BBC RP2/10
I have just ascquired the BBC version of it !
Can I easily connect it up to ballanced power amps ? Does it have the ballanced output at the back. Some BBC veterans warned me that I may have to play around with the special BBC output cables - can't wait :-(
I have just ascquired the BBC version of it !
Can I easily connect it up to ballanced power amps ? Does it have the ballanced output at the back. Some BBC veterans warned me that I may have to play around with the special BBC output cables - can't wait :-(
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Well this is a DIY forum and I suppose it depends on your aspirations. Like if a broadcast system is your choice; or if HiFi is what you want. £2.2K isn't going to buy much whatever, and servicing is very expensive, but as a DIY proposition it is OK.
Other may have a different take on this ?
Dave
Other may have a different take on this ?
Dave
When I bought two of these - different model with no phono section - from the BBC Redundant Equipment Store back in about 1990 they charged me £230.00 for the TWO sets - which worked perfectly within their limitations. One I had the motor control boards out-borded, the other I lent to a friend who is still using it!
I had mine completely overhauled and rebuilt by an expert who made a loom so that I could have just the motor in a new plinth with all electronics up to 1.5 metres away!
Sickness has prevented me finalising this build.
I had mine completely overhauled and rebuilt by an expert who made a loom so that I could have just the motor in a new plinth with all electronics up to 1.5 metres away!
Sickness has prevented me finalising this build.
What I find amazing is that a modern design for a motor control scheme has not - it seems - been forthcoming......things have moved on a long way since the SP10 control system was 'innovative'. We attempt to improve performance beyond the original spec. for the mechanical aspects of these great decks yet slave to find components and spend enormous amounts of time working on very aged PCBs when modern components are easily available and give a greater possibility of a simpler more accurate schema.
@6L6
Afraid I know nothing of motor supplies/controllers - other than they should be easily repairable/servicable.
In the past 50 years or so there ought to have been enough design and component progress to be able to do away with the original designs for those who want an excellent deck but do not care about originality. Further, few people really require 78rpm capability so a two speed design using modern components would probably cost less to build from scratch than a professional rebuild of the original.
Further still, I really think that keeping the resonant top-plate is a bit of a no no when the motor can be so easily mounted in a purpose built chassis/plinth and attached via an umbilical to the PS/motor control which can thus be kept well away from the tonearm/cartridge.
I know that Dave Cawley has made a basic PS generally available, but has anyone attempted to produce a motor control system?
@ Dave Cawley...the SP10MkII as that appears to be the model most people use.
Afraid I know nothing of motor supplies/controllers - other than they should be easily repairable/servicable.
In the past 50 years or so there ought to have been enough design and component progress to be able to do away with the original designs for those who want an excellent deck but do not care about originality. Further, few people really require 78rpm capability so a two speed design using modern components would probably cost less to build from scratch than a professional rebuild of the original. Further still, I really think that keeping the resonant top-plate is a bit of a no no when the motor can be so easily mounted in a purpose built chassis/plinth and attached via an umbilical to the PS/motor control which can thus be kept well away from the tonearm/cartridge.
I know that Dave Cawley has made a basic PS generally available, but has anyone attempted to produce a motor control system?
@ Dave Cawley...the SP10MkII as that appears to be the model most people use.
@6L6
Further still, I really think that keeping the resonant top-plate is a bit of a no no when the motor can be so easily mounted in a purpose built chassis/plinth and attached via an umbilical to the PS/motor control which can thus be kept well away from the tonearm/cartridge.
@ Dave Cawley...the SP10MkII as that appears to be the model most people use.
I'm about to go down this rabbit hole now. I have a spare mk2 that has the motor disassembled and is ready to go in a plinth. Electronics will be housed in a separate chassis (not the mk2 chassis).
I have also done a fair few measurements of the mk2 motor with both the OEM and stainless steel platter I made and have found a lot of flex in the bearing assembly, most of the flex is in the motor bottom housing
I am in the process of machining a Stainless platter to OEM spec then I plan to machine a new motor top and bottom housing from either 7075 or 6061 aluminium with a larger bearing housing and PEEK inserts.
To build, no would not be that expensive, though the motor drive circuit would probably not be that dissimilar to the original. I guess you could use the excitation signal into a ADC to give the basic motor timing and generate the three phase signal from that, but there would not (IMHO) be any performance gain. The digital board could be done with a microcontroller or FPGA depending if you prefer C or VHDL. But you are ignoring the maybe 500+ hours the design would take to get into a working state. I don't know how little you could get someone to do that work for, but I would charge maybe £20k to do it, more if you were buying the IP.
There are plenty of motor control chipsets out there some of which have some very fancy DSP features built in, but they are mainly focussed on high speed or robotics applications and may not be optimal for the very low speed performance of a DD turntable. I started looking at this a few years ago then parked it due to lack of time and space to work on it. About £60 for the EVM IIRC.
Hi Bill
It was an answer to Brian's post #1630 a page back.
I agree there are control systems out there that are "very" cost effective and even complete evaluation boards that would help. Also a simpler analogue section with new components and a PIC is an option.
Several years ago someone here suggested this (the EVAL route) and I and others offered help and encouragement, but it did not materialise. It would be good if someone could pick this up again ?
Dave
It was an answer to Brian's post #1630 a page back.
I agree there are control systems out there that are "very" cost effective and even complete evaluation boards that would help. Also a simpler analogue section with new components and a PIC is an option.
Several years ago someone here suggested this (the EVAL route) and I and others offered help and encouragement, but it did not materialise. It would be good if someone could pick this up again ?
Dave
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Drift is 0.002% and W&F 0.035%. I'm struggling to see how modern electronics will improve a mk2?
An improved bearing and platter would be money better spent and significantly cheaper. The mk3 bearing is 16mm vs 7.14mm and the housing fixture in the motor is far more rigid in the mk3.
Put a dial indicator on the edge of the mk2 platter and light finger pressure will deflect the indicator ±0.5mm. Then there is the fit of the spindle in the motor rotor another weak point prone to flex. I also took some measurements of the motor bearing housing to see what flex there is.
In this video I have put the motor housing in the lathe. I pushed down on the top edge of the motor and chuck jaw, there is almost zero flex, next I pushed on the bearing housing and was able to get 0.01mm flex from finger pressure. BTW I could not get a lot of pressure on the bearing housing without touching the indicator. It's a bit blurry as I'm trying to hold the phone and the skylight above does not help either.
SP10 Motor bearing housing flex - YouTube
An improved bearing and platter would be money better spent and significantly cheaper. The mk3 bearing is 16mm vs 7.14mm and the housing fixture in the motor is far more rigid in the mk3.
Put a dial indicator on the edge of the mk2 platter and light finger pressure will deflect the indicator ±0.5mm. Then there is the fit of the spindle in the motor rotor another weak point prone to flex. I also took some measurements of the motor bearing housing to see what flex there is.
In this video I have put the motor housing in the lathe. I pushed down on the top edge of the motor and chuck jaw, there is almost zero flex, next I pushed on the bearing housing and was able to get 0.01mm flex from finger pressure. BTW I could not get a lot of pressure on the bearing housing without touching the indicator. It's a bit blurry as I'm trying to hold the phone and the skylight above does not help either.
SP10 Motor bearing housing flex - YouTube
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