Hello. I recently came across a pair of NIB Ultron 12CG7 Special Quality tubes made in West Germany.
I can’t find much info on this tube and wondering if it can be a direct substitute for 12AU7?
My amp is a Rogue Audio Hydra. I’m currently using 12BH7 tubes in it.
Would be grateful for any advice.
Thanks legends!
I can’t find much info on this tube and wondering if it can be a direct substitute for 12AU7?
My amp is a Rogue Audio Hydra. I’m currently using 12BH7 tubes in it.
Would be grateful for any advice.
Thanks legends!
Attachments
Nope.
Close but not quite - you would need to rewire the heater, and change the cathode (or plate) resistors.
12CG7 is a 12SN7 in a smaller package,
Close but not quite - you would need to rewire the heater, and change the cathode (or plate) resistors.
12CG7 is a 12SN7 in a smaller package,
The 12AU7 and the 12CG7 are worlds apart and different animals.
So no, they are not interchangeable.
So no, they are not interchangeable.
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The more I see wiseoldtech post, the most I think I'm on his ignore list 🤣
They also aren't even close to being "world's apart"... A 12AU7 and a 6C33C? World's apart - two small signal dual triodes with slightly different characteristics? Not so much IMHO. (If it IS ignoring me, this kind of response is why).
They also aren't even close to being "world's apart"... A 12AU7 and a 6C33C? World's apart - two small signal dual triodes with slightly different characteristics? Not so much IMHO. (If it IS ignoring me, this kind of response is why).
Thanks for the responses guys.
Most of the info I found about this tube was from Quicksilver amp owners, who mention swapping between the two with no issues, so surprised to hear they’re very different. What are they doing to their amps by swapping?
Most of the info I found about this tube was from Quicksilver amp owners, who mention swapping between the two with no issues, so surprised to hear they’re very different. What are they doing to their amps by swapping?
They must be rewiring the heaters at least. 6CG7 will work in a typical 12AU7 circuit but it isn't optimal.
Well, you said 12CG7. In that case it doesn't need special consideration for heater voltage.
That is, the heater gets 12V between pins 4 and 5.
My brain wasn't working properly earlier... a 6CG7 would need modifications for heater.
Assuming they use 12 volts on 4 and 5 (instead of 6 volts from 9 and 4,5) they will plug in and work. They will bias hot. There may or may not be more or less distortion, but I don't believe you will damage anything unless the heater supply can't provide the current. 12CG7 will use 300mA for the heater but 12AU7 only needs 150mA.
EDIT: /rant Magic forum software! Putting * around something make it italic! Annoying example of software thinking it knows better 🙁
It's like Autocorrect on a keyboard correcting a word you manually entered. Or Google giving search results that are missing some of the search terms! Pure idiocy created by people who don't use the internet? Makes me wonder.
/end rant
Still if you're replacing a pair of them I doubt another 300mA will be an issue... Only if the manufacturer was being cheap will it be an issue, power wise.
Just my opinion, I could be wrong.
That is, the heater gets 12V between pins 4 and 5.
My brain wasn't working properly earlier... a 6CG7 would need modifications for heater.
Assuming they use 12 volts on 4 and 5 (instead of 6 volts from 9 and 4,5) they will plug in and work. They will bias hot. There may or may not be more or less distortion, but I don't believe you will damage anything unless the heater supply can't provide the current. 12CG7 will use 300mA for the heater but 12AU7 only needs 150mA.
EDIT: /rant Magic forum software! Putting * around something make it italic! Annoying example of software thinking it knows better 🙁
It's like Autocorrect on a keyboard correcting a word you manually entered. Or Google giving search results that are missing some of the search terms! Pure idiocy created by people who don't use the internet? Makes me wonder.
/end rant
Still if you're replacing a pair of them I doubt another 300mA will be an issue... Only if the manufacturer was being cheap will it be an issue, power wise.
Just my opinion, I could be wrong.
Yes, the 6CG7 is very much like a 6SN7 in a noval bottle. Radiomuseum says that the 12CG7 is a 6CG7 with a 12V heater (here: https://www.radiomuseum.org/tubes/tube_12cg7.html).
The 12AU7 and 12CG7 pin-outs are identical EXCEPT for pin 9, which is the centre-tap of the heater on the 12AU7, whereas pin 9 on the 12CG7 is the "internal electrostatic screen".
The 12AU7 and 12CG7 pin-outs are identical EXCEPT for pin 9, which is the centre-tap of the heater on the 12AU7, whereas pin 9 on the 12CG7 is the "internal electrostatic screen".
- Pin 9 is (most often) used when the 12AU7 is set up to run its heaters at 6.3V
- If your amp is set up to run the 12AU7 heaters at 6.3V, it uses pin 9 and the 12CG7 is not a plug-and-play substitute.
- On the other hand as kodabmx put it, if your 12AU7s use 12 volts applied to pins 4 and 5, then the 12CG7s will plug in and work.
But a Rogue Audio Hydra Amplifier would be very different to "Quicksilver amp owners"amplifier
Best to get schematics for both amps and proceed with caution.
Use http://www.tubedata.org/ for data sheet mining.
And r-type.org
But of course other sites are available.
Best to get schematics for both amps and proceed with caution.
