Presto 1C

[maniman]

Hi guys , I'm mounting a 6N in my free time and now have a 1C and the overhead , I'm a bit far of have nothing cutting and have a lot questions about the head ,that head is in cosmetically good ? state for his age , is a 15 Ohm Version and measured 10 Ohms (that is in relatively good state ?)

1 - First of , this head armature must be filled with fluid ? or its the rear part the part filled with fluid ? or this is only in the 1D , the 1C isnt fluid filled ?

2 - What stylus must i buy for that head ? the Transco 462 Fairchild / Presto Long Shank ?

3 - About the Blanks ? are rigth Apollo / Transco 12 " Dub plates? or better single sided for test ?

I request in the manuals section if someone have the 1C Manual , I read the 1D and don't have a lot info of nothing of that.

I'm searching for the complete drive but meanwhile I'm want to build a pre amp for the head , I'm thinking in the "Grampian preamp Jamaika style" from Flo omitting the feedback part.

And what can do about the amp ? how many power it's necessary ?

Thanks in advance
Mani

[piaptk]

Apollo 462 long shanks are what you need, although shorter shanks can be used if you have them hanging around. You just can't cut in as far.

Any blanks can be used.

[maniman]

Thanks Mike , that two things are now clear.

C'mon guys , 300 people have Prestos Here , Nobody knows how the head works ?
I can't believe it.

Please , someone can explain me how have the head up and sounding ¿? , or simply if the head have tank and if must be filled with what ?

Thanks in advance

[Kris D]

Hi - None of the Presto heads use damping fluid in the head. The Grampian type D and C both use silicon damping fluid. The only fluid used on a Presto is for the dashpot, which should be filled with glycerin. Manuals for nearly all Presto equipment are available from Mr. Alan Graves at the Presto history page. The 1C is very similar to the 1D and the manuals should be nearly interchangable. A reading of 10ohms sounds about right because an ohm meter will not give you true ohm value of the head. True value must be read at 1K using a different type of meter (If I remember right!)
Good Luck
- Kris

[maniman]

Ohhhh , thanks man , thats is exactly what i'm guessing , the internals don't look to have a dumping or nothing similar , yes yes the only dumping is on the own carriage , now all have complete sense.

About the drive I read somewhere 10 W of amp can be sufficient , what the people guess ? an amp that gives 10 w @ 15 ohms , can be easily needed a 25 W amp @ 8 ohms (so so the same true?) ?

[JayDC]

no no..


you need at least 1.2watts @ 15ohms x 10... I would use at least 120watts @ 15 ohms.. but the 1-D manual says a little more is required for music. I am cutting with a 100watt @ 16ohm home theater amp now, and after eqing the head, and the riaa curve, its not enough to fill a 112lpi pitch. It's almost there though..

I have sourced an amp that meets this requirement, both solid state and tube.

On the low price end is the pyle ppa300 (http://www.pyleaudio.com/itemdetail.asp?model=PPA300). As for a tube amp, there is a kit VTA M-125 Mono block (http://www.tubes4hifi.com/bob#M125), both of which will accommodate a 16ohm load.. The tube amp kit is almost $900 and it will cost another $400 for the best tubes.

I followed a suggestion in the 1-d manual to add at least a 1 ohm (up to 5 ohms) resistor wired in series to the negative side of the head (I used a 1ohm 10 watt resistor). I also have wired a .5 amp slow blow fuse on the negative side.

I found that covering the outer case with dynamat extreme improved the clarity of the cut. Dynamat is used in high end luxury cars to dampen exterior and interior sound. I think by applying this to the outer case, I successfully dampened the head, possibly removing some resonance.

I know for a fact that the original piece of rubber dampener can be replaced with sorbothane, you can get this from amazon.com.

In the circuit and schematics area, there is a post by me with test tones.. cut them with no riaa curve, at a low level so you don't blow your head. You can visually see a pattern, and can successfully calibrate an eq for your head to get the best response. Check that thread for more info

[maniman]

no no..


you need at least 1.2watts @ 15ohms x 10... I would use at least 120watts @ 15 ohms.. but the 1-D manual says a little more is required for music. I am cutting with a 100watt @ 16ohm home theater amp now, and after eqing the head, and the riaa curve, its not enough to fill a 112lpi pitch. It's almost there though..

I have sourced an amp that meets this requirement, both solid state and tube.

On the low price end is the pyle ppa300 (http://www.pyleaudio.com/itemdetail.asp?model=PPA300). As for a tube amp, there is a kit VTA M-125 Mono block (http://www.tubes4hifi.com/bob#M125), both of which will accommodate a 16ohm load.. The tube amp kit is almost $900 and it will cost another $400 for the best tubes.

aha , something like 450w @ 4 ohms , 225w @ 8 ohms , 112w @ 16 ohms , that type of amp ?

