Yet another newbie Dynaco SCA-35 query
Jim Kamp
I just bought a SCA-35 and matching FM-3 tuner last Friday and I have
some further questions regarding the tubes used in the SCA-35. The tubes
in mine are all original "Dynaco" brand (yes, they are all working).
1. Which companies made the tubes for Dynaco? I presume the ECC83/12AX7
tubes are Telefunkens because of the legend which says "made in West
Germany" and the "diamond" logo on the base of those tubes. Are the rest
of the tubes which say "made in the United States" from RCA? Sylvania?
2. Speaking of logos on the bases of tubes, what is the significance of
a "triangle" logo seen on one or more of the EL84/6BQ5s?
3. When it comes time for tube replacement, I would like to stick with
tubes that are OEM or better. Is the use of NOS tubes in this amp of any
significant benefit? Will tube life or performance be compromised by the
use of readily available Sovtek or other Russian made tubes?
4. What is that disgusting "pop" I hear when switching from Radio to
Phono? Sounds like a mic being plugged into a PA.
Thank you in advance for reading and responding.
--
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Jim Kamp wrote:
> 1. Which companies made the tubes for Dynaco? I presume the ECC83/12AX7
> tubes are Telefunkens because of the legend which says "made in West
> Germany" and the "diamond" logo on the base of those tubes. Are the rest
> of the tubes which say "made in the United States" from RCA? Sylvania?
RCA, Sylvania, GE; whoever David Hafler could get a good price from.
He also sourced from Telefunken (noted by you), Amperex and Mullard.
>
> 2. Speaking of logos on the bases of tubes, what is the significance of
> a "triangle" logo seen on one or more of the EL84/6BQ5s?
Means it is a Telefunken made tube. The <> is the distinguishing
characteristic.
>
> 3. When it comes time for tube replacement, I would like to stick with
> tubes that are OEM or better. Is the use of NOS tubes in this amp of any
> significant benefit? Will tube life or performance be compromised by the
> use of readily available Sovtek or other Russian made tubes?
OEM/NOS will cost you more. But, many consider the Telefunken 12ax7 to
be just about the best sounding variant available, so the cost may be
worth it to you. The 12ax7 Telefunkens as used by Dynaco (and Fisher/
Scott etc etc) will last for years. You would be surprised at the
condition of some of the components still containing good working
Telefunken tubes! If the ones in your SCA35 test and sound fine, keep
using them and save some $! As far as other choices, I've had success
with 5751 tubes (mil spec 12ax7 variant). The Russian tubes are
considered to sound good especially considering the cost. JUST STAY
AWAY FROM CHINESE TUBES! As far as the 7199 is concerned, either buy
NOS or try the new Russian tube
>
> 4. What is that disgusting "pop" I hear when switching from Radio to
> Phono? Sounds like a mic being plugged into a PA.
Could be indicative of several problems. First and most common cause
could be dirty contacts within the switch. Get a can of Caig De-Oxit
and spray out the switch (and all the others a well). Other than that,
it could be a cap or resistor responding to a change in load.
>
> Thank you in advance for reading and responding.
> --
>
> Jim Kamp - Webmaster
Good Luck!
Ross Lipman
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Wilfred
> Jim Kamp wrote:
> > 3. When it comes time for tube replacement, I would like to stick with
> > tubes that are OEM or better. Is the use of NOS tubes in this amp of
any
> > significant benefit? Will tube life or performance be compromised by
the
> > use of readily available Sovtek or other Russian made tubes?
>
> OEM/NOS will cost you more. But, many consider the Telefunken 12ax7 to
> be just about the best sounding variant available, so the cost may be
> worth it to you. The 12ax7 Telefunkens as used by Dynaco (and Fisher/
> Scott etc etc) will last for years. You would be surprised at the
> condition of some of the components still containing good working
> Telefunken tubes! If the ones in your SCA35 test and sound fine, keep
> using them and save some $! As far as other choices, I've had success
> with 5751 tubes (mil spec 12ax7 variant). The Russian tubes are
> considered to sound good especially considering the cost. JUST STAY
> AWAY FROM CHINESE TUBES! As far as the 7199 is concerned, either buy
> NOS or try the new Russian tube
> Ross Lipman
>
Why are people always putting Chinese valves down?
OK, most Chinese valves you see in the shops are definitely not the best
you can find, but there are also a lot of valves from Russia that are just
as bad.
When you compare current Chinese production to current Russian production
(and forget about the cheapest ones which you have in any country), you'll
find that the Chinese aren't as bad as their reputation makes you believe.
In fact, I think that most of them are even better!
I know a lot of people that have chosen to put Chinese valves in their amps
because they SOUND better.
To me, they have a musical quality that Sovteks just don't have.
The Russian valves in general have a bit too pronounced low-end, yet the
Chinese ones put out more power (both preamp and poweramp) and sound more
transparent.
When you look at EL84/6BQ5's, there is no substitute for Philips/Mullards,
but the Chinese ones come a lot closer than the Sovtek EL84M(=7189) which
sound a little harsh. I put Chinese EL84's in my Vox AC30 a couple of years
ago and they still work fine. So don't give me that 'Chinese tubes are only
good for fireworks'-routine; the AC30 is just about the most EL84
unfriendly amp there is, but no complaints from the output-valves (the only
valve that failed was the rectifier: a GZ34 from Sovtek...)
