which 12ax7 for a dumblator? Cathode follower questions-LONG

[sidehatch]

Long questions-sorry.

My EH in the redplate buffer died and I want to put something in there that will last.

Im curious if you guys hear a tone change between brands in that circuit? I dont want to waste my rca's if there isnt much difference there.

Is the D* lator a cathode follower circuit? I have some of the newer tung sol's that I like but it says not for cathode follower circuits.

Lastly, which position in a typical dumble is a cathode follower?

You probably can't answer from this but I have the Carr slant 6 that Henry modded. It has 4 preamp tubes, a phase invertor and reverb tube.

The manual says V1 is the clean, v2 is the clean stage 2 and reverb return, v3 is the OD channel and v4 is the cathode follower for the OD channel.

Im not sure what the tubes control now that Henry rebuilt my OD channel but it would help to know if a dumble used a cathode follower position.

On the redplate amp it has 4 tubes , v1 PI, v2 Clean channel, v3 preamp and v4 is the overdrive .

Ill email henry too but I've been inundating him with questions and thought I'd try here first.

I just recently read not to use certain tubes there but maybe Im wearing them out too soon?

Fuchs says that the only new tube that can handle it is the cinese r9(ruby)(which I dont have)

Thanks all!!

[dogears]

I have not had a single issue ever in this circuit. I do not use the Sovtek derived tubes though.

JJ ECC83 is 100% OK. So are older RCA, GE, etc.

The Chinese Shuanguang tubes are fine. Those are the R9. Even the older r*, R7, etc are OK.

For the record, half the tube is a follower and half is a gain stage. So, the tube does effect tone considerably.

[max_lwedge]

The only CF used that I know of is in Dumbleator loop.

Most tubes that say not for use as a CF have a low heater to cathode voltage rating. The CF in a Bassman or Marshall is DC biased off the plate of previous stage, at about 180v, and that is usually pushing the limit.

OTOH, the Dumbleator CF is self biased, and the 27k or similar tail keeps the cathode at a much lower voltage. I don't know where the Red Plate design sits. Your Tungsol might do just fine.

[glasman]

I agree with the post above. You only have to start worrying when you are talking about a CF that is being used in "bassman" style tonestack. the voltages are typically in the 180 to 190 volt range on the cathode.

Any 12AX7 will work in the d-loop CF. The max voltage your are likely to see is in the 25 to 30 volt range.

Gary

[briane]

hey sidehatch....

While the EH are a good tube for these amps, their quality is a bit piecemeal. I also use EH (almost exclusively in dclones), and have seen one or 2 die within a couple of weeks of first use....Thats out of about 100 EH tubes I have gone through.

Just replace that EH with another EH and I am pretty sure you will be fine. Its likely just one of those tubes that has issues right out of the box.

Now if it happens again, then yes you need to get your tech involved.

[sidehatch]

Henry told me tonight the v1 and v2 is the same but v3 is nowpreamp level and v4 is now the overdrive stage.

So I dont have to worry about putting the wrong tube in v4.

What's funny is yeasterday, because I love the sound of the REAL redplate build I have here that uses EH's, I decided to put EH's in V1,V3 and V4 . I put a new tung sol in v2.

Fired it up today and no sound.

That freaking Tung sol died in the clean preamp stage 2 and reverb return stage (v2) in a matter of minutes.

So as much as I like the tone of those for new tubes I'll never waste $20 on one again.

So now I installed all of my old RCA's and Im rolling again with great tone.


So it sounds like I dont need to worry about the tube for the D*later even though it is a cathode follower circuit and especially the amp anymore!!!

Maybe I should put a rca,ge or syvania? I also have some nos Jan Phillips and Jan GE 12axwa's. I think I'll try some of my best tubes in there when i get a moment. Thought I do agree witth what is said about teh Eh's. Just find a good one and roll with it.

I do have some JJ's here that I never like I could try in it again. It might have been my imagination but I thought the JJ was noisy and less solid feeling/sounding.

[bluesfendermanblues]

Well, Robben Ford use EH's

[heisthl]

Well, Robben Ford use EH's

Nice catch, I'd forgotten about that photo of changing a tube in his Dumbleator.

[heisthl]

OTOH, the Dumbleator CF is self biased, and the 27k or similar tail keeps the cathode at a much lower voltage. I don't know where the Red Plate design sits. .

It uses a 1k8/27k tail.

[bluesfendermanblues]

Well, Robben Ford use EH's

Nice catch, I'd forgotten about that photo of changing a tube in his Dumbleator.

I have my moments

[bluesfendermanblues]

OTOH, the Dumbleator CF is self biased, and the 27k or similar tail keeps the cathode at a much lower voltage. I don't know where the Red Plate design sits. .

It uses a 1k8/27k tail.

Why the stray from the Dumbleators 1k5/10k?? to get less output or a higher impedance?

[dogears]

I have seen more real deal Dumbleators with 27K/1.8K than the 10K/1.5K. It increases headroom on the cathode follower.

OTOH, the Dumbleator CF is self biased, and the 27k or similar tail keeps the cathode at a much lower voltage. I don't know where the Red Plate design sits. .

It uses a 1k8/27k tail.

Why the stray from the Dumbleators 1k5/10k?? to get less output or a higher impedance?

[bluesfendermanblues]

I have seen more real deal Dumbleators with 27K/1.8K than the 10K/1.5K. It increases headroom on the cathode follower.

It uses a 1k8/27k tail.

Why the stray from the Dumbleators 1k5/10k?? to get less output or a higher impedance?

Interesting, guess I have too much faith in the schematics that can be aroung the internet.

[Funkalicousgroove]

Well, Robben Ford use EH's

That photo is a decade old, robbens stuff has JJ's in it fwiw.

In my opinion, the BEST tube for a Dumbleator is a 1950's square getter sylvania/westinghouse, I have seen a Dumbleator with that very tube in it with a note from Alexander that said "DO NOT CHANGE TUBE" nuff said

[sidehatch]

Thats intersting about the square getter sylvania.


In general, in the D*lator, Do you guys like a bright tube like the EH (which sounds both hot and bright to me, Its probably 20% hotter than my other tubes) or do you like something more along the lines of a dark tube like the RFT or similar?

Besides a tube being bright or dark, breakup early or late, being loud, quiet or average, the only other tube quality that I'm sure I can hear is whether a tube has a lot of fundamental harmonic content or more non- fundamental harmonic content and it seems to me that the tubes that are closer to being microphonic have more non fundamental content.


On other forums, I hear guys go on with about 50 different adjectives decribing tube sound but honestly ,I can truly only hear those 3 or 4 things I described.

I'd imagine in a D*lator you'd want something loud,late break up,fairly bright and with a lot of fundamental harmonic content which to me says a tube like the EH or RCA, sylvania and even JAN GE or JAN phillips rather than tubes that provide a lot of charachter on their own. I have found that the new Tung-sols sound good in amps but are dark and loud tubes to my ears but the fact that a new one quit turns me off.

Am I close on this theory or off regarding D*lators?

quote="Funkalicousgroove"]

Well, Robben Ford use EH's

That photo is a decade old, robbens stuff has JJ's in it fwiw.

In my opinion, the BEST tube for a Dumbleator is a 1950's square getter sylvania/westinghouse, I have seen a Dumbleator with that very tube in it with a note from Alexander that said "DO NOT CHANGE TUBE" nuff said [/quote]