Van Eps Cutter Head

[GrobbingThistle]

Hi All -

I've recently come into possession of a sort of mysterious cutting head. It's a Van Eps Duotone (only other information on the front is "X-15"). Here's the info I've been able to gather on it.

The Van Eps was the cutter head of choice for Peter Bartok, son of the famous composer Bela Bartok and the recording engineer on many of the original Folkways LPs. Here are a couple of excerpts from an interview with him.

[GrobbingThistle]

The Van Eps is also mounted to the Arctarus, the somewhat mysterious, Les Paul designed lathe


Here's a photo from a recent ebay auction, and one I've taken of the guts of the thing


So, I don't currently have a working lathe to mount this on to test it out (I'm kind of frankensteining one together at the moment), but I already have a few questions. I'm curious to know if 4 Ohms sounds like a sensible reading for this head. The Ebay auction specifically states that the model for sale is 500 Ohms, and I've never heard of a 4 Ohm head, but that's what mine pretty consistently reads (3.6 - 4). Does mine need to be rewound? The Ebay picture kind of looks like it might read X-500. Maybe that would make mine a 15 Ohm model? Also, what is this "vibrating-reed design" that Bartok speaks of? Can this sort of cutter head be re-wound to 8 Ohms like a Presto?

Thanks!

[Serif]

Nice pictures. Grobbing Thistle. I used to have some Thob' on vinyl, back in the early 80's... Also, SPK and the Birthday Party. (:

As for the Duotone Van Eps cutterhead, from p. 53 of Disk Rercording (by Robert K. Morrison), "...A rather similar cutter [to the Grampian type B1/A and B1/B] was the Van Eps Duotone type X-500, but it did not have the silicone fluid damping as used in the Grampian. The Van Eps unit that I had experience with was a 15-ohm example and was capable of very clean response to about 9 kHz."

So, it reads as if you should probably be measuring 15 Ohms on the drive coils. Morrison describes them as moving-armature cutters. Olson was also named as a manufacturer.

Cheers,
Andrew

[GrobbingThistle]

Nice pictures. Grobbing Thistle. I used to have some Thob' on vinyl, back in the early 80's... Also, SPK and the Birthday Party. (:

As for the Duotone Van Eps cutterhead, from p. 53 of Disk Rercording (by Robert K. Morrison), "...A rather similar cutter [to the Grampian type B1/A and B1/B] was the Van Eps Duotone type X-500, but it did not have the silicone fluid damping as used in the Grampian. The Van Eps unit that I had experience with was a 15-ohm example and was capable of very clean response to about 9 kHz."

So, it reads as if you should probably be measuring 15 Ohms on the drive coils. Morrison describes them as moving-armature cutters. Olson was also named as a manufacturer.

Cheers,
Andrew

Thank You Andrew! I'm a Huge TG fan (as you guessed), I've been kicking myself for months that I didn't actually see them before Sleazy died.

I had a hunch that X-15 related to the ohmage of the head. Maybe I'm not measuring correctly? I have a multimeter, set to measure the resistance in Ohms, and have been taking the measurement with one probe on either terminal on the back of the head. Should I be taking the measurement somewhere else? What could cause a head to lose resistance? Should I consider it repairable?

[markrob]

Hi,

Andrew is not correct. If your head is 15 ohms, it will read a significantly lower DC resistance (I would expect something in the range of 8-10 ohms). The 15 ohm figure is an AC impedance and is usually obtained at a frequency of 1Khz. The Grampian, for example, is rated at 15 ohms and has a DC resistance of only 3.7 ohms. The inductance is 1.65mh. This accounts for the large difference between the AC and DC values.



Mark

[cymbalism]

Birthday Party

Huge Nick Cave fan. Still lack to own a copy of Door Door by Boys Next Door on vinyl, just can't ever seem to find one whilst digging

[Serif]

Hi,

Andrew is not correct. If your head is 15 ohms, it will read a significantly lower DC resistance (I would expect something in the range of 8-10 ohms). The 15 ohm figure is an AC impedance and is usually obtained at a frequency of 1Khz. The Grampian, for example, is rated at 15 ohms and has a DC resistance of only 3.7 ohms. The inductance is 1.65mh. This accounts for the large difference between the AC and DC values.
Mark

Thanks for the clarification, Mark. I didn't realize that the stated coil resistance is in AC impedance, which varieth with freq...

