gave the impression of detail, the mid range wasn’t terribly clear. The was a pronounced proximity effect similar to most large diameter cardioids, but a little boomier than normal. I was thinking that the boost was more in the low mids than in the bass frequencies.

The modification kit that I bought was from I chose the Apex 460 Mod Kit (not the SG version) and for a new capsule, I chose the RK7 which is a darker, more-colored U-47 style capsule. I like my mics darker. Most people choose the RK-12 which is based on AKG’s CK-12 which is much brighter and airy.

The kit including the new capsule is only $209, which seems like a great deal. The service at Microphone-Parts was great. Email questions were responded to quickly and completely. When I placed my order I received a bunch of updates and then the kit arrived in maybe 2 days tops. I was really impressed.

Everything was in order and the mod came with a really nice full-color booklet with directions. The directions are probably the best part of the mod kit. They are clear, specific, they have great suggestions and great advice. There are detailed instructions for desoldering and for how to properly use a solder-sucker pump. There were no weird tools required. A precision screwdriver (size 0 Phillips) was the most exotic tools required, but there are included in every $3 jewelers screwdriver kit. In the directions, emphasis is made on cleaning the flux off the board and connections afterwards which I admit I rarely do for cables or patchbay soldering. Still I had the solvent and QTips.

There are links on the website and in the text that point you to helpful videos and suggestions for tools and supplies to buy. I was able to do the complete mod and test in a leisurely morning. I was careful and I read the directions several times. I was fortunate to not have any missteps along the way and the mic sounds great!

All of the high frequency yuck is gone, the response seems very smooth and very detailed. The upper mid range is accurate and flattering for my voice and gave it the quality of a late 70’s radio personality mic, but with more detail and depth. A former professor of mine, Dr. William Moylan, was always very adamant about using objective, descriptive and accurate language to describe sound and timbre. Unfortunately, the word that seems the most descriptive to me is ‘silky.’ There is a slight bump around 4k and a slight dip at 8-9k. There seems to be a very slight natural compression to the microphone now. Before the mod, transient detail seemed too obvious, maybe even expanded. By constant the microphone seems to have a bit of natural compression. This might be due to the tube or to the slightly thicker and slower moving membrane. The RK7 is a 6 micron. I can’t say that I know for sure what the original in the CTM100 is. I did take some photos of the original diaphragm to compare it to the new one:

Original CTM100 Capsule

This is the original CTM100 capsule and diaphragm. You can easily see that the diaphragm is NOT flat.

Original CTM100 Capsule

In this angle of the original capsule you can see how much dust is on the surface of the diaphragm. This is a brand new mic, so I am pretty sure that the dust is from the manufacturing process.

Effectively all the sibilant frequencies were diminished to the point that I wouldn’t think about reaching for a de-esser. The proximity response seems more gradual and nuanced. The effect could be easily controlled for some reason and there seemed to be more gradations in the boost compared to distance. Overall, I think that the modded microphone sounds fantastic. It will certainly replace my other vocal mics for my own voice and I suspect that I will reach for this mic when I need to tone down an overly bright female or a sibilant/whistle-prone male vocal.


DIY Audio Mixing Circuits

Saturday, November 24th, 2012

For a while now I have been interested in summing in the analog as opposed to the digital domain and I built a 16 channel summing mixer with Daking-style amplifiers. I haven’t been very happy with the usability of summing mixers without linear faders and pan controls. It just doesn’t feel right. If you’re mixing with rotary knobs, you can only turn two knobs at once, but when you mix with faders you can do at least 8 at a time.

I basically started doing some research about the kinds of circuits that I need to build and I wanted to post links to the stuff that I found to be the most helpful.

Simple Mixer Schematics from All Electric Kitchen:

Slightly more complex mixer circuits (Pre’s, EQ’s, Line Drivers):

Elliott Sound Products (ESP) Article on Audio Mixing:

I will add information as I read more!

Cheaper Alternatives for Audio Cabling?

Tuesday, December 22nd, 2009

The following is a Facebook exchange that I had with a former student outfitting his new studio.  He raises some great questions about what makes a cable compatible with audio.

if i were to put an audio snake through 1 1/4 conduit and i were to use cat5 as a temporary cheap(free) way to do this would it work for 16 channels?

I know it will fit in the conduit.. at least thats what the electrician told me.
I am more interested in how well cat5 will work as a temporary audio cable

CAT5 unfortunately will not work as audio cable unless you convert all the audio to digital first and then shoot it down the line. This would be REALLY expensive. CAT5 isn’t shielded, though the “twisted pair” nature of it does help a little. CAT5 has 4 pairs of very thin solid core wire, so that you would only get you 4 channels, even if there was a shield.

Your best cheap option for 16 channels is to buy 16 channel snake cable and solder the ends without the breakout box. Redco does sometimes have used snakes for sale.
Do you need all 16 channels? What else is in the conduit? If there’s any power there don’t run any audio into it!

I like Clark Wire’s cable because of the color coding and a very convenient drain wire

Do you mind if I post your question anonymously on my blog?

Go right ahead and put it on your blog. I figured the lack of shield would destroy me. I am just in a situation where i can get way more than a hundred feet of it for free and was wishing it would work. i only need to go about 50-60ft so i would have done 4+ runs of it.

