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Post subject: Re: Speaker for Vibro Champ
Posted: Mon Mar 18, 2019 10:29 am
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Mud, it looks to me like you changed to a different speaker cable. If so, I suspect it's causing the hum issue. Maybe try the original cable, soldered to the new speaker.


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Post subject: Re: Speaker for Vibro Champ
Posted: Mon Mar 18, 2019 10:35 am
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The added efficiency of the Weber could be increasing the background noise. If the speaker cable ends up being okay, may need to re-position internal chassis wiring.

SE amps are notoriously noisy. Care in wire dressing is important.


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Post subject: Re: Speaker for Vibro Champ
Posted: Mon Mar 18, 2019 11:16 am
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sfceric64 wrote:
Mud, it looks to me like you changed to a different speaker cable. If so, I suspect it's causing the hum issue. Maybe try the original cable, soldered to the new speaker.

I did use a different cable hoping to be able to switch speakers out, as I think the stock speaker might be better when playing with another using an acoustic guitar, it is a lot softer. I am using 14guage speaker wire I'll take it out of the casing and give the wire a twist like the stock cable, of course if that fails I will try the original wire.
mud


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Post subject: Re: Speaker for Vibro Champ
Posted: Mon Mar 18, 2019 11:28 am
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BMW2002Ti wrote:
The added efficiency of the Weber could be increasing the background noise. If the speaker cable ends up being okay, may need to re-position internal chassis wiring.

SE amps are notoriously noisy. Care in wire dressing is important.

It sure is more efficient, and that's what I am truly thinking, I am going to try the a few things with wire dress, and hear what happens, and than I might hook the first stage to the 40mf lug. What I don't have is a 20/20/20/20 cap can, so I can't go that route using a resistor between to two 20's. I do have the 40/20/20/20, if it helps some I will consider getting the 20/20/20/20. I have seen all kind of solutions on how to kill the VC hum and you are right they have a reputation of being notoriously noisy
mud


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Post subject: Re: Speaker for Vibro Champ
Posted: Mon Mar 18, 2019 5:28 pm
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New can and metal oxide resistors in the PSU stage will help. You can (sorry for the pun) use the 40/20/20/20, just don't use the 40mfd section. New can and wire-wound resistors in PSU. Helped to drop the background noise. I used CE 20/20/20 at 525VDC (55C rating). Amp came with aftermarket MM OPT transformer. Before and after shot of my '64.

Image

Image

Image


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Post subject: Re: Speaker for Vibro Champ
Posted: Wed Mar 20, 2019 7:46 am
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mud wrote:
BMW2002Ti wrote:
The added efficiency of the Weber could be increasing the background noise. If the speaker cable ends up being okay, may need to re-position internal chassis wiring.

SE amps are notoriously noisy. Care in wire dressing is important.

It sure is more efficient, and that's what I am truly thinking, I am going to try the a few things with wire dress, and hear what happens, and than I might hook the first stage to the 40mf lug. What I don't have is a 20/20/20/20 cap can, so I can't go that route using a resistor between to two 20's. I do have the 40/20/20/20, if it helps some I will consider getting the 20/20/20/20. I have seen all kind of solutions on how to kill the VC hum and you are right they have a reputation of being notoriously noisy
mud


Based on your other thread, https://forums.fender.com/viewtopic.php?f=12&t=101115&start=60your cap can is a little less than 3 years old, replacing it seems non-productive.

Most likely it's the added efficiency of the speaker.

Would changing the heater circuit to a twisted pair with artificial center tap make any difference?
<edit>
After exhausting all other possibilities.

Cheers


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Post subject: Re: Speaker for Vibro Champ
Posted: Wed Mar 20, 2019 8:24 am
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vinyl wrote:
mud wrote:
BMW2002Ti wrote:
The added efficiency of the Weber could be increasing the background noise. If the speaker cable ends up being okay, may need to re-position internal chassis wiring.

SE amps are notoriously noisy. Care in wire dressing is important.

