ITT-KB KA650 Unit Stereo

[crackle]

I really must stop buying record players, but this one was interesting.

I believe it maybe the first Unit Stereo system to be introduced by ITT-KB. It was introduced in about 1969, just about the time that KB were going through the change of name to ITT-KB, and came with a choice of 2 loudspeakers.
It can be seen here on the right hand side of this page from the 1970 ITT-KB catalogue together with the famous omnidirectional KS651 cylindrical loudspeakers. Which were not supplied with this example when I bought it because they had previously been sold, but I already have a pair in the collection anyway.
You can read more on the specifications of the KA650 in the service manual available here.

The system is very well made, the electronics are all in modules, Power supply, 2 power amps, a preamp and tone control unit, FM front end, IF amp, and the FM stereo decoder. The cabinet is made with solid teak sides, back and front top panels. The rest of the cabinet is high quality birch ply, no hardboard or chipboard in here. It is equipped with an FM tuner and there was an option to have a stereo decoder module fitted, which luckily happens to be fitted in this example. It is also fitted with a BSR MA70 record changer, with a Sonotone 9TA HC cartridge.
It boasts an output of 15 watts per channel, enough for any room when used with a pair of efficient loudspeakers.

When I got the system home I soon discovered that a very ham fisted person had attempted to remove the record deck by unscrewing the transit screws to the point that the tips had sheared off releasing the toggle springs to fall back into the cabinet.

I found eventually found both toggle springs but I was concerned about what damage may have occurred if they had lodged into a part of the circuit whilst the unit was on.
Anyway my concerns were not justifies as when powered up on the lamp limiter there was no problems and after a bit of exercising of the controls it was working very well on FM.


I then started to set the system up with the upper half of the cabinet and deck still propped up but now horizontal so I could test the record deck. It worked but there was an apparent problem with the cartridge.
It only worked if excessive pressure was put on the stylus.
In investigation I believe oxide in the contacts which engage with the ceramic elements was causing the problem. But in the course of looking at this the yoke which the stylus sits in started to crumble and disintegrate.

So I am now looking for a replacement Sonotone 9TA HC cartridge going for a reasonable price.

Mike

[ben]

This looks like a very nice unit, Mike. The MA70 was a cut above the rest of BSRs especially back then, with its counterbalanced arm and 10.5" metal platter.

Unfortunately the Sonotone 9TA is long obsolete, as you have discovered they tend to disintegrate and the contacts oxidise. You can sometimes find them second hand but if they aren´t dead already, they soon will be. I would try a 3509 or 3559 if you want Sonotone. I have repaired these by cleaning the contacts internally and the nylon suspension usually survives (but, again, in view of the age, can fail).

I think on balance the easiest and safest investment would be a BSR SC11M/ 12M. These also sound very good. You may also be able to mount it without a clip using the screwhole. Many BSRs mounted them that way, there are grooves inside the headshell which ensure the cart is a perfect fit.

[crackle]

Hi Ben
Thanks for the advice.
Mike

[crackle]

I found this cartridge last night that I have had for a while and wondered if it might do for the KA650, I also have the mounting bracket, but I was wondering if;
A; is it a high output cartridge, too much for this record player.
B; what is it, it has no stylus and I cant find any references to it on the internet.
Was the cartridge a copy of another type and its stylus would be compatible.

Thanks
Mike

[ben]

That is a rebadged (Pinnacle) high output version of the Sonotone I mentioned above. I think it´s a 2509. Probably too high output for this player, and designed for high mass arms as found on the likes of the BSR UA15, Garrard Autoslim, etc. This would probably have been a replacement for a dead crystal cart. Stylus is a GDD1 or similar (plastic shank).

So, close but no cigar IMHO!

edit: I see you have the bracket. This can be used for the Sonotones I mentioned initially, so you might be able to pick up a bargain one with no bracket that would solve your problem. Bear in mind you´d need some new solder-on tags as the 9TA uses a nonstandard plug to connect the tonearm wires to the cart.

[crackle]

Thanks Ben

For general interest I have uploaded a few documents associated with this stereo unit.

