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Amp Doc
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Inverse RIAA curve Circuit + Info

Post: # 1365Unread post Amp Doc
Thu Jun 21, 2007 11:41 am

I Have Circuit and Info Could It Be Posted On Here[/code]
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JayDC
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Post: # 1366Unread post JayDC
Thu Jun 21, 2007 1:24 pm

cool.. post it..

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Amp Doc
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Post: # 1367Unread post Amp Doc
Thu Jun 21, 2007 2:20 pm

http://sound.westhost.com/project80.htm

This link should help

It sums up what the filei s all about without all the Math!
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cuttercollector
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reverse RIAA

Post: # 1370Unread post cuttercollector
Thu Jun 21, 2007 10:05 pm

Or this:

http://www.mcminone.com/product.asp?catalog%5Fname=MCMProducts&category%5Fname=3829530&product%5Fid=50%2D7240

It is important to remember that these sorts of devices beside giving you the inverse of RIAA playback, ALSO attenuate from standard line level (500-700mV.) to phono level, about 100 times less (2-4mV.) This means for what we would use them for you would then need to go from the output of the inverse RIAA device back into a flat (no eq.) high gain input like an insturment or perhaps mic. input to get enough gain to then drive your power amp for the cutter.

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Amp Doc
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Post: # 1373Unread post Amp Doc
Fri Jun 22, 2007 2:54 pm

the point of the post is to show a simple RIAA inverse curve circuit which could be coupled to a common base amp at front for low Z input, or collector amp fo high Z input, small driver amp for output to mixer.

I have many small(Building block) circuits and am currently setting up me presto 8N
Could do with a section for circuits ect..
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cuttercollector
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Post: # 1374Unread post cuttercollector
Fri Jun 22, 2007 4:45 pm

Yes and thanks for both designing and sharing this info.
Unfortunatly, probably a majority of people on this forum, including myself, are not capable of active filter design. or fully understanding how to impliment amp designs with op amps, much less discrete transistors or tubes. I am more of a systems level, plug boxes together sort, or if I have to, I can follow a detailed schematic designed by someone else, to build what is needed or repair something. The design of the electronics needed to drive a cutterhead, especially a feedback one, with proper inverse RIAA EQ and compensation for the frequency characteristics of the head itself is not trivial. Disc cutting and playback are the simplest of concepts, but to do it to the state of the art level it had evolved into is not easy!

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Amp Doc
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Post: # 1376Unread post Amp Doc
Fri Jun 22, 2007 6:30 pm

I am only just getting into cutting. but I read and whot seem to be common is that the BEST cuts use very little compreson or EQ only RIAA curve, clean basic analogue systems, sorce,RIAA,mixer,amp,head. Read a article on a guy who worked at JVC he said the best sound on the trillon dollar mastering consol was on bypass and same on some things in the neumann rack. CLean seems good. I

Like you have found there is not a lot of easy circuits on the net about cutting most are 50 and 60 makes them hard for me(Im electronics en.) strange inductors and Q values,resonances ect. That Why I Posted. if intrested I could Post other stuff eg. simple power meter at 4 or 8 ohms, headphone amp, simple mixer ect.
!Work or Bang Time!

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motorino
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Post: # 1377Unread post motorino
Fri Jun 22, 2007 9:09 pm

Amp Doc wrote:the point of the post is to show a simple RIAA inverse curve circuit which could be coupled to a common base amp at front for low Z input, or collector amp fo high Z input, small driver amp for output to mixer.

I have many small(Building block) circuits and am currently setting up me presto 8N
Could do with a section for circuits ect..
thanks! my friend and I, took to many days calculating that passive filter

it is very good idea to create a section in this forum on circuits..

