6SL7 Tube List

(5691, 6SU7)

5691

The type 5691 Tube is a "premium" version of the type 6SL7.  The "premium" qualities of the 5692 include a long-life cathode rated at 10,000 hours along with extra support rods and mica spacers to eliminate microphonics.  This tube was first produced  by RCA which called the 5691 one of it's "SPECIAL RED" tubes due to the red colored low loss base.  RCA rated these tubes for 10,000 hours . Other companies produced this tube with brown and black bases.  This tube is highly sought after and commands high prices due to its superior sonic qualities and long life.

5691 RCA Red:  These have red bases and were produced by RCA.  They may have other branding such as GE or Raytheon, etc. but will have been produced in the RCA factory.  They usually have black plates although later production units have gray plates.  Many say this is the best sounding tube ever......and they last forever!!  Like all premium quality, high demand tubes, these are always in short supply and continue to be harder and more expensive to find!  Get them while you still can.....only a very few in stock.

Type	Description	Price
5691 Red Base	RCA Red Base.  Older versions are Black Plate, Newer are Gray Plate.  Some have branding other than RCA, but are RCA manufactured.  Just like the 5692 (6SN7 version), these have 5 vertical support rods and extra heavy duty mica spacers for superior rigidity which result in superior microphonic performance.  RCA rated these tubes for 10,000 hours.  Many people think this is the best version of the 6SL7 ever made.	$75 Black Plate New $35 Black Plate Used $65 Gray Plate New $30 Gray Plate Used

5691 Black

5691 Black:  These are usually made by Sylvania  but just as RCA were sold to other companies such as GE to put their brand name on.  They still have the extra supports for the elimination of microphonic problems and many people claim they sound as good or better than the red based version.  These usually have gray plates.  While not as scarce as the red based version, these are also in short supply.  I only have a small supply on hand at any given time.

Type	Description	Price Each
Sylvania   5691   Black Base	All black based 5691's I've ever seen are all manufactured by Sylvania.  These are nice tubes with black plates and have the same kind of construction as the RCA red based tubes with the 5 support rods and extra heavy duty mica spacers.  Many claim these sound just as good as the RCA's.	$50 each New $25 each Used

6SL7

6SL7 RCA

Just like all RCA tubes, these are very high quality tubes and sound great.
Early versions made in the 1940's have a gray/black coating inside the glass which obscures the plate structure from view.  Later versions made during the 50's and 60's have clear glass with the getter down toward the bottom of the tube.  Extremely late versions made during the 70's have the coin or wafer style  base.  All of them including the latest type have the characteristic RCA black colored plate that helps contribute to it's excellent sound quality.  The plate is also cylindrical in shape rather than flat like its close relative the 6SN7.  Pretty good supply on hand at present, but RCA tubes are disappearing quickly. I expect this tube to skyrocket in cost in the next few years, so stock up now or pay the price later!

Type	Description	Price Each
6SL7 RCA Early	Early Version made in the 40's and early 50's.  Some have smoked glass	$50 ea new $25 ea Used
6SL7 RCA	Later version with clear glass, black cylindrical plates and bottom getter	$30 ea new $15 ea used

Tung Sol 6SL7

6SL7 TungSol:  This tube varied alot during it's production lifetime.  Earlier versions look very similar to the RCA's since they also had the black coating inside the tube. Early versions also had cylindrical  black plates like RCA's. Later versions had clear glass Later ones produced during the 50's and 60's had flat gray colored plates and look more like their 6SN7 counterpart.  The 6SL7WGT is the military version and usually will have more support than the commercial version.  More support usually equals less microphonic problems.   (Note that the "W" in the suffix of any tube means military ruggedized) Some of them also had brown bases which are probably repackaged military 6SL7WGT's.  Any of hese will certainly outlast and sound far better than ANY of the shit produced today.

Sylvania

Like all of the other brands mentioned, these also vary somewhat in appearance and construction depending upon when they were made.  Early ones have black cylindrical plates and bottom getters.  The glass is clear.  Later production units had the same plate structure but the getter was moved up to the top.  There is also a milspec version, the 6SL7WGT.  Earlier versions made in the 50's, 60's had brown bases and nice thick mica wafers for extra support and superior microphonic elimination.  The plate structure is shorter and heavier than the standard version.  Later units made under the Phillips ECG  during the 80's look exactly the same except for a black colored full base.However, I expect that even the late version made by Phillips ECG are probably still far better than the Russian/Chinese crap out there.Good supply of all versions on hand right now, but later???

Type	Description	Price Each
6SL7GT Early	Early version made in the 40's and 50's incl. VT-229	$40 ea new $20 ea used
6SL7GT Late	Later version made 60's through the 70's.  Full sized black bases	$20 ea new $10 ea used
6SL7GT	Latest version with the "wafer" or "coin" type base	$15 ea new

General Electric

These all look and sound pretty much the same throughout all production years.  All of them have cylindrical shaped, bright nickel colored plates and getters on the side.  The only exception in apppearance is the late production units which have wafer bases instead of the full base.  GE tubes are very well made tubes and sound great.  Good supply on hand today.

Type	Description	Price Each
6SL7GT	Cylindrical nickel plates	$20 ea new

Ken Rad

6SL7 KenRad:  These look almost exactly like the GE 6SL7 except that the getter is at the bottom instead of on the side.  They should look like GE's since KenRad was owned by GE.  They will be older than the GE's as GE dropped the KenRad name sometime during the late 40's or early 50's.  Not very many of these on hand.

National Union

These are all very old tubes as National Union disappeared shortly after the war.  Therefore most all of them were made during the 1940's.  They have the gray colored coating inside the glass so the plates are hidden from view.  I haven't had the heart to break one in order to describe the plate structure, so you will have to wait until I break on by accident!  Many of these tubes are in military packaging but do not carry the "W" desigination as I believe that the "W" designation didn't come until after the war.  Great sounding......very short supply.  Only a few on hand today.

6SL7 Misc Brands