SCORE!

[Marco]

Hi Rob,

What he said. The 5691’s are the holy grail of 6SL7 replacements. I have the Melz 6H9Cs in at the moment, which are very very good indeed, but these are the best of the lot apparently.

The buffer is on around 14 hours a day (on when I wake up, off when I go to bed - the system plays pretty much all day). That’s about 5,000 hours a year so these should do me four years, or more hopefully.

Nice one. How much did you pay for the quad? IME, NOS/NIB ones are normally around £70 a piece (or the equivalent in dollars).

I rate the 5691s highly, especially in terms of construction and reliability. I'm also a fan of Melz 6H9Cs. I've used both in my Croft. However, there are other 6SL7s that could also be considered as 'the holy grail'. If you get an opportunity, try some 1940s vintage [*must* be that, not later versions] black glass Tung Sol 6SU7GTY or Mullard ECC35 ['tall glass' with short brown base, such as shown here: https://www.ebay.co.uk/p/1008033773?iid=383269849766 ) both of which IMO would give your 5691s a run for their money!

However, as I've said to Andy elsewhere, much of this comes down to the circuit that the valves are being used in and your personal sonic preferences. Enjoy!

Marco.

[Marco]

Interesting thread here, from the Andy-boy, lol: https://theartofsound.net/forum/show...ENTURES!/page5

I have to say that I agree with Drew in preferring the Tung Sols to the 5691s - and for the very same reasons!

Marco.

[Marco]

Have you got the 5 hole version of the Melz? If so, interested in selling?

Andy, as far as I know (although I could be wrong, as I'm not 100% sure), the proper 'holed' version of the Melz is only available as 6H8C (6SN7), not as 6H9C (6SL7), which is what you need for your Croft.

The desirable 'holed' 6H8C look like this (I have some, which I use in my Copper amp): https://www.ebay.com/itm/2x-6N8S-6H8...wAAOSw-RlfsdZA

As opposed to the 'holes' in Melz 6H9C, which are quite different:https://www.ebay.com/itm/NEW-METAL-B...8AAOSwnHZYeuAO

You'll see that the construction of the (holed) anodes there is very different from those in the 6H8Cs, so bear that in mind

Marco.

[Filterlab]

However, there are other 6SL7s that could also be considered as 'the holy grail'. If you get an opportunity, try some 1940s vintage [*must* be that, not later versions] black glass Tung Sol 6SU7GTY or Mullard ECC35 ['tall glass' with short brown base, such as shown here: https://www.ebay.co.uk/p/1008033773?iid=383269849766 ) both of which IMO would give your 5691s a run for their money!

I paid £266 for the quad of 5691s (£66.50 per valve) plus £18 shipping. As I got them from a chap in Spain there were no import charges of course - that'll end soon no doubt.

Well so far the 5691s have been the best on my valve buffer, but I'm always keen to try other valves of course. I have to say that the Melz 6H9Cs really are splendid, especially the scintillating treble. I have another NOS pair of metal base OTKs winging their way to me from Ukraine, so I'll then have five pairs of valves in the cupboard (pair of 40s NOS Sylvania 6SL7GTs, 2x pairs of 50s Melz 6H9Cs [one pair NOS], The Tung Sols [below] and the other pair of NOS 5691s).

I did purchase a new pair of Tung-Sol 6SL7GT gold tips from Hotrox, but they were incredibly disappointing. Flat and lifeless, rolled off, dull. Granted I may not have given them enough time, but you know how it feels when you just know something won't improve *that much* - just a waste of time waiting.

I left the buffer stage switched on over last night to get a few hours of warming into the 5691s, and this morning they just sound absolutely stonkingly fabulous. The bass control, depth, punch and weight is the most staggering thing about them, so far anyway; the treble too is electrifying. Just playing a bit of YouTube Music autoplay currently, bit of chill out. Will listen properly later.

I'll look out for the Tung Sols and Mullards. I've read good things about their ECC35 tall glass jobs. I did have a scan around but couldn't see any matched pairs available, tricky find I reckon. I've spent enough for one month I think, those ECC35s ain't cheap!

