CJ58 mods mkII
Getting there
:
I assume all added parts are sprayed black if visible.
**************************
Subchassis
**************************
Remove the suspension cross piece, but first drill two screw holes for relocation.
Obtain some aluminum sheeting - I'm assuming here its 0.5 to 0.6 mm thick.
The subchassis is reinforced top and bottom with 2/3 layers of aluminum.
First remove the armboard - for further details see arm mounting.
Extend the cutout to clear the Rega arm nut.
The aluminum layers and the subchassis are glued together using contact adhesive.
(The model used here is constrained layer damping)
We are talking the proper stuff here - usually in the sniffing cabinet -
do not use the wimpy water based stuff - (well I never have).
Using these adhesives properly is an art in itself - so ask for more details
if you are not sure - it can't do any harm.
Cutouts are to clear the arm nut and for the main bearing, + various holes.
The top layer is extended at the arm end to completely cover the subchassis.
Make a bearing reinforcement, a diamond shape with cutout, 8/10mm wood/plywood/MDF.
Align and drill two screw holes for the bearing reinforcement.
Araldite the bearing into its new position, don't use too much araldite as its not
critical as the top has the flange, invert the subchassis and araldite the bearing
reinforcement into place. Araldite the cross member into position.
Weighting the subchassis at the spring on the bearing end will help if the
springs are not in even compression, but first you need to make sure that
if they have different rates, i.e. stiffness they are in the correct position.
**************************
Springs
**************************
Note that one spring may be a different rate to the other two.
If your spraying the plinth, then spraying the springs is worthwhile to dampen
somewhat the higher order transmission modes of the springs.
The springs can be seated in the subchassis by applying a ring of rubber glue
into to the corner of the cutouts and standing the springs in the cutouts.
Use the platter as a weight whilst drying if they don't seat easily.
The rubber mountings can be supported underneath with rubber tap washers, use
rubber glue to repair the mountings and/or glue them together if necessary.
**************************
Plinth
**************************
If the vinyl is wood effect - I'd suggest spraying the whole turntable silk black,
or possibly trendier silver, or possibly just spray the surround not the top-plate.
Acrylic car paint will probably be best on the vinyl, and fine on the wood.
Its possible to remove the top-plate and damp the underneath with two layers of
self adhesive vinyl floor tiles - use the cheapest and thinnest stuff you can
find - this is the best stuff for the job as it contains a large amount of filler
- consequently it is harder and stiffer than the more luxurious tiles - thinness
is also good as the adhesive layers add damping.
At the same you could add a glued on aluminum foil groundplane.
Replace the surround and then trim for a good finish.
And find a lid !
Building a new plinth is a possibility - but not needed in terms of sound quality.
**************************
Arm Mounting
**************************
A spacer made of plywood to take up the majority of the height requirements is used,
its hole needs to be a little bigger than the arm to allow it to be aligned in the
cutout. The spacer is attached by three hemi-head hex bolts passing through holes
to oversize holes in the subchassis to nuts underneath the subchassis.
Use spreading washers on the nuts underneath the subchassis.
A (Rega) spreading washer used above the spacer will prevent the arm from twisting
due to an offset hole.
The spacer is finally semi-permanently glued to the subchassis with PVA wood glue.
The spacer is shaped to the top cutout of the deck.
Go to a plumbers merchant and acquire some large nylon or similar hard plastic
washers to fit the arm.
They are used for height adjustment.
(I used a cut down felt mat between my platter and subplatter for fine height adjustment)
Tightening the arm nut will require the spacer to be removed, when you are finally
happy, retorque the nut after a day or so and then semi-permanently bond the spacer.
Don't use Rega locking washers they interfere with the energy flow.
The arm lead needs to be dressed. The cable retention part from a mains plug is a
very good part for the job. Put a twist in the arm lead and align it at right angles
to the subchassis, attaching to the bottom of the rear surround with the clamp.
Before tightening the clamp adjust the amount of 'feed' so the subchassis is free
and the lead is not in contact with the base.
**************************
AC Motor
**************************
On a subchassis turntable the motor should be solidly mounted.
(Do not overtighten the mounting plate screws if the topplate has been damped) :
If the belt does not run in the centre of the motor pulley, the inclination of the motor
is in need of attention, try tightening / loosening the mounting plate screws slightly.
