Location: Glasgow/Italy
Posts: 866
I'm Drew.
PT XVI - RCA Red base 5691
rca red base 5691.jpg
Sometime ago I heard about the RCA redbase 5691. There's plenty of information on the internet about them. They are perhaps the ultimate variant of the 6SL7 valve with many improvements over standard 6SL7'S. I liked this valve so much I had the Croft pre-amp modded to specifically run from them and I still have the flexibility to run all the old 6SL7 and GT / GTY variants as well. This valve put quite simply is the best thing I've ever heard in my Croft Pre-amp. Even though I have a pair of Bendix Red Base 6591 which I used for quite a while until they went tits up and then I got the RCA's. They are the same spec wise but the RCA's just seem better, it's probably down to them being a strong tested pair. They are very holographic and ideal for Jazz they have a midrange that beats anything that I've heard before. Vocals are also life like. Overall I think these are probably not going to be bettered, but I'll try!! I've still not heard Mullard ECC35's or the Melz 5 hole variants. So, these are now my new reference valves. Here's how things look now with the shoot out results.
1. RCA 5691 (Red Base) 9.75/10
2. Bendix 5691 (Red Base) 9.75/10
3. Tung Sol 6S7GT (Black Bottle) 9.6/10
4. Tung Sol 6SL7GT (Orange base) 9.5/10
5. Mullard 6SL7GT (Black base) 9.25/10
6. Ken Rad 6SL7GT (Black Base) VT229 9.25/10
7. Tung Sol 6SL7GT VT229 (Black bottle) 9.1/10
8. General Electric GSL7GT (Black base 1970's) 8.75 / 10
9. Slyvania 6SL7GT black base 7/10
10. Brimar 6SL7GT (black base) 6.25/10
11. Reflektor black base 70's version 5/10
Until next time.
SS
CD Teac VRDS25X(Audiotuned) DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10
VALVE
PRE Croft Epoch(Modded) AMP Sondex S100 (Modded) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Ref XO + Batpure supertweeters DECK Garrard 301 Mat Teunto Bearings 401(Bastin) Plinth Bamboo Arms 3009/3012 PSU Eagle+Tachometer MC Ag Meister II/FGS + Ortofon SPU MONO CABLES Arm Yannis 420.5 Litz+ SpeakerPC Tripple C+WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostages Paradise(4 Box Mega-Modded) / Croft Musicmaker
Location: Glasgow/Italy
Posts: 866
I'm Drew.
The RCA red base 5691 is indeed an excellent tube- I used these for some months till finding and settling on the smoked glass Tung Sol 6U7 gty. I find the latter more rounded and 'ballsy' and not quite as dry sounding
PT XVII - RCA "coin" base 6SL7GT
I'd never even heard of this one until Marco bought a pair. I decided to follow suit and see if they could usurp my 5691 reference valves. The "coin" base is very well made and dates from the 1970's. It's an extremely articulate valve. It demonstrates excellent timbrel decay and female vocals sound amazing. This valve produces a very well defined and powerful bass and it demonstrates amazing insight into recordings. It's a great valve and one that I'd quite happily live with but it does have it's issues. It produces a muted top end treble and looses out some of the clarity and precision of the 5691 I noticed this on the production of rim shots that were less well defined. I also noticed that this valve had no "air". Notes hang around in the soundstage with the 5691's this was not apparent with the "coin" base RCA's. I'd also say that the 5691 has a tad more delicacy than the "coin" base. Overall a great valve, the 5691 is still king of the tower. I'm going to give this one a 9.6 it's not as good as the Tung-sol black bottle so it can sit in the No 4 position.
1. RCA 5691 (Red Base) 9.75/10
2. Bendix 5691 (Red Base) 9.75/10
3. Tung Sol 6S7GT (Black Bottle) 9.6/10
4. RCA 6SL7GT (Coin base" 9.6/10
5. Tung Sol 6SL7GT (Orange base) 9.5/10
6. Mullard 6SL7GT (Black base) 9.25/10
7. Ken Rad 6SL7GT (Black Base) VT229 9.25/10
8. Tung Sol 6SL7GT VT229 (Black bottle) 9.1/10
9. General Electric GSL7GT (Black base 1970's) 8.75 / 10
10. Slyvania 6SL7GT black base 7/10
11. Brimar 6SL7GT (black base) 6.25/10
12. Reflektor black base 70's version 5/10
Next time around I will be looking at a very special 6SL7 variant the Black Bottle Tung-Sol 6SU7GTY from the 1950's.