It sure is more efficient, and that's what I am truly thinking, I am going to try the a few things with wire dress, and hear what happens, and than I might hook the first stage to the 40mf lug. What I don't have is a 20/20/20/20 cap can, so I can't go that route using a resistor between to two 20's. I do have the 40/20/20/20, if it helps some I will consider getting the 20/20/20/20. I have seen all kind of solutions on how to kill the VC hum and you are right they have a reputation of being notoriously noisy
mud


Based on your other thread, https://forums.fender.com/viewtopic.php?f=12&t=101115&start=60your cap can is a little less than 3 years old, replacing it seems non-productive.

Most likely it's the added efficiency of the speaker.

Would changing the heater circuit to a twisted pair with artificial center tap make any difference?

Cheers

Yeah the can is new and I also believe its the efficiency of the speaker. As far as the heater circuit goes at some point I may give it a go. I have seen a lot of internet threads dealing with the noise of a single ended amp, and VC's and will start looking into theses mods, I may be semi retiring in June so I will have some time to play around than. Also I play to loud for the 38 to 40db 250hz at 3 to 4 feet to annoy me when I play, it only gets me when I first turn on and warm up after that, when I'm making noise with my guitar :lol: I barley pay attention to it until I am done making my noise
mud


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Post subject: Re: Speaker for Vibro Champ
Posted: Wed Mar 20, 2019 9:09 am
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Here's a thought. Guitar speakers are not very "linear" compared to a hi-fi speaker. Temporarily hooking it up to a hifi speaker to measure the hum might shed some light on the source, 120 Hz rectifier ripple or 60 Hz heater noise.


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Post subject: Re: Speaker for Vibro Champ
Posted: Wed Mar 20, 2019 11:55 am
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vinyl wrote:
Here's a thought. Guitar speakers are not very "linear" compared to a hi-fi speaker. Temporarily hooking it up to a hifi speaker to measure the hum might shed some light on the source, 120 Hz rectifier ripple or 60 Hz heater noise.

Not a bad idea, will have to wire a pair of JBL control 25 in parallel to get 4 Ohms, but that is easy enough
mud


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Post subject: Re: Speaker for Vibro Champ
Posted: Sun Mar 24, 2019 11:04 am
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Any progress on isolating and rectifying the hum issue?

Overall, how much of a sonic improvement did the new speaker provide?

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Speaker for Vibro Champ
Posted: Mon Mar 25, 2019 3:10 pm
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Retroverbial wrote:
Any progress on isolating and rectifying the hum issue?

Overall, how much of a sonic improvement did the new speaker provide?

Arjay

No the hum is still there, I really haven't had time to do more than change out the speaker cable and than try twisting the new cable with no difference. When I get some time, and it will happen as I am semi retiring come June 1, I will be able to dig in to it. The 250hz hum according to my meter set to 30-90db at 8 feet is not picked up but my ears pick it up, but again as soon as I play, it is to quite to be noticed.
Now with that said, I have been banging away at it between, 1 1/2 to 2 hours a day since I put it in, and it seems it is starting to get the blanket off and starting to sing, I am using quite a bit of treble 8 with my strat and 10 with my SG, at around volume 6 to 7, and it is a lot louder to my ears than the stock speaker, and definitely has a bigger bottom end and doesn't get sloppy sounding at the higher volume.
In two weeks I am going to put he stock speaker back in, and switch back and forth and get a real comparison, and will let ya's know what I think
mud


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Post subject: Re: Speaker for Vibro Champ
Posted: Mon Mar 25, 2019 4:59 pm
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Did you clean both of the input jacks? They are self-switching but if corrosion accumulates on those contacts a hum or buzz is often the result. I use emery or krocus cloth to gently abrade both sides to ensure a positive connection.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Speaker for Vibro Champ
Posted: Wed May 22, 2019 10:42 am
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Hello have not spent too much time here lately. Since March I have been in a forced retirement situation from my job and I seem to not get here to often now that the job has me working part time, and paying me full time, until May 30. I did most of my communication in this forum from work, I see why there retiring me. Now I find my self more busy not coming to work, with less time for the forum, I guess I will have to figure out a balance.
Never the less I still put in my 1.5 to 2 hours a day making noise in my house with my guitar and amps, but have only used the VC since March 18 when I put the Weber in, I assume it is broken in by now. I did however last week decide to try the stock speaker for a comparison. I set up my test gear and did a few test with the different speakers, thought I did good notation on my measurement and after I compiled the data, something did not seem right, maybe I had a senior moment and now I just don't trust my data, so I will have to do it again. I will try to get to it in the next week or two.

