No matched quad, but 2 matched pairs

[VanR]

So I am going to change out the stock power tubes in my DSL100H. So in my tube drawer I have 2 matched pairs of Valve Art EL34B's I got from AES. One with 27 on the sticker, the other 29. So given that the DSL100H has 2 bias pots I should be able to set the bias on each set individually to match. Question is in what order do I install the tubes? If the power tube sockets are 1 2 3 4, do I put one matched pair in 1 and 2, and the other in 3 and 4?

 

[Woods]

That's what I'd do.

 

[danfrank]

27 vs 29 is very little difference; especially since you can adjust each side with the 2 bias adjustments. Put each matched pair together like the other guy said, and even the sides out with the 2 bias pots. When you have parallel push pull operation like in a 100 watt amp, it is much more important to have each of the tubes on the same side matched and operating evenly, so one of the two tubes isn't doing all the work and the other one is just coasting along.

 

[Jethro Rocker]

Isn't the 100H the same as most Marshalls where the pairs are 1,4 and 2,3?? Inner and outer pairs?

 

[Micky]

V5+v7 & v6+v8

 

[NewReligion]

As long as they're close in matching I have often used two different types of output tubes in order to achieve two sets to develop a fuller frequency coverage on the output section. The important thing to know is one set should be the outside set of tubes (1&4) and the other set should be the two inside tubes (2&3)...

Bias to the pott bias to the higher burning set of course.

 

[Matt_Krush]

Match 1 & 4 and Match 2 & 3

 

[johan.b]

As long as they can all be biased within 55-65 % of max dissapation range, you'll be fine..if they are too far appart, you might get hum (or rather lack of hum cansellation) but basicly, Matched output tubes is something that is post seventies. Think of all the marshalls, fenders, oranges, traynors and so on, built before "groove tubes" convinced everybody we MUST match our tubes...
j

 

[Ken]

Match 1 & 4 and Match 2 & 3

That will only work well if all 4 are matched. Remember, even though the tubes are paired to each other as you state, the sides also have to be matched and you're biasing each side together. This is as VanR and danfrank suggested. Put a matched set in 1&2 and the other in 3&4. This way each side will be working together with both themselves, and the other side as well, once you adjust the bias higher or lower to even the sides out.

Of course, the best solution is to buy a matched quad to begin with.

Ken

 

[Micky]

That will only work well if all 4 are matched. Remember, even though the tubes are paired to each other as you state, the sides also have to be matched and you're biasing each side together. This is as VanR and danfrank suggested. Put a matched set in 1&2 and the other in 3&4. This way each side will be working together with both themselves, and the other side as well, once you adjust the bias higher or lower to even the sides out.

Of course, the best solution is to buy a matched quad to begin with.

Ken

With the new DSL100h you can get away with matched pairs. There is a separate bias control for each side.

 

[Jazz P Bass]

Way, way, way too much discoarse about bias.

And to think Leo & Jim got away with set & forget.

 

[Ken]

With the new DSL100h you can get away with matched pairs. There is a separate bias control for each side.

Each pair, or each side? If it's each pair, 1&4 and 2&3 will work, if it's each side you still want 1&2 matched, and 3&4 matched.

Ken

 

[Ken]

Way, way, way too much discoarse about bias.

And to think Leo & Jim got away with set & forget.

Leo and Jim had much better consistent quality tubes to build amps with! These days, you can easily red plate a tube if you match it with a much lower value tube, as tubes today can be all over the place.

Ken