• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

April fool?

UK readers with a sense of humour might like to have a quick look at the article by Haden Boardman in the April 2013 Hi-Fi World. It purports to improve the phase splitter in certain old Leak amplifiers by replacing the ECC81/83 PS with an ECC82. This is said to reduce the gain (true) and improve the driving capabilities (unlikely). Of course, we all know that an ECC82 can drive more than an ECC83 - but only when it is properly biased.

The proposed 'enhancement' is a standard LTP phase splitter, with AC coupling and both grids grounded for DC (via 1M). One grid AC grounded, the other gets the signal from the input stage. Tail resistor is 22K, anode resistors are 100K each. That means each triode is biased almost to cutoff, with perhaps 0.4mA of anode current each. Would you run an ECC82 with, effectively, a 44K cathode bias resistor? (A typical ECC83 LTP PS runs with about 0.6mA each, but that valve is designed to be fairly linear at such low currents). It is just off the edge of the datasheet plots, but I estimate gm around 0.3mA/V and Ra about 45K. Voltage gain to each anode will be about x5. I dread to think what the distortion might be. Perhaps it is just as well that a pair of EL84s are easy to drive.

So, have I spotted the April spoof article? Or is it an entry for 'how can someone that confused get asked to write an article'? What do others think?
 
Hi-Fi World is not what it was. The DIY Supplements are way back in history (although I have many of them), and HFW now seems to love reviewing expensive cables.

I don't recall any measurements in the article - I didn't actually buy the magazine, just thumb through it in a shop. A few DC voltages might have alerted the author (and wise readers) to potential problems.

The author does not just write articles. Google tells me he also offers to 'upgrade' valve amps. Why do so many audio 'professionals' (i.e. people who make money from audio) not understand the basics? What is more, why do so many of them seem happy to advertise this in public? There are lots of things I don't know anything about, so I don't write articles about them.
 
It is a pity, I liked it a lot.
Great measuring instruments, technicians and journalists.
Each "interview" was accompanied by corresponding measurements.
My favorite section was the "D.I.Y. Supplement", of course.

I stop buying it because my budget does not allow me, but I have no regrets, here in the forum, we have all of you, that are better. ;)
 
Why do so many audio 'professionals' (i.e. people who make money from audio) not understand the basics? What is more, why do so many of them seem happy to advertise this in public?

Could it be because these 'professionals' appeal and suck up to all the myths they have themselves accepted as the truth, without often having a clue about anything.... and all gods forbid - NEVER ask or trust those who have actually dug into the matter - and maybe realized that are no simple answers and no free lunches...... :rolleyes:
 

jjman

Member
2009-01-17 2:41 pm
The internet has replaced paper periodicals. The whole world can "peer review" and we don't have to be spoon fed propaganda and advertising masked as journalism any more. Have you seen how thin Time Magazine is now?

The 1st few amp-related technically-oriented articles in Vintage Guitar Magazine contained so many errors I actually emailed them. I counted 6 errors in the 1st one. It was an “interview” with an alleged guru. I think part 2 had 4 errors.

They did a "shootout" article of various 6v6 tubes and I looked forward to seeing at least one objective measurement to be reported. Perhaps a frequency response curve, but that was just wishful thinking. Instead they reported stupid meaningless jargon. Seeing the pics was cool at least.
 
don't get me started - I like to look at the current hi-fi magazines in the local store but only for the pictures (funny how some things don't change!) because the drivel that comes out of most hi-fi reviewers is astounding. It could perhaps be an unrecognized literary art form in itself. Would I trust any kind of technical description in these magazines ?
 
Just re-checked the article. No measurements, as I said. However, I noticed that for those who feel incapable of carrying out this 'upgrade' themselves the author kindly offers to do it for them and says he has done it for lots of people. He doesn't mention a charge, but I guess if it is high enough nobody will complain.