Let me be clear in that I have no problems with Sovtek; I use
those too. It's just that the Chinese valves are treated unfairly.
The Sovtek 12AX7's are absolutely NON-microphonic; just perfect for the
first gain stage in a guitar-amp. Not too brilliant too.
Enjoy the music!
PS
I have the SCA-35 from a friend of mine to repair at the moment.
Not a bad idea to replace the filter-caps in the power-supply, the
capacitance of those caps is small as it is and it decreases over time.
RHersh
I'd like to weigh in here with an opinion, as I have recently posted to this
group regarding frustration with Chinese tubes. I have found the best quality
of Chinese production in the Golden Dragon lines. I have used them in five
VAC amplifier in which they came stock, and in three other power amps, a DAC
and a preamp. The small signal tubes sound very good to me, without any
distinguishing characteristics. I have had good reliability from them as
well.
Referring to the Tubes By Design ad from the current Stereophile, their
12A/7 line runs in cost from $18 for a single standard grade tube to $84 for a
low noise gold pin matched pair. That is a significant amount of money to pay
for these tubes and there are a number of NOS options that I would consider at
that price point. Maybe it's the mystique of out of production tubes that
adds percieved value, but I can say that substituting a properly selected NOS
tube of equivalent value has produced worthwhile sonic improvements in all of
my gear.
The power tubes are another story. They get $150/pair for their KT88s and
KT90s. Contrast that to $80 that I paid New Sensor for the last pair of GE
6550As that I bought. I'm listening to the KT88s right now in a pair of
MKIIIs. They sound quite good, smoother in the midrange and treble than the
6550As, but I wouldn't necessarily prefer this smoothness in all applications.
I have owned sixteen of the G-D KT88s and have had two go bad spontaneously
at under 200 hours. That was before their one year guarantee, so I was SOL
for $150. I also have two dead G-D EL34s out of about a dozen, and a dead
300B from a pair with <750 hours on them. The EL34s are $118 or $138 per
quad. That's used Mullard territory and I definitely prefer the Mullard sound
to Golden Dragon, no question. To be fair, I have some Golden Dragons from
early production that have several thousand hours on them and are still
usable.
The point here is that there are a number of alternatives at Golden Dragon's
price point and I would not touch any cheaper or less carefully selected
Chinese tube.
My experiences with Sovtek and Svetlana EL34s have been excellent. Both
types are considerably cheaper than G-D and give equivalent or better sound
quality in my applications. Out of a dozen of each in my and my family's
equipment, I have yet to see one fail or age prematurely in two years of
regular use. When I re-tube an amp for a friend, I recommend Svetlana without
reservation and know that they will be satisfied with the value. I am using
Sovtek 300Bs in my main SE amp at the moment, replacing the G-D's. At around
30% of the price (I bought mine at discount), they sound amazingly close. Not
as much midrange 'richness', but a more vivid presence and crisper highs.
Pardon the audiophile-ese, I have to describe sound somehow.
Conclusion: China sends too many tubes over here that are not fit for audio
use due to unreliability. The best ones are priced quite high and still have
too many failures.
I invite conflicting opinions or confirmations posted to the group or directly to me.
Regards
Ross Hershberger
Buffstereo
Hello! I had a Golden Dragon KT-88 fail in one of my VAC monos 2 hours after
I initially set them up! Not a very auspicious start . I recieved a
replacement soon , but I also bought a couple quads of 6550Cs from Svetlana
that I've really enjoyed. Every now and then I put the KT-88s back in for a
week or so as a lark but I want more than midrange from the music I listen
to. I've used the 6550s for a year and they are much more stable in terms of
drift in biasing compared to the KT-88s. I have RCA 12AU7s and GD 12AU7s for
the preamp stage. I honestly don't hear a difference between them. However
when I replace them I will try the 12BH7As in their place. I'm just not to
sure about 12AU7s in general. Anyway thats my dos centavos! From :
buffs...@aol.com(Robert Thompson)
Chris
Ned Carlson (postm...@triodeel.com) wrote:
: rhe...@aol.com (RHersh) wrote:
:
: > Conclusion: China sends too many tubes over here that are not fit for audio
: > use due to unreliability. The best ones are priced quite high and still have
: > too many failures.
: Considering what they are paying the help, namely zero, worthless
: Chinese yuan, they ought to go for half price or less for tubes of
: quality equivalent to Russian or other Eastern European tubes..
: not DOUBLE!
: 95% of what one pays for Chinese tubes (I regret that out of necessity
: I carry a few) goes right in the bank accounts of distributors,
: importers, and greedy Chinese bureaucrats. Most of the rest pays
: for duty & freight.
: Meanwhile the help is living on rice & 10 for a buck packs
: of ramen noodles. Or worse, that tofu stuff. YUK!
: Just my crank left-wing opinion.
Yup. And that's if they're paying the help at all. Using prison
labour is rather common in China.
Personally, I avoid Chinese products for this reason, but with
tubes you've also got the quality issues to deal with. Most folks
that I've spoken to have said the chinese tubes are substandard.
Chris