Ortofon A90

[rockitman]

Mush vs. being bright

so too high a load equals too bright ? I though it was the other way around...too low equals bright. I'm confused....

 

[ack]

I think his response was generic and not meant to be taken one-for-one

 

[rockitman]

I think his response was generic and not meant to be taken one-for-one

I'm curious why you load at 1000 for the A90. From all I have read, 10x source impedence or approximately 100 ohms. Interesting article here:

cartridge loading
Before considering how to match a moving coil cartridge with a transformer, it is worthwhile considering the effects of different loads on moving coil cartridges.
Most modern moving coil cartridges have a source impedance of about 10 ohms or less, with a very small inductance of a few microhenries. The inductance is so low that it can be virtually ignored. In theory, such a low source impedance should be able to work into almost any load without any ill effects on performance. The usual rule for audio equipment in general is to feed the signal into a load ten times greater than the source impedance to avoid any signal loss, and this is a good way to choose a suitable load for a moving coil cartridge. Given a typical source impedance of 10 ohms, 100 ohms is a good choice for load impedance. This is well in line with the recommendations from cartridge manufacturers (see the table of data below). Anything above 100 ohms should be equally suitable.
However, one thing to consider is the effect of the current drawn from the cartridge. As the load impedance is reduced, the current drawn from the cartridge increases. This current flowing through the coils sets up a tiny magnetic field which opposes the motion producing it due to Lenz's law and will impose a force which opposes the movement of the stylus. This is analagous to the back EMF in moving coil loudspeakers where the motion of the coil sets up a magnetic field in opposition to the loudspeaker's permanent magnet and which damps the motion of the coil. Just as a low amplifier output impedance maximises the damping of the loudspeaker cone, so a low load impedance on an moving coil cartridge will damp the motion of the stylus. However, although a near zero output impedance for an amplifier is both feasible and beneficial, a zero load impedance on a cartridge would silence it, so there has to be a limit to how low the load impedance can be. Unfortunately there seems to be no concensus on how significant the effect of stylus damping is, or even whether or not stylus damping is a good or bad thing. In fact, the effect seems to be so poorly appreciated that this author has only ever seen it refered to once, and that was by Graham Slee. He recommends a higher than usual load impedance to minimise the damping effect, but many people recomend a load impedance much closer to cartridge's source impedance for optimum sound (though without any convincing rationale for the recommendation).
The recommendation of Rothwell Audio Products is in line with Ortofon, Audio Technica and most other cartridge manufacturers - that 100 ohms is a good value for nearly all cartridges, but that the exact value is not critical as long as it is well above the cartridge's source impedance.
One thing is certain, and that is that the load impedance should not be equal to the cartridge's source impedance. The idea that having the load impedance equal to the source impedance achieves perfect "matching" is totally wrong and is the most commonly held myth about moving coil cartridges. It also gives rise to most of the confusion surrounding step-up transformers and how to select the correct one for any given cartridge.

http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html

 

[ack]

Suggest you read the quoted text carefully: As the load impedance is reduced, the current drawn from the cartridge increases

This is why 1000 works best for me - i.e. I am actually reducing the current drawn by increasing the load impedance, to reduce the effect of this force; and I think you will find that many (most) owners load it at that...

 

[Mike Lavigne]

30k-47k

 

[rockitman]

Suggest you read the quoted text carefully: As the load impedance is reduced, the current drawn from the cartridge increases

This is why 1000 works best for me - i.e. I am actually reducing the current drawn by increasing the load impedance, to reduce the effect of this force; and I think you will find that many (most) owners load it at that...

Holy Cow and looking at Mike's 30K-47K load i had better try that. I went to 400 once for a bit....Thanks for chiming in fella's.

 

[lasercd]

This has me curious and confused... With the ASR Basis I tried it at 100 ohms and didn't care for it. 100 ohms didn't work well with the Boulder 1008 I had on loan either. Everything was bleached out. I settled on 48 ohm for about a year but experimented a bit with the impedance settings in the ASR a couple of weeks ago and found that 57 ohms was the trick.

