The Secret Society of Lathe Trolls

prestok10 · Joined: 26 Aug 2006 Posts: 8 Location: West Michigan

Hi. I just discovered this forum, and it looks like THE place to find answers!

I've been experimenting with a Presto K-10 I got from Ebay, using Apollo dubs and a stylus from Transco, cutting 78s. I was not getting enough volume and apparently my recording head needed a rebuild, which is now in process by Bruce Leslie.

Amusingly, I've been feeding a signal into the Radio input from my iPod! Probably not up to RIAA specs for input, though Smile

I was also informed that I should be using a short-shank stylus, but the kind I have is long-shank. It was the only one on the Transco web site that mentioned Presto by name. I am investigating other sources for the correct stylus. Maybe another one from Transco will work, but I don't know which.

I can't seem to get a mike to work on the mike input despite buying an adapter so I could use the original Presto screw-on-type connector. I suspect it may be an impedence issue, on which subject I am totally ignorant.

My K-10 came with only three cutting gears, one of which was damaged. I had assumed the damaged one was for 78s to be recorded outside-in, and I had a friend with a machine shop make a new one for me, but I might be wrong as I am getting two 2 to 3-minute songs on one side of a 10 inch disc. If anyone has a picture of the correct gear, or some manufacturing specs, or a spare gear thay can sell or lend me, it would be greatly appreciated. I'd like to cut some 78s for my 1937 jukebox. With its newer, lighter needle, I think my 78s ought to play OK on it.

So far, half the fun has been designing my own labels!

cuttercollector · Joined: 11 Jun 2006 Posts: 307 Location: San Jose, CA

hi, Not the biggest expert here, but as to your questions, I think you can shorten the stylus shank to an appropriate length with a pair of stout cutters. I think the length needs to be correct to get the right cutting angle for a quiet groove. The radio input is a mono high impedance line level input. It has about the right gain to use with most modern "aux" level sources but of course stereo must be combined to mono and the appropriate adaptor used to fit the jack. As far as the mic input, it was designed to be used with a high impedance unbalanced dynamic or crystal mic. Beside the physical adaptor you probably need an xlr to high impedance transformer to use a modern low impedance balanced microphone and cable. If you touch the buttpn on the center of the screw on connector do you see hum on the meter or hear it when monitoring? Some of those had a sort of shorting or switch device where the pin was spring loaded and needed to be pressed in to activate the input. Others were just a solder blob for the center connection. Also does the meter/ monitor function give you about the right level at mid pot rotation from your ipod/line source? If all is ok there then it should work ok when you get the head working right. Otherwise you may need to replace various amp parts. Does the phono playback work ok with good volume and (relatively) low distortion on a good 78? Last, what ever eq curve is in that thing (waaay pre-RIAA) is in there, that is, you don't have to supply it on the input, although you could pre-eq something to give a little better result on playback to a limited degree. Just don't expect it to do really high level, wide range recordings like a late Lp or 45, but just mono. It can't really do that. Your gear sounds like it is slightly too fine for normal 78s. you did not mention whether you were trying to use a microgroove stylus or a "standard" 78 stylus to cut. If you cut wide 78 grooves at too high a level with too fine a pitch gear, they will run into each other and it will skip on playback. The old books told you that the land between the grooves and the groove itself should be about the same width when viewed under a microscope. The gear just controls how many lines per inch cut, not the groove width, which is related to stylus size and cutting depth.

charlief64 · Joined: 23 Jan 2006 Posts: 8

08/30/06 There is a short shank, saphire stylus on ebay right now for around 50 bucks. I would have bought it, but I use long shanks.

Charlie

prestok10 · Joined: 26 Aug 2006 Posts: 8 Location: West Michigan

Thanks much for your reply, cuttercollector. I should be getting my head back soon, so I can try out your suggestions.

I can play back regular (pressed) 78s really well and the ones I cut play back pretty good, too, on the Presto itself with its own playback arm/needle. Its only on a different player or my jukebox that I get low volume. If the newly rebuilt head doesn't solve my volume problem, then I can look elsewhere for the solution.

I get a bit of turntable rumble in my recordings as well, but it may be masked somewhat if I can get more volume with the new head. I usually fiddle a bit with the nuts on the motor mount to fine tune some of the rumble away. There might be some ill fitting (loose?) replaced parts on the motor mount (like possibly the rubber?) that could be causing rumble as well. I know that the capstan (?) is touching the rubber ring on the edge of the turntable at a slight angle instead of being perfectly flat, but if I bring it close enough to be flat against it, the rumble increases and it is very hard to start the turntable moving. My motor could be too old and has lost some "oomph".

Maybe I could trade my brand-new, just purchased, unused Transco long-shank stylus to someone on this forum for a short-shank Smile

BTW, how long do the cutting stylii usually last on average? (How many discs can be cut?)

cuttercollector · Joined: 11 Jun 2006 Posts: 307 Location: San Jose, CA

Probably your rumble is a product of lower level cutting and old hard rubber parts. Both the motor isolation mounts and the drive parts should not be "hard". Also the lathe drive itself might stand some re-lubrication as would the actual turntable motor. If you have good volume just using the thing to play records or play your Ipod through as an amp/speaker, then the head is probably to blame for most of the record level issues. It should be much better if the guy rebuilds and remagnetizes it. However any of these machines will not cut anywhere near as "hot" as a Westrex or Grampian feedback cutter. Again, no expert here, but with every ounce of power from the amp with good tubes and caps. etc. driving a rebuilt cutter to where you just start to really hear distortion on peaks, I think you could expect it to be about 80% as loud as a good commercial pressing. Volume is a relative thing. It sounds like the amp has plenty of gain off the playback cartridge now. As to cutting stylus wear, IF you set it up right and NEVER touch bottom by too deep a cut on fresh lacquer, you should be able to get many many sides out of one stylus. In other words they usually are destroyed by one "oops" rather than normal use. If you never "oops" you should just detect a slow rise in noise on a silent blank groove as it wears out.