Help ...... excesssssssive sssssssssssssssssssss

Speakers...
Hornshoppe are those very little very nice back horn loaded full range drivers, Fostex right?
I can bet your problem is the Whizzer...

I used to have a kinda Bazzilla speaker with DX3Lowthers on open bafle, I had to really fight ot get the SSSing down.
First point: silver cables give cleaner highs.
Second point. Add a super-tweeter, I started with a Fostex FT17H and then upgraded to a Beyma CP21-f
I have the Martin TL boxes with Fostex FE 207E drivers on a second system and its pretty nice, I got those to get better bass than I was getting with the the Lowthers, transparency is better with lowthers though.

I think you have a great system, I dont mean to be rude but I think its time to upgrade your speakers, I got Cabbase Loudspeakers after a lot of fiddling around with Full range drivers and they beat every Fullranger I heard in any aspect, more transparent more dynamic more coherent and of course better bass and better highs.
They say lowthers have a lot of bite, my Cabasse have more bite than my lowthers, I had to tame them good and they are sooo sweet now!!

PS- Not connected to Cabasse....

All the Best

Dear Socoaste: Shadorne is right on target: speaker/amplifier synergy, there is a severe mismatch between them because each other impedances.

If you like your speakers then you have to change the amplifier or the speakers if you like the amp.

It is a very hard task to match your amp to any speaker. I have a lot of respect for N. Pass but I don't know what he was thinking when put on sale those amps.

Btw, ask to N. Pass what to do about. His amp is the trouble.

Regards and enjoy the music.
Raul.

First off thanks for the ideas everyone....

The problem is showing up on digital And vinyl, but is
worse on vinyl playback.

speakers reflections......I don't think so, I have diffusers & studio foam to tame that area.

does not matter if at start of record or at last track.

speaker to amp mismatch....well, I know a few persons that
have the F-1/Hornshoppe combo & they are quite happy with it. the drivers I have are the Fostex 4" FE126E which are the latest driver that Ed (Hornshoppe) uses in the Horns.
most guys (including Me) are using accoustic stuffing in the horn throat
to damp the driver, since there is practically no damping factor with the F-1.

later this evening when it is cooler, I'll turn on the F-1
and maybe do a little more experimenting, (I don't have A/C
& that F-1 puts out some serious heat!).

-socoaste

Socaste, Logic, not hands on experience, leads me to a few conclusions based solely on what you have posted regarding your equipment and things you have done to solve your problem.

To review, as I understand it you have sibilence with any source materiel but it is worse with vinyl. The sibilence remains without regard to the amp/pre-amp or tubes you are using. You have ruled out room/set up acoustic related problems. What's left? Your speakers of course. Now that could be your speakers themselves(probable) or their interface with your amp (more likely, except you have tried other amps).

Perhaps it would be meaningful to review how your problem first manifested itself.
When did you become aware of the sibilence?
When you first introduced the speakers to your system?
When you first introduced your amp to your system?
When you first introduced or modified your TT system?

You have sort of dismissed the suggestion that your speakers and your amp might be a mis-match because you know folks who have them and are happy with them, but you do not indicate that you auditioned either or both in your home before your acquired them or that you auditioned them at the homes of the folks who were supporting the combo.

As your thread now stands the only common denominator for the source of the sibilence which you have not ruled out is your speakers. FWIW, some years ago, I bought some highly regarded and extensively reviewed, speakers which I auditioned in a showroom before purchase. I was a neophyte and didn't think about amplification issues. I spent the next two years looking for the right amp (my speakers were sibilent as hell!) and I finally discovered by accident the amp used by the manufacturer to voice the speaker. Bought the amp and the speakers were every bit as good as I had been told, except of course, by then I hated them!

Bottom line, call the Manufacturer and ask them what amp they used to voice their speakers. While most won't tell you, you might luck out on this one. :-)

Socoaste, I still think, based on the notes published on the First Watt website, that you should call them and find out how to configure the parallel loading networks to tailor the driver response. As Raul mentioned, and I agree, I think the problem is due to impedance mismatch between the amp and the driver, and it should be quite easy to rectify. With these kinds of amps and speakers, it's a bit like loading a moving coil cartridge -- very critical, and will (almost) never work "right out of the box."