surface noise and cartridge/ phono pre questions

Static charge on records is also a very strong candidate, especially if your in house conditions include lack of humidity. First things first.

Jcarr, I think you may find this article by Nelson Pass to be interesting:

https://passlabs.com/articles/audio-distortion-and-feedback

It seems to re-enforce some of your comments above. Norman Crowhurst wrote about some of this as well, although I'm don't have a link handy, I suspect I could find the article on Pete Millet's website given enough time :)

Essentially though, the issue as I see it is that as you add feedback, the problem/solution is in the way the 5th 7th and 9th harmonics are handled, but you also have concerns with intermodulation at the feedback node. This can result in a harmonic and *inharmonic* noise floor, with harmonics up to the 81st (although the circuit may lack the bandwidth for that).

The concern I have has to do with human hearing rules. The 5th, 7th and 9th are measured by the ear brain system to determine how loud the sound actually is; so if they are altered even in very tiny amounts the sound will be artificially louder and brighter than it really is.

There is also the issue of detail- due to the ear's masking rule, louder sounds can block the presence of quieter sounds. If the louder sounds are distortion then you will have less detail. It turns out that the one exception to the masking rule is the ability to hear into a noise floor composed of hiss; the ear can hear about 20 db into such a noise floor (something usually ignored by digital advocates). I suspect that this may be because analog hiss has a lot in common with wind noise, something with which our ear/brain system is very familiar. But if the noise floor is composed of harmonic and inharmonic noise, the detail below it will be lost as the ear cannot hear into that kind of noise floor.

If you want a link to Crowhurst's comments regarding this feedback phenomena, I can find it but may not be able to take the time until after CES.

Have a good show!

Ralph: I agree with everything that you have written above.

All distortion is not equal to the ears, and higher odd-order distortion sounds increasingly obnoxious.

Also, the character of the noise floor has a significant bearing on far into it the ear can hear. Completely random "soft" white noise, and the ear can hear deep into the noise floor. 20dB sounds about right, and correlates to what I have been told by Keith Johnson. But if there are harmonics, supply or signal-related rectification artifacts along for the ride, the ear's ability to hear into the noise floor stops much earlier.

If the designer doesn't pay attention to these areas, low-level detail is impaired while IMD or inharmonics typically creep into the noise and distortion products, and the result is a circuit that invariably does not sound natural or "believable".

Excellent post! And I hope that you have a good show, too.

kind regards, jonathan

not to change the subject too much , but in addition to ticka and pops whatwould cause those sharp "s" and "t" s too occur on some recordings . it can just appear on some recordings as it gets to the end of the record. is this a pre amp issue also ?

Panu21, it *can* be, but can also be a setup problem with the arm and cartridge. If the cartridge is not loaded properly, and is not set up correctly, it is conceivable that the additional RF energy that shows up at the end of the LP could bother some preamps.

However, it is far more likely to be an arm/cartridge setup issue.