Making great microphones even much more listenable

There seem to be 2 different approaches.


Mics that have acoustically implemented mid high rise. For example SM7, MD441. Then an L (in series with R or L winding resistance) in series with C for example on SM7 creates flat frequency response. It can be seen on Shure SM7 datasheet.


Other mics such as AKG D1000E seem to have a flat frequency response. Then an R is series with LC creates gentle mid high rise.


The above great filters are subtractive.
For example on the second everything but the mid high is gently and subtly reduced.
On the first example the broad mid high peak is reduced.


Pleiades inline filters operate on these principles. (R,LC) has not been much tried yet. Neither (R,L) cascaded to (R,C).

AKG D190E to Pleiades (130Ω,40mH) to Uher 4200 to BASF 911

It sounded like a sunny morning journey to the dentist.


The sound is very alive and clear but high frequency is too much.
Possible causes:
The particular Pleiades (130Ω,40mH) gives too much high pass
Inter modulation crossover distortion from Uher 4200 output stage driving the loudspeaker
Over,ovulating the record amplifier or tape
Gentle high cut needed to compensate for Equal Loudness curves, voice effort curves etc.


Signal path:


Bedroom with Tempur mattress - male singing voice - AKG D190E - Pleiades (130Ω,40mH) - Uher 4200 3rd arrival to Pleiades - BASF 911 - Uher 4200 3rd playing back - Pleiades linoleum Auratone 5C type monitoring speaker  - listener's ears, brain - bedroom


Recording while speaker is playing gave an interesting double tracking short of effect, phasing as speaker was only 1 meter away from mic


Listening to playback from adjacent rooms gives an impressive sound as edginess is smoothed out.


A thought is to also concentrate on Pleiades gentle slope high cut filters too.


Or (R,CL) filters, see AKG D1000E datasheet.


Later addition: The BASF 1/4in recording was transfered to TDK SAX cassette with the Sony TC-D5M. This was then played on Vicky's Pioneer, Musical Fidelity, Spendor playback system. Although Vicky did not like the s cliping problems she was amazed at the sound of a very bass male register voice recorded at half speed and then played at 7.5ips. She commented it was the best quality she has heard yet with no distortion whatsoever and pro sound. Male singer sounded like a female creature. She decided on buying a Uher 4200 report from eBay.de.


It is in current thought whether the s problems at normal singing voice where due to over loading the type. By watching the LED display on the pioneer cassette deck at s all red LEDs are suddntly lit.

Legendary Jazz recording engineer Rudy Van Gelder had been since childhood a radio ham building his radio, radio transmiters and then his first recording mixer (adder)

On interview in Tape Op magazine.

Hello to Germany and Hellas

AKG D190 E to Pleiades V(-1) low cut implemented after electron tube or to V1 or to Pleiades (130Ω,40mH) filter

At your risk. Take all safety precautions. A fuse should be in series to any battery for fire hazard safety.


V(-1) is one of the first Pleiades mic booster pre preamps.


Made before 2000.


With some mods it now consists of a neat gray painted diecast aluminium rectangular box. One electron tube 12AU7 for each channel.


Long tailed pair with short tail as cathodes of each pair are connected to Vb minus.


Heaters are in parallel so with the 12V battery power supply if one channel is to be used, only one electron tube can be pluged in for less power consumption.


The V(-1) internal signs, path or schematic signal flow is:
Mic XLR connector
Sowter 1:7 input transformer
Secondary feeding grids at space potential
Anodes feeding primary of Sowter 1:1 10K transformer, center tap to Vb=12V
Output XLR connector


Grids are floating as there is no centre tap return.
So amp is sensitive to light falling on electron tubes as possibly the photoelectric effect (photons colliding with matter, electrons etc) changes bias.
The amp might be used as a photo side chain compressor.


This amp has no resistors, no capacitors. Like one stage of a Langenvin amplifier.


So this is what happened by chance:


Since the output impedance is high it was decided to connect a say 10:1 German in line transformer to bring impedance down so that it can then be connected to Sony TC-D5 Pro low impedance XLR transformer input.


There was almost no signal level until some light fell on electron tubes after sunrise. Sound was low and bass heavy.


But fortunately the German in line transformer has a switch making it 1:1. It is clearly "wrong" to use a 1:1 setting but it sounded great, with loud sound and great treble. (Bass heaviness gone).


So this is another case where low cut or high pass is implemented after the first electron tube.


Signal path:


male voice singing Πως θα Ηταν in F minor - AKG D190E at say 3in - Pleiades V(-1) - German 1:1 transformer - Sony TC-D5 Pro or TC-D5M - Sennheiser HD580


Monitoring with the TC-D5M and recording was done to one channel (L) as there is no bridging mono mode.


In the case of TC-D5 Pro there are 3 transformers one cascaded to another, Sowter 10K:10K - German 1:1 - Sony mic input transformer


A recording was also done with Pleiades V1 (CV2269 electrometer electron tube operating with a 1.3V battery for both haters and anode). Anode feeding directly TC-D5M trough coupling capacitor, RL C coupling.


And AKG D190E was also connected directly to TC-D5M through a Pleiades (130Ω,40mH) gentle slope high pass filter.


All sounded nice. The cassette recorded must be listened too again to decide which may be best.


On preliminary real time listening tests on TC-D5 Pro before recording, low cut done on V(-1) by the interaction of anode internal resistance and transformer inductance sounded more natural bright and interesting than the Pleides filter implemented just at mic's output.


It is as if some kind of frequency or even non linear distortion makes the mic more sensitive, more revealing, perhaps more natural.


The Geraman transformer is GSM1 e+p and has at the 1:1 setting secondary inductance 600mH at LF (97Hz), 270mH at MF (around 1.028KHz) and primary inductance 470mH at LF, and if memory is correct 220mH at MF.

Rudy Van Gelder's comment on surround speakers

On Tape Op interview.


After reading the interview there seems to be a suggestion for the future.


One surrounded by fullrange speakers. Each speaker playing an individual instrument.

Rudy Van Gelder's comment on the Neumann U47 and Shure 545 microphones

On tape op (Tape Op Magazine) interview