300b operating specs / reliability...

an amp that i am considering has "440VDC effective plate voltage, 90mA idle current and 1.2A heater current" operating specs, meaning the 300b's are run flat out at 40W plate dissipation... the Western Electric spec is 40W.

of course, plate dissipation IS within the WE spec, but running almost flat out (within 10% of max).

however counter-intuitive it may seem (to me at least...), the manufacturer feels that they get BETTER reliability this way, and that it's a matter of circuit implementation, not how hard the tube is run.

is anyone familiar enough with 300b tube amps to comment on the veracity of the claim? i'm wondering if this would make the amp a bear when the time came to find reliable replacement tubes? and/or if this will shorten tube life or not as the manufacturer claims????

 

Hi Blakeaudio,

When you run a valve at the max of it's spec, it will generally won't last as long. Most 300B amps don't operate at the max end of the spec. Yes the amp should work ok at this spec, if the valves are of high quality. WE valves are well built and can last a long time. You may find you are changing the valves quicker.

Reliabilty of valve amps is not just the valves. It is also the circuit design, the component quality, layout and build quality.

Some 300B valves may not be as robust or as reliable as the WE300B valve, so may not be as sturdy being run at this level.

BTW, what amp is? I may have come across it and may be able to comment more.

SCIDB

 

it's a VAC phi 30/30. the specs are actually the Renaissance 30/30, but the circuit is supposed to be fairly similar, they have the same output, etc. i haven't been able to find the exact specs of the phi anywhere, so i just went with the Renaissance's numbers. i'm not worried about the amp being reliable, more about the going through a lot of tubes!!! especially if we're talking WE's for ruggedness!
i was actually wondering about tj mesh plates as 've heard they are supposed to offer the best value for money sound. however, i've heard that they are a bit fragile and don't like being pushed to hard... does that sound about right to you?

 

Hi Blake.

I think Chris Jennings in this forum works with Renaissance. You might want to drop him a PM

Chris

 

Hi Chris,

Blake is not talking about the amps that Chris Jennings has worked on. The amps he is talking about are made by a company called VAC from the States. It is this one I think,

http://www.vac-amps.com/page0048.html

The latest ones look like this.

http://www.vac-amps.com/phi_intro.htm

The amps that Chris Jennings deals with are these

http://www.highendaudio.co.uk/renaissance/index.htm

SCIDB

 

Oh I love amplifier porn!

 

they look cool don't they? a bit like a 300B goldfish bowl.

don't see much VAC in the UK though, which is a shame. I've yet to hear the range.

 

scidb is spot on. i am talking about the VAC PHI. someone accused me of having a totally child unfriendly amplifier at the moment, and i thought that this would be the perfect excuse to "make it child friendly"

 

Hi Blakeaudio,

Nice looking amp. Are you buying this new or 2nd hand? Are getting it from the States? Is there anyone doing VAC in the UK at the moment?

SCIDB

 

audio salon in scotland seems to be the only place in the uk that does any vac, but the one i'm after is in the states 2nd hand. at the end of this month i get paid my bonus, and i was thinking of treating myself.

 

like your style.

re-buff the ''valves are anti-kids'' arguement with an upgrade!

 

that was exactly where i was coming from! then lets see them argue with me!

 

If that is indeed the plate dissipation run by this amp,then as you say,it's right at the limits of a good 300B,and probably a little beyond some of the cheaper ones.

It may well shorten the life of the tubes,and my concern would be that WE 300Bs are extremely expensive currently,and unlikely to drop in price....the alternatives would be things like the TJ Meshplates,which are superb,and very robust,and also some of the KR 300Bs,which are again quite highly specc'd in terms of plate dissipation.

Having said all of that,VAC,as you know,have a reputation for excellent build,sound and quality,and I'd be amazed if they'd produced an amp that ran it's tubes so hard that it actually resulted in short life spans.

I have a set of WAD 300Bs which run the tubes harder than some,but not at the limits.

 

Hi.

The WE300b spec quoted a life expectancy of 10,000 hours at 28W anode disipation, the max design anode disipation is 40W with reduced life, I think 5000 Hours but my memory may be playing tricks.

The TJs are very nice sounding tubes. I've a customer who uses them several hours a day and all weekend, and is still on his first set after a couple of years. So they seem to be long lived.

Hope this helps.

Chris

 

the only thing that i've read about the tj is that the the mesh plates have a slightly lower capacity for plate dissipation. i'm not sure if that is true or not, but this is one of the things i'm trying to determine.

 

Take a look at KR Audio's website...you may find some useful data here regarding plate dissipation and their 300B clones.

http://www.kraudioproducts.com/tubes/

On the sophia electric webpages you will also find the plate dissipations for their 300Bs...incl the meshplates(at 40W).

http://www.sophiaelectric.com/

 

thanks for those! very usefull.

 

We use Golden Dragon mesh plates in our Border Patrol. They sounded no worse than General Electrics, and were a lot cheaper. Well worth listen to if you can sort out a dem.

Paul and Sarah

 

i still need to sort out the amp!! then i will get onto the tubes! as stated previously, i'm exploring the feasability of the 300b amp i'm considering in terms of running costs...

but thanks, it is certainly something to consider. vac was actually the US importer for golden dragons for a while, so one assumes that these tubes work in their amps.

 

In terms of running costs,apart from the inevitable replacement of output and driver tubes you shouldn't have problems.....the range of 300Bs is ever increasing currently,with the bottom end of the price range being around £80 per tube as far as I can see,but the quality varies a lot.

This review was very useful to me when I was deciding,as was trying one of the cheaper alternatives,before settling on a set of TJ meshplates.

http://www.enjoythemusic.com/magazine/equipment/1201/300b/

One final point....I noted that the power output claimed for these amps was 32W,which is really the highest I've seen claimed for a PP 300B amp of that type....most seem to manage in the 24-26W range,so it would seem to confirm your feelings,and the data supplied,about the tubes being run fairly hard....the KR tubes would be well within their limits,assuming electrical compatibility.