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VAC 90 EL34 tubes question.

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Posted on February 3, 2017 at 00:15:37
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005












I have these two quads of EL34s labeled VAC from the VAC90 amps I worked on four years ago.Anyway,I ended up putting KT77s in along with a host of other upgrades but being these looked so nice, I decided to give them a spin in the Eico HF60s.These tubes have a smooth and full bodied sound with a very dynamic bottom end.Like most EL34s IMHO,they do lack some presence in the top of the treble range but it's not necessarily a bad thing because you do hear the symbols and the shimmer of certain percussions so they are doing a decent job.
I am thoroughly convinced that EL34s are very circuit dependent and can give a very satisfying sound under the right circuit conditions. Unfortunately, amps like the stock Dynaco ST70 gave the EL34 a lot of bad rap because of cloudy overcast and limitations in the upper and lower extremes.I still prefer the KT77 and the 6L6 tube family however,I'm getting to like the EL34 a bit more.I have heard EL34s in a Citation 2 biased at 50ma and they sounded very good.I have also heard them in a pair of my Mc60s three years ago and again,they didn't lack any detail or dynamics in either amp. In the MAC amps,i did lower the negative bias by minus 6.8v at idle so the tubes would draw enough current at full power.
Now,here is my question. Who made these tubes for VAC? They look like the Mullard Matsushita but my gut tells me they are Shuggies. The bottles are bigger around than any EL34 other than the 6CA7 fat bottles.Take a look at the crease in the plate structure,just like Matsushita had.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

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    ...
There are no bad tubes, just bad circuits..., posted on February 3, 2017 at 04:44:01
Chip647
Audiophile

Posts: 2652
Location: The South
Joined: December 24, 2012
and detrimental financial objectives. (and oversimplification)

 

proper tool for the proper job... I'll run with that-nT, posted on February 3, 2017 at 06:40:59
Cleantimestream
Audiophile

Posts: 7551
Location: Kentucky
Joined: June 30, 2005
-!
The Mind has No Firewall~ U.S. Army War College.

 

Oh Mike are you confused again about how tubes work, posted on February 3, 2017 at 07:18:56
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
Oh Mike don't you know anything about tubes - read a book will ya!

Only kidding. I'm "sort of" glad in a way that even you like the EL34 but continually find that short fall on the top end.

Do you find that as well with the VTA kit I have or is that because of the Shaguangs I have and should try the EH 6ca7 instead????

Don't get me wrong about the VTA 70. I think this amp is absolutely fantastic with a set of GL KT66,77 and 88's

charles

 

RE: VAC 90 EL34 tubes question., posted on February 3, 2017 at 08:06:05
AJ
Audiophile

Posts: 532
Joined: February 24, 2001
These were Shuguang's for VAC

The EL34 is a great tube, too bad the sorry budget minded ST70 is used to evaluate the performance of this valve over the years.

Dynaco's were the Ford Falcons of audio and people continually attempt to make them performance machines that they are not. Good for the money not top ten performance.

Mods and rebuilds dump $100s or even $1000s of dollars into a machine that really can't live up to the best. Most of the time better performance is possible with a totally different platform . I know we are talking about EL34s and amps that use them but this is especially true of the Dynaco preamps.

For learning and entry level Dynaco's are great. Make them safe and enjoy for what they are. For high performance you need to move on especially if you wish to see what an EL34 really should be able to accomplish.

YMMV and all that.

 

RE: VAC 90 EL34 tubes question., posted on February 3, 2017 at 12:19:41
DannyR
Audiophile

Posts: 611
Joined: January 21, 2001
Looking at the measurements of a stock st70 done by Dave Gillispie the ST70 seems pretty linear unless some dc hits the inputs. Fix that and replace the gz34 with diodes plus a resistor to drop the voltage and it appears to perform great.

http://www.audioregenesis.com/documents/ST-70%20Base%20Line%20Testing.pdf

 

RE: Oh Mike are you confused again about how tubes work, posted on February 3, 2017 at 12:24:14
ahendler
Audiophile

Posts: 5151
Location: San Antonio, Texas
Joined: January 24, 2003
I tried most of the EL-34's in my VTL ST-80. Tried 6CA7's
GL KT-77's are the best
Alan

 

RE: proper tool for the proper job... I'll run with that-nT, posted on February 3, 2017 at 12:46:01
llwhtt
Audiophile

Posts: 192
Location: SOCAL
Joined: October 28, 2008
I used to buy Golden Dragon tubes from VAC's Kevin Hayes, so those tubes could be from that line of tubes, definitely Chinese. Now I use the Valve Art EL34s, never have any complaints with those even in gheetar amps.

Craig

 

RE: VAC 90 EL34 tubes question., posted on February 4, 2017 at 06:58:11
SETdude
Audiophile

Posts: 3944
Joined: January 20, 2000
Mike, they look like Shuguang EL34B's but looks can be deceiving. ;-)

 

RE: VAC 90 EL34 tubes question., posted on February 5, 2017 at 01:46:03
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
I think they are Shuggies as well..I definitely like them better than the XF2s in several areas.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

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