Has anyone tried out different tubes in a 737sp?

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I replaced the sovtek tubes in my 737 with a NOS set of RFT ECC88's.
There was no change in gain, and I could not detect any extra noise
compaired to recordings made with both sets of tubes. I have had them
in the 737 for about a year now with no problems. I didn't do a full
scientific test of all functions, but I did do pre and pre/comp
comparisons with prerecordrd tracks. The RFT's brought a slightly
different character to the sound of a Neumann TLM 193 and acoustic
guitar. They seemed to make the mids a little more pronounced with a
warmer top in the dog ear zone. The compressor results were similar
to the original tubes, but I didn't do any comprihensive comp test. I
thought it was a good combo with the TLM 193. I liked it and left
them in. The truth was the difference was very small to my ears, but
I have played a few thousand gigs. Just wanted to see if anyone
else out there has tried experimenting with the tubes in the 737.

David Brouillette

www.basswhore.com

Archived from groups: rec.audio.pro (More info?)

> I replaced the sovtek tubes in my 737 with a NOS set of RFT ECC88's.
> There was no change in gain, and I could not detect any extra noise
> compaired to recordings made with both sets of tubes. I have had them
> in the 737 for about a year now with no problems. I didn't do a full
> scientific test of all functions, but I did do pre and pre/comp
> comparisons with prerecordrd tracks. The RFT's brought a slightly
> different character to the sound of a Neumann TLM 193 and acoustic
> guitar. They seemed to make the mids a little more pronounced with a
> warmer top in the dog ear zone. The compressor results were similar
> to the original tubes, but I didn't do any comprihensive comp test. I
> thought it was a good combo with the TLM 193. I liked it and left
> them in. The truth was the difference was very small to my ears, but
> I have played a few thousand gigs. Just wanted to see if anyone
> else out there has tried experimenting with the tubes in the 737.

I regret to inform you that the term "NOS" can't be applied to RFT's since
they are current production. Sitting on a shelf doesn't improve a tubes
tone, NOS tubes were made much better back when they were in higher demand.
And while RFT's are among the better sounding current production tubes, keep
a set of back-ups, they're not very reliable. I've personally had 1 PCC88
and 3 EL34's die prematurely. The PCC88 didn't last 10 hours. The other
one of the matched pair I gave to a friend for his CAD M9 tube mic, it
lasted less than 6 months. The EL34's were part of a $300 matched quad, and
man was I pissed when the first one went at about 9 months. Hopefully YMMV.

Note that RFT tubes also get labelled with other brands, including
Precision, Siemens, and even Telefunken. Never buy a tube without being
certain of its true origin. I got shafted on a pair of NOS Telefunken
PCC88's to replace the RFT's, turns out they were current production Siemens
with Telefunken label. Case in point the "Philips JAN 6922's" that ship
with Rode NTK's which are actually just Sovteks tested by Philips to weed
out the duds. A US-made Philips JAN ECC88 sounds quite different and better
in most respects.

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"Scott Dorsey" <kludge@panix.com> wrote in message
news:cobci7$5q0$1@panix1.panix.com

> I'll say that I am starting to see this sort of thing with
> semiconductors too. I bought some 2N3055s from a dealer in the DC
> area. Put them into circuit and they went blam. Turns out first of
> all that they were NOT made by Motorola, even though Motorola's logo
> was stamped on them... Motorola never made the type of TO-3 package
> these had. Secondly, what was inside was NOT a 2N3055... it had
> about half the surface area and probably half the power dissipation
> too.

Regrettably, this is actually a very old story. The Aussies have written up
a number of articles about this recently, of which this is one of the better
ones:

http://sound.westhost.com/counterfeit.htm

Semi device manufacturers also do this to themselves!

The earliest story of the problem of undocumented derated semiconductors I
ever heard of happened to a friend of mine who was building pro audio power
amps, and was literaly just about put out of business by RCA. The background
is that RCA used to have a active fire hose of robust power devices with a
wide range of useful parameters for audio power amps, based on their volume
production of devices for automotive ignition systems. When they lost the
automotive contract they tried to make comparable devices intentionally to
keep the far smaller audio market. The resulting devices went over with the
same kind of literal bang that you mentioned, Scott. This was in the 1970s.

Motorola is reported to have had similar missteps related to mainframe disk
drive servo amp devices. An existing line of audio power transistors were
*close enough* to disk drive needs and sold in tremendous volumes to
computer makers. The production device parameters ended up getting tipped
towards disk drive servo amps, and away from optimal values for audio power
amps. People who purchased these devices for making high powered audio amps
suffered accordingly. This was in the 1980s.

Apparently it takes some careful time-consuming diffusion steps to make a
power transistor with good SOA. Not everybody with production ovens knows
the trick, and not everybody who knows the trick want's to tie up the
required production facilities, given the volume and permissable pricing.

Then, there are just some people who want to cheat. Everybody who is
surprised, raise your right hand! ;-)

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I am constantly amazed by how much Mr. Dorsey knows.

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Carey Carlan <gulfjoe@hotmail.com> wrote:
>genericaudioperson@hotmail.com (xy) wrote in
>news:6c38b64b.0411292211.47c047c6@posting.google.com:
>
>> I am constantly amazed by how much Mr. Dorsey knows.
>
>I'm no longer amazed except when he *doesn't* know something.

I just have a really good library. You don't have to know anything as long
as you know where to look it up within a minute or so.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."