"Hello everybody. Before I continue with the story of this amplifier, let me tell you a little bit of what I know and remember about the Linear/RSC products.
They were designed and manufactured up in the West Riding of Yorkshire, and I believe that the transformers were also wound somewhere in the same area. (?)
Though Linear amplifiers certainly had a place in the market back there in the sixties, they were actually like a "poor guitarists amplifier" (sorry Linear) but; in all fairness they were sort of alright. If one couldn’t afford a Vox, Marshall, Selmer etc, then a Linear would be the next best thing with whatever speaker one could lay ones hands on to go with it! These amplifiers have become known as a "Bird Cage" style amplifier, because of the grill type top cover they used.
If my memory serves me well, there were a few models. I distinctly remember the "Conchord" 30 watt, as I had two of these at one time, for my bass guitar. There was also the bigger daddy version of this too, designated simply the "L50". This was exactly the same design/circuit, but slightly bigger in size and with larger/heavier transformers too. I also remember a model called the "Diatronic". This was a baby version of the previous two, and featured two EL84’s at the output and a EZ81 rectifier, as opposed to two EL34’s and a GZ34 used in both the" Conchord and L50". The "Diatronic" was 15 watts whereas the "Conchord" was rated at 30 watts and the "L50" at 50 watts.
I have vague recollections of two more models. One of them had a pair of ECL86’s at a 12 watt output (I can’t remember the rest of the tubes) but, I think I had a pair of these for my stereo system in about 1966/7. If anybody can clarify this one for me with some more information, please do.
Lastly I also have the feeling that they did a small stereo amp of similar design, but once again, if anybody can refresh my memory on this please do.
One funny thing I do remember about all the various models is the fact that when you bought a new one of these, all the potentiometer spindles were left quite long. This row of white, old style gramophone knobs would be sticking out by about 2 inches! I think the idea was that if the amp was built into a wooden case, then the control shafts would then reach the outside. Strange but funny!
Although at the time the components would have been OK, unfortunately the type of cheap resistors and condensers that were used back then don’t stand the "test of time" too well, and are almost always faulty nowadays.
The power rating of all these models always left a bit to be desired! As I have said before, apart from a few companies like Vox, Marshall, Selmer, etc, a lot of these old sixties amplifier designers probably built their amps from and around valve data sheets (almost certainly Mullard?), and then simply marketed them as having the output stated on the data sheet. They just assumed that the data sheet output would be achieved, rather than actually pulling amplifiers off the production line at random and giving them a full test.
The "Diatronic" would make about 12 watts RMS, the "Conchord" would make about 22 watts RMS and the "L50" about 40 watts RMS. Of course all three would make their marketed power and beyond with a certain amount/percentage of distortion. One of the reasons for them not making the full power at RMS is because they were simply "a budget amp". To make a budget product of any description and in bulk means keeping all costs to a minimum. This would include the transformers. These transformers used by Linear were definitely not "world beaters". They are wound to "border-line" standards, but they are just suitable for the job. Both transformers do not use high grade steel, and the output transformer is the biggest let-down really. It is actually smaller than the 30 watt output transformer used on a Vox. If you disconnect the negative feedback on one of these amplifiers and then run it up on test gear, the output stage starts to clip before the drive, basically meaning the output transformer is "letting the side down", but only by a few watts.
I can remember on the many Linear’s I have had my hands on over the years, always thinking how rough the soldering and layout is on them. You couldn’t even remove the base off a new one, and then you would find at least a few of the wire links scorched and burnt. A case, I suppose, of the ladies (well……..I assume ladies, maybe some guys too?) who had been on a production line and taught "parrot fashion" how to solder, but not noticing or bothering about getting the soldering iron on adjacent wires!! Still they did at least work. (I do mean the amps!)
There was also another range of models coming from the same factory, I believe, under the marketing name of "RSC". Once again, the various models were basically the same as the Linear range but hey!..….these were more "guitarist-friendly". They had 4 inputs……yes FOUR..... front mounted, as opposed to 2 side mounted ones as on the Linear amps, and wow!....... they used real jack sockets too! Not silly co-axial sockets! (How many of you old guitarists remember having a Linear amplifier and having to have a TV aerial plug on one end of your guitar lead?)
Whilst all the above is as best as my knowledge allows, I mean no disrespect for the Linear/RSC products. Yes, they were cheap (about 15 – 25 guineas, and remember that one guinea was equal to one pound and one shilling), but they sold in droves for a good number of years and certainly brought a lot of pleasure to many people. Come on Linear. Where are you now? You should be jumping back on the bandwagon, now that valves (tubes) have become big business again!
OK, onto this amp in question. A gentleman named Frank both e-mailed and subsequently phoned me from his home town of Ware, in Hertfordshire, UK. Frank said he loved the redesign/rebuild of the Conchord on my site, and also explained that he too had a Linear Conchord that had been in his loft for about 30 years! He continued by assuring me that his loft wasn’t damp, but that he wanted to start using the amp again after all these years and thought a good service might be in order. He didn’t want to go to the extreme of a full rebuild, but simply a service and getting it working and back to life.
Now Hertford is a fair run from Nottingham but, as he had family in Chesterfield, which is about 30 minutes from Nottingham and that he was to visit this "neck of the woods" on the following Saturday, it seemed sensible to drop the amp off on-route and then pick it up again nearer Christmas on his next visit up here. So........that is what we arranged.
After Frank had left the tired old amp with me, I jumped on it later that night with nothing else pressing to do. Both the transformers were fine. Good, but as many-a-time before I spent a lot of time changing many dead or tired components. (On the photo below with the "red lines", you can see all that was replaced). I had to change both the very tired EL34 output valves, and a "very sagging" Mullard GZ34….now that is a shame! The ECC83 phase-splitter was very uneven so this went too. The two Mullard EF86’s are still fine and were retained. (Why is it that EF86’s always seem to be fine…I hate those things!!).
A replacement on-off switch, new power cord and grommet, and two jack socket inputs instead of the silly co-ax sockets were fitted. A nice pair of gold plated speaker output posts (instead of the silly little old fashioned, non-available anymore miniature type banana plug/socket) and a full check-up/test of the remaining components and……she’s back to life! Looking great on the scope and sounding pretty good on guitar too!
I do a couple of little mod’s on these Linear amps too which greatly improves hum and noise somewhat. If you would like to do these mod’s on your amplifier please e-mail me. I think Frank is going to be "well chuffed" when he collects this at Christmas 2006. Frank didn't want a complete rebuild, as he is going to do the cosmetic work himself. However, I did get the years of dust off it and gave it a general wipe over, but the rest is down to Frank now. I'm sure he'll send me some photos for the website when he has completed the restoration.
I hope you enjoyed the article and please, any employers/employees of the now defunct Linear/RSC company, can you give me more information on these products? I would be very grateful.
Cheers, John."
Underside of the amp prior to work commencing.
The amp after its service, showing the new valves and the gold-plated speaker output posts.
Underside of the amp as completed, with the red lines indicating the replaced components.
A new mains lead fitted.
The old coaxial input sockets changed for modern ¼" sockets.
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