[jupiterboy]

Looking for souces for caps that would be used in a phono preamp. Sound quality is priority, price, not so much. Most of what I find is availabe in a variety of voltages, but I do not know the exact spec here. Basically, it will be fitting a legged cap where an SMD was originally.

There are lots of ceramic SMD options, and I also find some Silver Micas. Comments about the sound quality of Silver Mica in general is also appreciated.

[BobM]

I would recommend the Sonicap II's at a budget price point. Very transparent.

At a premium price point you might want to look into the current king of the hill - Jupiter copper foil and wax.

[jupiterboy]

I would recommend the Sonicap II's at a budget price point. Very transparent.

At a premium price point you might want to look into the current king of the hill - Jupiter copper foil and wax.

Those are nice, but they are larger and would be right for a different sort of circuit—amp or crossover I would guess.

[Occam]

If you have issues with the size of the larger caps mentioned above, you could also consider silver mica caps
http://www.partsconnexion.com/capacitor_film_silvermica.html
or polystyrenes, which are readily available.
http://www.partsconnexion.com/capacitor_film_styrene_main.html
The micas can be had in in smt form, although at a substantial price (but not as large as the bespoke caps mentioned above).
Also, if the present smt cap is a ceramic, if its a COG type (aka NPO) its actually quite good.

[jupiterboy]

If you have issues with the size of the larger caps mentioned above, you could also consider silver mica caps
http://www.partsconnexion.com/capacitor_film_silvermica.html
or polystyrenes, which are readily available.
http://www.partsconnexion.com/capacitor_film_styrene_main.html
The micas can be had in in smt form, although at a substantial price (but not as large as the bespoke caps mentioned above).
Also, if the present smt cap is a ceramic, if its a COG type (aka NPO) its actually quite good.

Good info. As in the thread title, 20-30pF is probably ideal. If you know of a source for surface mount silver micas in this range, I'd love a link as I have never found these. COG or NPO—what do these acronyms stand for? Thanks.

[Quiet Earth]

You can search for "silver mica capacitor" on google and ebay and you should get lots of shopping results. Don't worry too much about the voltage rating of the cap, but do try to get the lowest possible voltage rating if you can. (I know that you are loading a MM cartridge.)

I honestly don't think you will hear much of a difference with only a single 30pF capacitor. You mentioned in a previous thread that the total capacitance of your arm wire + interconnect lead is only 32pF. That is so ridiculously low that you don't even need to worry about adding that into the equation. In my opinion, you really need to load a MM cartridge closer to the manufacturers recommended setting of 220pF and bring the resistive load back up to 47k. You are asking way too much from the first gain stage of your phono stage with nearly zero capacitance loading. And the additional resistive loading is really just a band aid. Again, this is just my opinion with my own MM experiences.

Anyway, silver micas are cheap and there is only one way to find out how much or how little you should use. I went through this same exercise a little while ago. In my own system I learned that a non-standard MM loading was only compensating for the limitation of the phono stage and the not-yet perfect cartridge alignment that I had. It can take a very long time to really understand how to get the best alignment out of your arm/cart.  I went back to the standard 47k/220pF and really honed in on the alignment. Also, I am using a better phono stage than my otherwise good sounding opamp based phono pre. It's amazing how good you can make an op amp sound, but they are not linear enough (before negative feedback is applied) to be a good first gain stage in a phono preamp (IMO). This may be part of the problem you are chasing.

[BobM]

Just realized you saif pF. Damn that is small.

[jupiterboy]

You can search for "silver mica capacitor" on google and ebay and you should get lots of shopping results. Don't worry too much about the voltage rating of the cap, but do try to get the lowest possible voltage rating if you can. (I know that you are loading a MM cartridge.)

I honestly don't think you will hear much of a difference with only a single 30pF capacitor. You mentioned in a previous thread that the total capacitance of your arm wire + interconnect lead is only 32pF. That is so ridiculously low that you don't even need to worry about adding that into the equation. In my opinion, you really need to load a MM cartridge closer to the manufacturers recommended setting of 220pF and bring the resistive load back up to 47k. You are asking way too much from the first gain stage of your phono stage with nearly zero capacitance loading. And the additional resistive loading is really just a band aid. Again, this is just my opinion with my own MM experiences.

Anyway, silver micas are cheap and there is only one way to find out how much or how little you should use. I went through this same exercise a little while ago. In my own system I learned that a non-standard MM loading was only compensating for the limitation of the phono stage and the not-yet perfect cartridge alignment that I had. It can take a very long time to really understand how to get the best alignment out of your arm/cart.  I went back to the standard 47k/220pF and really honed in on the alignment. Also, I am using a better phono stage than my otherwise good sounding opamp based phono pre. It's amazing how good you can make an op amp sound, but they are not linear enough (before negative feedback is applied) to be a good first gain stage in a phono preamp (IMO). This may be part of the problem you are chasing.

No op amps in the signal path at all—discreet, Class A, solid state. The phono amp designer had mentioned to me that the surface mount caps he liked were 100pF each, and that the 68pF caps he installed were possibly not going to sound as good as they were ceramic. That was several years ago, and he recently mentioned that he had a better sounding solution that was not surface mount. I trust him, but also wanted to assist with the research. I have located a mica surface mount—10pF and 20pF variants with tight tolerance and lower voltages.

