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ich sag' Dir lieber, welchen Unterbau ich gewählt habe: Xindak VT1-GP!

Posted by *** ( * ) on July 19, 2004 at 13:31:56
I bought a pair of Valve Art 300B 98C tubes a few weeks ago. They seem to work just fine and sound pretty good. However, I tried testing them on my Hickok 539A tester and they only test at about 3600 - 3750, where 2900 is minimum and 4600 is new/nominal. I am using settings suggested by Kara Chaffee for this tester (5.0 fil , JR 3200-0 set bias at 15.0v on your bias meter. Minimum gm 2900 on the 6000 scale. The target gm is stated as a minimum instead of the "typical" of 4600). Sovtek and Western Electric 300B’s test from 4,800 – 5,000 with these settings.
Other Chinese 300B’s (Spark, Shuguang, Valve Art 300BC) also test in the 3,600 – 3,800 range on this tester. The 98C is a so called mesh design(really a perforated plate?) and the others are solid plates.
I am wondering why all the Chinese 300B’s I have tested all test well below other 300B’s? Is there something in the design of the Chinese 300B’s that limits the transconductance to the 3,800 range, or is this caused by the design of the Hickok 539A tester?
Also, does anyone have any info on the longevity of the Chinese 300B’s? © audio asylum

Posted by *** on March 19, 2004 at ***

In Reply to: Re: help me pick a 300b!!! posted by *** on March 18, 2004 at ***:

Hi,

Here are my impressions of various 300B's tested in my system comsisting of the DIYHIFI Supply's LadyDay+ 300B Monoblocks with following mods:
Kiwame resistors, AudioNote Copper coupling caps and silver wire hookups, MU driver circuit parts (silver mica caps, wire wound resistors etc to convert the driver stage from SRPP to MU style), S&B grid chokes, ICW Clarity Caps to do the WE connection (2 pcs 22uf/630V and 2 pcs 66uf/160V),KR tube sockets, AN silver connectors with Mullard GZ34 rectifiers and Mullard ECC35 drivers.

In order of preferences:

1) TJ Mesh (perforated plate if you want to be accurate) 300B ST bottle (ceramic base, gold pins). This is the latest TJ 300B version and in an ST bottle. This has the lowest hum of all 300Bs I have tried. The most transparent 300B, most extension at high and low freq, best balance. Does not have the glow/bloom in the mids as compared to WE and Svetlana but I still judge the mids to be accurate, smooth and mellow.

2) TJ mesh plate, black base, steel pins, globe shape. This comes in second. Sound is thinner and less weighty but otherwise comparable to the above. Hum level is low

3) ValveArt 300-98C, Titanium oxide mesh. The best value. Mids are warmer than TJ. But highs are not as extended. Bass is fuller but less focussed. Overall not as transparent but very close to the TJ and more transparanet and better balance than WE. Hum level is higher but less than Svetlana

4) WE 300B 1988. Tried this is another similar amp and compared directly to VA 98C. The best mids. There is that magic glow/bloom but the highs are a ittle roll off and bass is softer. I think the lask of extension at the freq extremes further emphsizes the mids

5) Svetalana. Nice mids, second only to the WE. Has the glow/bloom but like the WE not as transparent and not as extended as the TJ's. Highest hum level in my amp

6) ValveArt 300-98B, Graphite coated mesh. Compared to the 98C version, bass is softer and more bloated, Some loss of detail in the highs and mids is not as transparent.

Above is IMHO and YMMV. Music is light classical and acoustic jazz.

Hope this helps you in your choice © audio asylum

vintage64 hat geschrieben:Heiner,

wie wär's mit einer "Golden Dragon 5U4G"
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oder "Golden Dragon 274B"
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oder einer "5U4G TAD PREMIUM SELECTED"
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oder einem "Groove Tubes Recitifier GT5U4"
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:!:

vintage64 hat geschrieben:Heiner, de geniale GT12AX7M hew ick all inbuet.