Archive for the ‘DIY’ 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!

JBL L100T: Speaker or Food Storage?

Sunday, July 17th, 2011

I was recently given a pair of JBL L100T speakers from the late 80’s.  They needed to have the foam surround replaced because the originals had started to rot away. I ordered new surround from Speaker Works ( so that I wouldn’t have to pay an arm and a leg for the repair.

In order to replace the foam surrounds, I needed to first remove the woofers from the cabinet so that I could work on the speaker more easily.  After removing the speaker, I discovered a large pile of what appeared to be cat food in the bottom corner of the speaker.

Here are some of the photos taken on my phone. Apologies for the poor quality, the room was dark and I had to use a flash for up close photos…

Inside JBL L100T Speaker

Cat food carefully collected and stored by a family of mice.

Underneath the fiber glass absorption...

More cat food and mice dropping found under the fiberglass insulation

Bag full of cat food pulled from speaker cabinet

I pulled the bag's worth of cat food out of the speaker cabinet.

More later when I get the speaker surrounds replaced!


Audio Interfaces and Patchbays Question

Monday, November 22nd, 2010


I have a question about the patchbays. I’ve laid out all my gear and figured out every I/O that I have and what cables I need, I started hooking things up and I’m slightly confused about how the audio interface (M-Audio Delta 1010) hooks up with the TASCAM DM-3200 through the patchbay.


The most common configuration for an audio interface, a mixer and a patchbay is as follows:

Directs outputs on the mixer would be half-normaled to the analog inputs on the audio interface.

Analog outputs on the audio interface are half-normaled to the line inputs on the mixer to allow for digital mixing in the mixer.

In the case of the TASCAM DM-3200, in order to get more analog outputs you would want to purchase 1 or 2 TASCAM IF-AN/DM 8-channel expander cards.  You would use these additional outputs as direct outputs or bus outputs.  Out of the box, the DM-3200 has only 4 assignable analog outputs, plus the main outs and the monitor outs.  The DM-3200 does have 24 channels of TASCAM Digital Interface outputs (TDIF) and you could buy an audio interface card that has TDIF digital inputs.

You could also purchase the TASCAM IF-FW/DMmkII a card the makes the DM-3200 into an interface eliminating the need for the M-Audio Delta 1010’s.  The only problem with this is that M-Audio has REALLY good drivers for the Delta 1010’s and TASCAM has a really bad reputation for their drivers and support. I have no firsthand knowledge of problems with drivers for the DM-3200, but I have experienced the disaster of Giga-Sampler, Giga-Studio and GVI which all used specialized drivers to work.

Hope this helps!

Classic Gear Directory

Wednesday, October 20th, 2010

This semester my Audio Technology 2 classes at the New England Institute of Art (or AI New England) will be compiling a list of classic gear with descriptions, links and information about why and how equipment became classic. This is the list I came up with while waiting in the airport in Detroit, so I am sure that I have left off at least a few classic items. I would encourage everyone to make suggestions of equipment to add to the list. Right now, for reasons of my class curriculum we are including only preamps, dynamics and spectral processors. Here is my first revision of classic gear:






Fairchild (mono or stereo)

Neve 33609

dbx 160

API 2500

API 225/525


Drawmer DS-201


Neve 1073

UA 610

API 212/512

Millenia HV-3C

Focusrite Red

Trident “A Range” – Daking MPIV

Ampex Tape Machine Pres


Massive Passive

API 550A or 550B

Weiss EQ-1

Pultec EQ (Original or Manley)

SSL EQ Module

GML 8200

Black Walnut Branches into Lumber

Wednesday, August 18th, 2010

As many of you already know, I love to build things out of wood: guitars, acoustic treatments, furniture, and assorted house-oriented projects.  What you probably didn’t know is that there’s a black walnut tree in my backyard.  For years and years the squirrels have been denting the hood of my car by throwing walnuts at it. You can’t blame the squirrels.  The walnuts do sound great when they bonk my car, but it still sucks. Partially from my frustration that cars are made out of aluminum foil instead of actual steel, I have been fantasizing about cutting down the two large branches above my parking space in the driveway. And I have been fantasizing about how great it would be if I could then mill the logs from the branches into usable lumber.

Last week my dreams came true and the next door neighbor hired a tree company to remove the branches because they were also above their parking spaces and creating a wonderful super-highway for the squirrels nests in the roof of their house. I then convinced the guys gutting the trees to give me all of the large branches from the walnut tree for free. Score! I was so excited.  Black walnut has an incredibly beautiful grain with a dark brown heart wood and a creamy tan sap wood.  Walnut makes amazing guitar necks, great furniture and is just generally really cool looking and feeling.