 

[microstrip]

I remember seeing some graphs of the effect of the loading resistance on the frequency response of some moving coil cartridges taken by Martin Colloms for Hif News long ago. The effect was noticeable, with a few dB variation at 20 kHz.

Although there is no consensus on an optimal value or absolute values, some people present some guide lines. See these notes on cartridge loading :

http://www.extremephono.com/Loading.htm

As usual, every system is a case and you have to try.

 

[MylesBAstor]

I remember seeing some graphs of the effect of the loading resistance on the frequency response of some moving coil cartridges taken by Martin Colloms for Hif News long ago. The effect was noticeable, with a few dB variation at 20 kHz.

Although there is no consensus on an optimal value or absolute values, some people present some guide lines. See these notes on cartridge loading :

http://www.extremephono.com/Loading.htm


As usual, every system is a case and you have to try.

I have to say that until recently, the vast majority of cartridges that I've played with sound best loaded at 47 K (now with the exception maybe of SUT). I find the biggest differentiator is whether or not you're using a solid-state or tube phono. Practically every cartridge run into a tube phono sounds best at 47 K. I really don't like the effects of loading and I see it as basically a band-aid. Yes the low end may be tighter but it comes at a high cost. The upper octave is lopped off, transparency is sacrificed and everything sounds slow and boring. If you need to load, get a better cartridge (just joking).

And by the way, since it's listed in the reference, Jonathan Carr recommends that all his cartridges be loaded at 47 K.

 

[rockitman]

I'm now running at 1000 (Thank you ACK) on my Pass XP-25 (SS). I can't believe I electro damped the stylus at 100 ohm. I thought since the load impedance in the specs recommends > than 15 ohm's, then 100 was the standard. I never even thought of turning it up above 500. Now I'm mad I listened for the past 4 month's with my A90 using a Chasity belt. No More ! Everything has opened up, especially the bass. No zingy treble either.

 

[ack]

Aren't these forums great? How are you doing on the SRA/VTA front

 

[rockitman]

Aren't these forums great? How are you doing on the SRA/VTA front

since I'm using the GRaham supreme with the pivot tower bubble level...no matter which record thickness I play, I adjust to zero (level) and tweak by ear from there. I adjust vta/sra for every record weight I play.

 

[ack]

since I'm using the GRaham supreme with the pivot tower bubble level...no matter which record thickness I play, I adjust to zero (level) and tweak by ear from there. I adjust vta/sra for every record weight I play.

Ah... I hand over the OCD trophy and badge my wife and colleagues awarded me years ago

 

[XV-1]

And by the way, since it's listed in the reference, Jonathan Carr recommends that all his cartridges be loaded at 47 K.

Not anymore Myles. Since he no longer makes a phono stage, I guess he is no longer dogmatic about 47k

In the Kleos manual he recommends anywhere from 86.6 ohms to 47kohms. he then goes on for several paragraphs for the mathematically correct input loading based on the total capacitance between the Kleos and the phono stagde ( comprised mostly of the toneram cable) - mine worked out be around 523 ohms.
I believe this will be the same principle loading instructions for the Atlas. And we thought only MM's were susceptible to capacitance

 

[MylesBAstor]

Not anymore Myles. Since he no longer makes a phono stage, I guess he is no longer dogmatic about 47k

In the Kleos manual he recommends anywhere from 86.6 ohms to 47kohms. he then goes on for several paragraphs for the mathematically correct input loading based on the total capacitance between the Kleos and the phono stagde ( comprised mostly of the toneram cable) - mine worked out be around 523 ohms.
I believe this will be the same principle loading instructions for the Atlas. And we thought only MM's were susceptible to capacitance

I played with capacitance when using the Avid Pulsare (since it was so easy). And it improved some such as the AT PC1 and didn't do anything for others except maybe at extreme values.

I know Jonathan says that in his lit but.....

