As well as microphones, Grampian made amplifiers and other PA equipment. Here’s an old Grampian amplifier and speaker set.
I found the amp a few years ago in Dave Dee’s junk shop in York. The circuit is actually very similar to a Mullard Twenty, with the addition of a transformer balanced mic input, and several taps on the output transformer for 8 ohm loudspeaker or 100V connection. I have even used this in the past as a mic preamp for recording, for some warm and slightly dirty vocal tracks.
The speaker is a recent purchase found on GroupDIY.com. It has a rather nice and unusual tapered shape, with (no longer very) white vinyl covering. The whole set has a really cool vintage look to it – very different from today’s ubiquitous square black boxes.
I am now using this as a guitar rig – it has a great vintage valve tone with just the right amount of breakup coming from the speakers. There is plenty of volume for recording, but I would hesitate to use it for rehearsals with a modern loud drum kit!
I am unsure of the age of these but I would guess 1950s or early 60s – they don’t appear in Grampian’s 1968 product line, and presumably pre-date that. If anybody knows more, please get in touch.
Don’t test a ribbon mic with a multi-meter or else…
I am particularly pleased to see the warning not to use a DC meter on these. Quite often I come across ebay auctions where the seller measures ribbon mics with a multimeter, unaware that the carrier current can bump the ribbon out of the magnetic field and stretch it. 🙁
Grampian also made matching transformers for their mics – we have a few available for sale. Here is the factory drawing for the transformer.
It is time again for microphone of the month, and for May we have these lovely Grampian ribbons.
Grampian ribbon mics
Grampian mics come in a variety of model names and numbers which we will try to decypher. These were made in the 1960s and 70s by Grampian Reproducers Ltd, of Feltham in Middlesex, England.
Grampian GR1/L and GR2/L ribbon mics
The mics are labeled GR (“Grampian Ribbon”), followed by a number and a letter. The GR1 designation was used for the semi-cardioid version, and the GR2 is the ‘normal’ figure-8 pattern. The letter shows the impedance of the mic, set by the output transformer winding. They come in Low, Medium, High, and ‘X’ flavours – the letter codes are as follows:
GR1/L and GR2/L … 30 ohms
GR1/X and GR2/X … 200 ohms
GR1/M and GR2/M … 600 ohms
GR1/H and GR2/H … 50K ohms
Here is a rather wobbly scan of the original Grampian data sheet.
The GR1 usually has a silver grill at the front, and a black one at the rear to show its asymmetry, whereas the GR2 has two silver grills. However, inside there is very little real difference between the two models, and any cardioidness* is imposed by additional foam padding around the rear of the ribbon. This foam usually depolymerises over the 40 years or so since manufacture, and the mics will typically fall apart when opened. If the mics have been stored for a long time they will require careful cleaning and new foam suspension before being put back into use.
The mics have a small thin ribbon, held in a removable plastic frame for ease of service. In that respect they are similar to the Reslos and Film Industries mics with which they undoubtedly competed. Unlike the Reslo and FI mics, the symmetrical magnet arrangement means that the GR2 has a true figure-8 response, and are suitable for Blumlein pair or a side mic in a mid-side array.
The internal transformers have a tendency to break, particularly on the H models which have very thin wires. If the break is in the right place the transformer can be repaired, but a rewind may be necessary.
Grampian plugs and connectors are a bit of a pain – they are getting scarce now, and rely on the barrel to make the ground connection, which can lead to hum if the connector is worn or oxidised. I have blogged previously about XLR conversions for these.
Grampian plugs
External matching transformers were also available, in case one needed to connect to an input of a different impedance. These are still handy for getting a bit more level out of the 30 ohm models.
These were mid-price microphones when they were made. I have a Grampian price list from June 1976, and the GR1 & 2 microphones were priced at £32.05 (plus tax) in a wooden instrument case, and £27.55 in a cardboard box. This would translate today as £180 to £334 plus tax, which would buy one of the better Chinese ribbons or a Beyer M260.
At Xaudia, one of the most common enquiries that we get is for replacement cables and connectors for vintage microphones. Very often we can help, but some of the connectors are becoming impossible to find in good condition and at reasonable prices.
Grampian GR1 ribbon mic with connector & cable
One example is the Grampian plug that was used for their GR1 ribbon and other microphones. These connectors are hard to find – they can be obtained by buying a less valuable Grampian dynamic mic, but we have found that the plugs come with various slightly different threads, which means that one plug cannot be guaranteed to fit another microphone. And the connector is not ideal in the first place – it has two prongs and for balanced use the screen of the cable is connected to the plug casing (and therefore the microphone) by pressure only. Grounding issues are therefore common.
There is, however, another approach, which is to dispense with the connector entirely, and replace it with a modern, industry standard XLR connector. This microphone arrived without a plug and with a rather battered and bent connector at the bottom of the mic.
The decision was made to replace it with a silver-plated XLR output, which also solves any grounding issues as the third pin may be connected to the body of the mic.
The old connector was cut off, and the housing threaded to accept the new connector.
The new XLR output is then simply screwed in place… and the mic rewired and put back together.
XLR modified Grampian
Everything works nicely – just plug a standard XLR mic cable and it is ready to record.
Some may see this as vandalism, and perhaps from a collectors point of view, it is. However, the conversion is sympathetic, and it is far better for the mic to be making recordings, than to be languishing in a box unused.
