Ampex MX35 Mod

Ampex MX35 Mod

Ampex MX35 ModAmpex MX35 MOd Extension Chassis Front Panel

(Click pic to enlarge)

 

 

 

 

Front Panel Controls:

  1. +48 switch turns phantom power on and off.
  2. -20 switch engage 20 db pad
  3. Phase reverse switch
  4. Mute switch mutes signal to the mix bus but not direct out
  5. Dir-D&M-Mix switch allows selecting to channel to go to Direct Out, Direct Out and Mix, or Mix only (respectively)
  6. 600 switch engages a 600 ohm load. This switch is to be enaged when the Direct Out signal feeds equipment that does not have 600 ohm input. Output transformers used in this design sound best when terminated with 600 ohms.

Ampex MX35 Mod

Ampex MX35 Mod Extension Chassis inside view

(Click pic to enlarge)

 

 

 

 

Inside view of the Extension Chassis:

  1. 9 pin dsub connectors mate with same from the MX35 chassis
  2. Discreet Opamps buffer the MX35 channel level controls and feed the vintage output transformers.
  3. Power supply with toroidal transformer for zero induced hum.

 

Ampex MX35 Mod

Ampex MX35 showing interface connectors for Extension Chassis

(Click pic to enlarge)

 

 

 

 

Interface connectors:

  1. 9 pin dsub connectors feed signal to and from the Extension Chassis
  2. This connector system allows the MX35 and Extension chassis to be separated for service.

Ampex MX35 Mod

Ampex MX35 Mod showing the two chassis separated

(Click pic to enlarge)

 

 

 

 

Interface Connectors:

  1. Another view showing MX35 intefaced to Extension Chassis with 9 pin dsub connectors.

 

 

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Ampex MX-35 Mic Pre Mixer Mod:

 

The Ampex MX-35  is a fine little mixer from the late tube era.  The circuitry is straight forward Class A (as are most tube circuits) resulting in an overall smooth, clean sound.  The microphone input transformer is interesting in that it is very small...sometimes referred to as a “thumb” transformer.  Usually a small transformer lacks low end response, as theory says it will saturate easily and thus attenuate peaks of low frequency signal.   Somehow the  thumb transformer in the MX-35 is able to pass low frequencies with minimal saturation.  The saturation or loss of low frequencies is evident when the the signal from the mic is on the hot side, yet still the MX-35 manages to sound pretty good.  A fine sounding little mixer to be sure, but it has it’s drawbacks.

This Mod came about from customer’s requests to have a more complete set of mic pre controls added on to the MX35 to overcome limitations to actual practical use in music and sound recording.

 

The Drawbacks  angry:

  1. All 4 channels mix into either A or B outputs, or both, limiting usefullness in multitrack recording situations. There are no Direct Outs for each input channel.
  2. No input pad 
  3. No phase reverse
  4. No phantom power
  5. No Mute switch

 

The Solution laugh:

A chassis extension is added underneath the original chassis.  The needed extra circuitry is added in the extension chassis and wires run between it and the original chassis. For each channel any or all of the following features can be added:

  1. Direct Outputs are added for each channel using discreet opamps and output transformers. A 600 ohm load switch adds the needed load when outputs are connected to bridging inputs, which is often the case.
  2. A -20 db input pad is added
  3. A phase reverse switch is added
  4. Phantom power switches and phantom power supply are added
  5. A mute switch is added.

 

See Details for more info.

  • Product Code: WPA-Ampex-MX35-mod
  • Availability: In Stock
  • $0.00

Tags: Mod, Ampex