I need a riaa circuit for grampian D :roll: and her caracteristics, maximun driving amp, any help?

cheers
Marcos

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cuttercollector
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Post: # 1382Unread post cuttercollector
Sat Jun 23, 2007 2:14 pm

Yes, the ideal would be a system that needed no compensation eq other than the RIAA curve. Just as with speakers, a flat neutral system that adds no coloration of it's own and was designed that way mechanically speaking would be best. Then you could add whatever your production values dictated in terms of eq, compression etc.
But in the real world people use microphones for example, for their characteristic "sound" and most cutters have a "sound" too. This almost always stemming from their deviation from flat broad frequency response and their particular charicteristic distortion when pushed hard.
some have more of a "sound" than others and people use this sometimes to good effect, just like with microphones, or guitar amps are a great example of this. No guitarist typically wants to play through a completly flat 20-20K speaker system that won't distort at all no matter how hard you push it or loud you play. That would be an atypical electric guitar "sound", like plugging it into the mixer directly and having all the eq flat.
I think though that the reason I am into discs and disc cutting is that somehow even with their real world faults, nothing sounds closer to "real" than a good disc recording.
Anyway, thanks for the circuits and being involved with our quirky art.

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Amp Doc
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Post: # 1386Unread post Amp Doc
Sat Jun 23, 2007 4:14 pm

From what I have found for grampian D feedback

250W min amp for headroom
500omh drive coil
20 ohms is for feedback seems very low Z

but mine has 4 ohm drive and slightly higher feedback 27 ohm.
Seem that you can wind coils to suit amp and electronics.

If I can find specs will post.
Am just simulating a amp power meter reading Power in Watts+dBm and current for monitering head would be a good post. Very usefull
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Cutterwoller
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Post: # 1389Unread post Cutterwoller
Mon Jun 25, 2007 7:11 am

Hey, I have the manual for the grampian amp that was made for the type D head. Includes power supply and schemtics. If you would like, I could email them to you.

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Post: # 3250Unread post Tinplate
Sat Aug 02, 2008 6:53 pm


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Steve E.
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Post: # 3253Unread post Steve E.
Sun Aug 03, 2008 11:05 am

Amp Doc wrote:
I have many small(Building block) circuits and am currently setting up me presto 8N
Could do with a section for circuits ect..
Your wish is my command.

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cd4cutter
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Post: # 3254Unread post cd4cutter
Sun Aug 03, 2008 2:41 pm

Once again, the discussion regarding the purpose of RIAA equalization given in the 'plattenspeler.com' link is WRONG, WRONG, WRONG !!!. Bass frequencies are NOT REDUCED during recording to get more level on the disc and highs are NOT BOOSTED to improve signal to noise ratio. It's just the opposite, actually. All this misinformation arises because people keep getting confused about what the typical published RIAA response really means. See my other posting about this which describes in detail what's really going on.

[EDIT by moderator...Here's the other posting:

https://lathetrolls.com/viewtopic.php?p=3239&highlight=&mforum=lathetrolls#3239

This claim by CD4cutter was challenged recently in a thread started by esteemed mastering engineer Kevin Gray. Please read it for a debate/point-counterpoint. I do not have the technical know-how to take a stand one way or the other....I'm the messenger. Judge for yourself!

https://lathetrolls.com/viewtopic.php?t=1417 ]


]

The confusion arises because the published playback compensation curve ALSO INCLUDES the 6dB/octave compensation for converting constant velocity playback transducers such as magnetic cartridges to constant amplitude response, together with the RIAA de-emphasis. You DO NOT need to compensate cutting systems to convert them from constant velocity to constant amplitude - they are already nominally constant amplitude, hence the extra 6dB/octave is not necessary when recording. If you try to use the inverse of this curve as RIAA pre-emphasis on your cutter, you will wind up with absolutely no bass at all in your cuts and outrageously screechy treble. Plus, you'll probably blow your cutter head trying to cut all that HF boost.

