quick GE 5751 question

[Funkdeal]

i recently won this:

http://cgi.ebay.com/ws/eBayISAPI.dll...088039968&rd=1

auction. I have to replace one of the tubes because it hums. i'm looking to purchase from vacuumtubes.com. their description for the ge5751 is " GE 3 Mica 5751 NEW (NOS) These have 3 mica spacers for extra support which results in a superior non-microphonic tube. There are also 2 support rods to aid in the mechanical rigidity of this excellent tube. These are thought of by many audiophiles as "the best". Some have black plates, some have gray plates. You need to specify which you want. Tested Good For Gain, Transconductance, Noise and Microphonics." My question is, is this the same tube? the tubes i won say "jg5751", yet i have seen other ge 5751s without this marking. All i want to do is replace this one humming tube with an identical, non-humming tube. thanks.

 

[Funkdeal]

.

 

[tomb]

VacuumTubes.com also says this in addition to what you quote:
Quote:

This is the "milspec" version of the 12AX7, but is also slightly different. The 5751 has the same plate resistance as the 12AX7, but the gain factor is only 70 compared to 100 for the 12AX7. The 12AT7 also has a gain factor of 70, but since the plate resistance is different, the 5751 is closer to the 12AX7. The older "real" 5751's have extra thick mica spacers and extra support rods to minimize microphonic response. 5751's also have matched triode units. Late versions produced by Philips/ECG don't have the extra support and don't perform as well as the older 5751's.

From Brent Jesse Recording/Tubes:
Quote:

5751: This version was usually the one made for the US military. These have a lower gain than the 12AX7, but are otherwise totally compatible. Great hi-fi tubes, as the lower gain reduces noise and microphonics. These are all ruggedized and most can withstand a drop on the floor. The internal triode elements are matched as well. The early versions are more sought after as they usually have extra support rods and an extra mica spacer on top of the plate structure ("Triple Mica"), as well as blackplates, all said to contribute to low microphonics. Don't overlook the greyplate versions, they are also excellent tubes, and many of these have the triple mica as well. The GE non-military version is usually the "five star" series, intended for broadcast use. The RCA broadcast type is the "Command" series. Both the RCA and GE broadcast types are scarce, as are any of the triple mica types.

Brent Jesse also says this in response to the question - "OK - so how do they sound?
Quote:

RCA, RAYTHEON, GE, SYLVANIA, and other USA made NOS: This group is very diverse. The RCA, Raytheon, and Sylvania blackplates are among the best here. These are very musical tubes with air and sparkle at the top end, warmth in the mids, and great bass. The RCA are drop dead beautiful in guitar amps, even the lower priced greyplate and longplate versions. They also have a wonderful "phat" gritty sound when overdriven in these amps. The blackplates and most tubes made for organs are very quiet. The greyplate GE is an all-around nice-guy tube to listen to, the longplate here possibly getting the nod for hi-fi use. The Sylvania greyplate and military versions are clean and a bit bright, but the Sylvania 5751 variants are very balanced and pleasant to listen to for hours. The GE blackplate 5751 triple mica is also in great demand as a very musical vintage tube. The RCA 5751 is more like the Mullard, with a rich warmth and wide bandwidth. Currently, the USA made tubes are a nice surprise with their low prices as compared to the European types.

Short of trying what you've bought or something else, I doubt that you will ever get more elaborate descriptions for a tube variant than this.

 

[d-cee]

yep, i prefer the 5751s over 12AX7s for their lower noise/gain

 

[Jon L]

Quote:

Originally Posted by Funkdeal /img/forum/go_quote.gif i recently won this: http://cgi.ebay.com/ws/eBayISAPI.dll...088039968&rd=1 auction. I have to replace one of the tubes because it hums. i'm looking to purchase from vacuumtubes.com. their description for the ge5751 is " GE 3 Mica 5751 NEW (NOS) These have 3 mica spacers for extra support which results in a superior non-microphonic tube. There are also 2 support rods to aid in the mechanical rigidity of this excellent tube. These are thought of by many audiophiles as "the best". Some have black plates, some have gray plates. You need to specify which you want. Tested Good For Gain, Transconductance, Noise and Microphonics." My question is, is this the same tube? the tubes i won say "jg5751", yet i have seen other ge 5751s without this marking. All i want to do is replace this one humming tube with an identical, non-humming tube. thanks.

The Ebay ones are 1950's "JG" models, which ARE different from the usual "5 Star" ones (ones with 5 stars on the glass). Sound-wise, they are very similar, but the "JG" model does sound more old-school, i.e. warmer, smoother, but not as detailed.

 

[djbnh]

Quote:

Originally Posted by Jon L /img/forum/go_quote.gif The Ebay ones are 1950's "JG" models, which ARE different from the usual "5 Star" ones (ones with 5 stars on the glass). Sound-wise, they are very similar, but the "JG" model does sound more old-school, i.e. warmer, smoother, but not as detailed.

I've used both NOS GE JG5751s and the 5 Stars in my JD-100. In that application, in my system to my ears, the JGs far outshone the 5 Stars in sound quality and detail retrieval; frankly, I had to return the 5 Stars to Brent Jesse because I found them patently unlistenable. I also felt that GE NOS JAN5751s sounded better than the 5 Stars, in the above application. YMMV.

Here's some 5751 tubes I've rolled in the JD-100. I still keep a pair of GE JG5751s in storage...