It's been months since I last responded to this thread, in truth I had forgotten about it. So it is long past time to do so. In my previous post I wrote about having a few problems with some of our Sophia tubes.
At the time I was trying to find out if anyone else was experiencing the same problems - so I could possibly find out why.
The grid voltage in our amplifiers at the time was set at 425 volts. Though this is well within the old standard Western Electric specifications which suggest a maximum operating voltage of 450 VDC - in the end we found that it may not be an optimum design voltage.
Since my early June posting, we have found that operating at such high voltages all the time is not necessarily the absolute best design point for an amplifier to have - especially considering the fact that an owner may indeed roll any number of 300B tubes through a product in its lifetime. And as all of us 300B lovers know, sometimes some sets of these tubes can equal the price of a nice house payment.
So extreme care and safety is always going to be a good choice.
Some current production tubes such as the EH Golden Lion for instance, may indeed give a much better experience when operated at a higher voltage. As a matter of fact, in one early prototype set of monoblocks we actually boosted the operating voltage to well over 500 volts with a set of Golden Lions in place and got the best sound we ever experienced from these particular tubes.
Still to this day eight years later that quad of 300B tubes are operating strong under this condition. But of course there is no way that we would ever consider using that high of a voltage in a production unit.
I will say though, that the sound quality from that early pair of prototype monos never surpassed anything that we installed Sophia products into.
It seems that possibly some of the newer tubes available today, especially those from the higher quality manufacturers like Sophia Electric just seem to like a lower operating voltage. And it will certainly give you a much longer tube life as well.
I called Richard of Sophia several times last June, and he helped us by suggesting that we lower the grid voltage in our 300B amps to between 350 and 400 volts. In doing so we have seen the merit of his vast experience working for years with a new line of vacuum tubes that does not stop with only the 300B.
So take this tidbit of knowledge for what it is, just a suggestion. In our latest round of experience, and with the help of Richard of Sophia Electric, who certainly knows more about 300B and other vacuum tubes than I ever will.
It may be a good idea to become well acquainted with the specifications of any amplifiers that you are considering in the future, especially the operating voltages of the power tubes. The lower the voltage the longer these sometimes very expensive tubes may last. And we now know that the with the proper design throughout, the sound does not suffer in the least.
All of our 300B amplifiers operate now with a grid voltage maximum of 380 to 385 VDC. We have not had a single bad experience since making this change. And though we install a myriad of different current production 300B tubes - according to what our customers' personal taste - the best by far, in my opinion at least, is the line from Sophia Electric.
Knowing that Richard and Sue stand behind their product line and take immediate action should anything ever go wrong is another huge plus for that brand.
Knowing that at any time I can call an experienced engineer like Richard when we are developing a new product also comes in handy. I might add here that since Sophia Electric also manufactures 300B amplifiers - he is actually if a direct competitor of ours!
I wish everyone in the high end electronics industry had such a high level of integrity! But alas.....
