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Post subject: wrong tube?
Posted: Thu Mar 11, 2010 7:36 pm
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Hi, just got in,via, our beloved ebay, A 12AU7 tube, by thier mistake! I wanted a 12AX7!! paid decent $$$ for it because it is a RCA 1960's old /new tube, grey plate, low noise, and supposidly tested before shipment. Anyways, can I use this tube in a twin, or old champ? You know, instead of shipping the friggin thing back??? thanks again! Ricstar


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Posted: Thu Mar 11, 2010 7:56 pm
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If it's their mistake why not just get them to replace it with the right tube?

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Posted: Fri Mar 12, 2010 3:44 am
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Different gain level used more in base amps.

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Posted: Fri Mar 12, 2010 4:32 am
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This tube is not useful for a amp, gain too low .

Send it back


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Posted: Fri Mar 12, 2010 6:20 am
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I have tried them in different slots...the others are right,low gain.
Now,a couple of weeks ago an amp tech told me it can be used in the reverb driver socket to tame down overly "surfy" reverb...I haven't tried it but will sometime,the reverb on my amps is intense to say the least.


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Posted: Fri Mar 12, 2010 7:36 am
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stratele52 wrote:
This tube is not useful for a amp, gain too low .

Send it back


They are used and designed for amps. Not everyone looks for more gain. The 12AU7 is very quiet and has very low microphonics. If you're looking for gain it's the wrong tube. I use a NOS JAN Phillips 5751 in V1 to tame the gain in my Egnater Rebel. The gain sounded great and well defined in my amp, but I don't do that style of music. So the trade off was less gain, but creamier more defined, smoother natural distortion. It's not a huge difference, but just enough to make me happy. It's just a matter of taste and the style of music you play.

I agree though, if you don't like it, tell them to make it right.


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Posted: Fri Mar 12, 2010 8:50 am
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63supro wrote:
stratele52 wrote:
This tube is not useful for a amp, gain too low .

Send it back


They are used and designed for amps. Not everyone looks for more gain. The 12AU7 is very quiet and has very low microphonics. If you're looking for gain it's the wrong tube. I use a NOS JAN Phillips 5751 in V1 to tame the gain in my Egnater Rebel. The gain sounded great and well defined in my amp, but I don't do that style of music. So the trade off was less gain, but creamier more defined, smoother natural distortion. It's not a huge difference, but just enough to make me happy. It's just a matter of taste and the style of music you play.

I agree though, if you don't like it, tell them to make it right.

63supro you should try the TAD 7025 in place of the Jan 5751 they are even better.

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Posted: Fri Mar 12, 2010 9:14 am
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Already did. That's how I wound up with a 5751. It pretty much depends on the amp design itself and your ears. My Egnater has both EL84 and 6V6 power tube that can be blended to any degree or in individual sets so the natural distortion has a really wide pallet. To complicate matters even further, the watts control changes the headroom of the amp. Tonally, the Egnater is way different from any Fender I've ever owned. Every time you turn the dials, you get something new and different, but somehow familiar too. Weird stuff. There was a lot of trial and error but I have a lot of old tubes laying around. SlapChop actually told me about the 5751 and he was totally correct. I tried it and totally dug it as soon as I started playing it.


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Posted: Fri Mar 12, 2010 12:03 pm
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My answer was about ricstar question :

He ordered 12AX7 and receive 12AU7

12AX7 have gain of 100
5751 " " 70
12AT7 " " 60
12AY7 " " 45
12AV7 " " 41
12AU7 " " 19 (!!!!!)

The firsts 4 tubes are often use in major amps

The 2 last tubes are almost never use.

So if ricstar is not a tubes amps builder, he don't need the 12AU7


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Posted: Fri Mar 12, 2010 10:59 pm
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Ric, I'd send it back and get a refund, if possible. Mistakes happen, but for a vendor to claim testing and to send you the wrong RCA, would make me wonder just how carefully things are done at their end. The 12AU7 is a good tube, but I doubt you need it. Actually, I use a RCA 12AU7A in a '68 Bassman, but I've tweaked the circuit, making it very useful. BTW did the tube come in the RCA box? Art

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Posted: Sat Mar 13, 2010 1:08 am
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63supro wrote:
Already did. That's how I wound up with a 5751. It pretty much depends on the amp design itself and your ears. My Egnater has both EL84 and 6V6 power tube that can be blended to any degree or in individual sets so the natural distortion has a really wide pallet. To complicate matters even further, the watts control changes the headroom of the amp. Tonally, the Egnater is way different from any Fender I've ever owned. Every time you turn the dials, you get something new and different, but somehow familiar too. Weird stuff. There was a lot of trial and error but I have a lot of old tubes laying around. SlapChop actually told me about the 5751 and he was totally correct. I tried it and totally dug it as soon as I started playing it.
Egnater are good amps and I know what you mean about sound discoveries as you play with the dial set much like Budda and a few others out there.

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Posted: Sat Mar 13, 2010 7:26 am
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stratele52 wrote:
My answer was about ricstar question :

He ordered 12AX7 and receive 12AU7

12AX7 have gain of 100
5751 " " 70
12AT7 " " 60
12AY7 " " 45
12AV7 " " 41
12AU7 " " 19 (!!!!!)

The firsts 4 tubes are often use in major amps

The 2 last tubes are almost never use.

So if ricstar is not a tubes amps builder, he don't need the 12AU7


The 12AU7 is used by lots of musicians that I know in many different amps to modify the tone and gain to their liking. Not all "major amps" are necessarily the best sounding amps. :wink:


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Posted: Tue Mar 16, 2010 5:53 am
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63supro wrote:
stratele52 wrote:
My answer was about ricstar question :

He ordered 12AX7 and receive 12AU7

12AX7 have gain of 100
5751 " " 70
12AT7 " " 60
12AY7 " " 45
12AV7 " " 41
12AU7 " " 19 (!!!!!)

The firsts 4 tubes are often use in major amps

The 2 last tubes are almost never use.

So if ricstar is not a tubes amps builder, he don't need the 12AU7


The 12AU7 is used by lots of musicians that I know in many different amps to modify the tone and gain to their liking. Not all "major amps" are necessarily the best sounding amps. :wink:
Exactly,I've heard an old Bogen PA head that sounded great for slide mid range tones...most people don't even know what they are.
In the past I bought all the tubes I could find that could be swapped in the amps I own and also others that could be used in amps I didn't own.You never know when you might find a beat up old amp that can be serviced to sound great.


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