The Secret Society of Lathe Trolls

aussie cutter · Joined: 18 Sep 2008 Posts: 4

Hi there everyone, I'm new to the record cutting game and would like to know if anyone can help me with some information / advice regarding cutting electronics and the presto 1c cutter head...

I recently aqquired an overhead lathe and some cutter heads
(one of them is a presto 1c), but with no electronics to drive them...

I've been reading a few posts regarding rewinding cutterheads to 15 or 8 ohms so they could be used on more modern amplifiers -

I have tried searching around on the net for info on old cutting amplifiers and have tried to find them for sale but with no avail...

the units that i can find are priced way out of my budget and living in australia dosn't help (cutting gear is extremly rare down here...)

I am very interested to know what/ which amplifiers could be used if i had my cutter heads rewound, I am not an electronics expert and would appreciate any info or advice given...

Regards Aussie Cutter

studiorp · Joined: 01 Nov 2007 Posts: 77

Hello, this is a good example of cutting amplifier :

http://cgi.ebay.com/Presto-Model-87-A-2A3-Amplifier_W0QQitemZ160284254303QQcmdZViewItem?hash=item160284254303&_trkparms=72%3A570%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

Greetings.

aussie cutter · Joined: 18 Sep 2008 Posts: 4

One of the amps that i am watching on ebay -

(price is out of my league at the moment, but maybe for some one here...)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=320300731832

Any info or advice regarding my previous post is much appreciated

regards

aussie cutter

vitanola · Joined: 10 Sep 2008 Posts: 6

For many years(from about 1952 until his death in 1975) my father sold acetate reference copies of performance recordings of operatic and concert material.

I cut literally thousands of discs for him when I was in my teens.

Our equipment consisted of a dual-turntable Presto Type Y recording system, 2 75A transcription lathes, and an 87A amplifier.

I found the 87A to be a bit lacking in headroom, and in my later days used one channel of my Harmon-Kardon Citation II, and then one channel of my Phase Linear 700.

Both of these amplifiers were a great improvement over the old Presto unit.

Almost any modern, quality amplifier with 8 ohm or 16 ohm output and a peak power of more than sixty watts will be perfect for use with the Presto 1-C.

There is a danger, however, when using a modern amplifier with these old cutting heads. One must carefully equalise one's material, and DO NOT PUSH THE HIGHS TOO MUCH! Over-emphasising the upper register can easily burn out your cutterhead (This is the voice of experience!)

If your upper register is not to your liking, please remember that the effective cut-off point of the Presto 1-C is about 10,000CPS. This is not as bad as it may seem at first blush. A flat response curve which cuts off rapidly after 10,000cps is perceived as "full-range" reproduction by a majority of the public, and can be quite musically satisfying.

One other point, if your cutter seams "Peaky" or dead at some frequencies, or your recorded product lacks brilliance, DON'T PRE-EMPHASIZE THE HIGHS to an excessive extent, LOOK TO YOUR VISCOLOID DAMPING BLOCK! If this has deteriorated, or has been improperly trimmed, the results that your cutting head produce shall be poor, indeed!

cuttercollector · Joined: 11 Jun 2006 Posts: 431 Location: San Jose, CA

Just make sure your cutter is low impedance before using it with a generic amp. It will either be "voice coil" (speaker) impedance of around 16 ohms or it will be 500-600 ohms. Both were made and there have been many many threads on this. A modern amp will not have much power at all into 500 ohms. I think you can get an idea of which it is with a simple volt/ohm meter. It will be measuring the DC resistance of the winding but should give you a result where you can tell if the cutter is low impeadance or high (or shorted or open). Just see if it reads in the single or low double digits vs. in the 100s of ohms (or a dead short or completly open)

aussie cutter · Joined: 18 Sep 2008 Posts: 4

All this information is wonderful... thankyou very much everyone, any more is appreciated (i would like to know as much as i can...)

The 1c cutter in that i have is stamped on the back for 500 ohms,
I was looking at getting it rewound to the 8 ohms because of the "extreme rare factor" of cutting amplifiers, particularly here in australia...

