Tube Recommendations?

[Jaicen]

Hi, it's me again!

I'm trying to decide which tubes to use in my first amp (Blackface Champ). I don't want to spend mega money on the tubes to begin with, just in case I mess up and cook something. But because there's only two tubes in there, I want to make sure I get it right! Obviously I plan to try out different tubes at a later date, but I'll have to live with the first set for a while.
I'm looking for a tube combo that wil give me that nice warm Fender clean sound, has a gentle early break-up but keep its definition when overdriven (Think Red House).
So, i'm thinking the Harma STR ECC83 would be a good choice paired with the JJ Tesla 6V6?? Would anyone disagree with that choice?

[stokes]

If $$ isnt a big problem I would suggest going for NOS tubes in that amp,after all there are only 3 tubes there.In mine I have a NOS RCA 6V6,an RCA 7025 and I changed the rectifier to a 5V4,I like the little bit of extra volts I get with the 5V4,a slight improvement in headroom,but is a little tighter when it does break up.

[Jaicen]

Unfortunately, money is something of an obstacle.
I did find some nice looking NOS valves from the 60's for sale in the UK, but they're £25-30 each, as opposed to £10 for the modern equivalents. As I said, this is my first amp so I don't want to use up some valuable old valves if I make a mistake.
My plan is to get a good sounding set of valves when I build it, live with them for a while and then see how I like the sound. Obviously i'd like some NOS RCA's, but they're pretty spendy!

[MWJB]

The Harma STR ECC83 & JJ 6V6 tubes will be fine.

[Jaicen]

I'm sure they'll be fine, but will they be Great?! Hehe, seriously thanks. I was pretty sure that was the way forward anyway, just wanted to get the thumb up from someone who knows better than me.

[stokes]

I am not familiar with the Harma,but if you want "Great" then NOS is the way to go.But this topic is totally subjective,what sounds good to me could be miles from what sounds good to you,since it is your first amp,you dont have much to compare it to,so the JJ and Harma will be fine to start with.I personally dont like the JJ 6V6 but there are many people who do.If I read your second post right you are building this amp,is that right?If so you will be so thrilled with it when you first fire it up and it actually works,the tubes wont make much of a difference anyway.Good luck with the project.

[Rob Mercure]

Jaicen,

How are your soldering skills? If I had to pick an amp whose sound is the most dependent on the output tube it would be the Champ - and I completely agree with Stokes about NOS tubes. But if you've got the skills to solder up an adapter - or three- to use miniature tubes there are lots of cheap - at least in the states - NOS options as the 6V6 characteristics were duplicated in several miniature tubes. First off there is the venerable 6AQ5 - your equivalent being the EL90 - which is a 7 pin miniature. While the common 6AQ5 would work well there are some industrial types that are a bit hardier - the 6004, 6094, and the higher rated 6095 which also probably have European equivalents. Then in 9 pin miniatures there's the 6CM6 and the 12AB5. I'm not sure that there are European equivalents but you could do some research. The 12AB5 needs 12.6 V for the heater but if your soldering/crafting skills are good enough your can cobble up a voltage doubler in the adapter (I did this a few years ago but it did take a while figuring out the how to get the largest value caps in the old tube base that I used). Oh, yeah, and then there's the Locktal 7C5 - I've never made a Locktal adapter but it shouldn't be problem.
So you've got four additional options if you like cobbling up adapters (hmmm, I guess I kinda "specialize" in this -ah well, we each have our oddities <grin>).
As far as the sound of these valves go there's no more variation between the sound of a 6AQ5 and a 6V6 than there is between 6V6s of various manufacturers and vintages and the same hold true for the other two miniatures (although I have used far more 6AQ5s over the years than the others as I've got scads of them - even a Telefunken EL90/6AQ5 new in the box).

Rob

[stokes]

Or you could just shell out the 30 pounds for a good NOS tube,it'll probably outlast 3 JJ's at 10 pounds ea.Besides,a month after you finish it and play it a while with the JJ, you are going to buy the NOS tube anyway,because everybody is going to tell you how much better it will sound with one,and you're just gonna want to hear for yourself.Rob,thats a good idea,must be a lot of killer tubes out there to be had for cheap,if your willing to make adapters or rewire.I gotta try that 6AQ5,I think I got a couple in a box with a bunch of "non-guitar amp" tubes.