Cutting systems are nominally designed to produce CONSTANT AMPLITUDE recordings. This means the peak-to-peak size or amplitude of the recorded wave is the same for all frequencies with the same input voltage, i.e. constant amplitude. The recorded wave looks thru a microscope just like it would if you viewed the input signal on an oscilloscope. CONSTANT VELOCITY means the peak velocity of the wave is the same at all frequencies. This is difficult to visualize, but the peak velocity of a wave is that point where it crosses the zero axis, that is where the stylus is changing from acceleration to deceleration when tracking the wave. It is this velocity of the stylus that determines the output voltage of a MAGNETIC PICKUP CARTRIDGE, which is thus termed a constant velocity responding device. (Crystal and ceramic cartridges are constant amplitude responding and require a different playback EQ from the published RIAA curve as well - they require the inverse of the actual RIAA recording curve.) It turns out that the amplitude of the wave has to change at a 6dB/octave rate in order to produce a constant peak velocity of the playback stylus at all frequencies. The proper RIAA pre-emphasis curve for recording actually results in a fairly small amount of change to the response curve from flat, constant amplitude. There is about 6dB of BOOST at 25 Hz and about a 6dB shelf of CUT at frequencies above 2kHz or so in the resulting RIAA compensated recording. To envision what the correct RIAA compensation is for recording, you have to subtract the 6dB/oct slope from the typical published playback curve, then invert the result. The proper RIAA recording compensation curve is very seldom seen published since only professional recording equipment users ever had any need to know what it is.
Collecting moss, phonos, and radios in the mountains of WNC

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motorino
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Post: # 3255Unread post motorino
Sun Aug 03, 2008 4:39 pm

and do you know exact recording curve? and this curve its aplicable to all magnetic cutterheads? or this curve depend of the cutterhead frecuency response?

y use a grafic eq for my Grampian cutterhead, y put a hi-pass filter at 35hz..(this cutter have a lot bass response...) i compare my cuts with pressed vinyls, sounds good


Image
Image

Image
Image


this passive circuit (with her consecutive preamp) put my amp in distortion (i believe its for high frecuencies), but before put in distortion i get good cuts...but using only the grafic eq get better sound, do you have some better passive circuit??
Marcos

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bancho
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Post: # 3256Unread post bancho
Sun Aug 03, 2008 5:51 pm

now this is something! I tried to cut with that "inverse RIAA curve" and the sound was terrible. It was much better with flat eq and even better if I added some bass. I thought the amp has some sort of built-in inverse riaa eq.
Finally it has more sense to me!
It would be awesome if you could post some graphs, pictures, circuits etc. about all this.

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flozki
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Post: # 3258Unread post flozki
Mon Aug 04, 2008 4:48 am

et voila.
here is a nice schematics of a riaa encoder.
jvo from StuKa (vinylium) did at that time.
i used in for my first cutting lathe in 94 already.
it is the way how to do. straight forward. no fancy stuff.

always think in modules. this is the encoder module.
maybe you need another head eq module, as long as you
dont cut with THE perfect cutterhead.
(even neumann sx74 heads have a cutterhead eq.)

so build this on a vero board. use a nice dual opamp.good components costs you $10 max. and a little time. thn you have the ultimate highend encoder....
then build another eq for the head. (simple for good feedbackheads sx74,68,sc99,es59,ds641...can be even passive) more complex for simpler heads...
a power amp and maybe a feedback amp, mixer
voila.
happy soldering...

flo

***vms82 up and running .schnippel schnappel.cut.***

---------
how can i insert pictures??? i never manage...maybe someone can explain....hehe


[url]http://www.floka.com/lofi/riaa_enc_flo.jpg[/url]
[img]http://www.floka.com/lofi/riaa_enc_flo.jpg[/img]

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flozki
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Post: # 3259Unread post flozki
Mon Aug 04, 2008 5:06 am

for all the grampian users:

here is a schematic i received in kingston jamaica.
they use this kind of preamp at a very famous dubplate studio in kingston.
at least two prestos with grampian type d.
the sound was very nice.

i never built myself.

build it and let us know how it sounds....

flo

***vms82 up and running .schnippel schnappel.cut.***


http://www.floka.com/lofi/grampian_pre2.jpg

Image

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flozki
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Post: # 3260Unread post flozki
Mon Aug 04, 2008 5:08 am

ok i think i got it with the images..
again the picture from my riaa encoder....

Image

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motorino
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Post: # 3261Unread post motorino
Mon Aug 04, 2008 5:39 am

:shock:

I have no words to thank you for this contribution, we are many people that we were hoping that someone provide some good circuits

I now make the list of components and run to the store to buy everything needed to manufacture the Jamaika Style

many many thanks!



The best contribution at day to this forum!
Marcos

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