[Dynaco ST-70 amp and Klipsch KLF-20 - buzzing sound]

Thanks to all with advises. it was a ground loop and buzz can be lowered greatly.

I'd like ask if any of you had used such equipment or can recommend which is better for producing clean sound:
http://accessories.musiciansfriend.com/product/Furman-S5500-Sequencing-Power-Conditioner?sku=180269
http://accessories.musiciansfriend.com/product/Monster-Power-MP-PRO-2500-Rack-Power-Center?sku=182650
http://accessories.musiciansfriend.com/product/Monster-Power-Pro-2000-Floor-Standing-Power-Supply?sku=182654
http://accessories.musiciansfriend.com/product/Monster-Power-PRO-1000-with-Clean-Power-Stage-2-Power-Outlets?sku=18

Thanks,
K

[KLF_20 Cabinets]

Questiion guys: I'v egot KLF20s without docs and wondering why there are 4 connections in back HF and LF - what does it mean and ho wto use it? Can you advise, please?

[Dynaco ST-70 amp and Klipsch KLF-20 - buzzing sound]

Hi all,

I recently acquired the Dynaco ST-70 set, which was serviced,
power plugs replaced to new, capacitors renewed in preamp.
Amp showed suberb graph on spectrum analizer.
There are original Western Germany made tubes.
(Didn't looks at what exact model number yet).

When I connected it to old speakers Sansui x6700 it worked perfectly
(Sensitivity about 94-96).

After connecting amp with Klipsch KLF-20 with sensitivity 100,
there started constant 'zzzzzzzzzzz' sound.
Like ground sound or I felt it was like sound from tubes buzzing.
Overal sounds amazing, but hum sound is pretty big.

Wondering what it might be and how to fix it.
Do you have any ideas or advices?
Thanks,
K