Another day another project! today my friend Jon from New Alliance Audio and i are cleaning up a pair of 50's era Berlant / Concertone Series 30 Preamps. I have had these for 10 years or so and they worked when i got them! I was impressed. So i didn't even give them a serious clean. But since jon was looking into replacing some now tired tubes, we decided to do a first level scrub down of the innards. Berlant / Concertone History
These were made between 1955 - 1958 and would have come with a reel to reel tape recorder. You often see them used as stand alone Mic Preamps in modern studios as they are built like tanks and have a lot of vintage vibe to offer.
There's a few things to keep in mind if you are thinking about getting a pair of these to use. They are designed to be used in a 50's era home hifi setup and often don't have the input and output transformers needed to work as stand alone mic preamps. This is surmountable in two ways. First, you can track down the original transformers with 11 pin octal sockets. Second, you can remove the sockets and mount any transformer you want inside!
We took a hybrid approach with this pair when i got them. I tracked down an old broadcast veteran on the Ampex list who had a pair of 11 pin Langevin Mic Transformers for this unit. They are big and hefty as you can see in the photos and offer a wide range of mic impedance choices. For the output we decided to modify the socket and mount a pair of UTC A27 transformers. They do the impedance matching to interface with any modern line level equipment we will use the Berlants with.
On to the photos! So these probably came from the estate of a serious smoker. They were sticky with gunk inside. We used rubbing alcohol and some gentle house hold cleaners to remove the gunk. It was a delicate process because it's easy to remove silk screen paint and even chassis paints on gear this old.
So, these may get another round of cleaning once we get the tube situation sorted. But they look a lot better! I have the manual somewhere and i need to find some replacement meter bulbs to get these puppies fully back to glory.
PS: The last picture is of some custom attenuators we made for these preamps. The Berlants have a lot of gain. Too much in fact for most modern microphones. So we devised these in line style XLR pads to bring the source level down 20dB before the preamp sees it. They live plugged into the mic XLR inputs.
PPS: One really cool feature of these units is that they have an input and output level control. This is great because it allows you to control how hard you hit the input tubes and output transformer individually.
PPPS: I have the schematics and product catalog for these somewhere, I'll be sure to scan them when i locate them. Home stereos were so much cooler back in the 50's and 60's...
::: I.F. :::