Use http://www.tubedata.org/ for data sheet mining.
And r-type.org
But of course other sites are available.
Thanks everyone. Appreciate all the replies.
By the sounds of it they may or may not be interchangeable. I’m still none the wiser. I think ill err on the side of caution and not try these tubes.
Cheers!
By the sounds of it they may or may not be interchangeable. I’m still none the wiser. I think ill err on the side of caution and not try these tubes.
Cheers!
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Plus, the operating parameters are vastly different with those tubes.
The 12AU7 is a "lightweight" type of tube, often used in those older vintage table radios and phonos.
Whereas the 'CG7'/'FQ7's are higher-current beefier tubes used as drivers with 6L6 or 6BQ5/EL84 outputs.
That Rogue amps is a "hybrid" thing with solid state outputs.
I never cared for that hybrid stuff.
Thanks wiseoldtech. I quite like hybrid amps. I run a TVC passive pre and find a class D hybrid allows me to clearly hear qualities between different tubes in it. I also have a SET 845 amp but the hybrid does rock and world music better, imho
Being a seasoned semi-retired old repair tech, I design and/or purchase my equipment around the best performance initially. - and not adhering to the "more expensive is better" tactics, because that's loaded with BS and holes too. - however the gullible and inexperienced/non-techs don't know any better.
So I'm not into all that "tube swapping-tube rolling" crap that so many seem to be attracted to.
I just want to turn the system on, and enjoy the music, not contemplating if or when it needs additional puttering with.
And I don't listen to those online "self-proclaimed gurus" that spout what they believe to others.
That's an internet madness association that I'm well aware of.
Just like those "capacitor re-capping" dudes instilling paranoia to the masses... they give me gas.
So I'm not into all that "tube swapping-tube rolling" crap that so many seem to be attracted to.
I just want to turn the system on, and enjoy the music, not contemplating if or when it needs additional puttering with.
And I don't listen to those online "self-proclaimed gurus" that spout what they believe to others.
That's an internet madness association that I'm well aware of.
Just like those "capacitor re-capping" dudes instilling paranoia to the masses... they give me gas.
Good for you old wise one. You’re obviously very sure of yourself. I hope your gas doesn’t keep you up at night 🙂
Wilsonron,
You said you are using a 12BH7 in your Rogue Audio Hydra. I hope that is what it was originally designed for.
The 12BH7 has an rp of 5300 Ohms, and a transconductance, GM of 3100 uMhos.
The other tubes mentioned in this thread as "equivalents" have rp of about 7700 ohms, and about 2200-2600 uMhos.
Even if we can forget about the different filament currents, different pinout connections, different size tube diameter, and the 9 pin Noval and 8 pin Octal socket sizes . . .
This is another case of Plug and Pray.
It is not a case of Plug and Play.
With different tube rp, and different GM, those tubes are not equivalent.
Not unless you are an experienced engineer who is going to change other circuit parts and parameters, sometimes that also require global changes through the amplifier.
I agree with at leas 99% of wiseoldtech's post above.
If you do not like the sound of your amplifier, try another make and model.
And, if you want to do Plug and Play tube rolling, do get an amplifier that has two things:
Self Bias
Tubes types that actually do have plug and play equivalents.
Just my opinions
You said you are using a 12BH7 in your Rogue Audio Hydra. I hope that is what it was originally designed for.
The 12BH7 has an rp of 5300 Ohms, and a transconductance, GM of 3100 uMhos.
The other tubes mentioned in this thread as "equivalents" have rp of about 7700 ohms, and about 2200-2600 uMhos.
Even if we can forget about the different filament currents, different pinout connections, different size tube diameter, and the 9 pin Noval and 8 pin Octal socket sizes . . .
This is another case of Plug and Pray.
It is not a case of Plug and Play.
With different tube rp, and different GM, those tubes are not equivalent.
Not unless you are an experienced engineer who is going to change other circuit parts and parameters, sometimes that also require global changes through the amplifier.
I agree with at leas 99% of wiseoldtech's post above.
If you do not like the sound of your amplifier, try another make and model.
And, if you want to do Plug and Play tube rolling, do get an amplifier that has two things:
Self Bias
Tubes types that actually do have plug and play equivalents.
Just my opinions
Since you already tried a 12BH7 I don't see why you can't try the 12CG7. McIntosh used 12AU7 and 12BH7 deliberately in different locations in many well regarded amplifiers. If a 12BH7 should have worked better in the low power applications I am sure their engineers would have used it instead of the 12au7 since they could have used anything. I don't know your amplifiers topology, but perhaps if it is different than the typical 1960s circuit that relies on the tube characteristics (ie you have a cathode follower or mild gain stage before solid state) then perhaps other tubes may work. Try a 12ax7 and 12at7 and 12ay7 while you are at it. It may not matter at all. As the others said just check the heater connections and watch the heater current.
Hi. Thanks for the input. I purchased the amp second hand with the 12BH7 tubes already in it. Previous owner had been said he’d been using them for years. I’ve continued using them with no issue.
As mentioned, I really like the sound of class d amps with tubes. I only really change tubes if I change piece of kit. Generally between brighter RCA tubes or warmer Brimars. The flexibility of being able to adjust the sound slightly is a great benefit of hybrid amps and has largely put an end to my upgrade bug.