A layer of vinyl floor tile may be needed to accomplish this.
The AC motor will make horrible grinding noises if its oil dries out.
Simply oiling the motor at the spindle (top & bottom) will improve its performance no end.
For an 'improved' PSU for the AC motor checkout Neil McBrides Naim site,
and the Armegeddon clone. I haven't tried it, but if I did I would use a
much smaller transformer, the transformer used is IMO utterly ridiculous.
**************************
Ground Plane
*************************
I've found a proper groundplane is essential for low noise / hum.
The earthing of the Rega arm via its lead should be removed and a separate earth
wire run back to the amplifier. All metal parts should be connected to this earth.
(I think the earth is connected inside the base of the arm - I can't remember)
These are the arm, motor and subchassis layers and of course the groundplanes.
The groundplane can be aluminum foil or sheet glued to hardboard.
Glueing to both sides will help prevent warping.
(A piece of hardboard with two layers of foil either side is very surprising)
Steel sheet helps magnetically if you have equipment directly below.
An easy way of damping steel groundplanes is a self adhesive vinyl floor tile.
Cutting out holes to access the suspension is fine.
A hole may need to be cut for the main bearing.
A groundpost should be drilled through and installed in the right rear of the surround.
The separate earth wire runs from this to the amplifier cartridge input ground post.
**************************
Cartridge
**************************
Is utterly dominated by the arm and turntable its connected to.
However they determine the tonal balance of the turntable and the quality
of the treble if the arm isn't getting in the way, generally it does.
The Rega arm gets in the way much less than most arms I've come across.
The tonal balance of the cartridge must suit the system.
Moving coils are simply not necessary for high quality.
To be further discussed.
************************
Further
************************
You've got enough bits to make another turntable ! I'm better with mods than ?.
Suggest you try this and then possibly build another turntable,
along mega-solid lines as by others - interesting to compare.
/sreten
Getting there
:I assume all added parts are sprayed black if visible.
**************************
Subchassis
**************************
Remove the suspension cross piece, but first drill two screw holes for relocation.
Obtain some aluminum sheeting - I'm assuming here its 0.5 to 0.6 mm thick.
The subchassis is reinforced top and bottom with 2/3 layers of aluminum.
First remove the armboard - for further details see arm mounting.
Extend the cutout to clear the Rega arm nut.
The aluminum layers and the subchassis are glued together using contact adhesive.
(The model used here is constrained layer damping)
We are talking the proper stuff here - usually in the sniffing cabinet -
do not use the wimpy water based stuff - (well I never have).
Using these adhesives properly is an art in itself - so ask for more details
if you are not sure - it can't do any harm.
Cutouts are to clear the arm nut and for the main bearing, + various holes.
The top layer is extended at the arm end to completely cover the subchassis.
Make a bearing reinforcement, a diamond shape with cutout, 8/10mm wood/plywood/MDF.
Align and drill two screw holes for the bearing reinforcement.
Araldite the bearing into its new position, don't use too much araldite as its not
critical as the top has the flange, invert the subchassis and araldite the bearing
reinforcement into place. Araldite the cross member into position.
Weighting the subchassis at the spring on the bearing end will help if the
springs are not in even compression, but first you need to make sure that
if they have different rates, i.e. stiffness they are in the correct position.
**************************
Springs
**************************
Note that one spring may be a different rate to the other two.
If your spraying the plinth, then spraying the springs is worthwhile to dampen
somewhat the higher order transmission modes of the springs.
The springs can be seated in the subchassis by applying a ring of rubber glue
into to the corner of the cutouts and standing the springs in the cutouts.
Use the platter as a weight whilst drying if they don't seat easily.
The rubber mountings can be supported underneath with rubber tap washers, use
rubber glue to repair the mountings and/or glue them together if necessary.
**************************
Plinth
**************************
If the vinyl is wood effect - I'd suggest spraying the whole turntable silk black,
or possibly trendier silver, or possibly just spray the surround not the top-plate.
Acrylic car paint will probably be best on the vinyl, and fine on the wood.
Its possible to remove the top-plate and damp the underneath with two layers of
self adhesive vinyl floor tiles - use the cheapest and thinnest stuff you can
find - this is the best stuff for the job as it contains a large amount of filler
- consequently it is harder and stiffer than the more luxurious tiles - thinness
is also good as the adhesive layers add damping.