[Rob Mercure]

Stokes,

Yeah, the 6AQ5's a rugged little bottle and the only reason that I can think of that they more weren't used more in MI amplification is the fact that they are a little "puny" looking and that the 6BQ5 was probably not that much more expensive (hmmm, must consult my old tube price lists). And after posting, while trying to get to sleep last night, I was "reviewing" my memories of TV servicing in the early 1970 when tubes still reigned ("the king is dead, long live the king") and I really don't remember replacing many 6AQ5s - not as many as 6V6s but obviously the samples are poor as well as my memory being a great record <grin>. But I remember a "conversation" on Ampage in the late 1990s with Doc Horner, I believe, about an amp that I had "reconstructed" using the 6005 variant. "Reconstructed" cuz I rebuilt an amp taken from a military film projector into a better "guitar" chassis and somehow managed to change the bias so that the PP pair of 6005s were dissipating over 15W each - for a 12W rated bottle. But since they weren't red-plating I just added fan cooling and just ran the amp like that for a year or so playing it on and off, sometimes for hours on end, with no 6005 degredation despite the grueling "punishment." Again, these were JAN upgraded 6005s but they still looked "teenie." I'll have to drag the chassis out and play with it again sometime.
Of course the 6CM6 looks more "stately" and cuz I've "inherited" a bunch of commercial phonos using these bottle I've had lotsa chassis to experiment with and I really like 'em a lot. Less experience with the 12AB5 - only one amp actually - but I was pleased.
Guess I'm just "cheap" - I won't buy a tube if I've got a reasonable "equivalent" - and there really are scads of great BPTs and pentodes setting in old tube caddies that easily equal current production tubes (and I'm only referring to the "audio" types - vertical, horizontal, and video output tubes, video especially, provide an entire 'nother "palette" to play with).

Rob

[Jaicen]

Thanks for the suggestion, but I don't think i'm quite brave enough to go building adapters just yet. I'm not inexperienced with electronics, but this is my first amp so i'm going with the KISS philisophy
I'll definitely upgrade to a NOS set at some point (mmmmm Mullards...), but I want to run the amp for a bit to iron out the creases before getting spendy with the tubes.

[Rob Mercure]

Jaicen,

I assume that we're referring to the same Champ with the long sting of posts under Guitar Amps Theory and Design? Anyway, as you've noted there the amp will cost a bit more why not, if you've got the chassis "real estate," add a seven pin minature socket on the chassis for the EL90? Carefully placed it wouldn't be noticable at all and this would give you the option of trying NOS valves. The cost of the socket should be less than a couple of US dollars (I'm too lazy to convert to Euros, sorry) and you can even use a separate cathode bias resistor and bypass cap to match the EL90 more specifically (if necessary) and/or tailor the stage frequency response such as putting a 20uf cap on the 6V6 socket and a 5 or 10uf on the EL90. Seems like it offers the best of both worlds without making an adapter.

And to tease and torment you further, if you've got a hefty enough tranny pair with multiple OT secondaries you could run both at once in parallel for more power and a "third" sonic signature (you need multiple secondaries cuz that's how you'd match the impedance for two tubes in parallel).

Rob

[Jaicen]

Yeah i'd thought of that actually. Well, actually I was looking on AX84, one of the schems showed a dual 6L6/EL84 output stage, but only one was available at once.
If I had two OT's, could I run the amp with an EL34 type and a 6V6 at once??
With regards to the 9-pin tubes, where would I look for info on them?

[stokes]

You could run two different output tubes in parallel thru the same OT.I did it with a 6V6 and EL84.Although it may not be an "ideal" impedance match for the OT,what I did was run a signal thru the amp and scoped the output across 4,8,and 16 ohm dummy loads and picked the one with the best waveform on the scope.16ohm gave the most efficient output.

[nico.verduin]

For Data specs about Tubes check www.duncanamps.com. For supplier specific data check the suppliers themselves.

[corwin81]

what is the difference in the bottle sizes of the 6cm6 tube>?