Rek-O-Kut Challenger and RIAA demands?

[Wagner]

I have a Rek-O-Kut Challenger with the Model R-8A amplifier, and I believe the original cutting head it came with (it's getting worked on at the moment so I can't check). I'm not sure the exact year this machine was produced ('52 I think), but I don't think the amp has any provisions for RIAA encoding.

I was seeing what users of this machine do for RIAA encoding. All my old books only have schemes for Playback RIAA networks, and a lot of the links on old threads on this site have expired. Let me know if the amplifier's Treble and Bass controls on the amp can get a decent approximation and I don't necessarily need an additional device or whether I should be looking to build a separate device, and if so what device you've found that works best, passive or active.

Big thanks to any good brothers that can provide help .

-DIGBEE

[markrob]

Hi,

I took a look at the R8A schematic I have here and it looks to me like they are relying on the bass and treble controls to provide the recording curve as I see no other EQ present in the circuitry. I did not spend time analyzing the response of the tone controls to see if they engineered the basic RIAA curve into the controls such that setting them to the center position provides the correct response. I see from an ad I found online that the bass an treble provide +/- 15 db of gain or cut which should put you in the ballpark (bass centered at 50hz and treble centered at 8Khz). The moving iron heads on these type machines typically have the RIAA 500hz turnover incorporated into the response. So you may really only need the treble boost to match the curve. Since it was made in 52' and it has 33 rpm, it should have some sort of RIAA like encoding/decoding present or it would not produce recordings that would play back correctly on a consumer record player. In 48' Columbia introduced the 33 microgroove which had the modern RIAA curve as part of the standard and in 49' the 45 was introduced by RCA and this also used the same standard. It would be interesting to see what the user manual recommends for the bass and treble settings. Do you have a copy?

Here is a link to the ad I found:

http://www.itishifi.com/2014/11/rek-o-kut-brochure.html

If you need copies of the schematic, PM with your email and i'll send it your way ( I see we are both in the Philly area).

Mark

[Wagner]

I actually recently got a copy of the Challenger manual, it is called 'Installation and Operation of "Challenger Deluxe Disc Recorder". I have to see if it is posted on the forum, because if not, it should be. I think that is why I ended up having to buy a physical copy, because I couldn't find it online.

Ok, and this is where our answer may lie and why I posted the question and suggested maybe the internal tone controls would be sufficient, the manual says (paraphrasing slightly) under "Recording at 78 or 33: when recording at 78 the following bass controls are recommended Bass at #1 on Max side and treble at #3 on Max side" "when recording at 33 bass set at position #3 on Min. side and treble at position #4 on Max side. to suit individual requirements or achieve certain effects the above controls can be manipulated to suit."

So perhaps that is all the calibration necessary, unless anyone makes a strong case to the contrary. What you were seeing on the amp scheme and that brochure all seem accurate then. I think it would be safe to go by ear from here on out, unless, like I said, someone has a different story to tell.

[TipiumGrove]

A print copy of the Rek o kut Challenger manual? I was starting to believe that it was a myth! Is there any chance I could get a pdf copy?

[timinbovey]

What? There's actually a manual? I've been looking for one for several years. If I can get a copy, pdf, carbon paper, blurry spy camera photos, or what have you, I'd be mighty darn happy!

Tim in Bovey