At the same you could add a glued on aluminum foil groundplane.
Replace the surround and then trim for a good finish.
And find a lid !
Building a new plinth is a possibility - but not needed in terms of sound quality.
**************************
Arm Mounting
**************************
A spacer made of plywood to take up the majority of the height requirements is used,
its hole needs to be a little bigger than the arm to allow it to be aligned in the
cutout. The spacer is attached by three hemi-head hex bolts passing through holes
to oversize holes in the subchassis to nuts underneath the subchassis.
Use spreading washers on the nuts underneath the subchassis.
A (Rega) spreading washer used above the spacer will prevent the arm from twisting
due to an offset hole.
The spacer is finally semi-permanently glued to the subchassis with PVA wood glue.
The spacer is shaped to the top cutout of the deck.
Go to a plumbers merchant and acquire some large nylon or similar hard plastic
washers to fit the arm.
They are used for height adjustment.
(I used a cut down felt mat between my platter and subplatter for fine height adjustment)
Tightening the arm nut will require the spacer to be removed, when you are finally
happy, retorque the nut after a day or so and then semi-permanently bond the spacer.
Don't use Rega locking washers they interfere with the energy flow
.The arm lead needs to be dressed. The cable retention part from a mains plug is a
very good part for the job. Put a twist in the arm lead and align it at right angles
to the subchassis, attaching to the bottom of the rear surround with the clamp.
Before tightening the clamp adjust the amount of 'feed' so the subchassis is free
and the lead is not in contact with the base.
**************************
AC Motor
**************************
On a subchassis turntable the motor should be solidly mounted.
(Do not overtighten the mounting plate screws if the topplate has been damped) :
If the belt does not run in the centre of the motor pulley, the inclination of the motor
is in need of attention, try tightening / loosening the mounting plate screws slightly.
A layer of vinyl floor tile may be needed to accomplish this.
The AC motor will make horrible grinding noises if its oil dries out.
Simply oiling the motor at the spindle (top & bottom) will improve its performance no end.
For an 'improved' PSU for the AC motor checkout Neil McBrides Naim site,
and the Armegeddon clone. I haven't tried it, but if I did I would use a
much smaller transformer, the transformer used is IMO utterly ridiculous.
**************************
Ground Plane
*************************
I've found a proper groundplane is essential for low noise / hum.
The earthing of the Rega arm via its lead should be removed and a separate earth
wire run back to the amplifier. All metal parts should be connected to this earth.
(I think the earth is connected inside the base of the arm - I can't remember)
These are the arm, motor and subchassis layers and of course the groundplanes.
The groundplane can be aluminum foil or sheet glued to hardboard.
Glueing to both sides will help prevent warping.
(A piece of hardboard with two layers of foil either side is very surprising)
Steel sheet helps magnetically if you have equipment directly below.
An easy way of damping steel groundplanes is a self adhesive vinyl floor tile.
Cutting out holes to access the suspension is fine.
A hole may need to be cut for the main bearing.
A groundpost should be drilled through and installed in the right rear of the surround.
The separate earth wire runs from this to the amplifier cartridge input ground post.
**************************
Cartridge
**************************
Is utterly dominated by the arm and turntable its connected to.
However they determine the tonal balance of the turntable and the quality
of the treble if the arm isn't getting in the way, generally it does.
The Rega arm gets in the way much less than most arms I've come across.
The tonal balance of the cartridge must suit the system.
Moving coils are simply not necessary for high quality.
To be further discussed.
************************
Further
************************
You've got enough bits to make another turntable ! I'm better with mods than ?.
Suggest you try this and then possibly build another turntable,
along mega-solid lines as by others - interesting to compare.
/sretenAttachments
cartridge
If you'd like some help with finding a cartridge
then the following information would be useful.
Do you have a good Moving coil input ?
Or would you need a transformer / upgrade ?
Does your ideal turntable sound like your CD player
in balance tonally, or do you want a 'richer' more
analogue sound from your records.
How many records do you have that have seen better days ?
(or have they all been looked after ?)
What amplifier and speakers do you have ( helps me ) ?
Whats your opinion of the AT95E sound character wise ?
Whats your opinion of the AT95E sound tonally ?
