The Cave Music Services

Ribbon Mike Restoration

Here's an interesting article about the guy who restored my RCA BK-5A:

The Man Behind the (Ribbon) Mic.


Sony Condenser Mikes From The 1960s.

I have this old Sony condenser mike.

Sony C-38B

An old Sony condenser mike

From the pictures and information I found on the web here, I thought it was a C-37-FET. I don't have the power supply that came with it, so I found circuit schematics to figure out how to hook up the five pin XLR connection. I tried reverse engineering the circuit in the mike, and found it's not quite like the circuit diagram in the C-37-FET Technical Manual (which is available on the above web site). Eventually I realized that it is in fact a C-38A (or B??), a 1969 update of the C-37 mikes! There isn't much info available on this mike - it seems quite rare - and I'm not sure all of the information I've found on the web is completely accurate. Apparently this mike has been used at Abbey Road studio to record the Beatles, and Herb Alpert's trumpet on A Taste of Honey:article here.

Update 2010.11.05: new information I have received indicates that my mike is almost, nearly, just about, absolutely for sure a C-38B.

I did get the mike working by building a simple five-pin to three pin XLR converter. The mike can be operated with a 9V battery inserted or an external 9V power supply. Both of these methods can be remotely switched. I suspect it also can run from phantom power since there is a centre tap off the transformer that feeds the powering circuit. But I need to verify that there is a voltage regulator that drops 48 VDC to 9VDC so the DC-DC converter doesn't get fried.  The information I found on the web suggests the C-38B, made in 1971, was modified to be used with phantom power. I'm almost sure that this one is not a C-38B, because it seems the C-38B has a three-pin XLR connection, while mine has a five-pin. The guy I got this from has the exact same mike with the power supply and the storage box with the model number on it (C-38A). Turns out his is a C-38B - but the box is from a C-38A!

There a few differences between the C-37-FET and the C-38B.  The switch on the C-37-FET can be set to BAT to check the condition of the battery.  On the C-38B, the switch is mechanically blocked from going to that position.  So don't bother trying (I did).  The internal circuitry is somewhat different, but I haven't completely traced out the schematic yet.  There are differences in the two internal switches (high cut and 8 dB pad) - see the pictures below. The C-37-FET pictured doesn't have a pad switch.

Sony C-38A - internal view.

Sony C-38B - internal view.

Sony C-37-FET - internal view.

Sony C-37-FET - internal view (from

Sony C-37-FET - close up internal view.

Sony C-37-FET - close up internal view (from

Sony C-38B inside the headbasket.

Sony C-38B inside the headbasket.

Below is the powering diagram from the C-37-FET Technical Manual, which also works with the C-38A/B. Option 1 uses the internal 9V battery, and the switch allows you to turn it off remotely.  The switch on the mike has to be on.  Option 2 uses the internal 9V battery and has the mike on any time the connector is connected and the switch on the mike is on.   This is how I wired my connector gizmo.  It seems option 3 is slightly wrong.  The jumper between pins 1 and 5 is also necessary here (or connect pin 5 to the shield - same difference).

