Preamp Tubes? - Who, What, When, Where, Why, and How?

[RiverRatt]

Yeah, I guess I just wanted to hear one for myself. I'm going to have to sell off some of these V3 and V4 tubes one of these days. I'm getting a ridiculous amount of glass, most of it sitting on top of my amp waiting for it's 15 minutes of fame.

I don't know how I got started down this path, but I'm glad I did. For awhile I was hung-up on making my Les Paul sound like an old one. PAF replicas, etc. Let me tell you, I can hear a hell of a lot more difference between a smooth plate Telefunken and a JJ ECC83 than I can between a Sprague orange drop and a bumblebee tone cap in a Les Paul. Anyone who can hear the difference between tone caps has a better ear than I do. I am amazed at the lengths some people will go to for the sake of tone, and then play through an amp loaded with cheap Russian and Chinese glass.

 

[thrawn86]

OK, so I have an excuse to post in this thread legitimately:

It's an EH 12AX7....does it count if I got it surrounded by a combo? Lettering is yellow, says Made in Russia. I assume it's a standard, ordinary CP tube. Here it is peeking through the rear grille:

 

[solarburn]

OK, so I have an excuse to post in this thread legitimately:

It's an EH 12AX7....does it count if I got it surrounded by a combo? Lettering is yellow, says Made in Russia. I assume it's a standard, ordinary CP tube. Here it is peeking through the rear grille:

Hey we up in yo grill man!

Yes it is a CP 12AX7. Just for fun I would put a Tung Sol or Mullard in it and see what happens. Personally I find the EH's a tad bright in my amps as well as the HT Dual pedal I have. So pretty much the same result across 3 different circuits. Anyways in a set up like this Vox AD30VT not a whole lot of change can happen due to the design. It would be just out of curiosity or fun to see...

 

[guitarmartin416]

Ok, so I'm new to the forum today, but I come here daily to read everybodys mind, and get ideas. I am a gear JUNKIE and TONE whore!!!!! I read the first 20 or so pages of this thread, and I have an interesting situation.
Because I collect gear (to play) I have collected quite a bit of very saught after tubes I have about 40 or so '58 RCA blackplate 12AX7, and some Telefunken (mullard made) ecc83 smooth, and ribbed. I'm goin for the Dickey Betts all natural thing.
Marty, you seem to have done the most testing, what order would you recommend for V1, V2, and V3. My biggest drawback is no tube tester
And tryin to decide what power tubes, 6l6 or el34?

SOMBODY HELLLLPPPP!!!!!!! my brain is ready to explode!

 

[MartyStrat54]

Because I collect gear (to play) I have collected quite a bit of very sought after tubes I have about 40 or so '58 RCA blackplate 12AX7, and some Telefunken (mullard made) ecc83 smooth, and ribbed. I'm goin for the Dickey Betts all natural thing.
Marty, you seem to have done the most testing, what order would you recommend for V1, V2, and V3. My biggest drawback is no tube tester
And tryin to decide what power tubes, 6l6 or el34?

SOMBODY HELLLLPPPP!!!!!!! my brain is ready to explode!

Yes I am going to need help from all of the regulars, especially BLACKDOG. I looked all over for that post on your Bluesbreaker. I can't remember the preamp layout. Gee this sucks. V1A was gain and then I think it was V2A and B. Your amp has an unusual signal path. If one of the guys has a better recollection of where that post is, I will save it on my hard drive. I forgot to do that.

However, without a tester and knowing the gain of the tubes, you will have to try a Telefunken in V1 and a Black Plate in V2 and try several to see what combination sounds best to your ears. That's your only option. The Black Plates work best behind the V1 tube.

Okay, once more...where is that Bluesbreaker post. Help me!

 

[guitarmartin416]

Yes I am going to need help from all of the regulars, especially BLACKDOG. I looked all over for that post on your Bluesbreaker. I can't remember the preamp layout. Gee this sucks. V1A was gain and then I think it was V2A and B. Your amp has an unusual signal path. If one of the guys has a better recollection of where that post is, I will save it on my hard drive. I forgot to do that.

However, without a tester and knowing the gain of the tubes, you will have to try a Telefunken in V1 and a Black Plate in V2 and try several to see what combination sounds best to your ears. That's your only option. The Black Plates work best behind the V1 tube.

Okay, once more...where is that Bluesbreaker post. Help me!

I will try that.
I seem to be having issues with V1, tried 5 different tubes, and all seem microphonic. Coincidence? or is the socket bad? or could V2 tube be bad?

 

[MartyStrat54]

Well you can have 40 RCA Black Plates and a whole bunch of them can be worn out or microphonic. With tubes in place, tap on the tube lightly with a pencil. If the tube generates unwanted noise, it is microphonic. Generally, it is most noticeable in the V1 slot.

 

[guitarmartin416]

Well you can have 40 RCA Black Plates and a whole bunch of them can be worn out or microphonic. With tubes in place, tap on the tube lightly with a pencil. If the tube generates unwanted noise, it is microphonic. Generally, it is most noticeable in the V1 slot.

what I'm gettin mostly is like the tube is not seating properly. crackle if you touch it

 

[RiverRatt]

Spray some contact cleaner on the pins and work the tube in and out of the socket a few times and see if that helps. I had the same issue with an eBay tube just this week.

