Few questions about 2 channel Triple Recto

[Werihukka]

I got my Triple Recto a while ago and now I have few questions about it.

I have to change the power tubes and it has STR 420's in it. Can I buy a pair of 440's and use them with those 420's?

Also, how are the power tubes set in pairs? Are they like A-B-C-A-B-C or A-B-C-C-B-A? (same letters are pairs) It would be nice to know before doing anything with it. This is my first tube amp after all.

 

[Platypus]

Do the 420's need a changing? I think you'll like them a lot more than the 440s if not...

And your pairs were your latter guess.. A-B-C-C-B-A

 

[Werihukka]

One of the power tubes was damaged during delivery from Germany and now it needs to be changed.

Thanks for the info. This helps me alot.

Edit: I guess they don't make 420's anymore, do they? I haven't seen any.

 

[Werihukka]

A-B-C-C-B-A

Yet one more question: Do I have to set the bias again if I take those "A"-tubes out and make the amp 100W?

 

[Platypus]

A-B-C-C-B-A

Yet one more question: Do I have to set the bias again if I take those "A"-tubes out and make the amp 100W?

Mesa amps are fixed bias unlike a lot of tube amps out there so there's no need to bias anything as long as you put tubes in it that are within the fixed bias range. I would make sure you know which pair to take out to run it at 100W.. you most likely will have to pull a rectifier tube as well and also change the ohmage of your speakers too.

Call mesa and ask them which pair to pull and which recto tube to pull to be absolutely sure. I will tell you that you're not going to really benefit much from doing this but don't let that stop you, just my two cents.

 

[Werihukka]

Ok, thanks a lot.

I think I'm just going to change one pair of tubes and that's it.

Can't wait to play with this beast.

 

[Elpelotero]

i've never promoted pulling tubes from a triple rectifier for the simple reason that wattage gets cut by 1/3 each time you pull tubes...last time i checked, ohms do not go down by 1/3, only by 1/2. then again, lots of people on this board have pulled tubes from a TR in the past and have not blown up their amps.....so who knows who is actually right about this. I've even gotten differing opinions from different Mesa employees. I guess the only way to know for sure would be to talk to Randall or Mike B. themselves...

 

[Werihukka]

Hi again,

Now I have a pair of tubes, but I noticed that there was 420's in there, but the first 2 in the line "A-B-C-C-B-A" says "50 AC GRN" and the others are "36 SK GRN".. Now what is this? A and B aren't pairs right? But how are they the same? I'm doubting it is like ABCCBA, because A and B are the same.

I'm lost.

Just trying to say that the first 2 of the tubes (from the left) are different from the other tubes and it seems like those are pairs. Or is this amp just set wrong in every possible way. Also, the bias switch was set to EL-34 and the tubes were 6L6's. Makes me even more confused.

 

[Russ]

Match the pair and match the quad. Then switch to 6L6 and you should be fine. If you want some 420's there was a set on e-bay in Australia last night that I saw.

 

[Werihukka]

I have 440's now. "ABCCBA"<- this bold one of the tubes (A) was damaged during the delivery of the amp so do I have to change both of those A-tubes?

 

[Russ]

Yes, change power tubes as pairs. Save your old good one as a spare.

 

[Werihukka]

I'll do that, thanks again.

 

[Russ]

If you stay with the same type and color code your mismatch to your old spare might be closer when you have a tube failure and have to use the spare in an emergency. It doesn't make that much of a difference though when you are talking a used spare because they will not wear evenly between sets or to each other or you wouldn't even have a spare. The spare is a nice alternative to finishing a set or not. The only other alternative in an amp with 2 or more pairs is to pull the matching tube of the dead one and reduce by 1/2 your amp output impedance. This will darken your sound some in a 3 pair amp like your Triple Rec because of a slight mismatch of impedance. A Dual Rec wouldn't see a mismatch. The reason is that you cannot reduce your ohms properly with a Triple Rec to match your speaker load when you pull tubes.