Point taken in regards to alignment. I have an atypical arm mounting, and am forced to make my own protractors. In my experience (I've been aligning carts in this arm/table for more than a decade) there is nothing more important and there is always some room for improvement. Generally, if I can run the +16 db track on the Hi-fi test record with no distortion, I am happy.

What I am working with is the measured response of the cart taken post phono pre, and in-room response. The manufacturer's recommended cap for this cart is 100-200pF.

[Quiet Earth]

What I am working with is the measured response of the cart taken post phono pre, and in-room response.

As you know, the correct loading has to do with what the cartridge sees. The way the cartridge behaves into its load will affect the performance of the first gain stage. You are measuring after the RIAA curve has been inverted and after the rising response of the cartridge has been normalized. I understand why you have to measure it there, but I don't think it tells you the whole story when you play around with cartridge loading.

I am certainly no expert in this and I have been wrong before, but I think it is extremely difficult for the first gain stage (tube or transistor) to handle the dynamic range of the RIAA EQ'd signal, PLUS the 6dB per octave rising response of a magnetic cartridge. It's really amazing that this all works in the first place. I think if you don't load the cartridge correctly (too little capacitance) a resonance will get out of control somewhere in band and overload the first active stage. This is what makes sibilance sound worse than it is.  This is the kind of distortion that won't show up in your frequency response graph because it is a moving target and dynamic in nature.

I also think that people are changing their MM cartridge loading because they are trying to extend the frequency response of their cart in hopes of getting it to sound more like a MC cart. This is just wishful thinking IMO. I think it is better to live within the frequency limitations of a properly loaded MM cart rather than tweak it into something that could send your phono stage into overload and make it sound unmusical. That's just my 2cents at this time, because I am still learning.

Anyway, good luck with your project and I look forward to seeing where you end up. 

[jupiterboy]

As you know, the correct loading has to do with what the cartridge sees. The way the cartridge behaves into its load will affect the performance of the first gain stage. You are measuring after the RIAA curve has been inverted and after the rising response of the cartridge has been normalized. I understand why you have to measure it there, but I don't think it tells you the whole story when you play around with cartridge loading.

I am certainly no expert in this and I have been wrong before, but I think it is extremely difficult for the first gain stage (tube or transistor) to handle the dynamic range of the RIAA EQ'd signal, PLUS the 6dB per octave rising response of a magnetic cartridge. It's really amazing that this all works in the first place. I think if you don't load the cartridge correctly (too little capacitance) a resonance will get out of control somewhere in band and overload the first active stage. This is what makes sibilance sound worse than it is.  This is the kind of distortion that won't show up in your frequency response graph because it is a moving target and dynamic in nature.

I also think that people are changing their MM cartridge loading because they are trying to extend the frequency response of their cart in hopes of getting it to sound more like a MC cart. This is just wishful thinking IMO. I think it is better to live within the frequency limitations of a properly loaded MM cart rather than tweak it into something that could send your phono stage into overload and make it sound unmusical. That's just my 2cents at this time, because I am still learning.

Anyway, good luck with your project and I look forward to seeing where you end up. 

Thanks. It seems from a listening and measurement perspective that this cart gets smoother with less cap. More cap increases or compresses the bump and brings is down into the audible range. Lower capacitance pushes it into higher frequencies. If you isolate the math, zero cap on a 490mH cart puts the resonance at almost 40mHz. The lower the cap, the higher you can set the loading, which actually does extend the frequency range rather than cutting it off.

I think all cart manufacturers tailer their specs to what is reasonable and common.

Every time I have lowered the capacitance on this cart, the high frequencies have become smoother and the timbre more realistic. When I lower the resistance, the treble extension becomes abbreviated.

That's where I'm at now.

[Quiet Earth]

I totally believe you. Especially if you say you prefer the sound, since that is all that really matters.

I have never heard your particular cartridge but I know that mine (which has a little more inductance than yours) also appears to sound better with zero capacitance at first listen or as an A/B comparison. The highs are clearly extended and detail is more apparent. But over extended listening I always go back to 220pF because it sounds too sharp and aggressive to me over the long run. Especially sibilance in pop records. My theory is that without the bandwidth limiting provided by enough C there is some ultrasonic stuff going on that gets out of control and makes it impossible for the front end to cope. If the cartridge really does rise in response at 6 dB per octave and we have a 40MHz limit before resonance, then the magnitude of whatever is going on ultrasonically might be too much for V1 to cope with.

I think I am digging myself a deeper hole.........  Thanks for letting me derail your thread a little bit.

BTW, you can get some of those silver micas in very small physical sizes. I bought a handful on ebay. They may not be the very best caps out there but they are great for experimenting.

[jupiterboy]

The AT carts are well measured and studied. I have seen so many users charts of response of many different phono amps. The general take is that the house sound of the 150MLX and the 440MLa is bright, and it shows up when measured. The stylus is very good at tracking, however, so people work to tame the brightness.

Here's a pretty decent thread of many, with interesting links.

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1334624405&read&keyw&zzps+audio

Other cartridges have rolled off response as part of the characteristic sound. Lots of people like the Shure carts at 62K loading.

The physics is always the same, but the cantilevers are different and the frequency responses are different, so trying to neutralize and flatten things out is different for different makes/models.

I enjoy MC carts, but I play enough records that replacing them several times a year is cost prohibitive.