I ended up finding out about Roy from A.W. Woodworking (phone: 401-219-1258) through Craigslist and he gave me a quote for driving all the way from Rhode Island up to Medford, MA to mill my black walnut into usable lumber. The price was about 1/4 – 1/3 what the lumber would have cost from a lumberyard locally. Hurray!  The following is a short photo story of the process:

Black Walnut Tree

The Black Walnut tree after the branches have been cut down

Black Walnut Branches

Black walnut branches waiting to be milled

Branches are somewhat less than ideal for milling because they aren’t straight and they aren’t very big. It makes is harder on whoever is milling the wood. Roy did a great job!

Log Section and Walnuts

A cross-section of a log and 4 fresh walnuts before the soft outer shell dries and falls off

Cross Section

Another cross section of a log with the bark still intact

Baby Walnut Tree

A tiny black walnut sapling growing from the neighbors' foundation

Waxed Log End

The waxed end of a cut branch

The Arrival

The saw mill has arrived and is backing into the driveway

The Portable Mill

The portable saw mill is in position and ready for work

The First Branch

Garfield places the first (and smallest) branch on the mill to rip it into planks

Blade Against Branch

The blade of the mill is lined up with the first branch ready to remove the first slab

The First Slice

The first slice comes off the first log while the saw exhausts on the driveway

Cranking the Mill

Roy cranks the handle pulling the saw blade through the log


Garfield rotates the log into position for ripping off the top slab

Squaring Off

Ready to rip off the top slab to create two square edges

Two Clean Edges

Now with two clean edges the log can be ripped into planks

Top View

A bird's eye view of Roy and Garfield working

Arched Grain

This ripped log shows the beauty of black walnut's grain


Discarded slabs of bark and pieces that are too short to mill


Black Walnut planks after milling waiting to be stacked and dried

Wood Grain

Top view of the black walnut wood grain showing both the lighter sap wood and the darker heart wood

Embedded Metal

This piece of embedded metal ruined the band saw blade

Detail of Wood Grain

A close-up view of the grain of the black walnut plank

Studio Construction Photos: Con-Fusion Entertainment

Saturday, June 12th, 2010

Several months ago I was approached by two former students (Evan Schlosser and Robie Rowland) at the New England Institute of Art to help them to design a studio in a rented space in Allston.  They introduced me to their partner Arjun Ray and I started consulting with them.  The space was being converted into rehearsal  spaces and construction was already underway in the space to convert it from an office building into a rehearsal room.  We would convert that into a fully-functional professional studio.

After measuring the space and investigating the existing construction, I came up with a design that would isolate the studio from their 3 neighbors as much as possible and that would provide them with 2 large and functional live rooms and  a good sized and well proportioned control room.  My initial design follows but had to be altered some to address problems such as sprinkler and HVAC locations.

Original Studio Design

The Original Design for Con-Fusion Entertainment's Studio

One of the things that is very nice about the space is the two large windows allowing natural light into the studio’s control room.  I designed all of the spaces to avoid parallel wall to help prevent problems with standing waves and the accumulation of low frequencies in less-than-ideal locations.  The rectangular space is broken up in such a way that the control room gets larger the further away from the mix position.  Both the live rooms have site-lines to the control room as well.  The control room, where the most time will be spent, is the largest room and will allow for comfortable seating for producers, engineers and their clients.

Here are some of the early construction photos.  In the pictures are Arjun Ray, Robie Rowland and Evan Schlosser (The 3 partners of Con-Fusion Entertainment), and Mike, Rick and Robie the Elder.  I tried to create some order to the photos to create a narrative.  At this point, nearly all of the metal studs are in place and drywall is starting to be hung.

Looking at control room from inside the large live room

Looking at control room from inside the large live room

View out of the control room door

View out of the control room door

View into the corner of the control room

View into the corner of the control room

View out the main control room window

View out the main control room window

The wall makes a slight job at the studio entrance

The wall makes a slight job at the studio entrance

Exterior walls filled with 703 fiberglass insulation

Exterior walls filled with 703 fiberglass insulation

Detail of the double wall construction

Detail of the double wall construction

3 Layer studio window in progress

3 Layer studio window in progress

Detail of finished studio window

Detail of finished studio window

Cutting metal studs makes sparks!

Cutting metal studs makes sparks!

Placing the first piece of gypsum board

Placing the first piece of gypsum board (from the left: Evan, Robie and Arjun)

Arjun sealing the top edge of the drywall

Arjun sealing the top edge of the drywall

Signatures of the builders on the first drywall

Signatures of the builders on the first drywall

So those are some of the pictures of the progress.  I would love to hear your thoughts!

