Animated, waving, US Flag

God Bless America!

Chattering smiley
Ribbon mic page 4
Yep, that's me, HAMMING it up! ;)


HOMEBREW ribbon microphone DELTA!

Yes, folks, I have now built FOUR of these things! They keep getting BETTER, so why not?! :)

Latest updates: 7/12/07
DELTA unit constructed! Alpha unit disassembled. Alpha's transformer re-used in Delta Unit. Preamp revised again, eliminating 3'rd stage. Now at design 3.0, the best yet. This new preamp is used in the new Delta Unit (details, below) and likely will be the design I will use from now on. Simpler = better!

Others in this series:

ALPHA UNIT *now diasassembled* (Page 1)

BETA UNIT (Page 2)


I'm breaking with "tradition", here, by showing the progress in REVERSE ORDER...

The Delta Unit, V2.0 - Electronics view
HOMEBREW Ribbon microphone Delta

This is the completed DELTA unit, with the V3.0 preamp shown. This preamp provides less noise, plenty of gain, good audio quality, and excellent dynamic range! The signal output can range from millivolts (very low sound level) to several VOLTS peak-peak. (Shouting close to mic.) This is also true of the others in this series. By eliminating the 3'rd stage, complexity is reduced with very little overall loss of performance. I am very pleased with the results thus far! :) I think I am going to stick to THIS version of the preamp if I build any more of these mics. I am also going to keep the name "DELTA" as this looks like the best all-around design I have come up with thus far. I'll just number them "Delta 3", etc.)

Here is another view of this mic, but with the 3-stage preamp and original transformer.
I called this one Delta 1. It was fairly quickly revised into the Delta 2, above! :)

Delta unit 1.0, with the V2.2 preamp
Delta Mic version 1.0

The Delta 2, oblique viewThe Delta 2, back view
Oblique view of Delta 2 HOMEBREW Ribbon microphone Delta

Once the ribbon is constructed, (see below) it can be mounted to the support and positioned within the magnetic field. In this unit, the small PC board has a hole drilled thru the bottom (ground) land, and is bolted securely to the metal frame. The paint on the frame was scraped away for a good electrical connection.

In the back view, the copper strap I use to ground the transformer frame to the preamp board is clearly visible.

View of the "Motor"
Delta unit 'Motor' view

This view shows the Delta unit's "Motor". The ribbon is positioned within the field of the upper magnet pair, only. This is done because the bottom magnets are the opposite polarity. For best performance, the magnetic field across the ribbon needs to be fairly uniform.

The white frame was salvaged from a defective computer monitor swivel-arm unit. It is solid steel, and makes a rather nice structure for a ribbon mic! Because it is ferrous, it also helps to provide some shielding against stray magnetic fields. This mic is much less sensitive to them than any of the others! As I said... "They keep getting better!"

View of the ribbon element
Delta unit ribbon

Jump to ribbon construction tips HERE.

With this unit, I built the ribbon element as a seperate module. Here is the Delta style ribbon assembly. This is how I will make my ribbon structures from now on! The construction is very simple - a small piece of PC board with a slice thru the copper to create two seperate foils. The board is about 1/2" wide by 1.5" long. The wires are plain copper 16ga which are attached to the board with solder. They are bent into shape, then the ribbon is attached to one side. The other is bent to meet the contact on the ribbon, then it is soldered. A hole in the board permits screwing the board to the frame.

There should be no tension on the ribbon. It needs to be slightly loose and flexible. You want the self-resonant freq to be well below 30Hz. Too much tension will raise this resonance well into the audio range, and it will sound terrible!

Delta 1 unit frame
Frame view of the Delata unitFrame view of the Delata unit

Here is the view of the Delta 1 unit's frame. This is showing the preamp PC board, prior to trimming and mounting of the parts. The ribbon unit's PC board and top wire support is visible here. The original transformer is also shown. It was unsatisfactory. The audio was very "muddy", probably because of too much inductance in the secondary. This transformer was originally a B+ choke salvaged from some old tube gear. It was at least several Henries. I wound a single layer coil on top of the existing coil. The fact that it worked AT ALL was a pleasant surprise. ;) Since the audio was so poor, I simply disassembled the Alpha unit and used that transformer in this one. After replacing the transformer and revising the preamp, I called this the Delta 2. Somehow, that name just sounds cool, don't you think? ;)

The Delta preamp board, etched
Etched Delta PC board, before parts

Here is what the PC board looked like after "etching". I simply used a cutting wheel on my Dremel tool, which is why there is some "overshoot" on some of the cuts. Hey, I did this in 10 minutes! ;) If I took my time, it probably would have taken twice that long! ;)

"Artwork" prior to etching
Pre-etch PC board artwork

Since I use a Dremel tool to do my etching, it's easier to just make fairly large pads and straight lines. Lately, this technique has been working extremely well with my projects, so I am going to continue to do it. It's like "big surface mount" with REAL components that you can actually work on! :)

UPDATES: 2.0: 12/27/2006, 2.2: 1/6/2007, 3.0 7/12/07

Delta unit preamp schematic V3.0
Preamp schematic V3.0

Here is the upgraded (AGAIN, 7/12/07) ribbon mic preamp. The first two stages are identical to V2.2 which I originally thought was the best preamp design! Well, now it's BETTER with one LESS stage! Even LESS noise, still PLENTY of gain, and good clean audio. Can't beat that! The former 3'rd transistor was essentially replaced by a 1K resistor to gnd between the two .22 caps. This rolls off the low frequencies nicely, allowing you to work the microphone much more closely, and not have so much "proximity effect". (Lows become unnaturally pronounced when you get too close to a ribbon mic, so this simple high-pass filter compensates for this.)

Keeping the feedback resistor definitely makes this amp a much better performer than the earlier versions!

"Stay Tuned!" ;) There's still MORE TO COME!!

(I will keep updating this page as I make progress with these units. Check back now & then.)

Others in this series:

ALPHA UNIT (Page 1) (Disassembled)
Jump to ribbon construction tips HERE.

BETA UNIT (Page 2)


Take me HOME...