C-37-FET powering

C-37-FET powering

Here is a summary of the information I have found on similar Sony mikes (I got this info from the internet and some sleuthing, so I'm not 100% sure of its accuracy. If you have any corrections please let me know.):
C-37A: A tube condenser mike introduced by Sony in 1958 intended to compete with the Neumann microphones. Because of the tube circuitry it requires a special external power supply.
C-37P: A FET version of the mike that can be powered with 48VDC to 54VDC phantom power.
C-37-FET: Made in about 1965, it's a version of the C-37A that uses a field effect transistor (FET). It can be powered with an internal 9V battery or an external 9VDC power supply. It has a five pin XLR connector for powering and remote switching.
C-38: I'm not too sure about this one, if it existed. It could be simply a re-labelling of the C-37-FET, or people just dropped the 'A' when referring to it. One source says that the C-38 and the C-37-FET are the same: the C-38 was sold in Japan and the C-37-FET was sold in the US. Update (2010.10.29): I found pictures and some brief information on the C38. It was built in 1965 and the windscreen design is quite different from the C-38A and B. It looks like the C-37-FET inside and out from the photos, but I have no documentation on the C38 to verify if the two are identical.
C-38A: An update of the C-37-FET, introduced in 1969 with a new windscreen design. It has a five pin XLR connector for powering and remote switching. Can be powered by an internal 9V battery or an external 9VDC power supply, and possibly phantom power (I will try to verify this). Update 2010.11.05: A service manual I have obtained (copyright 1980) for the US indicates that the C-37-FET and the C38A have the same internal circuitry. No phantom powering!
C-38B (1971): An update of the C-38A, introduced in 1971. I think it had a three five pin XLR connector (not sure - I have no documentation). Can be powered by an internal 9V battery or 24VDC to 54VDC phantom power.
C-38B (1977): A further update of the C-38B. According to a service manual I have found, it has a three pin XLR connector. It can be powered by an internal 9V battery or 24VDC to 54VDC phantom power.
C-38B (2003): Sony re-released the C-38B in 2003. Can be powered by an internal 9V battery or 24VDC to 48VDC phantom power.

If you have any information about any of these mikes, or corrections to the above, please send it to me, especially the C-38A and C-38B (original) since that information is quite rare.  This blog entry has become a little messy with corrections, so I plan to write an updated entry with the most complete information I can find. Owner's manuals and schematics would be great. Thanks!

Edit: Apparently this mike is the classic Manzai mike in Japan (thanks ratite!!). See this.


The Traditional Bluegrass Microphone Technique: Part 2

This article of mine appeared in the Northern Bluegrass Circle Music Society's December 2009 newsletter. Part 3 of of my two part article is now in the works!

The Traditional Bluegrass Microphone Technique. Part 2: How to Work the Mike

In Part 1, we discussed the basic characteristics of mikes. In this instalment, we talk about how to use a single mike. The single mike technique can work quite well, but it can also work really badly. The quality of the acoustic space, the mike and the sound system are important factors, and the sound person only has control of the overall tone and volume. Most of the success of the technique depends on the musicians' skill in working the mike.

The mike should be placed downstage (towards the audience) to minimize pick-up of echoes off the walls behind and to the sides of the mike. You may have to back it up a little if you get some feedback from the main speakers. Monitor wedges are occasionally used, but not very loud due to feedback. As we discussed in Part 1, proximity to the mike affects the loudness and tonal quality, so the mike needs to be set at the correct height for the band. Consider that the one mike has to pick up the vocals (mouth height) and the instruments (mostly belly height, except for fiddle), so take a look at the relative heights of everybody and their instruments and find a reasonable compromise that covers everything roughly equally. Since vocals are very important in bluegrass, the mike will be a little closer to the mouths than the instruments. The mike can be set a little lower than chin height as that will pick up a good blend of vocals and instruments, and will allow a good audience view of musicians' faces. About two-thirds of the way up, between the lowest instrument and the tallest singer's mouth is a good starting point, but you can experiment to find the best height.  The mike will pick up sound from below your mouth, so you don't have to bend over into it. The mike picks up approximately a 120 degree zone on one side of the mike, so cluster your band in a tight arc on the pickup side of the mike.

Fig. 1.  Mike height and player placement.

Fig. 1. Mike height and player placement.

Voices: Know Your Own Volume
There are louder singers, quieter singers, voices that project well, some that don't. Each singer's proximity to the mike will have to take that into account. The lead vocalist should generally be the closest and in the centre – 8 to 12 inches from the mike. Backup vocals should be off to the sides and a little further away, and louder singers will have to back off a little. Some people may have to lean in a little. If you have a quiet voice, get in closer, but not too close - six inches should be about the closest you ever get. During a quiet passage, you should get closer to make sure the words are intelligible. When you belt it out, you can back off a lot and still get the effect without knocking over the first few rows of the audience. Connect the dynamics of the song to the distance from the mike. During your band's vocal practice, it's a good idea to include mike technique practice.