 

[guitarmartin416]

unfortunatly stuck home with kids, and no extra car seats, and I'm outta cleaner. lol

 

[guitarmartin416]

So I'm gonna try Tele smooth V1
RCA black V2, V3
EH balanced in PI
I think its PI there, after power tubes?

 

[MartyStrat54]

That's correct, but the PI tube doesn't have to be balanced. If that's what you got, that's fine, but you could stick an unbalanced tube in there and not tell the difference.

When you get old tubes it is best to take a small piece of ScotchBrite to the pins. If you haven't cleaned your tube sockets in a while, yes clean them. If you still have a problem with a loose tube, you will have to pull the chassis and retension the socket. If you have to do this, leave a post and I will go into detail how I do it.

 

[30stringsandblackdog]

Yes I am going to need help from all of the regulars, especially BLACKDOG. I looked all over for that post on your Bluesbreaker. I can't remember the preamp layout. Gee this sucks. V1A was gain and then I think it was V2A and B. Your amp has an unusual signal path. If one of the guys has a better recollection of where that post is, I will save it on my hard drive. I forgot to do that.

However, without a tester and knowing the gain of the tubes, you will have to try a Telefunken in V1 and a Black Plate in V2 and try several to see what combination sounds best to your ears. That's your only option. The Black Plates work best behind the V1 tube.

Okay, once more...where is that Bluesbreaker post. Help me!

Marty, was this it? http://www.marshallforum.com/workbench/9634-problems-tremolo-my-sons-bluesbreaker-ri.html

Michael is still trying to decide if he is going to bother or not...everyone said the tremolo sucks anyway! I have a Dr. Scientist Tremolessence that he borrows.

For the SL100, I'm going to try the Brimar in V1, the Ei in V2, and the BP in V3, then reverse V2 and V3. I still have the original RFT EL34s in there, and will save the Sylvanias for now.

 

[guitarmartin416]

That's correct, but the PI tube doesn't have to be balanced. If that's what you got, that's fine, but you could stick an unbalanced tube in there and not tell the difference.

When you get old tubes it is best to take a small piece of ScotchBrite to the pins. If you haven't cleaned your tube sockets in a while, yes clean them. If you still have a problem with a loose tube, you will have to pull the chassis and retension the socket. If you have to do this, leave a post and I will go into detail how I do it.

gonna try it at rehersal tonight, I'll let you know how it goes.

Thanks a bunch........so far......

 

[MartyStrat54]

Marty, was this it? http://www.marshallforum.com/workbench/9634-problems-tremolo-my-sons-bluesbreaker-ri.html

Michael is still trying to decide if he is going to bother or not...everyone said the tremolo sucks anyway! I have a Dr. Scientist Tremolessence that he borrows.

For the SL100, I'm going to try the Brimar in V1, the Ei in V2, and the BP in V3, then reverse V2 and V3. I still have the original RFT EL34s in there, and will save the Sylvanias for now.

No that's not it. It was posted on the Preamp Tube Thread. I broke down the preamp tubes for the BB.

 

[MartyStrat54]

Here it is per Jon Wilder...

The Bluesbreaker is basically an early 60s JTM-45 Tremolo in a combo cab, which is the original circuit that Marshall derived from the 5F6A Tweed Bassman circuit. The tremolo was actually Marshall's own design...or they probably derived that from elsewhere as well, but it definitely didn't come from any Fender amps that I've seen. V1's gain stages are "mixed" instead of cascaded, then they enter the gain side of V2, then directly into the cathode follower side of V2, which drives the tone stack.

Once at the phase inverter (V3), there is some gain added there as well. Not as much as in the preamp circuit mind you, but there is some gain added via the phase inverter stage.

It's the same exact circuit as a 1987 or a 1959 basically, just slightly different component values throughout. The phase inverter stage is the exact same in all of the amps, with the exception of the earlier circuits using 0.1uF coupling caps between the phase inverter and the power valves ('68 and newer use the 0.022uF here). That and the negative feedback resistor in the earlier circuits was a lower value..starting at 27K, then they went to 47K while some of the later 100 watters feature the 100K NFB resistor.

 

[RiverRatt]

Hey Marty, is this what I think it is? I can't tell if that seam is Philips or NEC. Check it out and see what you think. That's a hell of a deal if it's a Matsushita.

Radio Tubes 1 Realistic 12AX7A 12AX7 ECC83 Tube Japan

 

[MartyStrat54]

Hey Marty, is this what I think it is? I can't tell if that seam is Philips or NEC. Check it out and see what you think. That's a hell of a deal if it's a Matsushita.

Radio Tubes 1 Realistic 12AX7A 12AX7 ECC83 Tube Japan

Only one photo. Enlarged it appears to be a seam top and the plate looks like a Philips. I would say a gold pin Matsushita. They were the main supplier for Radio Shack. I've never heard of a Hitachi or NEC Radio Shack tube.

The test readings are getting toward the low end.

 

[RiverRatt]

I was wondering about the test readings. Hickock numbers seem to vary a lot from model to model. Did you notice that it doesn't have the cutouts on the plates? The Matsushitas I have coming have a cutout on both sides like Mullards.

 

[MartyStrat54]

Well what we have already discovered is that when it comes to Philips tubes, there can be no cut-outs, outside cut-outs or inside/outside cut-outs. Why? I don't know. Personally I like the idea of the double cut-outs. I think the heater would last longer in this design.