Question: How bad an idea is this?

cvogue

cvogue

Yes, that's Oolong. :)
OK, so my Tung Sol EL34B's arrived in the mail today. Dying to try them out, but I don't have my amp at home. Won't have access to it until practice on Saturday.

It wouldn't be a big deal to just swap the old TAD EL34's out and put in the new Tung Sols... but cracking it open to rebias at practice just isn't feasible.

So... should I risk trying that (swapping in the TS's and see how they do)? Or should I just be patient and bring my amp home and check the bias with the old ones and then bias the new ones.

For the record my amp is a Blackstar HT-40 and has a bias pot that I can adjust.

Just wondering if I could damage the amp or would it just have crappy tone if the bias isn't set right. Who knows it may sound stellar out of the gate.
 
Hmm... I'm thinking that it is indeed... a bad idea!!!

OK, I'll forego the swap until I get the amp home. Why risk it. :cool:
 
In my 20+ years of tube amps I have never biased or had anyone else bias my amp when I changed the tubes. I'm not saying that's right, I just never have. Never had a single issue after doing it. I can't even remember how many times I've swapped tubes I've done it so much.
 
Chad said:
In my 20+ years of tube amps I have never biased or had anyone else bias my amp when I changed the tubes. I'm not saying that's right, I just never have. Never had a single issue after doing it. I can't even remember how many times I've swapped tubes I've done it so much.
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Curious, what tube amps have you owned?
 
cvogue said:
Curious, what tube amps have you owned?
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It might be easier to list what I haven't owned :grin:
Blackface Bassman
Silverface Champ
Silverface Vibro Champ
Silver Face Princeton Reverb
Marshall DSL50
Mesa Boogie Mark I
Mesa Boogie Nomad 65
Mesa Boogie Subway Rocket
Laney AC15 type amp
Vox AC15
Egnater Tweaker
Allen Hot Fudge
Fender Hot Rod deluxe
Fender Prosonic
Peavey Classic 50
Kustom Defender
Ampeg 15 watter
Zinky/Supro Sahara

And I'm sure I have forgotten a few :grin:
 
Chad said:
It might be easier to list what I haven't owned :grin:
Blackface Bassman
Silverface Champ
Silverface Vibro Champ
Silver Face Princeton Reverb
Marshall DSL50
Mesa Boogie Mark I
Mesa Boogie Nomad 65
Mesa Boogie Subway Rocket
Laney AC15 type amp
Vox AC15
Egnater Tweaker
Allen Hot Fudge
Fender Hot Rod deluxe
Fender Prosonic
Peavey Classic 50
Kustom Defender
Ampeg 15 watter
Zinky/Supro Sahara

And I'm sure I have forgotten a few :grin:
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Holy Shmolies that's quite a list! I'm wondering if you were lucky with not rebiasing after tube swaps or if it doesn't matter that much (but you do take a risk if the voltage is way off...)
 
cvogue said:
Holy Shmolies that's quite a list! I'm wondering if you were lucky with not rebiasing after tube swaps or if it doesn't matter that much (but you do take a risk if the voltage is way off...)
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I swapped tubes at least once in everyone of those amps. Hell in the bassman I knew nothing about tubes I don't even know if I put 6l6's in it when I replaced them. I think I replaced them 2 or 3 times and gigged the shit out of that amp. The first time I changed the tubes, I went to a local TV repair shop to get the tubes. I took the tubes in and told the guy I needed 2 new ones. No telling what he gave me.
 
Obviously Chad has had some freakish luck. But fwiw, and don't take this the wrong way, but if you don't bias the amp I think you're a fool. There's a reason amp makers make it adjustable...
 
