Really quiet cuts on a Rek O kut Challenger

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carldacorte
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Really quiet cuts on a Rek O kut Challenger

Post: # 46513Unread post carldacorte
Tue Mar 28, 2017 7:23 am

Hi everyone!

My studio purchased a Rek O Kut Challenger with TR12h table and M12 lathe last fall. Long story short, it was packaged horribly, insurance didn't want to pay out and it took way to long to get compensated for damages. Finally, I've got the various parts damaged in shipped repaired and I've been having a ton of fun learning how to cut!

Sonically, the cuts sounds good with decent bass and high end considering the limitations of the stock head. However, the cutting level is really low. I've been adjusting the various adjustments to try different cutting angles, weight, depth, etc... while some things have helped, nothing seems to do the trick.

I've tried NOS styli, the eBay Russian styli - very little difference. I'm cutting on apollo dubs.

Any tips or suggestions? Anyone out there with this setup making good cuts on it? Maybe I'm just totally overlooking something...

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markrob
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Re: Really quiet cuts on a Rek O kut Challenger

Post: # 46514Unread post markrob
Tue Mar 28, 2017 7:52 am

Hi,

I guess the first question is how low is the level? Can you provided a number in db referenced to something? For example, measure the average RMS of a commercial LP by capturing it to your computer and make a note of it. Take the captured file and cut this at the highest level you can. Now capture this cut using the same equipment and gain settings. Take the same average RMS measurement and note the difference. Now we have somethong to talk about.

Some other questions:

1. Are you driving the head with the on board electronics or using an external power amp?
2. Is the max level you are able to cut at limited by the drive electronics (e.g. clipping) or the head running into saturation?
3. Did you have the head refurbished?
4. When you cut, are you limiting the bandwidth or boosting the highs to try and get a more Hi-Fi result?



Mark

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carldacorte
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Re: Really quiet cuts on a Rek O kut Challenger

Post: # 46538Unread post carldacorte
Thu Mar 30, 2017 5:42 pm

Thanks for the reply Mark!

To answer your first question, there's about a 17 dBvu difference between a commercial pressing and my cut.

I am using the original, onboard electronics (R8a amp). I'm afraid to drive the amp too much because I don't want to blow the the original cutter head. My next step is to install a 1amp fuse between amp and head so I can work on driving it a bit more without fear of blowing the coil. I'll say that I'm peaking on the onboard VU just over the half way point (green zone) win the needle occasionally going into the read zone. No distortion.

I repaired the head myself (I restore vintage electronics) after the machine arrived damaged. The head measures just under 4 ohms (in doing some research, looks like they should be 8 ohms? - Astatic M-41.). The suspension inside is original but is not hardened.

As far as bandwidth goes, I've tried all things. LPF, HPF, equalizing for better fidelity, etc - no significant change in level.

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FFrankensteinRecords
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Re: Really quiet cuts on a Rek O kut Challenger

Post: # 46540Unread post FFrankensteinRecords
Thu Mar 30, 2017 7:59 pm

Sometimes quiet cuts can be the result of improper armature setting. I've noticed that on my Presto heads, don't know if your heaad might work the same way.

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markrob
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Location: Philadelphia Area

Re: Really quiet cuts on a Rek O kut Challenger

Post: # 46544Unread post markrob
Fri Mar 31, 2017 8:15 am

Hi,

-17dB is a pretty huge difference. I don't know the metering or the power output of your amp. It might make sense to attach an 8 ohm speaker or resistive load along with a voltmeter and see what the limits are as compared to the meter reading. Run a 1Khz sine wave to the input and drive it to just below clipping (a scope might help here). Read the AC RMS voltage across the load, calculate the power output of the amp,a dn see if that makes sense given the specs or the tube complement. For example a push pull set of 6V6's might do about 10 watts or so depending on the biasing scheme. Also, take note of the level meter reading at clipping. Is is pinned? Reduce the drive until it reads 0, record the new voltage across the load and calculate the headroom. I suspect that it would be hard to blow the head with the stock electronics. I assume they would scale the system to distort before the head was in danger. Still, use some caution. You might find that you are being too conservative on the levels or perhaps the 0 level calibration (e.g. amplifier gain ) is off due to component drift. If you read Wayne's recent post about recorded levels, it might make sense to cut a 1Khz reference and measure the output from your pickup directly (in mv) get an order of magnitude idea about where you are. Also, keep in mind that the head will probably not cut levels near a pro setup, but you should get quite a bit closer than -17dB.

Hope that helps some.

Mark

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carldacorte
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Re: Really quiet cuts on a Rek O kut Challenger

Post: # 47613Unread post carldacorte
Mon Aug 21, 2017 4:10 pm

It's been a while since I posted. I thought I would revisit this with my findings in case someone else out there has the same issue.

Observing through my o-scope, I drove a 1k tone into clipping and made a test cut. I was still cutting at really low volumes. Although, making adjustments to the head and stylus gives me MUCH better signal to noise ratio, I still can't get the cuts louder. I'm thinking at this point, the head needs to be rebuilt. The rubber suspension still has give, but I'm sure it's stiffened up quite a bit over the years. The head reads about 3 ohms on my meter (it should be 8). I'm going to send it out to Westport soon.

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