Another 5150 thread (the effects loop hum)

[kev]

Seems its fun times for the 5150 owners at the moment so I thought I may as well add to it .

Anyway... recently retubed the 5150 with JJ's all the way (first time doing it actually). However, since then the effects loop has decided to hum like a bitch even when the devices are powered on battery. From what I've read its probably the phase inverter tube, but you guys here are gonna have far more knowledge than most of the terrible idiots i've found giving advice through general googling.

If it's the phase invertor tube, forgive my electronic ignorance, but why should this occur with a set of brand new tubes when the old ones didnt sovtek/JJ combo didnt?

The irony is, i've been putting a decimator in the effects loop and since the retube, it actually increases noise to do this . Im not enamored with the idea of buying yet another tube

P.S Cleaned the jacks

 

[John_C]

well a quick diagnostic would be to swap the tubes around and see if it goes away...

 

[TheWinterSnow]

you didn't buy a balanced tube for the phase inverter did you? phase inverters are differential amplifiers meaning, they amplify the difference of two input signals, if both triodes in that tube don't conduct equally, any stray noise can be amplified. If such tubes are balanced, the noise is cancelled out. It is called Common Mode Rejection.

 

[Wolfeman]

I would check with a different set of tubes. I've never bought a good JJ yet. Other people seem to have more luck with them than I do.

 

[TheWinterSnow]

I would check with a different set of tubes. I've never bought a good JJ yet. Other people seem to have more luck with them than I do.

I am always hearing this, and I bought a set for my 5150 and my guitarist picked up an entire preamp and power amp set for his 5150 and everything has been smooth sailing.

 

[Wolfeman]

I am always hearing this, and I bought a set for my 5150 and my guitarist picked up an entire preamp and power amp set for his 5150 and everything has been smooth sailing.

I tried them a while back, I wanted to like them, but I had 3 microphonic from day 1, ordered some more and they went shitty sounding within a month. And that was from 2 separate supplieres. I think there was a bad run going around that time, because lots of others had the same issue. Even the KT77's I had only lasted a few months before something failed in it, went red on me.

They may be better now, but I won't spend a dime on them.

 

[kev]

you didn't buy a balanced tube for the phase inverter did you? phase inverters are differential amplifiers meaning, they amplify the difference of two input signals, if both triodes in that tube don't conduct equally, any stray noise can be amplified. If such tubes are balanced, the noise is cancelled out. It is called Common Mode Rejection.

Thanks guys. Nah mate, I read some stuff at the time which claimed it was pretty much a waste of cash. I will try fiddling with the tubes though and see if anything happens. Interesting post above Eric :/

 

[TheWinterSnow]

I tried them a while back, I wanted to like them, but I had 3 microphonic from day 1, ordered some more and they went shitty sounding within a month. And that was from 2 separate supplieres. I think there was a bad run going around that time, because lots of others had the same issue. Even the KT77's I had only lasted a few months before something failed in it, went red on me.

They may be better now, but I won't spend a dime on them.

Did you try Eurotubes, because Bob sends back more JJ's than any other supplier as he hand tests every single tube from every order, your chances of getting a bad one through him would not be from a bad tube but from shipping damages. My tubes have been amazing, everyone bitches about how noisy 5150s are but mine has been absolutely quiet, the tubes are the polar opposite of microphonic (tapping the tubes barely makes even the rumble/tap noise). I have been happy with them, but like you and many other cases I have hear many horror stories of JJs being DoA or with very short lifespans.

Thanks guys. Nah mate, I read some stuff at the time which claimed it was pretty much a waste of cash. I will try fiddling with the tubes though and see if anything happens. Interesting post above Eric :/

Its absolutely not a taste, it a whole 3 dollars extra for one tube and it ensures that they have near identical transconductance curves which is essential for a proper CMRR. The reality is that in a 12ax7 or any tube for that matter, the transconductance of the two triodes can be worlds apart, and the further they are from each other, the worse the noise will be if that tube is in the phase inverter slot.

 

[gixxsta04]

Which tube is the phase inverter?

 

[TheWinterSnow]

^^ closest to the power tubes.

 

[kev]

I read something a while back about something called a schmidt long tail design that defeats the need for the balanced PI- guessing the 5150 doesn't have that?

Edit: this was the post, you'll be able to make more sense from it than I! http://www.marshallforum.com/workbench/6064-balanced-unbalanced-triodes-phase-inverter.html

 

[guitarguru777]

I tried them a while back, I wanted to like them, but I had 3 microphonic from day 1, ordered some more and they went shitty sounding within a month. And that was from 2 separate supplieres. I think there was a bad run going around that time, because lots of others had the same issue. Even the KT77's I had only lasted a few months before something failed in it, went red on me.

They may be better now, but I won't spend a dime on them.

you ordered from Eurotubes didnt you... his tubes suck. i have gotten MULTIPLE bad sets from him. When I started buying mine on Ebay & Tubestore.com the shit stopped.

 

[John_C]

Eurotubes isn't really an option for us in the UK, try Watford Valves perhaps for a quality supplier with good testing.

 

[TheWinterSnow]

I read something a while back about something called a schmidt long tail design that defeats the need for the balanced PI- guessing the 5150 doesn't have that?

Edit: this was the post, you'll be able to make more sense from it than I! http://www.marshallforum.com/workbench/6064-balanced-unbalanced-triodes-phase-inverter.html

Yes the 5150 does have it, but there is only so much it can do as the design is more a current limiter more than anything, if the differences in gain are too far from each other, it won't matter.

 

[guitarguru777]

I read something a while back about something called a schmidt long tail design that defeats the need for the balanced PI- guessing the 5150 doesn't have that?

Edit: this was the post, you'll be able to make more sense from it than I! http://www.marshallforum.com/workbench/6064-balanced-unbalanced-triodes-phase-inverter.html

So you are using Marshall logic on a Peavey product created from a Soldano design.....

 

[TheWinterSnow]

Yes the 5150 does have it, but there is only so much it can do as the design is more a current limiter more than anything, if the differences in gain are too far from each other, it won't matter.

I should add that, particularly that design is designed to balance the final output on the plate because the Gain Factor will be uneven. So that design is more of a...gain balancer, not bias balancer.

 

[kev]

So you are using Marshall logic on a Peavey product created from a Soldano design.....

Nah, just general amp design Mr Cohen Ta for the further info wintersnow.

 

[guitarguru777]

LOL ... you know I am fucking with you right Kev

 

[kev]

LOL ... you know I am fucking with you right Kev

I knw too well man, plus dr spock is a cunt and i've got flu lol (and did i mention a humming 5150 when the effects loops on... : D)

AND... ive just received this message from msn. Im going to bed LOL

.....@gmail.com said (23:02):
you still there
Kev says:
yeh
...@gmail.com said (23:03):
is there any plugin out there
that can modulate your recording
to create the effect of multi track without having to multi track

 

[guitarguru777]

OMG dude .... hahahahhahahahah

GO TO BED!

Honestly Winter is probably right