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Marco
30-12-2009, 21:35
Guys,

I've been doing a little bit of tube-rolling with the Croft (as one does) and after some research decided to buy these NOS, new-in-box, 1950s RCA 5691 Red Bases (originals with black plates):

http://img526.imageshack.us/img526/7514/rca5691redbasematchedpa.jpg (http://img526.imageshack.us/i/rca5691redbasematchedpa.jpg/)

http://img41.imageshack.us/img41/7514/rca5691redbasematchedpa.jpg (http://img41.imageshack.us/i/rca5691redbasematchedpa.jpg/)

...which have replaced the NOS Brimar CV1985s I was using. These are the exact ones I've put in the Croft, pictures courtesy of the supplier I bought them from: http://www.hifitubes.nl/catalog/index.php

I've only put them in a few hours ago, but suffice to say even at this early stage, the improvement is not subtle and quite considerable, even over the already excellent Brimars.

Full report to follow... However in the meantime, does anyone else have experience with these particular valves?

Marco.

Jonboy
30-12-2009, 22:08
oooh they look pretty

Rare Bird
30-12-2009, 22:13
Guys,

I've been doing a little bit of tube-rolling with the Croft (as one does) and after some research decided to buy these NOS, new-in-box, 1950s RCA 5691 Red Bases (originals with black plates):

http://img526.imageshack.us/img526/7514/rca5691redbasematchedpa.jpg (http://img526.imageshack.us/i/rca5691redbasematchedpa.jpg/)




Seen a pair of those on E-Bay 150.00 quid :eek:

Marco
30-12-2009, 22:16
Yes that's roughly what I paid (as a Christmas present to myself) ;)

I've heard less of an improvement though from some box changes costing ten times that!

Marco.

Rare Bird
30-12-2009, 22:21
I could do with a single NOS 5670.

http://i12.photobucket.com/albums/a222/LIVING-SIN/5670.jpg

Rare Bird
30-12-2009, 22:23
Yes that's roughly what I paid (as a Christmas present to myself) ;)

I've heard less of an improvement though from some box changes costing ten times that!

Marco.

145.00 + post by any chance ;)

Marco
30-12-2009, 22:29
£141.20 including standard shipping + 7 Euros extra for 'super-fast' trackable delivery, to be precise ;)

I ordered them on 23rd of this month from Holland and they arrived today - that's not bad at all, especially considering the time of year...

The chap I dealt with was extremely efficient and professional.

Marco.

Jonboy
30-12-2009, 22:37
Seen a pair of those on E-Bay 150.00 quid :eek:


I saw the same ones and thought blimey as well, no pain no gain though, sometimes you just have to bite the bullet and take a chance, it looks like it paid off, we are now all the wiser for it ;)

As with all things Hifi sometimes you gain, sometimes you lose, and sometimes you just go sideways,

Marco
30-12-2009, 22:42
I could do with a single NOS 5670.

http://i12.photobucket.com/albums/a222/LIVING-SIN/5670.jpg

Not sure if this fits your criteria, matey:

http://www.hifitubes.nl/catalog/advanced_search_result.php?keywords=5670&x=4&y=7

It's from the same place where I got the 5691s :)

Marco.

Rare Bird
30-12-2009, 22:55
Cheers tarzan

Marco
30-12-2009, 22:58
Hi Jon,


I saw the same ones and thought blimey as well, no pain no gain though, sometimes you just have to bite the bullet and take a chance, it looks like it paid off, we are now all the wiser for it ;)


Yep, that's what places like AoS are for - sharing useful info for the benefit of everyone.


As with all things Hifi sometimes you gain, sometimes you lose, and sometimes you just go sideways,

Too true! I did some considerable research on the 5691s, though (as I always do with anything I buy), so I knew what the going rate was and what they were likely to bring to the party, sonically - and yes it's paid off big time :)

What they have over any other 6SL7s I've heard (and I've been through most of them) is absolutely superb transparency and clarity, and they also seem subjectively less 'noisy', so that detail retrieval is enhanced and musical nuances in familiar recordings as a result are rendered with greater definition (perhaps because they're less microphonic than the Brimars or other 6SL7s I've used). The 5691s (6SL7s) are high-gain valves, so any issues with microphony can be significant. They are also extremely solidly constructed and considerably heavier than the Brimars they replaced, which themselves were none too shabby in that respect.

More later, chaps, as I'm off now for another listen :cool:

Marco.

The Grand Wazoo
31-12-2009, 00:04
Hi Marco,
I used to own a Cary power amp & got some of these to put in it. This was about 1994/5 I think. They seemed very good but I never really got the opportunity to explore just how good they were, as the amp kept going grid short on the power valves.

