Peterayer and Stringreen,
Sorry to veer off on to record cutting.
To get back to the OP. The reason why there is an issue with regard to SRA and VTA is that they affect different things. An appreciation of what each term actually means helps to understand the issues. An appreciation of why cartridges have the geometry they do also helps. Reading the articles I linked to will be useful in doing this. Some might find them too technical, in which case, ignore the subject and set your arm up to sound as good as you can.
Csontas:
from your reply, it is clear that, if you have read the articles and are none the wiser, you fall into the last category above. Please don't insult me or question my motives.
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John goron. I don't see why you should feel insulted. But I certainly have been. To suggest that those participating in this thread don't understand the terms borders on an insult to them as well. We all understand the terminology and what's clear is that you've been just playing semantics. |
John, I appreciate your providing the links. I enjoy such articles and do find them helpful to understand the technical issues involved and why there are limitations to the medium.
I just thought I would share some listening impressions I've had recently and how small changes to SRA can in fact alter our impression of how an LP sounds relative to hearing something real like a solo cello and orchestra during an actual concert. |
Dear Peterayer: Good that you made " your work " that you took your time to made those tests nad good that you heard those differences.
The only way to grow up and improve our knowledge level is through listening tests even if some of them can be cumbersome or a night mare. I think there is no other way to learn.
It's no surprise that Dynamics improved with your set up changes because Dynamics ( as a main MUSIC characteristic. ) involve almost all other live MUSIC characteristics.
The main importance on those kind of tests is to understand the differences and know from there what looking for during other kind of evaluations or item comparisons.
That kind of " exercise " is time consuming but the rewards on the self learning is worth the effort.
In the other side, when I analize technical audio subjects or read what other persons post in that regard normally what I do is to go to my system and make the set up on subject and listen because I learned that several times the analog audio theory ( technical ) is not confirmed under listening in deep sessions due to that " analog imperfect world " we are dealing with. Btw, normally I don't question other persons opinions till I experienced those opinions or when I already had the experiences.
Regards and enjoy the music,
R. |
Csontas: If we must continue: John, have you read this article in it's entirety yourself? It corroborates every single point I've made without fail! I'm now wondering what your motive is in participating in this discussion. Yes I have. I read it when it was published. I understand the difference between SRA and VTA. My motive in contributing to this thread was to try and help those who obviously thought SRA and VTA were the same thing, see that they were different and had different effects. I have provided links which is more than you have. Make of them what you will. John goron. I don't see why you should feel insulted. But I certainly have been. To suggest that those participating in this thread don't understand the terms borders on an insult to them as well. We all understand the terminology and what's clear is that you've been just playing semantics. If everyone understood the terminology there would be no thread. You reckon the difference between VTA and SRA is a semantic one and so adjust the height of your arm on the fly and find it sounds better. Good for you. However, some might wish to know why it is the case in order to improve their understanding. From what you have posted anyone who knows the subject (some of the previous posters) will see that you are confused about why that is so. You are not alone Don't feel insulted. I don't know why you are so concerned with what I have posted and why. I simply post when I feel I can contribute to what appears to be a misunderstanding or a confusion regarding vinyl replay. I don't care what your motives are, and I will leave it there. |
But when the cutting stylus records any signal other than a pure mono one it must move more and less deep into the lacquer, otherwise how can the signal be cut? That was what I was getting at and confused by your answer. I didn't mean the whole mechanism moved, solely the cutter itself John, you might want to re-read my prior posts as my answer here will be very similar. But to be clear, part of the groove does show variable depth with the signal.But regardless of what that signal is doing, if you look at the center of the groove it will be the depth described by the adjustments on the cutterhead, and not related to the signal, and that is what is called 'groove depth' in the parlance of the field. The only exception is if out-of-phase information is being recorded, which I covered previously- that will cause the center of the groove to seem to change in depth. |
Atmasphere:
Thanks for that. I was obviously on a different track regarding the terminology of record cutting lathes- the meaning of groove depth, cutterhead, centre, etc.
It is a good example of why familiarity with specific terms in unfamiliar areas is beneficial. Which type of lathe do you have?
John
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There is some confusion here due to terminology, I believe, as well as a lack of clarity, in some cases, of what is really happening.
An attempt to clarify:
1. The cutter head height is constant across the lacquer, an therefore, the final pressed record.
2. The "no signal" actual groove depth is a constant due to #1, if we ignore slight differences in thickness of the lacquer, slight vertical error of the lathe platter, and other such imperfections.
