4212 Preamp Tubes Question

  • Thread starter Thread starter Len Rabinowitz
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Len Rabinowitz

Len Rabinowitz

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Busy putting new tubes in my 4212 Tourmaster and have a few questions for you experts.

It has 8 pre-amp tubes. Each has a different function. Looking at the manual, here is what they are:

Positions 1-4 are basically just gain staging for the 4 channels

Position 6 drives the reverb, and position 7 drives the effects send.

Here are the two I don't get:

V5- Contour Circuit buffers for overdrive channels

V8- Phase splitter

What are they? What do they do? Anybody know?

Thanks!
 
Hi Len...don't know if you need this info still, but here goes...The contour tube is only if you have the contour button in and you use the control...if you don't use the contour, like me...it's not used...the phase inverter tube is part of the power tube section....it's part of running the class AB power to the power tubes...It is part of your tone...Ideally, when you replace it, get a JJ matched triode tube for this ...Doug's tubes or Euro tubes are good outlets...I've had some bad tube failures with my Tourmaster...just preamp tubes, but still...a royal pain at a gig....IMHO, don't waste your $$ on Groove tube pres...I don't think their testing is worth a damn....get good tested ones from those other outfits....In mine, I just retubed it with a combination of RFT's Sovteks, JJ's, Mullard and Electro Harmonix,,,it sounds wicked!!
 
RockStarNick":2rs57z4z said:
Ok, one of you HAS TO change your avatar!!! :lol: :LOL: :lol: :LOL: :lol: :LOL:
Click to expand...
Len had his first, but I can't find a picture of the Tourmaster head....does anyone have one, then I'll change it.... :rock: :rock: :doh: :gethim:
 
More questions:

I do actually use the contour control- I actually really like Egnater's suggested settings, although I wish they would reverse them in the manual for the 4212!

So does the tube for that circuit just power the contour control, or does it actually effect the sound of that control?

What tubes would you put in the first four slots if you really wanted to exaggerate the sound of the 4 different channels, so that channel 1 would be absolutely shimmery cleans, 2 would be clean with a little hair on it and some snap, 3 would be your basic distortion channel, and 4 would be over the top gain?

I'm thinking that cheaper GT's would work just fine for things like powering effects loop, and get the more expensive tubes where you can really hear the difference.

:student: :inlove: :loco: :cheers2: :gay: :salute:
 
The contour tube is merely a tube buffered mid EQ section that is only used when the contour button is turned on for a channel. Like a sweet tube EQ section built for mid range only if you would. Very high end for such an affordable amp.

The PI (phase inverter) is what you would call a driver section. While it does have a pretty huge affect on overall tone it's primary purpose it to fix a great phenomenom that a 12ax7 or any triod tube causes.

While your signal passes through the gain stage tubes the signal is actually being changed in phase like flipping positive to negative and then back for a generic explaination of this. Well when it leaves the final gain stage and has to hit two power tube sections IE the 2 tubes for the first 50 watts adn the second two for the other 50 watts. the nature of the 9 pin triod will have one phase being 180 degrees out of phase with the other phase.

This will instantly cause phase cancellations on the signals going into teh power tube grid feeds. The result of an out of phase signal hitting the power tube section would be a very weak and thin (NO BASS) tone and I am sure a comb filtering effect of the mids canceling out many of the needed mid frequencies.

The phase inverter tube because being a 9 pin triod is then used to merely invert one phase that is 180 degrees off to match the other phase so you have a balanced in phase signal hitting the power tube grids. Now you get the full bodied killer tone that would have been lost from an out of phase signal. That is why this critical tube is called the phase inverter. All it is doing is switching the phases of two signals so they are in phase when they hit the power amp section. This does effect tone however because the signal is pasing through another tube.

Sovtek and Electro Harmonix are nice choices here but try and stay to short plates. The longer the plate the better chance of it getting microphonic on your and your PI driver tube is not where you want microphonics getting into the mix of things.

Hope this helps better understand why it is a needed tube.
 
OK, so it sounds like the PI tube is really important- want a top quality tube there.

Still sounds like a basic GT might do it for the contour tube.

What are the plates in a tube? What does long plate and short plate mean?

Thanks!

:confused: :confused:
 
evink1":u8ujrmc6 said:
The contour tube is merely a tube buffered mid EQ section that is only used when the contour button is turned on for a channel. Like a sweet tube EQ section built for mid range only if you would. Very high end for such an affordable amp.

The PI (phase inverter) is what you would call a driver section. While it does have a pretty huge affect on overall tone it's primary purpose it to fix a great phenomenom that a 12ax7 or any triod tube causes.

While your signal passes through the gain stage tubes the signal is actually being changed in phase like flipping positive to negative and then back for a generic explaination of this. Well when it leaves the final gain stage and has to hit two power tube sections IE the 2 tubes for the first 50 watts adn the second two for the other 50 watts. the nature of the 9 pin triod will have one phase being 180 degrees out of phase with the other phase.

