5E3 hiss/buzz on max volume with no guitar?

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nickt
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5E3 hiss/buzz on max volume with no guitar?

Post by nickt »

I've just completed a (nearly) stock 5E3 and all's well except I get a loud "sucking buzz/hiss" :shock: with no guitar connected and both vols maxed. If a guitar is connected (to either channel) all's well 8)

Now to explain "nearly" stock - everything is stock except
- 0.022uF coupling cap in the brite channel (standard mod!)
- neither input has the standard 68K resistor network
- only one jack is connected to each channel (with 1M to ground on the jack)
- both input lines are RG174 shielded (shield to jack ground).

I'm suspicious the problem is caused by having no snubbers on the inputs.

Has anyone else experienced this sort of thing?

Thanks
Nick
riscado
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by riscado »

every tweed deluxe circuit, I've worked on had hiss if you had both volumes maxed at the same time, even without an instrument plugged in...
muchxs
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by muchxs »

The last one I built was dead quiet without a guitar plugged in and with both volumes maxed. That's pretty funny because I used a defective pilot light, no matter what I did with that pilot light assembly I couldn't get continuity to the bulb. Sometimes it's the simple things that kick my ass...

I expect it might be noisy without grid blockers on the input. I've even seen grossly mismatched tubes that will pass crosstalk and noise section to section without grid blockers. Hint: The stock 12AY7 preamp tube will be much less noisy than a 12AX7. Disreputable techs sometimes swap a very low gain tube like a 12AU7 into an amp with a noise or hum problem, it's a quick and dirty way to quiet an amp that really needs a cap job or service. Less gain equals less gain to your noise equals less audible noise equals less overall volume.
paddy
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by paddy »

Hi there
Mine is dead quiet.Are your input jacks shorting to ground when the guitar
cables are unplugged?

Cheers
Paddy
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nickt
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by nickt »

riscado wrote:every tweed deluxe circuit, I've worked on had hiss if you had both volumes maxed at the same time, even without an instrument plugged in...
Nah - this is more than just regular hiss. I'm used to amps hissing and spitting - I own an old vox and play a strat !!! :shock: 8)

This is a hissy buzz and comes on really suddenly and is super loud. Basically you only have to back one of the vol pots off by a small fraction (2-3%) and it stops (goes back to normal hiss). This makes me think its some sort of oscillation that starts when both plates are connected together (via the maxed pots).

Originally I had the two channels internally jumpered and thought it was that but removing the jumper made no difference.

I'd hoped someone else might have had this issue and could say something like "geeze you removed the snubbers what do you expect! everyone knows that's a bad idea - newbies..." which might point me in the right direction :)

Thanks
Nick
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nickt
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by nickt »

paddy wrote:Hi there
Mine is dead quiet.Are your input jacks shorting to ground when the guitar
cables are unplugged?
They should be - that's how they're wired - I'd expect a gradual increase in hum/hiss if they weren't not the sudden buzz/hiss I'm hearing.

Thanks
riscado
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by riscado »

I think it's funny when people talk about amps like the deluxe and say, it's dead quiet, I never heard a deluxe that was dead quiet with both volumes maxed, I'd say it's inherent to the circuit, the hiss might be low but it's definetly there, not dead quiet by all means...

Anyway have you checked the filter caps, even if they're new, I've had situations where one bad filter cap was causing a huge buzz/hum that got even more noticeable as the amp was turned up.

Also is the noise there if you remove for example the V1 tube?
muchxs
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by muchxs »

riscado wrote:I think it's funny when people talk about amps like the deluxe and say, it's dead quiet, I never heard a deluxe that was dead quiet with both volumes maxed, I'd say it's inherent to the circuit, the hiss might be low but it's definetly there, not dead quiet by all means...
When I say "dead quiet" I mean dead quiet. That's why the pilot light thing was such a goof, I sparked up my fresh build, turned the volumes all the way up and... nothing. No noise, no hum, no hiss, no crackle. It took me a minute or so to realize that everything was indeed o.k., the only flaw in my fresh build was a defective bulb holder in the pilot light.

(Knock wood) My builds usually work correctly from the get-go, I'm not bragging because there are probably a hundred things per build I can screw up. Oddly enough I do pretty good work these days, write that up to "Learning from my mistakes"!

There's no reason for a vintage circuit like a Deluxe to be noisy. It's not like there's a bunch of gain stages in there to pick up and amplify stray hum and noise. The simpler an amp is the quieter it should be, look at hi-fi amps. Part of the process is that I spec EVERYTHING, that means I screen my caps for value and leakage, I measure resistors for value and screen them for noise, I carefully check and match my tubes, then I arrange my build so it's not a series of little transmitters and antennas.
nickt wrote:I'd hoped someone else might have had this issue and could say something like "geeze you removed the snubbers what do you expect! everyone knows that's a bad idea - newbies..." which might point me in the right direction :)
Then add "snubbers" to your circuit. 33k, 47k, or 56k will work if you don't have 68k. Or add 220k mixer resistors to isolate your plates on your preamp tube.