The conduit is going to be along the baseboard and the power is going to be ran through the ceiling and come down where needed about 12-18inches up the wall.

My parents have a mid sized barn(closer to small i guess) that they currently rent out. The renters have told my parents they will no longer need it after January. I was hoping to get a little project space for when i am not busy over the summer. i might “steal” some of the “broken” dmx/XLR from work and see what i can do with that before buying stuff i can’t afford ha ha.

on a side note…
Will 5 wire DMX work if i just don’t use a wire?

DMX Cable has higher impedance than audio cable because it’s for data. DMX is around 110 Ohms while audio cable is around 70 Ohms. I also think DMX cable has thicker shielding. You could probably use DMX cable for digital connections like AES-EBU which also uses an XLR connector.

It’s possible that you could send audio on a DMX cable but you might get signal loss because of the higher impedance. I wouldn’t risk it personally. I would see if you could find a used snake somewhere and fix what needs to be fixed.  Sometimes companies have short lengths of cable that they will sell for a discount.

Good luck!

Please let me know if anyone finds out some new cheaper ways of doing our work!

Daking FET II Compressor Review: Super Fast and Transparent

Monday, November 2nd, 2009
Daking Audio Gear: Mic Pre IV and 3 FET II Compressors

Daking Audio Gear: Mic Pre IV and 3 FET II Compressors

I currently have three of these units in my studio right now and I have had a chance to really put them through their paces.

First, I should say that the sound quality on these units is pristine. There is very little coloration of the sound even when using heavy compression. Many compressors seem to roll off high end when they attenuate heavily, but this is not the case with the FET II. The FET II uses Jensen transformers both in and out of the unit and the pc board is extremely clean and well designed. The FET is in a socket so if it were ever to go bad, it is easy to replace.

The FET II excels at transparent compression and is easily used on bus or program material where lesser compressors really start to sound yucky. The attack times vary between 250 micro seconds to 64 milliseconds and it’s fast enough to be used effectively as a brickwall limiter if desired. The release characteristics are I think what really set the compressor apart though. You have some standard settings of .5 – 1.5 seconds, but also some really nice dual time constant releases designed to mimic some of the nicest compressors in history. The idea behind dual time constant release is this: the compressor releases a little fast at the beginning and then slows down. This effectively eliminates the “pumping and breathing” sounds associated with more abrupt release times.

I have also been able to get some really nice vocal distortion (think Flood’s production techniques) out of it by using the fastest attack and release times and a very high ratio (20:1). Then I drive a very hot signal (over +20) and get a very pretty sounding harmonic distortion very appropriate for alternative rock vocals like NIN, PJ Harvey or Smashing Pumpkins.

I recommend using only XLR cables in and out of the unit, you can use a 1/4″ input but it boosts the signal 14 dB to make up for the -10/+4 difference in operating levels between consumer and pro gear. Another odd thing is the power supply (external, but not a wall wart) uses a DB25 connector which looks pretty weird, but works perfectly well. Just make sure your intern doesn’t try to run the power supply into the DB25 input on an audio interface or multitrack….Bad intern! Bad intern!

You can link two units together to work in stereo with a 1/4″ guitar cable. The sidechaining connection uses DC summing to tell the linked unit when to compress and does not send audio. The FET III does audio summing, but it’s in stereo and is geared more towards working in stereo anyway.

All of the knobs on the unit are switches so you can set two or more compressors exactly the same way and repeat your settings later on. The knobs are really heavy and feel like you’re really working with pro gear.

All in all this is a great compressor with excellent transparent compression that doesn’t color the sounds you are working with. You can use it to chase the waveform to create harmonic distortion with the fastest attack settings to add a little crunch to vocals, bass or drums.

I can’t recommend it more highly.

The Best Vise for Electronic Projects: Panavise 350

Wednesday, January 21st, 2009
Panavise Model 350 Electronics Vise

Panavise Model 350 Electronics Vise

One of the the most important tools on your workbench is your vise.  Without a strong, stable support for your work you will spend hours knocking over junior size vises or “helping-hands” alligator-clip toys. My personal favorite vise is the Panavise 350 [] shown to the left.

The 350 is actually 3 products shipped as a single product. First you get the heavy-duty base, the Panavise 312.  It weighs 2 pounds by itself and at 8 ½ inches wide you won’t be able to tip this baby over. It comes with nice rubber feet to help keep it from sliding and you can mount all of the Pro (300 and series) mounts as well as the Jr. (201) mounts.

Next is the standard 300 base which can hold all of the vise jaws that you could possibly want. It weighs in at 1 ½ lbs, which adds a good deal of stability in itself.

The 350 also comes with the Model 376 self-centering extra-wide jaws!  These jaws have a number of really convenient features.  First the vise is opened and closed with a rotating handle with ball bearings.  You can open or close very quickly without having to take your hand off the handle.  The jaws are reversible so you can hold small items or PCB as big as 9 inches across.  The neoprene jaw pads are grooved to hold your boards and they are replaceable if they should ever wear out.  The Panavise 350 comes with a lifetime warranty also, so no worries about quality here. has the best deal on the PanaVise 350 Multi-Purpose Work Center which is $69.50 at the time of this posting.