3. Groove depth at any point, when stereo signal is present, will vary if there is any difference between the left and right channel recorded information. This MUST be the case, as this is how stereo records work: the vertical modulation of the groove (which indeed represents changing depth) represents left minus right channel information.
4. If we define "groove depth" as the actual measurement of the the distance from the bottom of the groove to the top of the record at any point on the record, #3 above is true. IT DOES CHANGE.
Now, if we define "groove depth" as a no-signal SETTING based on the height of the cutter head when cutting a particular record, that does not change during the cutting of any one particular lacquer after the cutting process begins.
To sum up: as I read this thread I perceive that some are talking about a SETTING with no signal going to the had when referring to groove depth, while others are talking about the ACTUAL measured groove depth at a given point on the record. They are two difference concepts.
The actual measured depth, if one physically cut a record and looked at the grooves on end with a powerful microscope, would indeed be a changing measurement on a given stereo record when there is indeed a difference in left and right channel information. This change will be small, as bass information is not recorded in stereo, but vertical modulation (and modulation means a changing parameter!) is indeed there.
Confusion like this often exists when one party with experience in a given field sticks to the terminology used in that field, instead of trying to put himself in the place of someone who is not in that field and not experienced wiht the typical jargon of the field. In technical teaching situations I have always found that it is best for the experience person to not get hung up on the "insider terminology", but rather to put himself in the position of the inexperienced person to try to understand exactly what that person is trying to ask.
Trying to help clarify, not criticize.
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Dear Kiddman: Great post/contribution. Thank's for that.
Regards and enjoy the music,
R. |
@peterayer: adjusting VTA/SRA affects tracking force and other parameters, so what you are hearing is probably a combination of all these parameters, and perhaps more of the tracking force than the very tiny SRA/VTA adjustment you affected (if you do the math for your 12" arm, you will probably see that the difference is less than 1/4 of a degree for a 1mm vertical movement of the arm at the pivot point - perhaps significant, but I somehow doubt it). |
Although my own experiments and experiences cause me to doubt some of the charts and statements on Yosh's webpage about VTA, overall it remains worth reading.
http://www7a.biglobe.ne.jp/~yosh/vta.htm
I will add that speaking as a cartridge designer, I find SRA and VTA to be different. For example, designing a cartridge with increased VTA will allow a shorter cantilever to be used, but doing so has the side-effect of stiffening the suspension vertically while leaving the horizontal compliance more or less unaffected.
As a rough guide, at 0 degrees VTA, horizontal compliance and vertical compliance of the suspension wire will be the same. At 90 degrees VTA (which no cartridge does), the vertical compliance will be 0, while the horizontal compliance will remain the same as it was at 0 degrees. For all angles in between, you can figure out how the ratio of horizontal to vertical compliance changes in the suspension wire by calculating the cosine of the VTA angle.
Note that I have deliberately not included compliance of the suspension dampers, therefore you should not jump to conclusions from the above. Some suspensions have linear characteristics, while other types have progressive characteristics, making it impossible to generalize.
kind regards, jonathan |
Which type of lathe do you have? Its an old Scully (well, *all* Scully lathes are old...) equipped with a Westerex 3D cutterhead. The cutterhead does not need a lot of power and has a moderate impedance, we are easily able to drive it with our M-60 amplifiers. Kiddman, it helps to take a look at what is happening in the groove with a microscope. Of course every lathe has one, you can't do the work without it! We have a multi-color LED light source that we installed, so we get different colors depending on what we are seeing- the lands, the groove wall, or the bottom of the groove. As I said before, the defining quality of groove depth is the center of the groove. If you have high frequency modulation, that shows up under the 'scope like a groove with modulation on the walls. If you have bass information, the *entire* groove moves from side to side with the bass modulation. If the bass is out-of-phase, the groove will stay in one spot and seem to vary in width and depth. This sort of condition will knock the stylus right out of the groove and so has to be avoided. In natural 2-mic recordings it does not show up- only if the recording is multi-tracked to start with. I Googled for images of this stuff. Without a multi-color light source it can be a little hard to see, but there is a photo that appears at this link that is not bad for what I am talking about http://en.wikipedia.org/wiki/Gramophone_recordScroll down aways, the photo appears on the right hand side about half way down, just above the heading 'vinyl quality'. If you look closely at the grooves, you will see that they squiggle a bit. Those larger squiggles are bass notes. This is why I say the groove depth does not vary all that much, as the *entire* groove has to move to make the in-phase bass note. |
Google 'record groove modulation photo' |
I'm still wondering why, if slant angle varies not only from record to record but by the signal itself, by a cutter who's VTA is for all intents and purposes static, does cartridge VTA/SRA need to match VMA? Does it not stand to reason that in the same way variations are produced, the same information will be retrieved? Albeit once external influences such as adverse lacquer/cutter interactions are compensated for via SRA adjustment? Once adjusted, will the play back stylus not follow the same behavior as the cutting stylus. Same VTA constant. |
When I adjust SRA to where it sounds correct, how close is it to (average?) VMA? It sure sounds like the entire frequency spectrum is correct, not just parts of it. |
Ack, that may well be the case. As overhang changes, so does zenith along the tracing arc. I can see by how much at the null points on my MINT protractor. I lent out my VTF gauge, so when I get that back, I will see if it can measure a difference of 0.1 gram, for such a tiny VTA adjustment. Don't know if it will.
