Dear guys,
after years of troubles with the current tube production we
finally made a decision for the next coming years.
As You know we got a bad call concerning the reliability of
our amps. This is 99% tube related. In our price range, customers
are running hot very soon if the amp gets broken. Most people don´t
know or don´t want to know that the tubes are coming from
manufactures around the world and that we can only do our best
to get the best quality.
People don´t blame the tube company, they blame the amp
manufacture.
Blown tubes can destroy components inside the amp and can make
a repair expensive. As for example: A customer was complaining
about midi problems and a frozen midi controller. We replaced the
chip first and later the midi board. At the end we found out that
a bad power tube caused spikes in the high voltage supply and
was the reason to get this issue.
In 1982 I started with repairs and mods. I had some plexis on my
workbench with a plate voltage of 540 volts and a power output
of 150 watts. This EL34 tubes were 15 years old with a rating of
25 watts power each tube.
This is history. Todays EL34 or 6L6 types get problems with much lower
ratings. It´s not the plate voltage, it´s the screen grid voltage that
causes problems. Most class AB amps have screen grid stoppers but
they work only if the amp is running with a certain amount of power.
Most issues happens during less or no load.
I don´t trust any EL34 or 6L6 with a screen grid voltage higher
than 400 volts. Of course we can decrease voltages but it would
destroy power and sound.
We do a test mangement that includes 2 days burn in and a one
hour full load run. Then we knock on the tubes slightly. 30% of
tubes were broken during the test. After shipment another 10%
were broken at the customer.
............. so it was time to find a solution.
The most reliable tube on the market is the 6550 from the SED
factory but it´s sound different from our used EL34 types.
The EL34 has a certain midrange punch and musical response
that a lot of players depend on.
I found a way to get out the same frequencies of the 6550-SED
but the response is of course different. This tube has a very
articulated midrange thightness with a clean bass amount
and big headroom.
Some people will like it, some not. We give only warranty
on the 6550-SED tube to stop the trouble and internet
discussion about the expensive Diezel crap.
Expensive ....... the tube is very expensive but much more
cheaper than the warranty replacements and shipping
costs we had in the past.
Of course You can replace it for Your favourite tube and
Your taste.
The 6550 should be biased to 100 milliamps each pair
means 50 milliamps each tube.
For me the 6550-SED is a further improvment looking
for sound and quality.
Excuse my bad English and have a great day,
Peter
*schlechte-witze-galore*