Unfortunately the VTA don't work at 220 V@50Hz (the standard AC in Spain) , and aren't shipped out of USA/Canadá , but I guess can start to do tests with a simple amp that fit the specifications.

I followed a suggestion in the 1-d manual to add at least a 1 ohm (up to 5 ohms) resistor wired in series to the negative side of the head (I used a 1ohm 10 watt resistor). I also have wired a .5 amp slow blow fuse on the negative side.

Aha , the 1ohm 10 w is a ceramic resistor true ?
And a 0.5 amperes slow blow fuse true ?

Why in negative wire ? , sorry my ignorance , instinctively I was thinking the opppositte.

I found that covering the outer case with dynamat extreme improved the clarity of the cut. Dynamat is used in high end luxury cars to dampen exterior and interior sound. I think by applying this to the outer case, I successfully dampened the head, possibly removing some resonance.

Aha , but i'm seeing Dynamat is a brand , and have hundred of products , I need to watch better the web , but i don't understand this part at all , are you referring to something like a foam ? like auralex one or something similar ?

I know for a fact that the original piece of rubber dampener can be replaced with sorbothane, you can get this from amazon.com.

Aha , something like this ? (seems have the most convenient form to fit like the original)

http://www.amazon.com/Sorbothane-Vibration-Isolation-Square-Thick/dp/B0042UAHHK/ref=sr_1_11?ie=UTF8&qid=1301487702&sr=8-11

In the circuit and schematics area, there is a post by me with test tones.. cut them with no riaa curve, at a low level so you don't blow your head. You can visually see a pattern, and can successfully calibrate an eq for your head to get the best response. Check that thread for more info

That one true ?

https://lathetrolls.com/viewtopic.php?t=2450&highlight=calibration&mforum=lathetrolls

I'm gonna to study well the entire thread.

Thanks for all Jay , a lot of info , I need 2 or 3 days to assimilate all that. Hehehe

And thanks to all the others too , be patient with me please , sometimes are given by known many things that I don't know , and until I find my own way of understand a concrete thing can pass some time.

Thanks friends.

[JayDC]

power is pulled from the negative and drawn to the positive. So the fuse goes there to prevent the current going through the head prior to the fuse blowing. I thought the opposite at first too, but this is how my electronics books says it is..

Its just a 1ohm wire wound resistor, just coz its all I could find at the time.

The pyle ppa300 is rated at 320w @ 8ohm bridged mono, or 160 @ 16 ohms bridged mono.

Dynamat is a name rand of sound isolator, I'm not even sure what to call it other then its trade name.

Dynamat is a rubber adhesive sound isolation pad with think aluminum foil on the top, and paper on the bottom. you cut it to shape, peel off the paper, and stick it to whatever you want to dampen. Once you stick it, you need to roll it with a roller, or press it down really well, and get all the air bubbles out.

[monkey1553]

Just to chime in here. I'm using presto heads with my presto 90b amp which is rated at a monster 10watts power. Everything runs just fine and I'm not seeing any need for more headroom. The sound seems clean and clear as loud as I dare push it. Both of my presto heads are wound at 8ohms. Go figure!

[JayDC]

Just to chime in here. I'm using presto heads with my presto 90b amp which is rated at a monster 10watts power. Everything runs just fine and I'm not seeing any need for more headroom. The sound seems clean and clear as loud as I dare push it. Both of my presto heads are wound at 8ohms. Go figure!

well if i recall my 90b, it only had 500ohm taps on it.. 10w @ 500ohms is a lot of amp at 8ohms..

[monkey1553]

Hey Jay,

I think you're right. It seemed to have more than 10watts! I took a quick look at the manual here and it looks like it is for sure based off of the 500ohm taps. I'm also very curious about doing the sound dampening mod to my 6n. Did putting that stuff on the platter seem to have the greatest effect on quieting things down?

~Michael

Just to chime in here. I'm using presto heads with my presto 90b amp which is rated at a monster 10watts power. Everything runs just fine and I'm not seeing any need for more headroom. The sound seems clean and clear as loud as I dare push it. Both of my presto heads are wound at 8ohms. Go figure!

well if i recall my 90b, it only had 500ohm taps on it.. 10w @ 500ohms is a lot of amp at 8ohms..