Instruments: Know Your Own Volume
The same idea applies to the instruments. In general, instruments playing rhythm can be further away because they're providing a supporting role, and an instrumental break requires that the instrument be closer to the mike. Usually the acoustic guitar is the quietest instrument, but it depends on your playing style. You can make that Martin project pretty loud (ask your Bluegrass Workshop instructor how), but generally the guitar needs to be quite a lot closer than most instruments, and you may have noticed how the other players in bands usually quiet right down when the guitar takes a break. The main difficulty with the guitar is that getting in close can completely change the tone so it's good to know how different regions of the instrument sound different in front of a mike. If you put the sound hole right in front of the mike, it can sound too boomy with poor definition. Move the guitar over so that the 12th fret on the fingerboard is right in front, and the sound gets much tinnier. Somewhere in between should be optimal so experiment with your own guitar to find the best sounding mike-guitar orientation.

Mandolins generally pick up fairly well even at a distance and they cut through because of their tone. When players do the chop, they can be quite a ways back, but they do need to get a little closer to the mike for the breaks. The banjo is often the loudest instrument, so it can be further away (outside in the parking lot is good).

Due to its size, the standup bass usually ends up the furthest away, and often the bottom end of the instrument sounds fairly weak through the sound system. However if it gets closer, there may be too much string slap. Many top bluegrass bands (such as the Del McCoury Band) will compensate for this by plugging the bass into a separate channel using a direct input (DI) box (oops, did I say "plug-in" in a bluegrass newsletter??).

Side Mikes
You may have noticed a lot of bands use a side mike or two. The placement of one or two small hyper-cardioid (very directional) mikes can make playing instrumental breaks and incidental fills more convenient. These mikes can be placed at more appropriate heights for the instruments. Both Cherryholmes and The Steeldrivers made great use of side mikes at the Edmonton Folk Music Festival this past summer.

Fig. 2. Cherryholmes. Single mike (looks like a Shure KSM44) in the centre and two side mikes for instrumental breaks and fills. (Photo by Kevin Jacobson)

Fig. 2. Cherryholmes. Single mike (looks like a Shure KSM44) in the centre and two side mikes for instrumental breaks and fills. (Photo by Kevin Jacobson)

Fig. 3.  The Steeldrivers. (Photo by Kevin Jacobson)

Fig. 3. The Steeldrivers. Single mike (far right, in front of guitar player's face). IMO, the mike was a bit too high - the fiddle player had to stand on tippy-toes to sing into it. Shure SM57s being used as side mikes. SM57s are cheap dynamic mikes, but surprisingly good. (Photo by Kevin Jacobson)

Practice and Experiment
Just like anything else, it's a great idea to practice mike technique with your band. If you can, set up a mike and a simple recording system at home and try it out. Try it by yourself, try it with your whole band. Try it vocals only, instruments only, and then all together. When you play somewhere, have someone in the audience listen carefully so they can provide some constructive advice. Search for Del McCoury videos on youtube and watch some pro-level microphone work. In particular, check out their performance of Nashville Cats in Austin (below) - a great example of mike technique.  Watch how close they get for lead vocals, backing vocals, and instrumental fills and breaks.

Make a Show of It
The most important thing is to sound good, so at the very least your band needs to practice moving around the mike and each other to accommodate what's happening in the song. The lead vocalist needs to move aside for the instrumental breaks, instrumentalists and backup vocalists move in and out as needed. So practice this for every song you do. Once you get skilled, you can choreograph an interesting show with mike technique. Have people zip around the mike to new positions, shuffle people around. Fool around and have fun!

by Kevin Jacobson (