Bruel & Kjaer - Vintage Microphone Amplifier Type 2603

Brüel & Kjaer - Microphone Amplifier Type 2603

From the late 60s.

The 2603 is about 58 years old, it dates back to 1966~1969.

This preamp needs some care, but the overall condition is good, and fair given its age.

Was planning to restore it but never got to it so I'm letting it go.

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There are 6 or more tubes in the circuitry, and as far as I can tell most, if not all of these tubes are still available in case you need a replacement one day.

I have no idea of the condition of these tubes. Neither do I know if the caps need replacement. I never switched it on; it was sitting in my studio as an eye catcher, waiting to be restored one day. All parts are there. And the unit looks well preserved, which is a good indicator.

- It could be non functioning, and require quite some work.

- It could require just a minimal check up and of you go.

I can give no guarantees. The unit is sold as is.

To know how it sounds: click the Youtube link in the last pic of the galery - or look on Youtube for:"Brüel & Kjaer Type 2603 vacuum tube preamp"

I collected several PDF's of this device and line of equipment, including the schematics etc. I will happily send them to you (saves you some research)

Please note: this preamp does not work with regular XLR mics - although you could mod it to do so.

It does accept line signals, as you can see from the linked video.

It partners with the following mic capsules from B&K: 4131, 4132, 4133, 4134 ..

Combine the above capsules with a B&K "Cathode Follower" type 2612, 2613, 2614, or 2615.

The above parts are available on Reverb here and through other places and sellers.

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The inputs and outputs require a type of B&K plug that is hard to find. Luckily these connections accept simple banana plugs as well, which fit like a glove. The ins and outs are basically (unbalanced) line signals. One could easily fashion a set of adapter cables that go from banana plugs (male) to 1/4" jack (female) for day to day use.

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PS - Someone on GroupDIY modified their B&K 2604 so it accepts XLR's and it even provides phantom power. The 2604 is similar to the 2603, in fact they are like twins; the 2604 records 10Hz~200kHz, the 2603 records 2Hz~40kHz. The person on GroupDIY also included a recording of their modified 2604 somewhere in the thread. It is a basic recording, and it sounds gorgeous. Turns out this preamp is comparable to a Telefunken V72 (which is from the same era more or less; the V72 is fifties, the 2603 is sixties. And the V72 is quite expensive and valuable as you might know). That is the mod I would do if I were to keep it. I can not post the link here, but it is a simple "2604" search on GroupDIY.

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Connections are as follows:

- "Amplifier input" = the main line input, which accepts a banana plug

- The small hole underneath this and other plugs is ground; accepting a banana plug as well

- "External Filter Input" = actually an output !! Clean signal from this out

- "Recorder" = allegedly this is a more fuzzy / slightly distorted output

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The overall gain is adjustable by the "Input Potentiometer" and "Meter Range" switch.

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The power connector is a Nema 5-15R.

Adapters are available to regular IEC etc.

Alternatively you can connect a power cord directly using the screws adjacent to the inlet pins.

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My location is Belgium. Items are shipped safe and secure with tracking etc.

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The SHIPPING PRICES published here are indicative and *not* final.
Please contact me for a shipping quote for your specific location.
I am happy to make you a personal quote.

Have a nice day!

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