S.E.X. amp seconde hand

[oguinn]

Oh lord, thank you: I am in the learning mode now.

Will do the measurements again.

We were all new at this at one point in time or another. I still mess at least one thing up per build.

[mwgrient]

 

[Oyvindk]

Hi.
I buildt this amp 6 years ago and recently sold it to mwgrient. I am not an experienced amp-builder, but it worked fine all the time I had it. If anyone is interested, here is the building process documented (in Norwegian, but with many pictures)  link was not allowed, but google  “
hifisentralen Bottlehead Single Ended eXperimenter's kit“ and the thread should appear.

I listene to the amp for two hours (no issues) before it was double-boxed and shipped. Obviously, something must have happened during shipping, and therefore my first suspicion would be (besides damaged tubes, which was  ruled out) a bad solder joint, as Doc B mentioned.

The amp is wired for 8ohm output as I mainly used it with horn speakers.

[Paul Birkeland]

So far there isn't any indication that there's an issue with the build.  It could simply be some external interference. 

[mwgrient]

I have tried to eliminate interference. Other room, divert power cable and wall-plug. Shutting down the computer. Nothing.

I can hear music, but when the volume is turned off, de loud signal is back. I will try to install the noise eliminator.

[mwgrient]

Here is a link to my amp, with a sample of the sound it gives true my headphone left channel.



regards, Marco.

[mwgrient]

Hi all, I have soldered the sockets lower than they where soldered. And re-soldered all the ground wires/points again and again. There is no oscillation anymore!
Only a faint hum when I connect my headphone; It is also there when the volume is turned down//closed.

[Tom-s]

Glad it worked out!

I have soldered the sockets lower than they where soldered.

To further explain to others on this forum.
What you've done here is relocate the grid stoppers closer to the socket pins (1,4) of the tube as a preventive measure for oscillation.


Now enjoy it!
Let us know how you like the SeX 2.1!

[Paul Birkeland]

Oh man, that's quite a noise! 

[mwgrient]

Yeah! It is still not quiet, but doing a lot better now. Pffiew!

I would like to replace the potentiometer, jack socket and RCA terminals.

Does someone know where to get the distinctive Bottlehead knop?

[Paul Birkeland]

I would like to replace the potentiometer, jack socket and RCA terminals.

Why?

[mwgrient]

The RCA sockets are fried, at least one. And do not look nice anymore. My fault!
The potentiometer gives noise at the end of the volume (almost open wide)

The big black knob is not detachable since the screw is broken that will hold him in place.

[Paul Birkeland]

The potentiometer gives noise at the end of the volume (almost open wide)

This is a function of the high input impedance of the amp, not the pot itself.

The big black knob is not detachable since the screw is broken that will hold him in place.

Hmm, you'll have to maybe melt it off then to get it off. 

https://no.mouser.com/ProductDetail/Eagle-Plastic-Devices/45KN014-GRX?qs=EiTGd8sy9OrVz4TOJLy7AQ%3D%3D

[Deke609]

you'll have to maybe melt it off then to get it off. 

 A really small diameter extractor bit might work - and then you'd be able to use the knob again, provided you can find or make a replacement set screw. Failing that, I'd drill it out with regular bit made for metal.

cheers, Derek

[Doc B.]

Ever tried to melt one? I have not, but I think maybe they are bakelite and won't melt.