Until next time....
SS
CD Teac VRDS25X(Audiotuned) DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10
VALVE
PRE Croft Epoch(Modded) AMP Sondex S100 (Modded) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Ref XO + Batpure supertweeters DECK Garrard 301 Mat Teunto Bearings 401(Bastin) Plinth Bamboo Arms 3009/3012 PSU Eagle+Tachometer MC Ag Meister II/FGS + Ortofon SPU MONO CABLES Arm Yannis 420.5 Litz+ SpeakerPC Tripple C+WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostages Paradise(4 Box Mega-Modded) / Croft Musicmaker
I certainly agree with your top placing. Superb valves.
SS
CD Teac VRDS25X(Audiotuned) DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10
VALVE
PRE Croft Epoch(Modded) AMP Sondex S100 (Modded) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Ref XO + Batpure supertweeters DECK Garrard 301 Mat Teunto Bearings 401(Bastin) Plinth Bamboo Arms 3009/3012 PSU Eagle+Tachometer MC Ag Meister II/FGS + Ortofon SPU MONO CABLES Arm Yannis 420.5 Litz+ SpeakerPC Tripple C+WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostages Paradise(4 Box Mega-Modded) / Croft Musicmaker
Be interested to read your findings.
I've got big expectations now that Marco bigged 'em up.
SS
CD Teac VRDS25X(Audiotuned) DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10
VALVE
PRE Croft Epoch(Modded) AMP Sondex S100 (Modded) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Ref XO + Batpure supertweeters DECK Garrard 301 Mat Teunto Bearings 401(Bastin) Plinth Bamboo Arms 3009/3012 PSU Eagle+Tachometer MC Ag Meister II/FGS + Ortofon SPU MONO CABLES Arm Yannis 420.5 Litz+ SpeakerPC Tripple C+WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostages Paradise(4 Box Mega-Modded) / Croft Musicmaker
6SU7GTY - Have landed today from US of A, I shall be installing these over the next few days for evaluation.
SS
CD Teac VRDS25X(Audiotuned) DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10
VALVE
PRE Croft Epoch(Modded) AMP Sondex S100 (Modded) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Ref XO + Batpure supertweeters DECK Garrard 301 Mat Teunto Bearings 401(Bastin) Plinth Bamboo Arms 3009/3012 PSU Eagle+Tachometer MC Ag Meister II/FGS + Ortofon SPU MONO CABLES Arm Yannis 420.5 Litz+ SpeakerPC Tripple C+WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostages Paradise(4 Box Mega-Modded) / Croft Musicmaker
Just out of interest I found this on a website and thought it might be useful for those of you that dabble with these valves. THIS IS NOT MY TEXT!
The 6SL7 is a high-mu twin triode in an octal based glass package. To my knowledge, there were not any metal shell versions made. Each triode section operates as a
class-A amplifier. This tube has much higher mu than it's cousin, the 6SN7. It's factor is 70, whereas the 6SN7 is only 20, therefore these two tubes are not
interchangeable. There is still a good population of hi-fi and musical instrument amps using this tube in the preamp stage out there, and these tubes are still
available. The 6SL7 was never as popular as the 6SN7---due to the 6SN7's widespread use in television chassis design---so this tube does not turn up as often whenever
vintage tubes are being sold. It is, in the proper circuit, a wonderful sounding tube, and audiophiles would do well to try the NOS vintage 6SL7 tubes before buying
anything currently made today.
