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September 28, 2020, 12:53:58 AM

Author Topic: Crack 1.1 noise in right channel  (Read 2640 times)

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Offline Robbo

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Re: Crack 1.1 noise in right channel
« Reply #30 on: June 27, 2019, 12:12:14 AM »
Hi Guys,
I had the same problem with noise on the right channel. It turned out to be the red/white wires going to the headphone socket running parallel to the group of wires that run under ther big ceramic resistors shown in the manual as neatly grouped together. Lifting the two wires away from that group of wires so they were floating free solved the probem for me. Turnes out the red right channel wire closest was picking up noise from that group. I raise this potential issue in my review article on the hificollective blog.

First pic - Shows the wires grouped together. Has a buzz on right hand channel.
Second pic - Though hard to see because the choke obscures the view you can just about see that the two wires are lifted up. Buzz gone.

Regards
« Last Edit: June 27, 2019, 01:33:22 AM by Robbo »

Offline fromnowon

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Re: Crack 1.1 noise in right channel
« Reply #31 on: June 27, 2019, 02:57:34 AM »
That's a nice write-up on hificollective!

I'm curious about how you mounted the choke - it looks like you didn't drill at all, just used some two-sided sticky pads maybe and it's held securely?  Maybe there are some benefits from mounting that way.  It helped me a lot to see your choke location and also how you grounded it to tab 16.  I think I'll copy your method for that.

Also, those are really nice interconnect cables running to the RCAs.  Really well insulated it seems.  I wonder where a person could obtain a piece of that cable or something similar to it.

Offline Robbo

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Re: Crack 1.1 noise in right channel
« Reply #32 on: June 27, 2019, 03:12:47 AM »
Yep, selotape strong double sided sticky pads in a row accoss the bottom of the choke double layered accross the middle part as that bit is raised slightly higher than the mounting tabs. Then soldered a wire to the ground lug u16 from the corner of the choke to make sure its grounded. It actually stuck really strong, infact i could pick the whole thing up by the choke.

Yeah that interconnect is really nice but not cheap (£58.44 incl vat for 1m), it's like hose pipe and quite stiff (Yarbo Audio silver interconnect), hificollective sell it. I had about a foot of it left over from my ANK EL34 modification work.

And yeah choke should be either mounted as far away from the power transformer as possible or perpendicular to it to avoid or cancel out the effects of the magnetic field respectively.

Be warned getting the solder to stick to the choke needs loads of heat the metal casing disipates the heat quite well so getting it hot enough was hard work. After some trial and error i eventually figured that the little crack in the metal frame on the corner of the choke might give something for the solder to flow into and grip better. I sanded the corner a bit to remove any varnish and expose the metal before soldering and used a bit of rosin flux to help clean the surface at the same time.
« Last Edit: June 27, 2019, 05:26:10 AM by Robbo »

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #33 on: June 27, 2019, 12:47:17 PM »
Welp, problem solved. New tube arrived today. No more chassis noise, no more right channel issues. There is a very slight noise in both channels but that's disappearing as the tube burns in. I'll wait until all noise is 100% gone and mark this resolved.
« Last Edit: June 27, 2019, 01:17:36 PM by A Jedi »
A Hristov

Offline Robbo

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Re: Crack 1.1 noise in right channel
« Reply #34 on: June 28, 2019, 01:30:36 AM »
Welp, problem solved. New tube arrived today. No more chassis noise, no more right channel issues. There is a very slight noise in both channels but that's disappearing as the tube burns in. I'll wait until all noise is 100% gone and mark this resolved.


If its a shhhh noise that goes after 15 - 20min once warmed up its prob a little tube rush, nothing to particularly worry about.

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #35 on: June 28, 2019, 01:58:36 AM »

If its a shhhh noise that goes after 15 - 20min once warmed up its prob a little tube rush, nothing to particularly worry about.

It's a kind of grainy shhhh....
A Hristov

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #36 on: June 28, 2019, 02:34:33 AM »
Come to think of it, it's exactly the noise you hear when you walk by a street lamp. Given that a tube is essentially a bulb, the noise should be tube based. Can't wait for it to go away...
A Hristov

Offline Robbo

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Re: Crack 1.1 noise in right channel
« Reply #37 on: June 28, 2019, 03:26:35 AM »
Does it go away once everything has warmed up, say after 15-20min? If its a persistent buzz of around 60hz or 120hz id say maybe check your signal wireing inside isnt butted up against other power wires inside or ground wire inside, paralelle to them perhaps. I thnk 60hz buzz might be power interference, 120hz could be ground interference. Im not sure if the symptoms could be interchaingable though.

As i said in my earlier post i had issues with the red/white wires going to the headphone socket running parallel to the group of wires that run under where the two large wirewound resistors are, lifting them both clear of that group solved the buzz issue for me, my guess is that it was probubly interference from the black ground wire. I could actually change the buzz by waving my hands around the amp hence my guess that ground was my issues cause.

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #38 on: June 28, 2019, 10:31:15 AM »
It's a higher frequency sound. More in the mid/high range. A light tap on the 6080 makes it go away. When I say "light tap" I mean very light - with the tip of a pen.  It's definitely less noticeable with the new tube but still there for now. At least the chassis isn't generating noise on its own anymore lol. I'll have to flip it over and poke around the wires again but last time I did that there was no change.
A Hristov

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #39 on: June 29, 2019, 05:25:29 AM »
 >:(

Starting to suspect transformer vibrations getting into the tube.
A Hristov

Offline Doc B.

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Re: Crack 1.1 noise in right channel
« Reply #40 on: June 29, 2019, 05:31:18 AM »
Sounds like an oscillation. Those can come about from less than perfect contact of the tube in the socket. Try cleaning the tube pins.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #41 on: June 29, 2019, 05:51:50 AM »
Sounds like an oscillation. Those can come about from less than perfect contact of the tube in the socket. Try cleaning the tube pins.

Thanks will do.
A Hristov

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #42 on: July 01, 2019, 05:38:23 AM »
Ok so cleaning the tube pins has helped. There is still a very low hum though. It's hard to pinpoint the frequency but it's somewhere in the midrange...maybe around a thousand-ish Hz? And once in a while there is a louder higher pitched tone - that one goes away if I tap the 6080. Any more thoughts/ideas?

This is my first experience with tube equipment so perhaps I'm expecting too much? Should it be dead quiet or is some noise normal? Should I just call Bottlehead?
A Hristov

Offline Paul Birkeland

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Re: Crack 1.1 noise in right channel
« Reply #43 on: July 01, 2019, 06:02:19 AM »
Tapping the tube jostles all the connections in the amp, and a less than perfect connection can be temporarily restored by doing this.  Perhaps you could take some new photos since you've reflowed a bunch of joints.

While you are certainly welcome to phone in, any details discussed on the phone will not be present on this thread and will complicate providing future tech support.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline A Jedi

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Re: Crack 1.1 noise in right channel
« Reply #44 on: July 01, 2019, 10:05:14 AM »
I've had it upside down and running and poked all connections with a chopstick and could not induce/reduce any noise. But here goes nothing:

A Hristov