Building a New 20-Space Rack

Tuesday, June 8th, 2010

I was really bummed when my 20-Space Raxxess mobile rack disintegrated on me with all of my most expensive gear in it.  The bottom collapsed and then the whole thing twisted breaking the sides as well.  I was not at all impressed with Raxxess’ design after looking at it closely.  The entire weight of both sides of the rack is held up by 6 metal pins in 3/4 inch particle board.  Not a good design.  So I called Raxxess and they agreed to send me the broken parts after they grilled me about how heavy my equipment was and what I was using it for.  It’s a rack and I put audio gear in it and it broke because the design is bad.  The guys on the phone were pretty snotty, but they did agree to send me the replacement parts and they did it pretty quickly.  Then I thought, “Do you want to put your favorite rack gear in a rack that previously disintegrated?”

Broken Raxxess Caster Plate

The broken pin holes on the bottom plate of the Raxxess rack

Detail of Broken Raxxess Rack

A detail of the broken particle board

So I decided to build a replacement instead.  The new version is MUCH stronger, better designed, has bigger casters and it is generally awesome.  I DIY.  It would have been faster and maybe cheaper just to buy a new crappy rack, but I wouldn’t be very proud of it!

Top Corner of New Rack

Top Corner of New Rack

Big Fucking Wheels

Big Fucking Wheels (For Off-Road Recordin')

Side View of New Rack

Side View of New Rack

Cable Tie Mounts

Cable Tie Mounts

Cable Tied Power Cables Down the Right Rear

Cable Tied Power Cables Down the Right Rear

Fully Wired Rack

Fully Wired Rack with Optional Squirrel's Nest

I would love to see other people homemade audio equipment racks!  This one is probably only going to be loved by me and the family of squirrels that made their home in the back!

Tracking an 8-Piece Drum Kit for 5.1 Surround

Monday, February 1st, 2010

The Project: Drums in 5.1

I am currently working on a recording of music that I have been writing with Penny Larson, the awesome-est drummer ever. We tracked the drums at U. Mass Lowell’s wonderful Rm 114, which is by far the best room I have ever worked in. Big enough to make great drum sounds with lots of diffusion and enough low frequency absorption to prevent the room from being boomy or rumbly. It’s just totally delicious.

Penny and I first worked together recording Bryan McPherson’s “Fourteen Stories” and then subsequently on Sierra’s EP “Rocks.”

Penny Larson's 8 Piece Drum Set

Penny Larson's 8 Piece Drum Set

The record will be released in 5.1 Surround at 24bit 88.2kHz so there is a lot of opportunity to use the 360 degree soundstage to allow the kit to be heard in all of its glory. There are lot of issues that arise when recording a really large drumset and I will talk a little about these types of issues.

mkit from the Front

8 Piece Drum Kit from the Front

Problems Micing a Large Kit

More Drums = More Mics = More Problems

As you add microphones to a drum setup, the potential for phasing and bleed problem increases exponentially. More drums usually means closer together drums, so isolating the drums becomes difficult. When sounds bleed into unintended microphones the possibility of phase cancellation or other problems increases as well. Adding to the mix problems are a zillion cymbals that will cause physical problems with mic placement as well as bleeding problems. Two objects can not be in the same place at the same time.

Microphone Selection and Techniques

Surround Microphones

Although I love recording with omni’s and a Jecklin Disk, I decided to try something different for this particular drum tracking session. The Jecklin Disk technique creates a very nice realistic stereo image, but I am not going for realistic in this case. I want drums that are bigger than life and over-the-top.

Used a variation of spaced cardioids very similar to that used in the Decca-Tree style employed in the Fukada tree. In this case I chose to use 2 Neumann KM140 Cardioid Small Diaphragm Mics for the left and right speakers and an AKG 414 XLS in Cardioid for the center channel. I used a pair of Neumann TLM103 for room mics facing into an RPG Schroeder Diffusor away from the drum set.

Front 3 Microphones: Neumann KM140's with AKG 414 XLS in Cardioid in Center

Front 3 Microphones: Neumann KM140's with AKG 414 XLS in Cardioid in Center

Rear Surround Left Neumann TLM103 toward RPG Diffusor

Rear Surround Left Neumann TLM103 toward RPG Diffusor

To recap the surround microphone setup: Left, Center and Right “overheads” are actually in front of the kit to enable better balance between cymbals and drums. Rear surround large diaphragm cardioids point away from the kit into the corners of the room.

Kick Drums (plural, as in two!)