This will instantly cause phase cancellations on the signals going into teh power tube grid feeds. The result of an out of phase signal hitting the power tube section would be a very weak and thin (NO BASS) tone and I am sure a comb filtering effect of the mids canceling out many of the needed mid frequencies.

The phase inverter tube because being a 9 pin triod is then used to merely invert one phase that is 180 degrees off to match the other phase so you have a balanced in phase signal hitting the power tube grids. Now you get the full bodied killer tone that would have been lost from an out of phase signal. That is why this critical tube is called the phase inverter. All it is doing is switching the phases of two signals so they are in phase when they hit the power amp section. This does effect tone however because the signal is pasing through another tube.

Sovtek and Electro Harmonix are nice choices here but try and stay to short plates. The longer the plate the better chance of it getting microphonic on your and your PI driver tube is not where you want microphonics getting into the mix of things.

Hope this helps better understand why it is a needed tube.
Click to expand...

This is what I call a thorough explanation. :thumbsup:
 
It is, and I appreciate it! Still, it sounds like the contour tube doesn't actually affect the sound- the control does, but it sounds like the tube just powers the control. So maybe a cheaper tube can go in there. The PI tube makes sense now- that should be a tube quality tube.

Nick- I PM'd you about the footswitch if you are actually interested.

Any preamp tube recommendations?

:thumbsup:
 
I just had a nice post typed out, then it disappeared?? :confused:

Anyway, don't go with GT anything just like Rod stated above. They just label and test and charge you more. Doug will do the same and better and you will pay less.

Personally I'd go with maybe a Sovtek LPS in the PI slot, Chinese or Tung Sol reissue in V1, then just the basic Sovtek or chinese tubes for the rest. Good and reliable.

Call or e-mail Doug at dougstubes.com and he'll help you out.
 
The Contour tube will effect the sound on any channel you actually turn the contour on with. Bruce wants to offer us a very clean and smooth contour control so he chose to drive that circuit with a tube. Anytime sound passes through a tube you can bet a dollar it will change your tone.

I have to agree with not going the groove tubes route because they don't make tubes they just stamp their name on them. The last run of groove tubes that Eggie's were running were actually JJ Tesla tubes and they are being manufactured in China now.

Problem is CHina is having a hell of a time getting the black protective coating to stick to the plates and they are pealing off. This material is to extend the life of the tube but it is metal flake so it will carry high currents. Well you tell me what happens when a sliver of that metalic flake breaks off one end and comes in contact with the -45 volts of the grids. Pretty sparks in the tube and blown fuses.

Stick with Ruby, and Sovtek for sure they are Russian made and only the Russian made tubes are holding up. I talked to Jeff a while back and they were testing EL34 tubes and all were blowing up quick on them except the Ruby's.

As for what the plates are those are the thick metal looking shield type looking pieces of metal going verticle inside the tube. If you put a JJ next to like an Eloctro Harmonix tube you will see the internals are longer. They are the high voltage suckers that transfer the sound signal to the next tubes grid where it goes through the whole process again until we get the juicy sweet goodness Eggie gives us out the speakers.

OHHH the Eggie goodness !!!!!!!!! :rock: :rock:
 
I went to Doug's Tubes. Here's what he recommended, which I ordered:

V1: Input gain stages to all channels, first gain stages of clean/vintage channels (channels 1 and 2)
Ruby 12AX7AC5 slect HG+
V2: First and second gain stages of overdrive channels (3 and 4) Tung-Sol
V3: Second and third gain stages of overdrive channels Penta 12AX7M
V4: Third gain stage and cathode follower of overdrive channels Penta Labs 7025F
V5: Contour circuit buffers for overdrive channels Ruby 12AX7AC5 select HG
V6: Reverb drive and return Ruby 12AX7AC5 select
V7: Effects send buffer and effects return mixer Ruby 12AX7AC5 select
V8: Phase splitter Sovtek LPS

:rock:
 
Len Rabinowitz":3tj0bk89 said:
I went to Doug's Tubes. Here's what he recommended, which I ordered:

V1: Input gain stages to all channels, first gain stages of clean/vintage channels (channels 1 and 2)
Ruby 12AX7AC5 slect HG+
V2: First and second gain stages of overdrive channels (3 and 4) Tung-Sol
V3: Second and third gain stages of overdrive channels Penta 12AX7M
V4: Third gain stage and cathode follower of overdrive channels Penta Labs 7025F
V5: Contour circuit buffers for overdrive channels Ruby 12AX7AC5 select HG
V6: Reverb drive and return Ruby 12AX7AC5 select
V7: Effects send buffer and effects return mixer Ruby 12AX7AC5 select
V8: Phase splitter Sovtek LPS

:rock:
Click to expand...

Len
how did this turn out for you? what can you offer that this tube set gave you over the stock GT's??
 
They turned out just fine- They are still in there. Hard for me to say about differences because it has been so long since the stock ones were in there.

:rock:
 
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