What plate voltage is it in my amp? Can it be changed?

[joey_truelove]

I was considering the 5881 for my 50/50 but then I read the oldstyle 5881s shouldn't operate at more than 400V to the plates. Would be a pity and a costy lesson to learn to blow my poweramp for a different flavour of tone, wouldn't you say? Cheers!

 

[stokes]

Some new production tubes are okay.The ones Mesa sells are safe to use.I also believe the Sovteks that are labeled 5881 are also okay to use.It is the NOS 5881's that should be avoided.

 

[fatboy135]

I think that 400 Vdc is too much for any power tube, if you want to change the plate voltage you must to change the plate resistor, but think that a lower voltage into the plate means a highe current through the tube and that modifies your bias point so you also will need to change the cathode resistor, and even grid resistors, and recalculate your new bias point, did you still think that installing that tubes is your best option???

 

[stokes]

I think that 400 Vdc is too much for any power tube, if you want to change the plate voltage you must to change the plate resistor, but think that a lower voltage into the plate means a highe current through the tube and that modifies your bias point so you also will need to change the cathode resistor, and even grid resistors, and recalculate your new bias point, did you still think that installing that tubes is your best option???

What????

 

[fatboy135]

what what???

 

[stokes]

What plate resistor?What cathode resistor?400v's is too much for any power tube?Most Boogies have well over 400v's on the plate.The 50/50 is fixed bias,no cathode resistor,and the plate is connected to an OT so no plate resistor.

 

[fatboy135]

you are right, and I also want to rectified my statement that with a lower anode to cathode voltage the current increases, it was a totally lapsus, the current decreases

 

[stokes]

Okay,you scared me there for a moment,fatboy.I dont think changing his plate volts for this tube change would be a viable option,maybe if he had a tech install a bias pot,it would give him a wider selection of tubes to choose from,but he is better off sticking with the Mesa or GT grading scheme.

 

[joey_truelove]

Cheers guys! Speaking of GT: I see they do offer something they call 5881 that puts out 30W a bottle and is said to be suited for Mesa/Boogie rack gear. From what I can tell it's of their own design, so probably not a who-knows-what-it-is Sovtek but closer to the original, yet with a higher power output.

 

[stokes]

Probably made to their "specs" but made overseas somewhere.

 

[joey_truelove]

Probably made to their "specs" but made overseas somewhere.

http://www.groovetubes.com/ second from the top. "GT exclusive design" is all it says. On other valves the country of production is mentioned but not on the 5881.

 

[stokes]

I dont know for sure if things have changed,but many years ago tube production in the USA stopped because of environmental issues,mainly due to the costs of disposing of some of the toxic by-products in the process.I dont use current production tubes at all so I am not 100% sure but I would think these are made overseas somewhere.You notice that they dont specifically say Made in the USA,which would be a big selling point.

 

[joey_truelove]

I dont know for sure if things have changed,but many years ago tube production in the USA stopped because of environmental issues,mainly due to the costs of disposing of some of the toxic by-products in the process.I dont use current production tubes at all so I am not 100% sure but I would think these are made overseas somewhere.You notice that they dont specifically say Made in the USA,which would be a big selling point.

One wonders which tubes other than the clone of the GE 6L6 they do make themselves... Those 12,000 sq feet can't be just offices.

 

[stokes]

If you read the description it says "from the last American tube factory..."
And it says "GT reissues which have a majority of USA components..".I dont think they are made here in the USA or they would outright say that,no?I think they bought a lot of old parts when they liquidated the"last American tube factory" and are actually made overseas.JJ's are made on the original Tesla machines using the old formulas etc.,but I can tell you they are not Tesla's,not by a long shot.Dont get me wrong,I am sure they are very good tubes,but I just have my doubts about them being made here,since they are not coming right out and saying they are,just alluding to it.

 

[joey_truelove]

If you read the description it says "from the last American tube factory..."
And it says "GT reissues which have a majority of USA components..".I dont think they are made here in the USA or they would outright say that,no?I think they bought a lot of old parts when they liquidated the"last American tube factory" and are actually made overseas.JJ's are made on the original Tesla machines using the old formulas etc.,but I can tell you they are not Tesla's,not by a long shot.Dont get me wrong,I am sure they are very good tubes,but I just have my doubts about them being made here,since they are not coming right out and saying they are,just alluding to it.

Oh, yes - I get your point. We're so used to have valves made in Russia, China and recently Yugoslavia we more or less take that for granted. Hadn't the Russian valves been, we probably wouldn't have valve powered amplifiers today. As with so many other things, gear like these made in the western world, though necessarily not of higher quality, always comes with a heftier pricetag. The Brits, the Germans and the Deutch used to put out great valves too but as demand dropped and out-sourcing became the order of the day Mullard, Telefunken,Philips, and what-have-you was history.

Yeah, then that story about the US rights to the brand Svetlana. Laughable. The print on the bulb does only tell half the truth if even that sometimes.

 

[stokes]

Luckily,there are still a lot of NOS tubes available,both USA and European made,though pricey,they are well worth it,in my opinion anyway.