I have always been a fan of the delicious warm thump produced by micing the front hole in the kick with an AKG D112. It always provides a great tone, but can lack a little bit in fast transient response and clarity. I have been using Earthworks TC25’s and SR25’s for the kick and snare drums. The tiny diaphragms offer a tremendously accurate transient response and can handle very high SPLs. I use the Kick Pad which ships with the SR25 to pad the mics output and scoop out the middle frequencies to create a great kick sound. With most double kick players, one drum is the main drum and the other is used for accents and kick fills.

First Kick Drum: AKG D112 and Earthworks TC25

First Kick Drum: AKG D112 and Earthworks TC25

Second Kick Drum: AKG D112 and Earthworks SR25

Second Kick Drum: AKG D112 and Earthworks SR25

The Earthworks TC25 is an omni-directional microphone while the SR25 is Cardioid and provides a little bit of isolation with the pickup pattern. I used the SR25 on the second kick drum and employed the Kick Pad in the signal chain, while I used the TC25 turned off axis on the main kick drum. The TC25 has a flat response all the way down to earthquake, so I chose it for the main kick drum, while the second drum was happy with the slightly tighter sounding SR25.

Snare Drum

The first secret to a good snare sound is a good drummer and a good snare drum. For this particular recording Penny brought 5 snares to choose from and I selected the one that sounded the closest to my ideal of the Al Green and Fleetwood Mac snare sounds: excellent attack, white noise snare sound, warm woody tone (sometimes obtained from Brass and Copper drums!), good tonal variation (rim, sidestick, center, flam, rim shot, etc), and a lot of low midrange (150 Hz – 300 Hz). Again I used a two microphone technique using a traditional snare mic, Sennheiser 421, and an Earthworks TC25 omni. The 421 provides the traditional proximity effect low mid whap (technical word) while the omni fleshes out the toal tone and timbre of the snare. I place the omni pointing at the shell of the snare drum so that it picks up both the top and the bottom of the snare.

Snare Drum: Sennheiser 421 Over the Head (Warning: Never Try This Without A Great Pro Drummer

Snare Drum: Sennheiser 421 Over the Head (Warning: Never Try This Without A Great Pro Drummer

Snare Drum: Sennheiser 421 (View 2) DANGER! Amateur/Intoxicated/Drunk/Average Drummers WILL Destroy Mics in this Position!

Snare Drum: Sennheiser 421 (View 2) DANGER! Amateur/Intoxicated/Drunk/Average Drummers WILL Destroy Mics in this Position!

Snare Drum: TC25 Pointed at the Shell of the Drum

Snare Drum: TC25 Pointed at the Shell of the Drum

Toms (All Five of Them!)

There’s really no super secret tracking technique here, just 5 Sennheiser 441’s. Currently the 441 is my favorite dynamic microphone period. It has a wonderful pickup pattern rejecting sources to the sides and a very small rear lobe behind the microphone. The 441 has fantastic tone, a great bump in the lows and low mids from the proximity response and rejects the other toms, drums and cymbals in the vicinity. The hardest part of micing the toms on Penny’s ginormous kit was getting around the cymbals and other hardware. Obviously the 441 is a large microphone and this does make it hard to use in tight spaces.

Tom No. 5: Sennheiser 441

Tom No. 5: Sennheiser 441

Tom No. 4: Sennheiser 441

Tom No. 4: Sennheiser 441

Tom No. 3: Sennheiser 441

Tom No. 3: Sennheiser 441

Tom No. 2: Sennheiser 441

Tom No. 2: Sennheiser 441

Tom No. 1: Sennheiser 441

Tom No. 1: Sennheiser 441

Notice in the Tom No. 1 photo that I had to use a mic clip from a 421 and LOTS of GAFFER’S TAPE to fashion a mic clip. Sennheiser makes great sounding microphones but by far the absolute stupidest microphone clips EVER. EVER.

Flat Ride Cymbal Spot Mic

After doing a few test takes, it became evident Penny’s flat ride cymbal just wasn’t cutting through the rest of the drum kit. The tone of the flat rides is superb, but they become inaudible with a large or loud kit. I used an AKG 452 under the cymbal to get it to push through the masking. Even though the mic is pointing up, the cymbal isolates the mic from the other sounds so phasing wasn’t much of a problem.

Flat Ride Spot Mic: AKG 452

Flat Ride Spot Mic: AKG 452

Again, I cannot stress enough how important a great drummer and good drums are to getting the sound of a great kit. Thanks Penny!

Penny Larson: The Great Drummer in the Center of the Sound

Penny Larson: The Great Drummer in the Center of the Sound

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!