Cutterhead SX-74 problems!

[leo gonzalez]

i think you really need a pro there to assist you. where are you located?

i might be wrong here but if you took the coils from the head armature then you could have demagnetized it.

i was reading your post and the terminology you use is wrong or incorrect.

you say you replaced chips and capacity. capacity meaning capacitors? hope you did a good job there! not easy.

calibrated 1000 ways? there is 1 calibration for the head and its 9/10dB of drive signal cancellation done with the feedback gain pot. this done with a 5khz sine wave (i believe this os done at 0vu) and then match the nab / riaa level.

then you say frequency response being linear.. that means its flat or are you using the term linear in the right way which is associated with the amount of distortion of the system?

20 minute lacquer?what does that mean?what is the relationship between the length of the program and the problems you are having? -8dbfs? remeber that as you go into the center of the record the distortion levels are higher.

distortion at 10k. is this on both channels?

you could try swapping the cards from one channel to the other but i would suggest to
start the calibration from step one. then you could rule out if its the cards and not the head. i would have tried that before doing what you did to the head.

good luck.. if you are in europe dont hesitate to call flo or ivo to help you out.






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[StanSimon]

Check out Roberto at cutter head repairs in Bologna. Italy
Best

Hi. Can't find his contacts. Do you have?

[petermontg]

Roberto at Cutterhead Repairs in Bologna. Italy

Email : info[at]cutterheadrepair.com

[StanSimon]

Hi, Leo. This is my bad English. Sorry.
I took the coil together with the head armature.
Of course I meant capacitors.
I did a calibration by Chris Muth's method with some variations (5kHz -20dBU).
I generated a sweep (20-20000Hz), analyzed the monitor output signal in position FB, where I got an almost flat frequency characteristic.
20 min is the time of the disc. 8 dBFS is the peak level. Music sounds without distortion with this level, but if doing a normal level, have distortion in both channels.
Swapping cards from one channel to another does not give any results.
Flo can't come to us now. Who is Ivo? Where to find his contacts?

[mossboss]

Be good to tell people where you are located my good man.
Best

[StanSimon]

I am in Russia, in Moscow.

[The Shank]

Get in touch with Florian from Flokason. He's your best solution.

[flozki]

when i read this , it does not make sense to come over.
i guess your diy head experiments wont match the neumann specs anymore....
and to bring it back. i can do it only at my place.
also the cards need some more updates. which was not possible on site.

so. send someone (the former cutting eng.) with all the cards here to my lab.
i can fix and AFTER that i can come over to align again. completly booked out until feb. 2016

it was all nice working when i left. even when i was there for short trip last time summer 2014.
got some nice sounding laquers...

[mossboss]

That be right. Nothing new, these machines have they own little identity and quirks
We seen it many a time
So when a little glitch appears, the "experts" fark with it, nine times out of ten before the issue is correctly identified.
Seems the case here, but far worst, open the head?
Phewwee

[StanSimon]

I don't know why, but Muth's method of cutterhead calibration is not suitable for my system. After I did the calibration from the Neumann's manual it worked correctly. I think all the steps we made had a positive effect. Thank you all for your help. Good grooves.

[leo gonzalez]

whats is the muth method? if you drop 20 dbs @ around 5k then most likely you would go into positive feedback oscillation and breakers would trip.


u should try to use an fft to measure or compare your distortions levels against another reference cut. you have a nab test record?

i think you are still at square one. u need to swap channels to the head to discard its not the rack.

good luck though.


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[opcode66]

Chris Muth posted a video on his site essentially running through the calibration procedure.

http://www.taloowa.com/files/Download/SAL_SX%20alignment.wmv

[StanSimon]

.
u should try to use an fft to measure or compare your distortions levels against another reference cut. you have a nab test record?
i think you are still at square one.

Yes, I still don't know much...
Can you tell more about FFT? How to do it? I have no NAB test record, but here is: http://store.acousticsounds.com/d/35532/Analogue_Productions-The_Ultimate_Analogue_Test_LP-Turntable_Set_Up_Tools
I think it's the same. Or not?
And i don't understand why to swap channels to the head?

[StanSimon]

I don't have FFT analyzer