What has enamoured me though is the quality of sound valves bring to a system. There seems to be lots of nonsense written around the web (surprise surprise) saying that they colour the sound, kill the treble, add distortion etc etc., but I've only heard 'more' with the valve buffer in place; more life, more musicality, more detail, more impact - with no detriment. I can't believe I've been into Hi-Fi for 35 years and never bothered with valves.

Andy, as far as I know (although I could be wrong, as I'm not 100% sure), the proper 'holed' version of the Melz is only available as 6H8C (6SN7), not as 6H9C (6SL7), which is what you need for your Croft.

The desirable 'holed' 6H8C look like this (I have some, which I use in my Copper amp): https://www.ebay.com/itm/2x-6N8S-6H8...wAAOSw-RlfsdZA

As opposed to the 'holes' in Melz 6H9C, which are quite different:https://www.ebay.com/itm/NEW-METAL-B...8AAOSwnHZYeuAO

You'll see that the construction of the (holed) anodes there is very different from those in the 6H8Cs, so bear that in mind

Marco.

I searched through hundreds of images of the Melz 6H9Cs to see if there was a different build, but I too could only find the 6H8Cs with the holes in the anodes. My Melz 6H9Cs are these ones, but I'm not selling.



The RCAs are lovely looking things too...

[da2222]

What he said. The 5691’s are the holy grail of 6SL7 replacements. I have the Melz 6H9Cs in at the moment, which are very very good indeed, but these are the best of the lot apparently.

Great tubes for sure but IMO not the best of the lot. That accolade goes to the Tung Sol 6U7GTY: slightly less dry and full bodied with glorious mids...

[Filterlab]

They must be good!

[REXTON]

I do not think that the 5691 and the Tung Sol 6U7GTY are entirely the same thing, in fact I'm sure that they have different specs and as such I think the 6U7GTY will not correctly work to full efficiency with a 6SL7 only circuit, that is unless it's been tweaked to do so. This is my understanding, I could be wrong and would like to be corrected if I'm talking knackers. My Croft which was designed to run with 6SL7's it would run 5691's but not to full efficiency and needed an upgrade to get the 5691 heaters working to full capacity. I wonder if this is the same with the 6U7GTY???????

[REXTON]

Andy, as far as I know (although I could be wrong, as I'm not 100% sure), the proper 'holed' version of the Melz is only available as 6H8C (6SN7), not as 6H9C (6SL7), which is what you need for your Croft.

The desirable 'holed' 6H8C look like this (I have some, which I use in my Copper amp): https://www.ebay.com/itm/2x-6N8S-6H8...wAAOSw-RlfsdZA

As opposed to the 'holes' in Melz 6H9C, which are quite different:https://www.ebay.com/itm/NEW-METAL-B...8AAOSwnHZYeuAO

You'll see that the construction of the (holed) anodes there is very different from those in the 6H8Cs, so bear that in mind

Marco.

Thanks for the heads up, that's one less thing to buy!

[da2222]

I do not think that the 5691 and the Tung Sol 6U7GTY are entirely the same thing, in fact I'm sure that they have different specs and as such I think the 6U7GTY will not correctly work to full efficiency with a 6SL7 only circuit, that is unless it's been tweaked to do so. This is my understanding, I could be wrong and would like to be corrected if I'm talking knackers. My Croft which was designed to run with 6SL7's it would run 5691's but not to full efficiency and needed an upgrade to get the 5691 heaters working to full capacity. I wonder if this is the same with the 6U7GTY???????

The 6SU7GTY is essentially a premium 6188 tube and a very close sub for the 6sl7- the specs are virtually identical with the exception of the Va max for the 6SU7 which is 250, while the 6SL7's is 300. It works like a dream in place of the 6SL7

[Filterlab]

6SL7
6SL7GT
ECC35
6H9C
6188
5691
6SU7
6SU7GTY
6N9S

All interchangeable with little issue I understand. There’s probably more monikers for the same convention.

Correct me if I’m wrong.