I'm hardly going to adjust all parameters for each LP. I'm going to settle on an overall good sounding average and decide how often I want to adjust VTA. I'm guessing it won't be too often, though I've found during the last few evenings, that adjusting VTA on my SME is not that difficult. There just is not a convenient scale marked on a tower like some other arms have.
I think these parameters vary less with a 12" arm than they would with a 9" arm, but then a 9" arm would have to move less than that 1mm for the same 1/4 degree SRA change. Admittedly, these are tiny changes and many will not find them worth the effort or sonic improvement to make.
I wonder if anyone has thought about designing an arm which would automatically compensate overhang and VTF for VTA changes. |
A question was posed about why the angle of the cutter and angle of the stylus need to be the same.
The trigonometry dictates that for small angles of deviation it does not matter much as the cosine is changing extremely little for angles of 1,2,3 degrees. For instance, cos 3 degrees = .9986!
Visualize this: a pointed shovel whose shape is a "V", with the "V" portion 10 inches tall. Put the shovel straight into the sand to a depth of 5 inches, and then pull it along making a "V-shaped" groove in the sand.
Now, with the shovel in the groove, lean it 3 degrees forward or back. The "V" shape of the shovel fits the V groove almost perfectly at the 3 degree angle, even though the groove was cut with the shovel vertical, or at 0 degree lean angle. It has to: the cosine of 3 degrees is .999!
But, if you lean the shovel to 15 degrees you will see that only the upper part of the groove will contact the sides of the groove, the rest of the shovel will be pulled up away from the groove. We'll only have 2 short contact points.
The shovel represents the stylus, of course, the sand the record, and the V-groove the cut groove in the record.
So, in reality, small deviations of stylus angle compared to cutter angle mean very little. Large deviations represent a increasing compromise as the difference in angles gets larger. |
Peterayer:
>I wonder if anyone has thought about designing an arm which would automatically compensate overhang and VTF for VTA changes.
Certainly. To maintain a constant VTF, the tonearm vertical bearing should be kept at the same height, regardless of VTA changes. It is probably best to align the vertical bearing axis to the LP surface, as doing so will minimize changes in effective arm length that would be induced by VTA changes or record warps.
To maintain a constant overhang requires that the tonearm pipe is raised and lowered on a curved rail or post that has the same radius as the stylus-to-tonearm-bearing distance. Easy to do with a linear-tracking tonearm (the Eminent Technology designs are a good example), a bit of a head-scratcher otherwise.
hth, jonathan carr |
I think the Arche headshell (from Dertonearm, aka designer of the Axiom tonearm) allows for changing VTA at the headshell. I think this would fit Jonathan's requirement for changing VTA without changing the height of the vertical bearing, so as not to alter VTF. And of course the Arche could be used with most pivoted tonearms. I have no affiliation of any kind; nor do I own an Arche headshell. I don't find it to be a terrible bother to re-adjust VTF. What I usually do is get the VTF in the right ballpark, then settle on VTA, then finalize VTF, and Bob's your uncle. There is such a thing as "good enough". |
There is such a thing as "good enough" indeed!
As for no VTF change with VTA change, it is complicated. Springs do NOT do acheive this as they are linear force per displacement devices, and VTF varies as a trigonometric function. Therefore, the compensation system for changing VTF with VTA to make VTF constant would need act in proportion to a trig function. Too complicated, best to adjust center of gravity height for minimum change in VTF with a given VTA change, and if you make a big enough change in VTA to actually change VTF meaningfully then just adjust VTF.
All tonearm guys who say their perfect height of the pivot point, the height of the counterweight, the underslung nature of their counterweight, or their spring, are not very good at trig, calculus, and running the experiments or they would know that they are wrong and then confirm it with the tests.