It's really tough to diagnose anything online, what you'll get is a "virtual diagnosis". If you were sick, would you subscribe to an online doctor? Imagine that... you go to "MD.com" with the sniffles, you tell the doc, "I got the sniffles"... the doc can't tell if you're 83 years old, you're overweight have herpes and a peg leg! Like that.

When someone says, "Tweed Deluxe" I visualize a chrome chassis with a black eyelet board, tube lineup 5Y3 6V6 6V6 12AX7 12AY7. I know what the circuit looks like, I have a pretty good idea of which layouts work. If you have a 'scope available you could start poking around with it. If you get a big ol' burst of hash at a particular location you're probably close to your problem. Or we can do the Three Blind Men and an Elephant thing then share your epiphany when you solve your own problem.
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sliberty
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by sliberty »

I think the "inherent noise" in the 5e3 circuit is not in the circuit at all, but in the layout. Modern layout techniques can improve the noise floor considerably. Isolate the inputs from the chassis and run an explicit ground wire instead. Use a false center tap on the heaters (a pair of 100 ohm resistors), reduce the number of places where ground loops occur, etc. and you will quiet your amp considerably. I just went through this with my own 5e3 build, which was actually the first build I ever did, and took it from VERY noisy to VERY quiet. It was quite satisfying too - makes me realize that I have learned a few things.
riscado
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by riscado »

When I talk about tweed deluxes, I'm refering to amp that follow the traditional layout and standard wiring/components, I'm sorry but I haven't heard a single one that did not hiss...

Despite the fact that the amp has few gain stages, the ones I've seen with close to zero noise had been worked out, until perfection, mostly using hoffman type layouts and isolated inputs.

I'm not saying I don't believe you, I find it funny that's all! It's one of those see to believe type of things.
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nickt
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by nickt »

riscado wrote:I think it's funny when people talk about amps like the deluxe and say, it's dead quiet, I never heard a deluxe that was dead quiet with both volumes maxed, I'd say it's inherent to the circuit, the hiss might be low but it's definetly there, not dead quiet by all means...

Anyway have you checked the filter caps, even if they're new, I've had situations where one bad filter cap was causing a huge buzz/hum that got even more noticeable as the amp was turned up.

Also is the noise there if you remove for example the V1 tube?
Like I keep saying this is a sudden hiss/buzz - like switching on a switch "shhbzzzt!!!" :shock: not regular background "hisssss..." that goes up and down smoothly with volume. :wink:

I'll do some surgery and report back. Thanks for the thoughts.
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sliberty
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by sliberty »

I am a little confused by your description:

>>sudden hiss/buzz

seems to be the opposite of

>>that goes up and down smoothly with volume

Can you clarify a bit?
riscado
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by riscado »

well if it's a sudden noise and not a continuous one, than you may also discard my filtering section sugestion...
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nickt
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by nickt »

sliberty wrote:I am a little confused by your description:

>>sudden hiss/buzz

seems to be the opposite of

>>that goes up and down smoothly with volume

Can you clarify a bit?

Sure (and I wish I'd never said "hiss" :lol:)

What I'm getting is the "sudden hiss/buzz" NOT the regular kind of hiss and yes, it is the opposite of regular hiss.


Seems no one else has had this problem or no one else has removed the 68K resistors on a 5E3. I'll do some surgery and report back. :?
muchxs
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Re: 5E3 hiss/buzz on max volume with no guitar?

Post by muchxs »

nickt wrote:[What I'm getting is the "sudden hiss/buzz" NOT the regular kind of hiss and yes, it is the opposite of regular hiss.

Seems no one else has had this problem or no one else has removed the 68K resistors on a 5E3. I'll do some surgery and report back. :?
I wouldn't think of removing the 68k resistors. They're there to block RF at the grids, any noise that gets in there will just get bigger. With your two input 5E3 you can drop them down to 33k. We can debate whether or not they're necessary or you can add them to your circuit and decide for yourself.

I seem to remember something from Gerald Weber about shortening signal path in a 5E3 to eliminate oscillation. If you've ever looked inside a Kendrick (by Gerald Weber) "Deluxe" it looks nothing like a stock Deluxe. G.W. uses much larger filter caps than stock with a 5AR4 rectifier and he's spent a lot of time with lead dress to tame the buzz.
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