• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Found a box of various 9 pin tubes....

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mondogenerator

mondogenerator

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Joined 2009
#1
Hi.

I have found some old tubes:

2 of 12ax7/ecc83 (brimar and mulled 70''s era)
2 ecc88
2 ecl83

Now I am aware that the first on the list are commonly used for input stages of guitar amplifiers amongst other things.

I am also aware that the others are UHF types (or at least one of them is)

But can they be turned to AF use?

Can anyone offer any advice/links to projects using these tubes?

Many thanks in advance for any help you folks can give an SS guy like me.
 
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#3
You can make a complete audio power amplifier with just that ECL83!
ECC88 is also usable for audio.

Can anyone offer any advice/links to projects using these tubes?
Click to expand...
Asking this is like asking what can you build with BD139 or BC547. What do you want to build? Perhaps guys here can then conjure a schematic using those tubes.
 
#4
Im hoping to build a small simple amplifier, likely a couple of watts, just enough for a small speaker. Mainly just for kicks. I may also have a couple of transformers, though once ive removed them ill know more about them (I suspect one is for the B+ but the others may be useless (I salvaged these partd from old instrumentatiom so any OPT is likely very low rating.

Thanks Jon,

I will check those links out when I get back to my desktop-I have some info from the valve museum but I'm sure it lacks app ccts, like so many IC datasets possess.

I'm currently trawling second hand bookshops for valve books to help me out.

Ball pencil,

Yes I agree that it's a dumb question (currently reading the mullard SS amplifier book and trying to find equivalents for the old AC*** output transistors (bc547, bd139 and 2n3055 look like likely candidates )
 
#5
The ecc88 is a 'nicer' 6dj8 type tube. Popular for audio preamp where not a lot of gain is needed.

Morgan Jones' books are good.

And yeah, you can build a small amp adequate for near-field (or horn-loaded) with just the ecl83 pair.
 
#9
Thanks Tom,

In the limited time I have had so far, I have compared the ecc83 and ecc88, and my conclusions were similar (although I'm still a beginner ).

The ecc83 being old stock brimar and mullard brands are likely to get tested in the V1 position in my guitar head amplifier (perhaps, assuming they have life left in them, they may be comparable to the GE tubes that are currently in place). If there is really all that much perceived difference between these 70s era tubes and the 80s GE types.

Besides that I have read the ecc83 isn't particularly linear, and a bit weedy for a driver stage, so I was hoping the ecc88 was an improvement in both areas.

I'm not sure I really have a use for the ecf80, and i dont think i will need the gain of athe pentode half, so I may sell these on cheap, with the caveat that I don't know if they are functional (filaments are ok but that's all I can tell)

Thanks all for the help so far.

I think I might be catching the 'bug' 🙂
 
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#11
Too many options!!!

This idea to use these salvaged tubes was spawned by my desire to build a small ~10W amplifier (stereo would be nice but I'm taking baby steps).

To this end I have several options, mostly SS, but I've not built a tube amp before and it has a certain appeal.

1/ TDA2004 amplifier (I have loads of chip amps already lol )

2/ something discrete with the help of the mullard transistor audio amplifier book I was recently gifted.

3/ a tube amplifier using these salvaged tubes, and a couple of salvaged 6L6GC I also have laying around.

I like option 3 most at the moment, in all ways except the necessity for Iron!

I'd really like to use the mazda 1505 one day, when I can build enough stages to drive it!
 
#12
It's not that ECC88 is somehow 'better' than ECC83. They're both good (or bad) in different ways.

ECC88 has a lower plate resistance, lower gain, runs at higher current.

ECC88 has a much higher plate resistance, high gain, runs at very low current for a vacuum tube.

ECF80 is a combination triode-pentode in one envelope. That can be used for quite a lot of different projects too. Maybe even an RIAA preamp. The triode looks like it has a plate resistance of about 4k ohms, amplification factor of about 20, transconductance of about 5mA/V. That's not all that far from ECC88, come to think of it. The pentode part looks like it could be fun to work with. It would make a reasonable input voltage amp and phase splitter for a push-pull amplifier with 6L6 outputs.

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