[JayDC]

to be honest, I put it everywhere, and used up all 32x18 of it. I did he head last, so I cut a few things prior. There is a difference between none and some. I notice a much clearer sound once I applied it to the head, and that really when i started to notice my setup is under powered. The THD in the high end is starting to be a problem, and the only way to fix that is to get more power.

It kills the rattling of the cutters case, and seems to dampen the resonance that is caused by this.


The motor noise in the the cut is so much lower now, I feel I could cut a passable master on my system now, if I had a stereo head.. I might even try cutting a mono master, who cares when its going to be played at a club.. they all use mono systems anyway..

[monkey1553]

I'm gonna look into doing the dynamat then. I figured it could really help the platter rumble but that is good to know that putting it on the head helped so much. I wouldn't have thought to try it there. Very cool to hear you're getting such improved sounds out of our old gear! Thanks alot for the tip on this. I'll let you know how it goes for me.

~Michael

to be honest, I put it everywhere, and used up all 32x18 of it. I did he head last, so I cut a few things prior. There is a difference between none and some. I notice a much clearer sound once I applied it to the head, and that really when i started to notice my setup is under powered. The THD in the high end is starting to be a problem, and the only way to fix that is to get more power.

It kills the rattling of the cutters case, and seems to dampen the resonance that is caused by this.


The motor noise in the the cut is so much lower now, I feel I could cut a passable master on my system now, if I had a stereo head.. I might even try cutting a mono master, who cares when its going to be played at a club.. they all use mono systems anyway..

[JayDC]

well, take caution if you apply it to the platter..

It will take you more then 3 days 30 minutes per day of rolling it to get it flat once applied.. Cut a 18 x 18 square, pop a hole in the middle, and make sure you pop a hole of the dub pin. Align the center hole, and dub pin as you stick the square on the platter. Roll it to get most of the air out, you can use a needle to get rid of bubbles. Then use a razor or exacto knife to trim the dynamat to the shape of the platter. Continue to roll it for as long as you feel that it's not flat. My method to test this was to put a slate on the platter, and spin it.. see if the slate stays flats, or wobbles.

I used a hot iron on day 2 to heat and smooth out the material..

The roller I used is wooden, with a wooden handle.. I broke the plastic one i used at first by applying to much pressure. You need alot of pressure. In cars, it doesn't matter if this material is perfectly flat. It matters alot on the platter.

I also cut a 12" circle with a 3" center hole for the underside of the platter.

One thing is for sure, the platter does not ring any longer...


So after all that, I put the original rubber mat back over the dynamat, and had to readjust the height of the over head.

So i ripped off the rubber from the bottom of the overheads drive collar, then put dynamat there, and glue the rubber back on.

Then I applied 4 layers of dynamat to the spot where the overhead attaches to the body. to raise the height, mainly coz the ring that is for this adjustment got stuck, and I couldn't get the height i needed.

Then I took scraps, and stuck them to the motor, and body. used it up..

[maniman]

power is pulled from the negative and drawn to the positive. So the fuse goes there to prevent the current going through the head prior to the fuse blowing. I thought the opposite at first too, but this is how my electronics books says it is..

Aha , for me its sufficient explanation , hehe.

Its just a 1ohm wire wound resistor, just coz its all I could find at the time.

Aha , the electronic guy at my work says to me 10 w isnt the common for that , but is easily findable.

The pyle ppa300 is rated at 320w @ 8ohm bridged mono, or 160 @ 16 ohms bridged mono.

O yes , if the system is mono the amp can be bridged , I'm totally stupid for no thinking that.

Dynamat is a name rand of sound isolator, I'm not even sure what to call it other then its trade name.

Dynamat is a rubber adhesive sound isolation pad with think aluminum foil on the top, and paper on the bottom. you cut it to shape, peel off the paper, and stick it to whatever you want to dampen. Once you stick it, you need to roll it with a roller, or press it down really well, and get all the air bubbles out.

Oh ok , now I know , that is one of the articles I saw ...

Thanks man

[markrob]

Hi,

Back from Barcelona. Had a great trip! Thanks for the tips on places to go.

On the 1C, damping is via provided by a piece of rubber coupled to the armature. Its visible if you remove the top cover. If that is dried out, you may need to replace it. 10 ohms sounds like its in the ball park for the DC resistance. You will need to add an external resisitance in series with the head to make it meet the low frequency RIAA 500 Hz turnover. I don't have a 1C manual here (only a 1D) It shows a value of 3 ohms for a 15 ohm head. This means that your RIAA EQ should not have the 500 hz turnover included or you bass response will be off. I have a VST plugin that does this. PM me if you want a copy. These heads only need a about 1.2 watts of drive to reach a standard 5cm/sec cutting level at 1Khz. I think a 10 watt amp would be ok, but 50 watts would give you some extra headroom. It must be able to drive a 15 ohm load. Most solid state amps will produce 1/2 the rated power into 16 ohms (compared to 8 ohms). Check the specifications of the amp you plan to use. If you have a tube amp, just use the 16 ohm tap and you are fine.