These tubes come in glass packages, and have envelope sizes similar to the 6SN7 family. GE usually used a short glass shell, RCA used the medium, and Sylvania,
Westinghouse, and Raytheon often used the "tall boy" style. There are many variations among brands, and even within brands. Here is a summary of what is most often
available:
6SL7GT / G:
This is the standard version of this tube produced by most USA makers. Nearly all have a pair of cylindrical plates, usually mounted low in the tube. Early versions
have an RF shield sprayed on inside the glass (greyglass), and then since about 1952 were made of clearglass. RCA used the famous blackplates and a bottom getter, as
did early Sylvania. In the 1950s, Sylvania went to a top getter, called chrome tops, and used both a short and a tall boy style. General Electric used a short glass
envelope, bright nickel plates, and a side mounted getter. They also made tubes for other brands. Whenever you see the bright plates, even in tall boy glass with
bottom getters they were most likely made by GE. Ken Rad tubes are just like GE. Early Tung Sol tubes looked like RCA, but later went to small grey rectangular plates
that looked like tiny 6SN7 GE plates. Tubes made after 1975 used the coin or wafer base. These are all great vintage tubes.
5691:
This is the "industrial" version of the 6SL7, and has premium qualifications. These include a long life heater, extra thick mica spacers, extra support rods, and often
a low loss micanol base. RCA made these in their famous "red base" line, identified by their red marbled micanol base. Other brands sold a 5691 with brown or black
bases, but virtually all were made by RCA. The early versions have dull blackplates and the old circle RCA logo on the base and/or the top of the tube. Later versions
have greyplates, and the modern RCA logo in orange on the redbase. Both sound and perform identically. Since the greyplates are usually easier to find, they are
usually priced lower, giving a great opportunity to own a real 5691 at a savings. These tubes are great, and last a long time. They have also nearly disappeared. Their
high price is justified by their high quality and demand in the market. The military versions of the 6SL7 are often just as good, so don't despair if you can't find
5691 tubes!
ECC35:
A very rare European type of 6SL7. Philips are what are mostly seen, if rarely. The Holland made versions are similar in size to the "tall boy" USA types. These
usually have high-mounted cylindrical plates, and brown micanol bases. These are sweet and rare versions of the 6SL7, and are plug and play compatible with any 6SL7 or
5691 type tube. Some say they have all the best attributes of the 5691, with better richness and vocal clarity. Very hard to find in the USA, and worth grabbing
whenever you can find them!
JAN 6SL7GT, JAN 6SL7WGT, VT229:
These are the military versions of these tubes. The Joint Army-Navy used the term "JAN", sometimes (but not always!) with the letters WGT, and / or (but again, not
always!) with the designation of VT229. A true military tube will always be marked "JAN". They may or may not have listings such as "WGT", which is mil spec
ruggedized; or VT229, which is the military type number of this tube. A common belief is that VT229 tubes are better than JAN or WGT types. Not true! These ARE ALL THE
SAME TUBES. They may or may not have brown micanol bases. All have extra support rods and mica, and are very rugged tubes that sound wonderful. The RCA, Sylvania, Ken
Rad, and Tung Sol JAN blackbase tubes look much like their civilian counterparts. JAN Sylvania, Tung Sol, GE, and RCA also made versions with brown bases, mostly with
short glass envelopes. The JAN Sylvania have a light marbled base, and the plates inside are very short black cylinders. These milspec versions are an endangered
species, and stocks may be wiped out when the 5691 series of tubes vanish. Prices are on the way up because of this.
6SU7GTY / 6188:
This is a premium version made by Tung Sol, possibly made by them for other brands as well, as GE lists it in their own "Essential Characteristics" book. It has a
brown micanol base and the triode sections are factory matched. Sometimes the tube is listed by the industrial number of 6198, some military types list both numbers on
the tube, and yet some don't use the industrial number. It's the same tube regardless. These are great 6SL7 substitutes said to sound sweet, but are rare.
SS
CD Teac VRDS25X(Audiotuned) DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10
VALVE
PRE Croft Epoch(Modded) AMP Sondex S100 (Modded) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Ref XO + Batpure supertweeters DECK Garrard 301 Mat Teunto Bearings 401(Bastin) Plinth Bamboo Arms 3009/3012 PSU Eagle+Tachometer MC Ag Meister II/FGS + Ortofon SPU MONO CABLES Arm Yannis 420.5 Litz+ SpeakerPC Tripple C+WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostages Paradise(4 Box Mega-Modded) / Croft Musicmaker