Koss ESP-9 ESL Head Phones
SCompRacer
Posts: 9,077
I've had these Koss ESP-9's here since February when Ed the SRT King dropped them off picking up his R2R. I figured I'd better dig into them. They didn't work. A little research, foam deteriorates in the cans and can corrode the traces on the PCB's.
The energizer connects direct to amp. There are outputs for speakers. A switch on front panel selects output. Headphone output has SE and AC choices. SE is self-energizing for the bias supply, or AC energizing through the ac line.
Foam was deteriorated. Fortunately, the traces were good after cleaning, they Ohm'd out OK.
I had some foam here. Not as wide as original but enough to cover the back of the ESL panel. Cleaned up the felt and reinstalled. Still unsure if they will work. I can always go back in.
Next up was inspecting inside. Found a wire broken off and noticed a plug in board with some dirty looking connectors.
Better, the main thing the board contacts were clean. I need a tiny brass brush to get at the top of contacts. Notice how there are contacts on only the right of connector.
Cleaning the board contacts, I notice they are only on one side. The connector only has contacts on the outer edge.
Yes, the board was in backwards. Connected it up, powered it on and they work. Sounds pretty darn good too. Very surprising, some of the carbon resistors I tested are still in 10% spec.
The energizer connects direct to amp. There are outputs for speakers. A switch on front panel selects output. Headphone output has SE and AC choices. SE is self-energizing for the bias supply, or AC energizing through the ac line.
Foam was deteriorated. Fortunately, the traces were good after cleaning, they Ohm'd out OK.
I had some foam here. Not as wide as original but enough to cover the back of the ESL panel. Cleaned up the felt and reinstalled. Still unsure if they will work. I can always go back in.
Next up was inspecting inside. Found a wire broken off and noticed a plug in board with some dirty looking connectors.
Better, the main thing the board contacts were clean. I need a tiny brass brush to get at the top of contacts. Notice how there are contacts on only the right of connector.
Cleaning the board contacts, I notice they are only on one side. The connector only has contacts on the outer edge.
Yes, the board was in backwards. Connected it up, powered it on and they work. Sounds pretty darn good too. Very surprising, some of the carbon resistors I tested are still in 10% spec.
Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
Comments
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oooh-whee!
Nice.
I've never heard a pair of the Koss electrostats...
Indeed, not any electrostatic headphones.
I have heard numerous Stax electrets, which were quite fine sounding.
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This is my first time listening to electrostatic headphones. They are very lively and dynamic. They bite too. Found out by letting my pinky stray doing some voltage testing before assembly.Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
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Well when you're ready for a Sansui TU-719 let me know
It unfortunately got left behind when my basement flooded. It turns on and best of all the fluorescent display STILL worked. Those are unobtainable.... -
Yup, that aspect of electrostatic transducers I have experienced.
Sort of like our electric fences.
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Went to a cousin's farm when I was a little kid. My older brothers and cousins got me to touch the fence. Fortunately, it wasn't set to Bull. They told me I was going to die. I ran to the house yelling Mom, I'm gonna die!
My stepbrothers also put me on a 26" bike that I couldn't reach the pedals on, then pushed me down a hill.
What doesn't kill you can make you..... mean with little tolerance....lolSalk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 * -
Well when you're ready for a Sansui TU-719 let me know It unfortunately got left behind when my basement flooded. It turns on and best of all the fluorescent display STILL worked. Those are unobtainable....
I'm getting behind. Got Jay's TT here, some crossovers for Ed, another R2R. I'm overwhelmed, need a helper!
LOL Legend 1, 120dB, Threshold of pain...
Post edited by SCompRacer onSalk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
