Two Matched PAIRS instead of matched QUAD in AD30

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ArtyArson
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Two Matched PAIRS instead of matched QUAD in AD30

Post by ArtyArson » Wed Oct 18, 2017 9:32 am

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 :((

Les Paul Lover
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Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by Les Paul Lover » 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.
Ant

Orange Gear: RV50 MKI, R30, AD15, PPC212
And.... Genz Benz Black Pearl 30
Past Orange: AD30TC Combo, TT, AD5


Guitars: Gibson Les Paul Standard Faded, Vigier Expert Retro 54, Gibson SG 70s Tribute, Aria Pro II RS X80, G&L ASAT Special Tribute

Jondog
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Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by Jondog » 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.
Image

Les Paul Lover
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Posts: 6821
Joined: Tue Aug 18, 2009 9:08 am
Location: Derby, England

Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by Les Paul Lover » 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?
Ant

Orange Gear: RV50 MKI, R30, AD15, PPC212
And.... Genz Benz Black Pearl 30
Past Orange: AD30TC Combo, TT, AD5


Guitars: Gibson Les Paul Standard Faded, Vigier Expert Retro 54, Gibson SG 70s Tribute, Aria Pro II RS X80, G&L ASAT Special Tribute

Jondog
Duke of Orange
Posts: 7234
Joined: Thu Aug 21, 2008 12:16 pm
Location: Ontario, Canada

Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by Jondog » Wed Oct 18, 2017 4:13 pm

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
Image

bclaire
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Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by bclaire » Wed Oct 18, 2017 7:13 pm

No bias adjustment necessary.

fiveightandten
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Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by fiveightandten » 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.
Image
'71 GRO100 || '96 OR-80 || AD30 || '64 AC-50 || AC-30TBX || Hiwatt DR504 || HI-TONE HT30
LP Standard || LP Studio || LP Custom Lite || Ric 620 || Ric 360 || MIA Tele || SG 61 RI

ArtyArson
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Joined: Tue Dec 06, 2016 10:45 am

Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by ArtyArson » 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

Les Paul Lover
Duke of Orange
Posts: 6821
Joined: Tue Aug 18, 2009 9:08 am
Location: Derby, England

Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by Les Paul Lover » Thu Oct 19, 2017 8:34 am

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.
Ant

Orange Gear: RV50 MKI, R30, AD15, PPC212
And.... Genz Benz Black Pearl 30
Past Orange: AD30TC Combo, TT, AD5


Guitars: Gibson Les Paul Standard Faded, Vigier Expert Retro 54, Gibson SG 70s Tribute, Aria Pro II RS X80, G&L ASAT Special Tribute

fiveightandten
Orange Master
Posts: 3845
Joined: Sat Apr 05, 2003 6:18 pm
Location: Connecticut, USA

Re: Two Matched PAIRS instead of matched QUAD in AD30

Post by fiveightandten » Thu Oct 19, 2017 4:08 pm

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.
Image
'71 GRO100 || '96 OR-80 || AD30 || '64 AC-50 || AC-30TBX || Hiwatt DR504 || HI-TONE HT30
LP Standard || LP Studio || LP Custom Lite || Ric 620 || Ric 360 || MIA Tele || SG 61 RI

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