/sreten.
If you'd like some help with finding a cartridge
then the following information would be useful.
Do you have a good Moving coil input ?
Or would you need a transformer / upgrade ?
Does your ideal turntable sound like your CD player
in balance tonally, or do you want a 'richer' more
analogue sound from your records.
How many records do you have that have seen better days ?
(or have they all been looked after ?)
What amplifier and speakers do you have ( helps me ) ?
Whats your opinion of the AT95E sound character wise ?
Whats your opinion of the AT95E sound tonally ?
/sreten.Wow - you've been busy - thanks!
About the cartridge...
My MC stage is a NAD 1240 pre amp, which I assume is okay. Probably not great, but I don't intend to keep it forever. This feeds a Sugden P28 and a pair of AR18s (with new foam surrounds).
Although I am a believer in the inherent superiority of analogue, I would like a balance closer to that from CD, so that I can tweak the rest of the system to get a balance I like from both CD and LP. Having said that, I play much more vinyl than CD and many of my LPs are very worn.
I am a fan of the AT95E as far as budget cartridges go, but ultimately I find it's lacking in treble extension, clarity and detail. The last MC I owned was a Denon DL110 (on a lux pd300) which I loved frequency-wise but found maybe a bit lacking in dynamics - maybe due to turntable though... The Denons are great value but are hard to get hold of.
I've always fancied trying a Dynavector 10X, but they seem pricey these days compared to the Denons. Shame Audio Technica don't do any budget MCs any more. Would love a koetsu...
About the cartridge...
My MC stage is a NAD 1240 pre amp, which I assume is okay. Probably not great, but I don't intend to keep it forever. This feeds a Sugden P28 and a pair of AR18s (with new foam surrounds).
Although I am a believer in the inherent superiority of analogue, I would like a balance closer to that from CD, so that I can tweak the rest of the system to get a balance I like from both CD and LP. Having said that, I play much more vinyl than CD and many of my LPs are very worn.
I am a fan of the AT95E as far as budget cartridges go, but ultimately I find it's lacking in treble extension, clarity and detail. The last MC I owned was a Denon DL110 (on a lux pd300) which I loved frequency-wise but found maybe a bit lacking in dynamics - maybe due to turntable though... The Denons are great value but are hard to get hold of.
I've always fancied trying a Dynavector 10X, but they seem pricey these days compared to the Denons. Shame Audio Technica don't do any budget MCs any more. Would love a koetsu...
I've found cartridges that sound nice e.g. Grado's in the end
deviate somewhat from the balance you get from CD players.
In modding turntables / arms I've nearly always found problems
are related to the turntable / arm than the cartridge, perhaps
different cartridges just interact with these problems differently.
Try Mantra Audio
You can get the Denon DL110 for £80.
Other choice could be an Ortofon MC 10 Super. (£100).
I use an MC15 because the extended contact stylus seems to be
good at reading a less damaged part of the groove. I track it at
2.5 grams - due to the extended contact line this is not a problem.
Sounds very good to me. Allegedly suits the Rega arm.
For the last turntable I rebuilt (SystemDek / Linn LVX fixed) I
ended up swapping a Grado Black to an Ortofon 510 to get
that CD balance (and more top end).
Was very impressed with the 510, completely did the job,
though I thought a better stylus was needed for better treble,
or was it the LVX doesn't match up to the Rega, probably both.
510 £34, 520 £63, 540 £102.
Now my favourite MM's for CD-like balance.
/sreten.
deviate somewhat from the balance you get from CD players.
In modding turntables / arms I've nearly always found problems
are related to the turntable / arm than the cartridge, perhaps
different cartridges just interact with these problems differently.
Try Mantra Audio
You can get the Denon DL110 for £80.
Other choice could be an Ortofon MC 10 Super. (£100).
I use an MC15 because the extended contact stylus seems to be
good at reading a less damaged part of the groove. I track it at
2.5 grams - due to the extended contact line this is not a problem.
Sounds very good to me. Allegedly suits the Rega arm.
For the last turntable I rebuilt (SystemDek / Linn LVX fixed) I
ended up swapping a Grado Black to an Ortofon 510 to get
that CD balance (and more top end).
Was very impressed with the 510, completely did the job,
though I thought a better stylus was needed for better treble,
or was it the LVX doesn't match up to the Rega, probably both.