I chucked bundles of cash at that amp & ended up losing another bundle!

Marco
31-12-2009, 00:37
Yep, Chris, it doesn't surprise me that those valves were used in quality equipment like Cary...

I think it's significant that 6SL7s are largely an American creation, so I guess it makes sense that they made the best ones - especially those designed during the heyday of the 50s!

Marco.

Mike
31-12-2009, 11:32
Guys,

I've been doing a little bit of tube-rolling with the Croft (as one does) and after some research decided to buy these NOS, new-in-box, 1950s RCA 5691 Red Bases (originals with black plates):

RCA?... They look like General Electric to me! ;)

One thing to watch, you may want to check with Anthony if you haven't already, the 5691 draws double the heater current of a 6SL7. Make sure your amps heater windings are up to it!

Marco
31-12-2009, 11:59
Hi Mikey,

Thanks for that... It'll be Glenn I need to speak to as the new valves are in the Croft, or is it liable to also affect the Copper amp?

I thought that RCA and GE were one and the same (or certainly related in some way)?

Marco.

Mike
31-12-2009, 12:08
Hi Mikey,

Thanks for that... It'll be Glenn I need to speak to as the valves are in the Croft :)

That would make sense, the 6SL7/5691 being high Mu!

HERE'S (http://www.mif.pg.gda.pl/homepages/frank/sheets/084/5/5691.pdf) the data sheet for the 5691, you'll see heater current is mentioned compaired to the 6SL7.


I thought that RCA and GE were one and the same (or certainly related in some way)?

Could be... I'm not sure on that one.

Cheers...

Marco
31-12-2009, 12:19
Cheers for that - I'll have a goosey :)

Are you all ready for a party tonight? :cool:

Marco.

Will
31-12-2009, 12:39
http://www.vacuumtubes.com/6sl7.html

.

Marco
31-12-2009, 15:32
Hi Will,

Happy New Year, mate :cool:

Interesting link......


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!!


That clears up Mikey's earlier point about RCAs and GEs - I also agree that the 5691s are without question the best sounding 6SL7-types I've heard :)


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.


What's mad is that I honestly had no idea about the existence of "extra support rods and mica spacers to eliminate microphonics", yet the system resolved the effect and I could clearly hear the difference they make!!

There's a distinct absence of background 'hash' and 'noise', due to lower microphonic effects, which allow these particular valves to unravel all sorts of subtle musical nuances, diluted by others valves of their type, simply because they're more microphonic.

I'd love to see some bloody objectivist try to measure the difference, which is why there's no substitute in hi-fi for experienced ears! ;)

Anyway, clearly the 5691s are a bit special, so I'm well chuffed with my purchase... I'll toast my good fortune, chaps, with a nice glass of Amarone - Happy New Year! :cheers:

Marco.

SPS
02-01-2010, 22:19
- I also agree that the 5691s are without question the best sounding 6SL7-types I've heard :)



.

happy new year to you all...

what are they like compared the the ecc35 marco?

steve

Marco
03-01-2010, 12:51
Hi Steve,

Happy New Year, matey! :)

The 5691s (to my ears in my system) have much less of a sonic signature. I find ECC35s a bit 'boom 'n' tizz for my liking (i.e. they emphasise the frequency extremes too much), so they're not really my thing. I'd far rather use Brimars, Tung-Sols or Sylvanias, but the 5691s, for me, are in a different league to any other 6SL7-type I've heard so far.

Marco.

ElTwang
14-03-2010, 22:58
I just ordered two of these for my Croft Vita pre-amp. Now the big question is where to get the most out of them? I have 4 6SL7s in the amp. Anyone knows how the 4 tubes works in the Vita?

Marco
15-03-2010, 15:05
Hi (any chance of a real first name and location please - have you posted yet in the welcome area?) :)

Where did you order the 5691s from?

If the Vita is anything like my Charisma-X, the first two valves (from the left) generally make the most difference to the sound...

Well, let me clarify that more - my CX has five 6SL7s in total. The first two (from the left) control the line output, the third (middle one) seems to affect both the line and phono output, and the last two control the phono stage.

I presume your Vita has a phono stage? If so, I'd imagine that the four valves are split evenly between the phono and line stage - dunno why it hasn't got five valves though like mine :scratch:

Anyway, let us know how you get on :cool:

Marco.

ElTwang
15-03-2010, 21:19
Cheers Marco,

Yeah, the Vita has a phono stage. So it's probably like you say. Maybe the Vita has a more simple phono stage although Glenn told me it's pretty much the same as the Charisma! I found the tubes in Denmark, where I live. If this turns out to be a considerable upgrade as you state earlier in this thread I'll be right off looking for two more.