Vinyl I did not do this test yet but when I am testing out the speakers again I will add a more linear speaker to the test
vinyl wrote:
Here's a thought. Guitar speakers are not very "linear" compared to a hi-fi speaker. Temporarily hooking it up to a hifi speaker to measure the hum might shed some light on the source, 120 Hz rectifier ripple or 60 Hz heater noise.

No progress the 125 and 250 Hz hum is still present. With my meter set to 30db-90db and 5 feet away the Weber reads 38 db at 250, and with the stock speaker 1 foot away from my meter, it reads 34db at 250Hz. As far as the sonic improvement goes, now that I switched back to the stock speaker I feel the Weber took the Fender sound away, to my ears it did sound like a different amp not a Fender,
What got me was at one point I plugged into my early 1968 PR and it had this tone that was not in my VC any more and than I plugged into my 1969 SR and there it was that sound I did not have in my VC anymore, I call it breath it just was not there, now that the stock speaker is back in it now has breath. I will admit the Weber did sound very good and articulate at higher volume and I feel it was a lot louder than the stock speaker. If I was in a situation where I was going to use the VC in a small band, I would use the Weber, as it might get over the drums, of course it depends on the drummer, but than again I would most likely just use my PR of my SR instead.
In conclusion I liked the Weber it does in my opinion take some of the fender sound out of the VC, I would think it's the difference between the Alnico and Ceramic magnet that make the big difference, as mentioned I have a VC, PR, and SR they all have ceramics, must be some reason Leo specked these speakers for these amps, my guess it was for a certain sound.
For my needs playing and practicing in a small room by myself the stock speaker works best as the Weber defeats the purpose of a quieter amp,in volume, and of course in my situation that 250Hz hum that is there always but much more present with the Weber.

Retroverbial wrote:
Any progress on isolating and rectifying the hum issue?

Overall, how much of a sonic improvement did the new speaker provide?

Arjay
Yeah I gave that a go with no change
Retroverbial wrote:
Did you clean both of the input jacks? They are self-switching but if corrosion accumulates on those contacts a hum or buzz is often the result. I use emery or krocus cloth to gently abrade both sides to ensure a positive connection.

Arjay

mud


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Post subject: Re: Speaker for Vibro Champ
Posted: Wed May 22, 2019 11:46 am
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As speakers go, the efficiency difference is likely a player in the increase of the 250hz noise also.

As for the early retirement, you'll get it sorted out soon enough. I refer to it as living better and sleeping longer.

Maybe re-test the ground on the new cap can as well as the continuity of all the ground points. If you have a scope, maybe try testing each circuit element @ 250hz to find the culprit or at least narrow down the component.


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Post subject: Re: Speaker for Vibro Champ
Posted: Wed May 22, 2019 12:57 pm
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If the noise is there with the stock speaker, it seems to me that going back into the amp is where you will get to the bottom of the problem. You either have a power supply hum or a radiated hum.
First, try replacing the rectifier tube. There are two sections to the tube. If one section goes out, it will still work. But the other section then runs as a half wave rectifier that has to supply twice as much current at half the frequency. This causes hum and poor sound.
Second, radiated sound shows up in the first peamp tube. Pull the tube and see if the hum goes away. If it does, you have a loose ground or a wire dress problem. Make sure the filament wires to the tube sockets come straight up and away from the sockets and other wires. Look for broken solder to the brass plate ground plane.
Then, place the amp facedown and unbolt the speaker. Turn on the amp and move the speaker around to see if its position changes the hum radiation. If it does, ground the frame of the speaker to the negative terminal. You can see this on the original. That is to prevent the speaker from acting as a radiator for AC hum.


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