Changing VTA at the headshell brings with it several other problems while trying to solve a problem that readjusting the counterweight would have solved anyway. |
Lew, I haven't carefully studied the Arche headshell, so take this with however much salt as you want.
Since the Arche's pivot for VTA adjustment appears to be placed above the top of the cartridge rather than at the stylus tip, it seems to me that it will alter the overhang and effective length along with the VTA.
hth, jonathan carr |
Thank you Kiddman. But my question is really an assertion or really an assumption that although the angles may not have to match, SRA still needs to be precise and exact irrespective of the stylus still making full contact with the groove within that 3 degree allowable tolerance. I'm suggesting that that 6 degree margin is actually far larger sonically than the math suggests. Where mathematically that exact point is, is anybody's guess and seems to me what this discussion is all about according to the op. |
...and hence the need to find it on the fly. |
Jonathan, Thank you for your response. I too have never beheld an Arche headshell in person, but from what I've read about it on other threads, you are correct. So, my concept of how that works is to rock the cartridge either forward (and downward from the horizontal plane with respect to the top surface of the cartridge body) or backward (and upward from the horizontal). True, this would very slightly alter overhang and effective length, in either case, because the stylus tip must move in an arc along with the cartridge. But since very tiny movements of this kind have a drastic effect on VTA and SRA, perhaps the effect on those other two parameters would be minimal, i.e., acceptable. I guess there's no free lunch. |
I was trying to fix my post when I accidentally posted it. I obviously was referring to the front end of the cartridge body when I wrote that a "forward" tilt would move the cartridge body "downward". The rear end would move upward. |
I'm still wondering why, if slant angle varies not only from record to record but by the signal itself, by a cutter who's VTA is for all intents and purposes static, does cartridge VTA/SRA need to match VMA? The SRA of the cutterhead does not vary with signal. It is a constant. |
I have been reading this thread with interest. Lots of valuable information.
Since VTA/SRA adjustment changes Overhang/Zenith and VTF and vice versa,
what would be a typical cartridge/tonearm set-up proper sequence (1 to 6) if you start from scratch. Would this sequence make sense.
VTF
Overhang/Zenith
VTA/SRA
Antiskating
Azimuth
Damping |
..regarding the Arche headshell.....there are cartridges that have this ability as well....Soundsmith's Susurra, etc. I wonder if this adjustment affects resonance frequencies, which should be avoided to retrieve what the cartridge "sees" on the record. |
Smoffat, I think your sequence would work, except then the truly precise audiophile has to start over back at "VTF". In other words...
VTF
Overhang/Zenith
VTA/SRA
Antiskating
Azimuth
Damping
VTF
Overhang/Zenith
VTA/SRA
Antiskating
Azimuth
Damping
Etc. |
Thanks Lewn. You've confirmed my understanding of the adjustment sequence. Understood that once VTA/SRA have been adjusted, Overhang and VTF have been compromised and need to be re-visited.
I do have a USB microscope (Dino) that i have been using to assess my SRA angle. I had sent a few pictures to Wally Malewicz to get a feel on accuracy. The first one was not clear enough. The second picture, which i thought was right on 92 degrees was actually 94 as per Wally. The 3rd one which i also thought was right on 92 degrees was actually at 91 as per Wally. So you can make your own assumptions but unless you're a rocket scientist able to use a USB microscope properly, i suggest that you throw it out on the sidewalk and adjust (repeatedly i must admit) by ear as described by Doug and others in this thread until it's dialled in to your own ears.
Sly
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Smoffatt, Here is my sequence, (SME V-12 arm) realizing that others may do it slightly differently. I tried the 92 degrees with USB scope and now just start with arm horizontal and adjust VTA for favorite LPs by listening. If lazy, I just pick a good, average VTA setting.
Start with arm horizontal and anti skate at zero
VTF
Overhang (with Mint protractor)
Zenith (Mint protractor)
anti-skate
Azimuth (not adjustable on my arm)
Damping (tried it, don't need it)
Listen
VTA 2nd round fine tuning by listening to representative LP
anti skate back to zero to
reset overhang for new VTA
reset zenith due to new overhang
reset anti skate by listening
decide if re adjusting VTA for each LP is right for you.
Ready to listen and enjoy the music |
Thanks Peterayer. I have a Mint LP for my Graham Phantom II. My cartridge is Ortofon A90.
I would also re-visit VTF the second time around.
I will find a good compromise/average for VTA/SRA and set it and forget it. I'm no longer using my Dino-Lite USB scope for viewing/setting VTA/SRA.
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