John Shearne amps

Hi,

Yep that Alchemist. I was Chief Engineer for a part of their existence....

Andy Light is the name I think you're looking for.

Ha! Jez is back 😊

I think it's probably wise to avoid politics as a subject, Personally I think it just creates about as much division and animosity as religion.

I am sure that if we all talk about the subject that brings us to this forum, HiFi, then apart from the odd disagreement about hifi bits, the forum has ticked along nicely, and Andrew and I are determined to keep it that way!

We don't discuss other forums or it members because of the example set by the old HFS and how it became a beacon for those determined to spread hatred.

Thankfully, Paul is doing a good job there and it's now a different direction all together. Bravo to him! Sincerely.

Whatever happened at PFM, it's done and dusted. Share your posts here, start your own Arkless thread in the blogs section. Make it your forum home.

Welcome back.

HiFi nuts aint bothered about music

Music? I use test recordings and signal generators. You can't beat a bit of pink noise to highlight peaks and resonances. 

We use systems to listen to our music.

You

I have, done album reviews on AoS in the album club.

Posted my latest fuzzy purchases.

Like the title of this forum says, it's all about the gear, here

Remember, this site is all about the gear. Music comes second!

S.

That's how it goes.

S.

In my case you weren’t too far off the mark

Bakers dozen eh

There's been a few Shearmes on eBay. One currently on auction and not expensive.

Hi,  I've just joined this forum to share with you the fix I've just done on my John Shearne amp.  Bit surprised to find lots of political blustering about Brexit inter alia, complete with a picture of Jeremy Corbyn giving a Hitler salute.  Are there any moderators on this forum?

Anyway, I like my JS amp but have been bothered by a faint 100 Hz buzz/hum.  Tried disconnecting things, swapping power feeds etc, with no joy, it was definitely coming from the amp itself.  Removed the cover, couldn't see any problems with bad joints, loose bits or wire routings.  After much trial and error I found two causes - an earth track needed a bypass, and a problem with the volume control extension rod.

Attachment Deleted
Rec Out extension rod removed for clarity.

The two stubs indicated are the ends of the speaker ground wires, soldered into the ground track at the power supply. I clipped on a jumper lead at this point and probed around while listening on headphones.


Clipping the jumper to the longer strap connecting the Left and Right amp blocks stopped the hum.  I soldered a wire between the two points.

Second problem - using the volume control caused a crackle/hum.  It sounded like a dirty pot track but it's been replaced.  Pushing the knob up and down made the hum come and go as the brass extension rod made and broke contact with the edge of the aluminium front panel hole, confirmed by bridging the rod to ground with the jumper.  First thought was to replace the brass rod with plastic, glass fibre or even wood but I didn't like to change the appearance - pointless I know!  Have I got OCD?  If you go this route, don't use carbon fibre - it's conductive.
I enlarged the spindle hole to 7.5mm and shrunk a short piece of heatshrink tube onto it at the knob end (sorry moderator).  This insulates the rod from the front panel and is barely visible.

Result of these two mods is an almost silent amp, apart from a very faint fizz probably from the input ICs, but it's almost inaudible.  I have no idea why the earth strap mod worked, it's just bridging two points on the same ground circuit track - but the fact is, it works!  Anyone who can explain is most welcome.

It's on the first page of this thread.