Orange Amps Forum

Hi there!
Need your advice. Can two matched pairs of el84 from the same tube batch (Sovtek) be used in power-amp of AD30? Which is the correct way to install theM: 1-2-2-1 or 1-2-1-2 ?

Thank you!!!

P.S. I've ordered a quad beforehand, but the delivery got stuck for much longer time, than expected, and I've got concert tomorrow (

How big is the mismatch between the matched pairs?

In any case, I think you will be fine, but would recommend your approach re: 1221 / 1212.

I think it's the first config, but wait for confirmation from someone else.

Les Paul Lover wrote: ↑

Wed Oct 18, 2017 10:42 am

How big is the mismatch between the matched pairs?

In any case, I think you will be fine, but would recommend your approach re: 1221 / 1212.

I think it's the first config, but wait for confirmation from someone else.

Either is good. Good idea to label the pairs to avoid confusion.

Jondog wrote: ↑

Wed Oct 18, 2017 11:44 am

Les Paul Lover wrote: ↑

Wed Oct 18, 2017 10:42 am

How big is the mismatch between the matched pairs?

In any case, I think you will be fine, but would recommend your approach re: 1221 / 1212.

I think it's the first config, but wait for confirmation from someone else.

Either is good. Good idea to label the pairs to avoid confusion.

Is the cathode bias done on each individual valve or by pair?

Les Paul Lover wrote: ↑

Wed Oct 18, 2017 12:17 pm

Jondog wrote: ↑

Wed Oct 18, 2017 11:44 am

Les Paul Lover wrote: ↑

Wed Oct 18, 2017 10:42 am

How big is the mismatch between the matched pairs?

In any case, I think you will be fine, but would recommend your approach re: 1221 / 1212.

I think it's the first config, but wait for confirmation from someone else.

Either is good. Good idea to label the pairs to avoid confusion.

Is the cathode bias done on each individual valve or by pair?

Pair

No bias adjustment necessary.

If the mismatch is large enough, the pair drawing more current could self destruct and see a premature death. But if the pairs are in the same ball park you're probably fine. Look for any visible red plating in low light and if you don't see any, you're probably ok to run them.

Mind you, a quad of EL-84s is pretty cheap, and the AD30 has pretty low headroom to begin with. I think you'd be best served by getting a matched quad in there.

fiveightandten wrote: ↑

Wed Oct 18, 2017 10:17 pm

If the mismatch is large enough, the pair drawing more current could self destruct and see a premature death. But if the pairs are in the same ball park you're probably fine. Look for any visible red plating in low light and if you don't see any, you're probably ok to run them.

Mind you, a quad of EL-84s is pretty cheap, and the AD30 has pretty low headroom to begin with. I think you'd be best served by getting a matched quad in there.

The seller says that the tubes are from one factory batch and the difference wouldn't be too big. Sure, a match quad is the normal solution. As I said, I've ordered a quad beforehand, but the delivery got stuck, so I was in search of temporary option (ALL quads are sold out in the city LOL).

Thank you all very much for response!! I've found the main board schematics, according to this which would be appropriate pair placement?

http://www.prowessamplifiers.com/schema ... board.html

2 things:

1) if valves coming from the same manufacturing batch were all in the same ballpark, we wouldn't have the issues with valve matching we have these days. Are the pairs you have actually graded?

2) from the schematic, it looks like 1122 arrangement. I'd like to see the PCB to confirm though. I think the cathode resistor (fixed bias) is linked to pin 3 on EL84, and here R29 is connected to V4 & V5, R33 to V6 and V7. Wait for someone else to confirm though, I'm very much a hack.

ArtyArson wrote: ↑

Thu Oct 19, 2017 8:02 am

fiveightandten wrote: ↑

Wed Oct 18, 2017 10:17 pm

If the mismatch is large enough, the pair drawing more current could self destruct and see a premature death. But if the pairs are in the same ball park you're probably fine. Look for any visible red plating in low light and if you don't see any, you're probably ok to run them.

Mind you, a quad of EL-84s is pretty cheap, and the AD30 has pretty low headroom to begin with. I think you'd be best served by getting a matched quad in there.

The seller says that the tubes are from one factory batch and the difference wouldn't be too big. Sure, a match quad is the normal solution. As I said, I've ordered a quad beforehand, but the delivery got stuck, so I was in search of temporary option (ALL quads are sold out in the city LOL).

Thank you all very much for response!! I've found the main board schematics, according to this which would be appropriate pair placement?

http://www.prowessamplifiers.com/schema ... board.html

The right pair is grounded together and the left pair is grounded together. 1221 or 1212. Check for any visible red plating in low light while playing at the volume you will be playing at.