Chad said:
Check out #4 :embarrassed:

http://tone-lizard.com/biasing/

Also all Mesas have non adjustable bias and cathode biased amps down by need to be biased at all.

http://www.thetubestore.com/Resources/Matching-and-other-tube-info/Bias-Types
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Various amplifiers have either adjustable or non adjustable bias settings. An amp that is non-adjustable is, obviously a "plug and play" type installation. But any amp with an adjustable bias point would need to be adjusted.
Now, in my Splawn Quickrod, Scott Splawn marks his tubes with a rating system. In theory, if I were to buy tubes from him(which I have) that have the same rating I should be able to just install and go. Groove tubes uses their own rating system also. You can buy tubes from them that are early, average and late distortion(breakup) points. These will all bias at different settings.
A couple of months ago I had broken one of my tubes and ordered a set from Splawn with the same rating as the ones originally in the amp. When I installed and checked the bias it was off. Not a tremendous amount but off enough IMO that it needed adjustment. All that said, the OP bought a completely different brand of tubes for his amp and we have no idea where they will bias up with the new brand. If he biases this brand and later down the road re-tubes with the same brand then there is a better chance that a bias MAY NOT be necessary.
I feel that for the 10-20 minutes it takes to bias an amp, to insure that it is running optimally and the correct current is flowing through the tubes/system it is a small effort to put out.
I'm actually amazed the you've never had an issue especially with all of the amps you listed!!!
At the end of the day it's you're amp and you're free to do what you want with it. But as for me, I bias every time I change tubes. I have a bias probe from eurotubes that I spent $100 for. It makes the process virtually fool-proof.
 
cvogue said:
Uh... wait... what?

No worries, I hear you gtrjunior. :thumbup:
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Thanks man.....the last thing I'd want to do is offend you. But you did ask for opinions. This is just something that I personally ALWAYS make sure I do with my amps.
Let us know what you decide.
 
I knew I forgot some.

2- Fender Musicmaster bass amps
Silverface Bassman
Reissue Deluxe Reverb
Reissue Vibrolux
Silverface Bassman 100
I had a Mesa Mark I combo too
A Frezel Champ clone
Monkeymatic dual 6v6 custom amp

I'll probably think of more later
 
In the dark ages (B.I - before internet) my friends and I knew nothing about tube amps or bias. We went on the advice of the guys behind the counter at the local music store who would say, "just take out the old ones and plug in the new ones." Or we'd take the amp to the TV/stereo repair guy who'd just rummage through a box of tubes and swap 'em out and send us on our way for $20. And yeah, sometimes the tubes didn't last very long and some times the amps didn't sound as good as we knew they could but nothing blew up.
Would I do this today, armed with more knowledge & experience? Nah.
 
Guys - bias'ing is important, but it isn't the be-all-end-all of tube life. My MESA came stock running its EL84s ludicrously hot. In my conversations with MESA about that they said they've been selling amps running like that for years without a problem... except the (MESA branded) tubes redplated in my MESA. To appease me, MESA sent me 4 sets of MESA tubes - they weren't well balanced and they too pulling too much current for an EL84 with the bias set at the factory in my amp. I eventually modded the amp with a cooler bias and am running the coldest set of EL84s that eurotubes sells. This put a higher voltage on the plates, but a lower current - knock on wood, no more redplating EL84s.

Way back when I swapped the EL34s in my JCM800 (which I wish I still owned) and didn't rebias. Probably got lucky, but nothing bad happened and I ran that set of EL34s for years (as in at least 15 years) before selling the amp. Maybe I got a colder set, maybe I didn't, but the amp never once hiccuped.

People have been swapping tubes and not bias'ing for years and years. Some probably had catastrophic results, most didn't.

Anyway, if the amp is running fine, I'd practice with it as is and change the tubes/bias when it's possible to do so safely without a rush.
 
cvogue said:
Holy Shmolies that's quite a list! I'm wondering if you were lucky with not rebiasing after tube swaps or if it doesn't matter that much (but you do take a risk if the voltage is way off...)
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All those amps were probably biased really cold. Won't destroy the tubes but also won't sound fantastic. Biggest complaint about the original Peavey 5150.
 
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