510 £34, 520 £63, 540 £102.
Now my favourite MM's for CD-like balance.
/sreten.I have used a CJ61 (which has the same internals as the CJ58 I think) for many years. I bought it directly from Colin Walker in kit form before he stopped making turntables. I do wonder about all the drastic modifications proposed here. Why mess about with the hardwood chassis when it is one of the strongest aspects of the design and works so well?
The mods I have done are much simpler and they work.
1. Remove foam cores from suspension springs. This makes the turntable rather bouncier to handle but it greatly improves the bass.
2. Check the speed with a strobe. Depending on the motor pulley tolerance, the turntable may run a little slow. (Mine ran about 1% slow.) Where this is problem the cheap and cheerful solution is to apply thin coats of nail varnsih to the motor pulley until the turntable runs at the right speed. This was suggested to me by Colin Walker himself and works OK, although it is not ideal as a longterm solution. I ended up paying a local engienering shop to turn me a new pulley of the correct dimensions, as I do notice the difference. If your turntable runs slow, then correcting the speen gets the pitch and foot-tapping rhythm right.
3. An outboard power supply can lift the performance to another level. I was surprised just how much the sound improved when I added a HiFi News Flutterbuster power supply.
As for cartridges, the sky's the limit. I use a Denon DL103 in a Mayware MkV but if I remember rightly Colin Walker ran his with an Alphason arm and a Koetsu into Quad ESL63s and the sound was absolutely beautiful.
The mods I have done are much simpler and they work.
1. Remove foam cores from suspension springs. This makes the turntable rather bouncier to handle but it greatly improves the bass.
2. Check the speed with a strobe. Depending on the motor pulley tolerance, the turntable may run a little slow. (Mine ran about 1% slow.) Where this is problem the cheap and cheerful solution is to apply thin coats of nail varnsih to the motor pulley until the turntable runs at the right speed. This was suggested to me by Colin Walker himself and works OK, although it is not ideal as a longterm solution. I ended up paying a local engienering shop to turn me a new pulley of the correct dimensions, as I do notice the difference. If your turntable runs slow, then correcting the speen gets the pitch and foot-tapping rhythm right.
3. An outboard power supply can lift the performance to another level. I was surprised just how much the sound improved when I added a HiFi News Flutterbuster power supply.
As for cartridges, the sky's the limit. I use a Denon DL103 in a Mayware MkV but if I remember rightly Colin Walker ran his with an Alphason arm and a Koetsu into Quad ESL63s and the sound was absolutely beautiful.
Re: modifications
I can.
The biggest changes are the configuration of the drive electronics.
I would agree that a simple servo loop feedback path gives fairly poor results but this is no longer the only option.
I x R or current feedback compensation is the key. This removes the influence of the speed / torque characteristics of the motor.
sreten said:
I can.
The biggest changes are the configuration of the drive electronics.
I would agree that a simple servo loop feedback path gives fairly poor results but this is no longer the only option.
I x R or current feedback compensation is the key. This removes the influence of the speed / torque characteristics of the motor.
Alasdair Beal said:
Hmmm.......
About 4 years too late.... Nevertheless "drastic" mods are needed
to address the sound issues described. Two pieces of MDF stapled
together is not "hardwood" and how do you know "it works so well" ?
How do you know it a strong part of the design ? IMO it is not .....
Obviously if you like the sound do not mess about with it.
Ludicrously expensive cartridges in cheap turntables are a waste of
time. Far better to spend money on a very good turntable and arm.
/sreten.Re: Re: modifications
Hmmm .......
Current feedback (i.e. negative output impedance) helps in allowing
the speed / voltage of a DC motor to work, i.e. compensates for the
windings DCR. Speed / Torque is not the issue.
IMO changing the motor will not fix the described sound issues.
/sreten.
Mark Kelly said:
Hmmm .......
Current feedback (i.e. negative output impedance) helps in allowing
the speed / voltage of a DC motor to work, i.e. compensates for the
windings DCR. Speed / Torque is not the issue.
IMO changing the motor will not fix the described sound issues.
/sreten.It's nice to see that this old thread has been revived! Just thought I'd give my thoughts on what everyone has to say here...