If Grobbing is reading 3.6 Ohms DCR, and if the Duotone has the same inductance as the Grampian, then shouldn't the impedance at 1kHz be closer to 11 Ohms? (At 1k5 Hz, it should be darn near 16 Ohms, yes?)

Cheers,
Andrew

[markrob]

Hi Andrew,

I get the same results as you assuming 1.65mh and 3.7 ohms DCR. Not sure under what conditions the Grampain was measured (the spec states 1Khz). So ,I can't quite make the numbers jibe, but they are in the ballpark. I think in any event, the DCR readings are probably fine. I'd be concerned if he was reading anything close to or over 15 ohms DCR. Like speakers, these ratings are really just a ballpark since they vary vs. freq. I'd go ahead and fire the head up and see how it performs. Using a solid state amp rated for 8 ohms should be fine to get started. I'd assume the head is indeed 15-16 ohms and apply drive voltage to the head with that in mind. The Grampian states a drive level of 1.5 Watts into 15 ohms at 1Khz produces 7cm/sec peak recorded velocity. This represents a drive voltage of about 4.75 Vac RMS to the head at 1Khz. Seems like a good place to start.

Mark

[Serif]

Thanks, again, Mark. Your walk-though is reassuring. Works that way in my calculator, too, as long as I keep it RMS and don't do something silly like divide by 0.707 and multiply by 2.

(:




Best regards,
Andrew Hamilton

[GrobbingThistle]

Hi Andrew,

I get the same results as you assuming 1.65mh and 3.7 ohms DCR. Not sure under what conditions the Grampain was measured (the spec states 1Khz). So ,I can't quite make the numbers jibe, but they are in the ballpark. I think in any event, the DCR readings are probably fine. I'd be concerned if he was reading anything close to or over 15 ohms DCR. Like speakers, these ratings are really just a ballpark since they vary vs. freq. I'd go ahead and fire the head up and see how it performs. Using a solid state amp rated for 8 ohms should be fine to get started. I'd assume the head is indeed 15-16 ohms and apply drive voltage to the head with that in mind. The Grampian states a drive level of 1.5 Watts into 15 ohms at 1Khz produces 7cm/sec peak recorded velocity. This represents a drive voltage of about 4.75 Vac RMS to the head at 1Khz. Seems like a good place to start.

Mark

Great, you've been extremely helpful. My Rek O Kut R8-A actually has an output on the back for 15 ohms, so if I ever end up getting it back from the amp shop I guess that'll put me in business rather nicely. In the meantime, maybe I'll give it a whirl with a regular old power amp. Thanks again!

[GrobbingThistle]

Birthday Party

Huge Nick Cave fan. Still lack to own a copy of Door Door by Boys Next Door on vinyl, just can't ever seem to find one whilst digging

Funny you should mention that. My girlfriend just found a copy of that a week or two ago.

[piaptk]

Saw an episode of the reality show "Oddities" yesterday and Genesis P'Oridge was selling them his thigh bone flutes to raise money for a Lady J memorial or something.. Genesis is not looking good these days.

[GrobbingThistle]

Going on Mark's advice, I'm going to try to get this thing going with a solid state stereo receiver putting out 100 watts at 8 ohms. In the long run, do I need to worry about this damaging either the amp or the cutter head?

Additionally, would anyone happen to know what stylus I should get from Apollo? I'm a little flummoxed at their selection. The fact that they don't list prices on their website doesn't help either.

[cymbalism]

I would bet it's a short shank based on the size of the head but I'm totally guessing. Unless their prices went up they're usually around $90 USD

[piaptk]

I just acquired part of Peter's estate, and got his Van Epps heads. If anyone is interested in buying them, let me know. I have one with the original 500 ohm winding and two that I recoiled to 8 ohm because the original coils were fried. They all sound amazing.