Help with Tubes in AD30HTC

[Mike7300]

Hi,

How can I tell which tubes run channel 1 vs channel 2. I am asking because I would like to buy new tubes but only for channel 1, as I use that channel 99% of the time. Keep in mind I am relatively new with tubes. Thank you!

[Les Paul Lover]

The EL84, the rectifier gz34 and the ECC83 used for the PI (phase inverter) are for all channels.

Then you have 2 more ECC83, one for each channel.

To be honest, you could perhaps spare yourself the expense of that valve, but valves tend to wear out at the same rate, regardless if whether you use that channel or not, and failure of any of those valves will probably pop the fuse and render your amp unusable.

On a side note, ECC83 usually last 3 to 5 time as long as the EL84.

[Mike7300]

ok thanks for the info! I have never changed tubes so I am sure they all do need to be changed.

So say I do want to replace all tubes, but not spend as much on tubes that effect only channel 2. Basically I would only be talking about 1 ECC83 preamp that effects only channel 2? All the other 8 tubes effect both channels?

Based on research I was thinking to get NOS JAN GE, Sylvania or Phillips 5751s for preamps.

[fiveightandten]

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-Nick

[Les Paul Lover]

download/file.php?id=467

-Nick

That's for the AD30r I believe.

[fiveightandten]

download/file.php?id=467

-Nick

That's for the AD30r I believe.

Look again, at the top of the diagram.

-Nick

[Les Paul Lover]

download/file.php?id=467

-Nick

That's for the AD30r I believe.

Look again, at the top of the diagram.

-Nick

Doh!!!

Funny, I assumed the 4 valves at the top represented the EL84.

I forgot the AD30HTC has a phase inverter per channel..... I wasn't expecting to see that.

So I was wrong - each channel has 2 dedicated ECC83.

[fiveightandten]

Doh!!!

Funny, I assumed the 4 valves at the top represented the EL84.

I forgot the AD30HTC has a phase inverter per channel..... I wasn't expecting to see that.

So I was wrong - each channel has 2 dedicated ECC83.

Yup! Each channel has one 12AX7 for the pre-amp and one 12AX7 for the long tail PI circuit. I'm not sure why the PI circuits are separate, because they're dead on identical.

-Nick

[Mike7300]

So if I want to change tubes effecting only channel 1, I would change the 4 power tubes, and 2 of the preamps?

[fiveightandten]

So if I want to change tubes effecting only channel 1, I would change the 4 power tubes, and 2 of the preamps?

That is correct. And the rectifier tube. Although the rectifier tube is not in the signal path, I would recommend changing that. Modern rectifier tubes are garbage, and they like to short and pop fuses at the most convenient of times.

-Nick

[jontheid]

I'm not sure why the PI circuits are separate, because they're dead on identical.

I always thought it is so you can have two separate post-phase inverter master volume controls.

[Les Paul Lover]

I'm not sure why the PI circuits are separate, because they're dead on identical.

I always thought it is so you can have two separate post-phase inverter master volume controls.

And it all makes sense now..... Thank you!!!

[fiveightandten]

I'm not sure why the PI circuits are separate, because they're dead on identical.

I always thought it is so you can have two separate post-phase inverter master volume controls.

Yes...doh! That makes perfect sense.

-Nick