Non-Boogie tubes in a Boogie?

Markedman

Well-known member
I have a quad of 1970 RCA 6l6 tubes that I tested, they tested very strong and matched. So I put them in my boogie 50-50 power amp and I was blown away at the difference. I had to turn down the treble and the volume was perceivably louder. I was overjoyed until I realized, I’m not supposed to use anything but Boogie tubes. The mA is in the 50s whereas the boogie tubes are in the 20s. I did switch them out and put the boogie tubes back in but it’s been on my mind and I’m thinking about getting the $50 mod that’s available for the power amp. What damage am I doing by using the higher mA tubes?
 

Racerxrated

Well-known member
You’re just gonna run the tube life down. Plus it should sound a bit harsh; if it’s too hot. If it sounds good hot, get that bias screw mod done and it’ll be killer in the 30-40 range
 

Mikeyboyeee

Well-known member
Mesa Boogie doesn't make tubes. Like everyone else, they buy them in bulk (probably cheapest they can). Test, grade and label them. Either get the mod or stay within the fixed bias range of the Amp.
 

midnightlaundry

Well-known member
What's the math work out to be?? What's the plate voltage?
You're not going to hurt the amp. I did a poll a while back about bias percent. Lots of different opinions, but 70% dissipation is perfectly safe and it's what I like for my amps.
You saving those things for a rainy day? The time to live is now. Run them.
 

Dale B

Well-known member
I have a quad of 1970 RCA 6l6 tubes that I tested, they tested very strong and matched. So I put them in my boogie 50-50 power amp and I was blown away at the difference. I had to turn down the treble and the volume was perceivably louder. I was overjoyed until I realized, I’m not supposed to use anything but Boogie tubes. The mA is in the 50s whereas the boogie tubes are in the 20s. I did switch them out and put the boogie tubes back in but it’s been on my mind and I’m thinking about getting the $50 mod that’s available for the power amp. What damage am I doing by using the higher mA tubes?
Like the other guys have said, you're not really doing any damage to the amp. The power tubes are just too hot for the non adjustable bias resistor that's in the amp right now. The problems can arise after that when/if the tube shorts (dies). If it croaks, it will most likely take out the screen grid resistor on the failing tube's socket. One of the biggest things I see when purchasing a used Boogie is a screen grid resistor is usually dead, and I have to replace it.

Get the mod done.
 

blackba

Well-known member
I agree with the others to get the bias mod done so you can run whatever tubes you want.

You really need to now your plate voltage to know if the tubes are biased too hot. Let’s say you have 450vdc on the plates, just take that times the mA you measured and divide by 1000 and you will get the wattage. Should be between 15 to 21w for a 30w 6L6GC. So with the example I said of 450vdc on the plates, that comes to 22.5 watts or about 75%, so very likely too hot.

Another option to the bias mod is to lower your wall voltage with a variac or amprx brown box. Take it down to like 110 to 115 VAC and your tubes will likely be in range. I would just get the bias mod done though, why hassle with taking an extra piece with you to lower your voltage.
 
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