Reisong Boyuu MT-88 MKII KT88 Push Pull Tube Amplifier

That is good to know. It seems like it might be a problem when the tubes get older as they might still be as closely matched. If you are using four EL34s and one fails with the cathode bias you might have to buy four new matched tubes whereas maybe if you could could adjust the bias on each tube you might be able to just replace the one bad tube. I like just being able to check the bias once and awhile to see if everything is OK. I don't see how it could be any easier to check the tube bias than the way Willsenton has implemented it. They have a switch on the top panel that is spring loaded in the up position. You just push the switch either forward or backward and hold it in that position to adjust either of two tubes. Using a screwdriver you just adjust the pot until the needle on the front panel meter is at the 12 o'clock position. There are two switches so you can adjust all four output tubes. I have a question about the stock 12AX7 and 12AU7 Willsenton tubes that come stock it the R-35i. Should I try replacing the 12AX7 first for most improvement? What would be a good new issue tube to replace it with; I'd rather not buy a NOS tube.
 
I'm looking at new tube replacements for both the 12AX7 and 12AU7 and the Tung-Sols sound pretty good at half the price of the Gold Lion tubes. Does anyone think it is worth paying the extra for the Gold Lion? I'm thinking of maybe getting Gold Lion for the 12AX7s as they have a gain factor of 100 and the Tung-Sols for the 12AU7s that have a gain factor of 20. Does that make any sense?
 
Personally, I don't live my life thinking that a tube is going to fail. This is just me, but I have never had a tube fail. I am still using the original Bogen 8417 tubes I have in my Bogen amplifier since 1978. It could be because they are self bias and run pretty conservatively and they still test strong after 43 years. :angel:
 
wag12 said:
I'm looking at new tube replacements for both the 12AX7 and 12AU7 and the Tung-Sols sound pretty good at half the price of the Gold Lion tubes. Does anyone think it is worth paying the extra for the Gold Lion? I'm thinking of maybe getting Gold Lion for the 12AX7s as they have a gain factor of 100 and the Tung-Sols for the 12AU7s that have a gain factor of 20. Does that make any sense?
Click to expand...

Dave Gillespie has documented in a couple of threads that the Gold Lion KT88s are the best of the newly manufactured KT88s, by a considerable margin. As for 12AX7s and 12AU7s, they all have the same specs. I'd suggest that if you've spent good money for a new tube amp, get the best tubes available so you can hear what it really can do.
 
wag12 said:
That is good to know. It seems like it might be a problem when the tubes get older as they might still be as closely matched. If you are using four EL34s and one fails with the cathode bias you might have to buy four new matched tubes whereas maybe if you could could adjust the bias on each tube you might be able to just replace the one bad tube. I like just being able to check the bias once and awhile to see if everything is OK.
Click to expand...

A lot of self bias amps just require a matched pair, 2 matched tubes or a single, I would probably just buy a pair anyway.
Some builders bias each tube so any tube is fine.
I have owned several fixed bias and self bias amplifiers, never lost sleep over any of them.
 
wag12 said:
I'm looking at new tube replacements for both the 12AX7 and 12AU7 and the Tung-Sols sound pretty good at half the price of the Gold Lion tubes. Does anyone think it is worth paying the extra for the Gold Lion? I'm thinking of maybe getting Gold Lion for the 12AX7s as they have a gain factor of 100 and the Tung-Sols for the 12AU7s that have a gain factor of 20. Does that make any sense?
Click to expand...
All 12AX7s have a mu (amplification factor) of 100 and all 12AU7s have a mu of 20. It doesn't vary by brand.

I would suggest that you consider old production tubes. Forget about whatever NOS "magic tubes" the boutique dealer$ are hawking at the moment and just find some strong testing used ones. 12AU7s, in particular, are quite cheap and strong old production 12AX7s probably won't cost any more than new production.

Please be aware that the new production versions are not the same tubes as the old. Someone bought the right to use the famous brand names but the tubes are not the same. They aren't necessarily bad tubes but a lot of newbies don't realize that it's just a marketing ploy.
 
JJ's and EH signal tubes are pretty cheap. Usually cheaper than old stock. Unless your into the gold pin versions. I have yet to have a JJ signal tube become noisy, fail or go weak.
I've only lost one JJ power tube. But I lost one half of the voltage gain tube that was driving it at the same time. Not sure what happened there.
 
I, too, have had good luck with JJ signal tubes, both short- and long-plate versions of the 12AU7 and 12AX7 tubes. I have also had good performance from the JJ EL84 and KT77 power tubes. Very nice tubes for the price.
 
Lavane said:
I have both fixed and cathode biased amplifiers. They all perform just fine. As long as you start with macthed set of tubes, cathode biased amplifiers will last a long time. Look at all the old console amps. I have several and one was still in the old console and working just fine with the original tubes. I will say I prefer fixed bias with higher powered amplifiers. You can always split the cathodes with a resistor for each pair instead of one resistor for all four if you wish.
Click to expand...
You are right, the bias setting are more important when using a push-pull amplifier and you want to make sure the two output tubes in one channel are balanced so one of them isn't working harder than the other one. It doesn't seem so important in a SET amplifier that only has one output tube in each channel. One advantage of being able to set the bias manually though is that you don't have to buy matched pairs and if one of the tubes goes bad you don't have to replace both of the tubes. The Willsenton RF-35i was out of stock so I ended up buying a RFTLYS A3 SET 300B integrated tube amplifier instead from China HiFi Audio. I got a good deal on a open box one for $725 shipped. It comes with a pretty good set of tubes standard: Psvane 300B-L x 2, Psvane WE 274B x 1, 6H8C(made in Russia) x 2 , 6922EH(Made in Russia) x 2. I figured out if I was to buy all of these tubes myself it would probably cost me about $500. The two Psvane 300B-L x 2 sell for $280 a pair, and the Psvane WE 274B rectifier tube sells for $174. I haven't received it yet anxiously waiting it's arrival.
 
You must log in or register to reply here.
Back
Top Bottom