As I've heard, loading will really depend upon whether using a tube or solid-state phono section.

The other thing is Shane that I don't expect that Jonathan used just one phono section to evaluate his cartridges--and that's where the range in values may have been derived from. (Know for a fact that he uses a slew of arms.)

 

[mep]

As I've heard, loading will really depend upon whether using a tube or solid-state phono section.

Why would that matter? If there is an optimum loading value for a cartridge, that is what should be used.

 

[XV-1]

Why would that matter? If there is an optimum loading value for a cartridge, that is what should be used.

From my experience, generally with SS the higher you go up in loading the brighter the balance and the less bass control. With tubes you seem to get more upper frequency air without brightness and space without loosing too much in the bass dpt. YMMV

 

[mep]

From my experience, generally with SS the higher you go up in loading the brighter the balance and the less bass control. With tubes you seem to get more upper frequency air without brightness and space without loosing too much in the bass dpt. YMMV

My mileage does vary. Interesting, but counterintuitive. If it sounds brighter with SS when the cartridge is unloaded at 47K than it does with tubes, it may because your tube design doesn’t have the same top end extension. I can’t possibly think of a reason why a SS phono preamp would lose control over the bass more than a tube phono preamp. It just doesn’t make sense.

I think that David Wilson wrote one of the best thought out articles on the importance of loading MC cartridges many years ago in TAS (back in the day before David went full bore with Wilson Audio). I believe that once you get much above 1K, you are essentially unloading a MC cartridge. The high end gets brighter and out of proportion to the rest of the music and the bass suffers. Your tightness of bass is out the window.

 

[XV-1]

My mileage does vary. Interesting, but counterintuitive. If it sounds brighter with SS when the cartridge is unloaded at 47K than it does with tubes, it may because your tube design doesn’t have the same top end extension. I can’t possibly think of a reason why a SS phono preamp would lose control over the bass more than a tube phono preamp. It just doesn’t make sense.

I think that David Wilson wrote one of the best thought out articles on the importance of loading MC cartridges many years ago in TAS (back in the day before David went full bore with Wilson Audio). I believe that once you get much above 1K, you are essentially unloading a MC cartridge. The high end gets brighter and out of proportion to the rest of the music and the bass suffers. Your tightness of bass is out the window.

Its all relative Mep. There is not much difference in sound between 1k and 47k. much bigger difference between 50 ohms and 100 ohms. The bass control of the SS is tighter at say 100ohms than any Tube phono stage - is it more natural? - another topic. relative to the 100 ohms, the SS does lose more bass control. of course it depends on the phono stage, cartridge and rest of the system- but we were talking in general.

I am not saying I load all my carts at 47k, depends on the cart and phono stage I am using.

BTW, I think I would listen more to J Carr on cartridges and D Wilson for speakers - not visa versa.

 

[mep]

Its all relative Mep. There is not much difference in sound between 1k and 47k. much bigger difference between 50 ohms and 100 ohms.

Agreed, and it’s for the exact reason I stated in my first post. Anything above 1K and you are unloading the cartridge so you really aren’t going to hear much change with most cartridges.

The bass control of the SS is tighter at say 100ohms than any Tube phono stage - is it more natural? - another topic. relative to the 100 ohms, the SS does lose more bass control. of course it depends on the phono stage, cartridge and rest of the system- but we were talking in general.

You lost me here with your comment that “relative to the 100 ohms, the SS does lose more bass control.” Do you mean above 100 ohms SS loses bass control? As the cartridge edges past the point where it becomes unloaded, the bass will become looser because you have lost your braking action. If you prefer the sound of bass that is not being reproduced optimally with tubes more than SS, I really don’t know what to say.

BTW, I think I would listen more to J Carr on cartridges and D Wilson for speakers - not visa versa.

That sounds like an intelligent statement, but David Wilson’s knowledge extends beyond how to build speakers. I’m not saying he knows more about cartridges than J Carr, I’m just saying he wrote a great article about loading MC cartridges and why it matters.