BSR UA70 user instructions

ITT-KB 650 user instructions

ITT-KB 650 sales brochure

Mike

[Nuvistor]

That Pinnacle cartridge brought back a few memories, we had their valves, components, stylus etc, I had completely forgotten about the cartridges.
I found most of their products were ok, and they never quibbled about the odd return.

[ben]

They also made (rebadged and distributed more likely) blank cassettes, and I think record care equipment like dust collector arms etc.
I have a few Pinnacle boxed TV valves somewhere.

[crackle]

Originally Posted by ben

Bear in mind you´d need some new solder-on tags as the 9TA uses a nonstandard plug to connect the tonearm wires to the cart.

I see lots of people are selling the gold plated multi-pin plug push-in inserts as cartridge connectors. I have some of those but they are a bit long and although will work as a last resort are not really the correct item for the job.

Mike

[crackle]

Can someone please explain the difference between the 9TA and the 9TA HC.

Thanks
Mike

[crackle]

Here are some photos of the ITT-KB KA650 "Unit Stereo"

[BRASSBITS]

The HC version is high compliance

[crackle]

What does "high compliance" mean in practical terms? What is better high or low. What difference does the mass of the arm make, and how does a high compliance help?

thanks
Mike

[Herald1360]

For a given applied force, a high compliance part will deflect further than a low compliance one. What that means in practice for cartridges, I've no idea. Over to the experts.....

A high mass arm with a high compliance cartridge would hold the cartridge steady as the record waggled the stylus and low mass arm with a low compliance cartridge would presumably let the cartridge waggle with the stylus.

[crackle]

Thanks Chris, that makes some sense.

So a high compliance cartridge is always better than a low compliance one.
But a low compliance cartridge is not too bad if used in a high mass arm.

Am I correct in thinking that high compliance just means it takes less force to vibrate the stylus and ceramic elements.

Presumably age could cause a stiffening of the rubbers used in the stylus suspension and yoke, and turn a high compliance cartridge into a low compliance one with age.

Mike

[AC/HL]

Some posts copied to a new thread for reference: https://www.vintage-radio.net/forum/...d.php?t=155447

[Hartley118]

Originally Posted by crackle

Thanks Chris, that makes some sense.

Am I correct in thinking that high compliance just means it takes less force to vibrate the stylus and ceramic elements?


Mike

Yes - true in general at low frequencies, so discs with heavy bass modulation are generally tracked better with a high compliance cartridge.

However, as usual, spring/mass resonances do make matters more interesting. The mass of the arm will resonate with the cartridge compliance at a low frequency. This can be quite critical: if it's in the audio range, it will boost the bass. In fact, back in the day of heavyweight low compliance pickups in the 1930s, the high head mass and low armature compliance created an LF resonant peak sufficient to more or less provide the right bass equalisation to compensate for the 78 recording characteristic.

Returning to the present day, there's an issue that one can overdo the stylus compliance. With a high mass head, such as those generally on autochangers, a very high compliance cartridge could push the LF resonance so far down that it coincides with the 'bounce' frequency of the turntable mounting springs, or a warped or off-centre record. That in turn can lead to the stylus leaving the groove. So a substantial massy pickup head may do better with a stiffer (lower compliance) cartridge.

And there's of course another thing - if the cartridge/arm combination needs a fairly high tracking force for decent mid and high frequency groove tracing, excessive stylus compliance can result in the cartridge 'bottoming' on to the record surface, which is clearly a bad thing.

At high frequencies, stylus compliance leaves the picture and stylus tip mass is then the significant factor. Our mass/spring resonance of interest becomes now the stylus mass 'bouncing' on the compliance of the record groove material. The lower the tip mass and the stiffer the record material, the higher the HF resonant frequency; it's this HF resonance which generally sets the upper limit to the cartridge HF response. Interestingly and paradoxically, when compliant vinyl began to replace stiff shellac as a disc material, it was more difficult for manufacturers of top-grade cartridges to achieve the extended HF response that the new-fangled LPs demanded. A well-recorded 78 could typically give a wider HF response than a vinyl LP because the cartridge HF resonance is higher on hard shellac.

Martin

[crackle]

Wow its complicated, thanks for the explanation.
Anyway I have ordered a new diamond stylus for my spare Pinnacle cartridge, even if I dont use it in this record player its seems a shame for it to not have a stylus.

Mike