I greatly appreciated Sreten's ideas and advice and very much respect his obvious experience and knowledge. However in the end I have to say I kind of agree with what Alisdair has to say (although Sreten is right - the subchassis is Medite/MDF, not hardwood). I think that most of the deck's "issues" that I mentioned were to do with setup and the basic cartridge fitted at the time. My fault, and a lesson (re)learned.
In the end I just re-fitted the deck's original arm - a budget Mission 774 LC. I also removed the foam suspension bungs and the deck's hardboard base and fitted some better feet. I put the deck on a nice Target 2-tier welded table and spent an evening leveling the suspension, and carefully fitting and aligning an AT440ml.
After this simple tweaking I have to say the deck sounded excellent. Sure I've heard better in some respects, but the sound from the CJ was detailed and musical in equal parts and left me very satisfied. It certainly did not sound like a "cheap turntable", and although Colin Walker's decks were certainly excellent value for money I think it's unfair to describe it as such. To put it into perspective it sounded closer to an Ariston or (early) LP12 than a Dual or a Rega.
Having since owned all of the other CJ Walkers, I can safely say that I do like their sound. I'm also convinced, having owned numerous other suspended decks, that the inherent resonances and "give" of the wood-based subchassis, together with the low mass of the simple design, form a very important part of their sonic character.
Modifications are always fun, but IMO often it's design "weaknesses" that make a given product work well. Consider the wooden armboard (and it's mounting) on the LP12. The decoupling in this part of the subchassis is a big part of why the deck sounds as it does and is one of the few areas which has never really been "upgraded" by Linn. Although it doesn't fit in with the "closed loop" school of turntable design it's very possibly one of the factors that gave it the edge over otherwise very similar designs from Ariston etc. Musicality, sadly, is not a science!
I would argue that the CJs (and quite possibly Koetsus) would be an exception to this rule, particularly using bass-light speakers like the Quads. Although the CJ58 has its limitations it is basically a well sorted and balanced design without major flaws. A Koetsu might be silly money, but they do have a magic midrange that I don't hear in sub-£300 cartridges. The CJ's main limitations are to do with ultimate bass extension (not a problem with ESL63s) and pitch stability (which bothers some more than others - The CJs are certainly no worse than a Systemdek). I'd be fairly confident that the qualities of a Koetsu would shine through clearly in a well set-up CJ Walker with a suitable arm.
Anyway, enough babbling. I appreciate everyone's comments and advice, and I'm happy to hear from another fan of these decks - shame I never got to meet the man himself (I'm assuming he's no longer with us, but someone please correct me if I'm wrong). I'm off to put a record on. No longer on a CJ but that's another story...
I greatly appreciated Sreten's ideas and advice and very much respect his obvious experience and knowledge. However in the end I have to say I kind of agree with what Alisdair has to say (although Sreten is right - the subchassis is Medite/MDF, not hardwood). I think that most of the deck's "issues" that I mentioned were to do with setup and the basic cartridge fitted at the time. My fault, and a lesson (re)learned.
In the end I just re-fitted the deck's original arm - a budget Mission 774 LC. I also removed the foam suspension bungs and the deck's hardboard base and fitted some better feet. I put the deck on a nice Target 2-tier welded table and spent an evening leveling the suspension, and carefully fitting and aligning an AT440ml.
After this simple tweaking I have to say the deck sounded excellent. Sure I've heard better in some respects, but the sound from the CJ was detailed and musical in equal parts and left me very satisfied. It certainly did not sound like a "cheap turntable", and although Colin Walker's decks were certainly excellent value for money I think it's unfair to describe it as such. To put it into perspective it sounded closer to an Ariston or (early) LP12 than a Dual or a Rega.
Having since owned all of the other CJ Walkers, I can safely say that I do like their sound. I'm also convinced, having owned numerous other suspended decks, that the inherent resonances and "give" of the wood-based subchassis, together with the low mass of the simple design, form a very important part of their sonic character.
Modifications are always fun, but IMO often it's design "weaknesses" that make a given product work well. Consider the wooden armboard (and it's mounting) on the LP12. The decoupling in this part of the subchassis is a big part of why the deck sounds as it does and is one of the few areas which has never really been "upgraded" by Linn. Although it doesn't fit in with the "closed loop" school of turntable design it's very possibly one of the factors that gave it the edge over otherwise very similar designs from Ariston etc. Musicality, sadly, is not a science!
