Preamp,How the Tubes run in Signal line

[dumbassbob]

I have a 4 tube preamp to run my FX, the old tubes that have been in it for 25 yrs started to go bad,If one tube at the end in the Hot lead #4 was bad even if I do not use that side of the preamp,will it make a problem.Volume drops. What I am trying to say is if One tube is bad,even if it is not used will it effect the whole thing Are all the tubes working all the time

[Enzo]

Well WHAT preamp do you have?

In tube amps all the tubes are running all the time, but that doesn't mean they affect the signal path. Like four autos at the stop light, they are all running, but if one stalls, it doesn't make the others stall too. In a Fender Twin or something, I can pull the tubes for the Normnal channel and still use the vibrato channel. However, depending on the circuit, you generally have more than one tube in the signal path, so if one dies, the signal won;t get past it to the next tube. That is why we need to know what you have.

How did you determine the problem was a tube rather than a connection? For example a Peavey Rockmaster preamp has just a boatload of FX loop jacks, and that is almost always what is wrong when there is any sort of signal intrruption.

[dumbassbob]

It is a SoHo Quatro Tube Preamp It was designed after the Kitty Hawk Quatro preamp.I have a Good ,Bad tube Tester,and even new JJ tubes I had were wavey when I tested and they all gave a different reading I used 3 JJ's and a old Marshall branded china tube ,it solved the problem ,but it doesn't sound as good as the RCA,and Mullards I had in it for yrs...I need to go through my box of NOS tubes.I also had the front input jacks threads break,and the only 9 pin jack I found has metel threads,I need to figure out how to grownd it .It is a good Preamp I only use the clean crunch channel(green) to run my rack reverbs and DDL

[mojah]

I have one of those soho preamps that I modded years ago. Trying to put it back to stock I think I made some errors. My notes weren't that good. If anyone can could they either post it here or send me a couple of gushots looking down on the top ( component side) of the pc board? The qtr-1 tubes share channels ie 1/2 of v-1 is is common to all the channels. V3 and v4 do the overdrive channels. The other 1/2 of v1 and all of v2 do the clean and crunch channels. The Soho is a copy of the Kittyhawk Quatro.

[Chuck H]

Another thing to consider is that, WRT "channel switching" amps, some triodes serve double duty. Most, if not all, multichannel amp designs in the last thirty years don't have entirely independant channels. So there there is a great likelyhood that a triode stage or two (or even three) is used in ALL the channels of the amp. With no actual "independent" channels. In this case there is a every possibility that any tube failure could affect more than one, or all of the "channels".

[dumbassbob]

Another thing to consider is that, WRT "channel switching" amps, some triodes serve double duty. Most, if not all, multichannel amp designs in the last thirty years don't have entirely independant channels. So there there is a great likelyhood that a triode stage or two (or even three) is used in ALL the channels of the amp. With no actual "independent" channels. In this case there is a every possibility that any tube failure could affect more than one, or all of the "channels".

Thanks..I had one will worn 50 yr old Sylvania microphonic tube in V3...

[Chuck H]

Well... Just because a tube is 50 years old doesn't mean it's had 50 years of hard use on it. It might be 50 years old in the sealed box it was packed in! Tubes don't age if they're not used. So it's more about milage than age. I've had a few old Sylvania 12ax7 tubes (still have ONE actually) that test and sound great. Very good sounding tubes IMHE. But once a tube is worn out, it's worn out. Many newer tubes don't last quite as long as the older ones. But the newer tubes sound just fine. Lots of different flavors to choose from. The Sovtek WA, WB and WC tubes have a short plate and virtually zero microphonics for life. Try finding that in NOS! But they lack top end clarity and sparkle. The Sovtek LPS won't handle cathode follower circuits well and is usually too microphonic for the first stage. But it sounds about as good as any NOS tube with plenty of highs, gain and balance. JJ's have a good rep., haven't tried them. Shuguang (did I spell that right?) sound much the same as many old tubes and, like NOS, may or may not be too microphonic for a first position. I'm pretty sure they can be ordered "select" for low microphonics for high gainers in the first slot. The extra expense is not a big deal if your only doing it for the first tube. They also don't last as long as the old tubes. Since they're not expensive it's a wash.

I guess my point is... If a tube is microphonic or worn out, replace it. You really don't even need to sweat whether or not it's an "RCA" or "Telefunken" or whatever. The difference is mice nuts.

[dumbassbob]

I got lucky and got a box of NOS RCA Sylvania Telefunkens and Mullards.This man who lives next door,his father was a radio tech,he gave me this box with all these 12ax7 6l6gc and el-34,I do like the Shuag%^&&$#*&el34 the chiness make pretty good power tubes,I can save my Mullards for recording

[J M Fahey]

mice nuts

Well, you'd be surprised, but rodents have, proportionally to their body, *huge* nuts.
So large in fact , that although they are internal, they change body shape and serve to easily distinguish male from female.
They *need* them, by the way, to reproduce in such huge numbers.
Just another example of useless Internet knowledge
Why are rat testicles so big?

[Chuck H]

From the article:

Humans fall between gorillas and chimpanzees

I think this statement is relevant on more levels than testicular.