Mark

[JayDC]

50 watts seems a bit low, especially since i'm using more then that atm, and need more. The 1.2 watts is more for speech, not music at high levels, so it all depends what you are using the cuter for.

In my setup I tend to use subtractive eqing for things like head calibration which lowers the output signal to the amp. My output does not get any higher then -4db/0 with your riaa plug-in. Mainly coz I'm trying to make sure there is no distortion.

So, sure I could raise the volume for my sound card, but I rather not. The amp is already at its highest setting.


I'd like to be setup in this way:

sound card @ -6db/0
amp @ 1/2 volume

and get a full loud cut at 112lpi with no distortion.

other then that, right now it sounds beautiful...

[maniman]

Hi,

Back from Barcelona. Had a great trip! Thanks for the tips on places to go.

Hehe I'm very glad to listen it Mark , I hope you've enjoyed it , Barcelona it's a nice city , and the city's nightlife it's absolutely awesome , but do not know if you noticed that the atmosphere is rarefied this past weeks , a lot of police , etc... , but nothing new.

10 ohms sounds like its in the ball park for the DC resistance.

That is saying "The head is in the sunset of her life" ?

You will need to add an external resisitance in series with the head to make it meet the low frequency RIAA 500 Hz turnover. I don't have a 1C manual here (only a 1D) It shows a value of 3 ohms for a 15 ohm head. This means that your RIAA EQ should not have the 500 hz turnover included or you bass response will be off.

That is say "when put the correct ressistor your RIAA doesnt need the bass cut , only the high end correction" ?

I have a VST plugin that does this. PM me if you want a copy. These heads only need a about 1.2 watts of drive to reach a standard 5cm/sec cutting level at 1Khz. I think a 10 watt amp would be ok, but 50 watts would give you some extra headroom. It must be able to drive a 15 ohm load. Most solid state amps will produce 1/2 the rated power into 16 ohms (compared to 8 ohms). Check the specifications of the amp you plan to use. If you have a tube amp, just use the 16 ohm tap and you are fine.

Aha , as example , my solid state amp is 250w@4 ohms in bridge , 125w@8 ohms , and near 37 w @ 16 ohms (instead of the instinctively think anyone 75 w @ 16 ohms ) , that is what you mean?

u are PMed.

Cheers

PD : That famous RIAA VST plug are programmed by you Mark ?

[markrob]

Hi Mani,

I saw quite a few security and police on La Ramblas and the few times we strayed a bit too far off the main areas into iffy areas, but I figured this was normal.

We were lucky to catch a classical guitar concert by Manual Gonzales at the Basiclica Santa Maria del Pi. We were just walking around before eating and stumbled upon it just befroe starting time. Bought tickets and went in. It was a great performance!

I was also amazed at an electronics shop called Onda Radio on Gran Vía Corts Catalanes. There is nothing like this near me in the US. I made my wife tag along as I checked out the parts and test equipment. If I lived in Barcelnona, I probably shop there daily.

Yes, I programmed the series of VST RIAA plugins. I originally did the playback version so that I could copy older recordings with different EQ settings before RIAA was adopted (my plugins allow you to change the turnover frequencies and save as presets). So, you just need a flat preamp with a gain of 40 db or so to bring the pickup level up to line level and you can correct for most any recording, including RIAA). Then once I got the cutting bug, it was easy to adapt the plugin for the recording curves. I recently found a stupid bug in the plugins that would cause the wrong version of the plugin to be loaded if the whole set was installed. This was due to not giving them unique internal names. This confused some VST hosts. I think I have this fixed now.

The Presto and Grampian (when run without feedback), don't need the 500hz turnover as this is built in to the head resoponse by design. You just need to adjust the turnover using an external resistor to get the response correct. So, you just need the high frquency boost starting a 2125 Hz. There is also a low frequency boost defined at 50 hz that you may be able to eliminate. The Presto version of my plugin provides only these two turnovers (50hz and 2125hz).

As far as power amps go, if your amp is rated 125 watts into 8 ohms bridged, it will produce 62.5 watts into 16 ohms bridged. Solid state amps can deal with a larger range of loads than a tube amp, but the tradoff is that the output power changes with the load. In a tube design, the power output is constant vs. load, but you need to select the correct tranformer tap or you risk damage to the amp.

Mark