(i'll take some photos of the cutters and lathe i have and get them uploaded...)

It is fantastic to know that it is possible to use modern amplifiers to drive the cutters...

I have a full pioneer system (which is about 20 years old that can switch from mono/ stereo and has an equaliser on it, the system i think is about 475 watts it has phono, cd, aux lines & i think it has DAT (i'll have to check)

appart from the amps already reccomended - would this amp be possible. (if test driven at low levels on eq & volume to start with...)

I have also been tossing up on trying to use an old mono amplifier but have no idea about which and what type to try...

Any reccomendations...

vitanola · Joined: 10 Sep 2008 Posts: 6

For experimental purposes, you could always use a high-quality paging amplifier. The 70V line output will properly drive a 500 ohm cutterhead.

Or, use a matching transformer salvaged from a music system. Your upper register will be somewhat attenuated, but you will be able to get a "feel' for the use of your new machine.

If you decide to have your cutting head rewound, send me an e-mail. I have a couple of spare 1-C heads with burnt coils. No sense in modifying a still-usable original unit.

cuttercollector · Joined: 11 Jun 2006 Posts: 431 Location: San Jose, CA

I have driven a crystal cutter head off of a PA amp with a 100V output.
They are much higher impedance than the 500 ohm Presto. It was not a good match but it worked with a 100 W amp.

Actually. by ohms law it needs to be higher than 70V. to get enough power across 500 ohms. If you take the 70V out (which is the voltage any given transformer output PA amp will produce across that output tap when driven to full power) and divide by 500 ohms to get the current you come up with .14A and .14 amps X 70V only gives you 9.8W which is a little marginal to drive the cutter. So, while a 10W PA amp will match on the 70V out, that's not much power. If you use a standard modern amp unless it is really high power and designed to do so, it won't produce such high voltages across it's output.
To give a good solid 50W. across a 500 ohm cutter, which would be about all you could hope to drive into one of those Presto units, you would need an amp capable of aprox. 158 V out ! You can do anything with transformers but I am beginning to se why Presto used those transmitting high voltage triodes in their amps. If the plate voltage of the tube is higher the output impedance and voltage are higher, thus you don't need an extreme winding in your output transformer to get the necessary voltage and power.

piaptk · Joined: 25 Jan 2008 Posts: 186

So, I've been scouring the search function on this site looking for this info, and this was the closest thread I could find.

As I said in another post, I bought an old home cutter (which turned out to be relatively useless and didn't have a cutting needle like the listing said it did).

My friend James was helping me work on it, and he had two Presto 6Ns that are jsut sitting in his basement that I've been begging him to get working so he can sell me one. He finally partially cracked and told me that if I could find a place to get the 1-c head (500 ohms) fixed that we could "probably work something out".

The 1-c has been taken apart, I think he tried to rewind it, and just didn't really have the expertise or equipment to do it right. So, right now it is in pieces, but should be totally fixable.

Where do I go to get these things fixed for a reasonable price???

markrob · Joined: 28 Nov 2007 Posts: 198 Location: Philadelphia Area

emorritt · Joined: 09 Nov 2006 Posts: 248 Location: Tennessee

Talk to Gib at West Tech for these heads. He rebuilt my 1-C and it works/sounds fine. I noticed he replaced the old semi-clear amber colored viscoloid material with what appears to be sheet rubber. Probably through trial and error he would have had to have found the correct durometer rating of rubber to replace the viscoloid material since something too stiff or too pliable would radically change the audio characteristic of the head. And this would have been somewhat difficult since because of the aging of the original material, you couldn't go by it's current status to determine a suitable replacement as it wouldn't be what it was the year the head was originally manufactured. Don't know if he'd work on a head that's already disassembled, but it's possible.

I have an old Western Electric head from the late 20's (the "rubber line" recorder) which needs the damping material replaced in order to work again. In addition to the fact that it looks like two different grades of rubber are used together, as well as being in a long cylindrical shape, it will be a difficult task at best.