I would argue that the CJs (and quite possibly Koetsus) would be an exception to this rule, particularly using bass-light speakers like the Quads. Although the CJ58 has its limitations it is basically a well sorted and balanced design without major flaws. A Koetsu might be silly money, but they do have a magic midrange that I don't hear in sub-£300 cartridges. The CJ's main limitations are to do with ultimate bass extension (not a problem with ESL63s) and pitch stability (which bothers some more than others - The CJs are certainly no worse than a Systemdek). I'd be fairly confident that the qualities of a Koetsu would shine through clearly in a well set-up CJ Walker with a suitable arm.
Anyway, enough babbling. I appreciate everyone's comments and advice, and I'm happy to hear from another fan of these decks - shame I never got to meet the man himself (I'm assuming he's no longer with us, but someone please correct me if I'm wrong). I'm off to put a record on. No longer on a CJ but that's another story...
Re: Re: Re: modifications
Different ways of saying the same thing.
The speed / voltage curve of a DC motor is strictly due to the back EMF of the generator. If the motor is unloaded it will run at this speed (not possible due to bearing and other drags inherent to the motor)
When the motor is loaded, it requires a current through the windings to create a counter torque. The voltage required to create that current is equal to the winding resistance times the current.
The I x R compensation creates the required voltage in addition to the "no load run voltage" so that the motor runs at constant speed regardless of load.
Whether you call this speed / voltage compensation or speed / torque compensation is semantics. I think speed / torque compensation is clearer.
sreten said:
Different ways of saying the same thing.
The speed / voltage curve of a DC motor is strictly due to the back EMF of the generator. If the motor is unloaded it will run at this speed (not possible due to bearing and other drags inherent to the motor)
When the motor is loaded, it requires a current through the windings to create a counter torque. The voltage required to create that current is equal to the winding resistance times the current.
The I x R compensation creates the required voltage in addition to the "no load run voltage" so that the motor runs at constant speed regardless of load.
Whether you call this speed / voltage compensation or speed / torque compensation is semantics. I think speed / torque compensation is clearer.
Re: Re: Re: Re: modifications
Hi,
I agree its different ways of saying the same thing .....
But the details differ .... compensation does not "add in"
"no load run voltage" its inherent in the compensation.
The "compensation" gives constant speed for any load for a given
"voltage with compensation". As you say a "no load" "no current"
case does not exist due to friction and drag in the motor.
I'd suggest most people buying a "high torque" DC motor for
use with their turntable have got it all wrong and simply do
not understand the motor characteristics required.
/sreten.
Mark Kelly said:
Hi,
I agree its different ways of saying the same thing .....
But the details differ .... compensation does not "add in"
"no load run voltage" its inherent in the compensation.
The "compensation" gives constant speed for any load for a given
"voltage with compensation". As you say a "no load" "no current"
case does not exist due to friction and drag in the motor.
I'd suggest most people buying a "high torque" DC motor for
use with their turntable have got it all wrong and simply do
not understand the motor characteristics required.
/sreten.Hi,
IMO FWIW the subchassis construction determines the subtle points
of reproduction of a well set up turntable. Thorens decks for example
IMO are difficult to get to really fly without subchassis modifications.
And like I said if it isn't broken do not fix it .....
But the sound of the Walkers can be changed, IMO more neutral/ better .....
A Koetsu in a 774LC in a budget Walker ? not sensible .....
/sreten.
IMO FWIW the subchassis construction determines the subtle points
of reproduction of a well set up turntable. Thorens decks for example
IMO are difficult to get to really fly without subchassis modifications.
And like I said if it isn't broken do not fix it .....
But the sound of the Walkers can be changed, IMO more neutral/ better .....
A Koetsu in a 774LC in a budget Walker ? not sensible .....
/sreten.I agree completely. Although I'd say the old TD150 is a subjectively good sounding turntable as-is, inspite of it's physical flimsyness.
Changed, yes. Better... well, maybe. But IMO the Walker's colourations are subjectively pleasant to listen to - more so than many more expensive turntables.
I never suggested putting a Koetsu in a 774LC. That would be silly. The cartridge certainly needs a better/more suitable arm. But I'd argue that the Walker is up to the job within a given system.
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