The Marco-boy main system, as of August 2020

[Wakefield Turntables]

I use these voltage regulator tubes in my Croft preamp, and I've been wanting this one for a while, as it's a special (and rare) military spec version, from the 1950s, of the 85A2:





I've rolled these VR tubes before, and the best ones always make a nice difference, so will be interesting hearing what this one does!

For the Croft's line stage, I've also just bought a rather nice matched Pair of 1940s Raytheon 6SL7GTs in gray glass:



Looking forward to hearing those, too!

Marco.

Tried those exact 6sl7gt they are ok but there are better to be had

[Marco]

Lol, churz. I'll let you know what I think mate, as results vary wildly with tubes, depending on the kit used and also the system

Marco.

[The Black Adder]

Lol, churz. I'll let you know what I think mate, as results vary wildly with tubes, depending on the kit used and also the system

Marco.

I'm also looking to roll the ECC88s. The Mullard are always a great choice in our pimped up pre amps, Marco [emoji16][emoji106]

I've also used NOS Teslas too... They were excellent.

Sent from my 9001X using Tapatalk

[Marco]

Lol, cheers, Jo. Did you mean ECC83s, though? There are no ECC88s in my Croft, and the M8137 is a premium version of an ECC83. It'll have to go some though to better the vintage RTC 12AX7S, I'm currently using. However, I'm confident it will, or run it very close. It certainly should at £175!

I just wanted to introduce some 'Mullardy goodness' into the mix, as I haven't had any in the Croft for a while, so hopefully the M8137/M8098 combo will prove fruitful! Both are due to arrive tomorrow, so all will be revealed shortly!

Marco.

[The Black Adder]

Lol, cheers, Jo. Did you mean ECC83s, though? There are no ECC88s in my Croft, and the M8137 is a premium version of an ECC83. It'll have to go some though to better the vintage RTC 12AX7S, I'm currently using. However, I'm confident it will, or run it very close. It certainly should at £175!

I just wanted to introduce some 'Mullardy goodness' into the mix, as I haven't had any in the Croft for a while, so hopefully the M8137/M8098 combo will prove fruitful! Both are due to arrive tomorrow, so all will be revealed shortly!

Marco.

Agh... 88s? Nah, 83s for defo... Sorry bout that.

Sent from my 9001X using Tapatalk

[Wakefield Turntables]

Interesting to see what your doing with valve rolling. I've got the Tunsgram 85A2, I've tried the GEC CV449 and Phillips CV449. The Tunsgram sounds so the best so far, I've not even seen that Mullard before so I might have a go with one. I didn't realise the Mullard 8137's were going for £175 a piece I've got 6 in a stash, 3 of which are in my 834p clone. The valves are worth more than the clone. FWIW I think the 8137 are the best ECC83 variant I have ever heard.

[Marco]

Agh... 88s? Nah, 83s for defo... Sorry bout that.

Lol - no worries. What kind of valves (makes) have you got in your Croft - do you remember, when was the last time you were in there?

Marco.

[Marco]

Interesting to see what your doing with valve rolling. I've got the Tunsgram 85A2, I've tried the GEC CV449 and Phillips CV449. The Tunsgram sounds so the best so far, I've not even seen that Mullard before so I might have a go with one. I didn't realise the Mullard 8137's were going for £175 a piece I've got 6 in a stash, 3 of which are in my 834p clone. The valves are worth more than the clone. FWIW I think the 8137 are the best ECC83 variant I have ever heard.

Yeah, there are military spec versions of pretty much every Mullard valve, as back in the day many of them were used in military applications, and then later in professional civilian ones, such as the telecommunications industry, both of which where reliability and longevity was paramount.

This meant that the build quality needed to be top-notch, and subsequently the best materials were used for constructing every aspect of the valves, and which is precisely what improves their performance, from an audio perspective [usually resulting in them being less microphonic, for starters].

It's also why they're worth paying a premium for, as not only are they likely to sound better than other valves of the same type, but will last maybe 100 times longer! Simply because in most audio applications, compared with where they would've been originally designed to operate, they're not really being 'taxed'.

Therefore, valves such as this, along with the likes of original GECs, etc, are generally always worth the investment!

Marco.

[Marco]

Just scored a nice matched pair of these vintage tubes. 'Coin Base' RCAs are often frowned upon by audiophiles, but I actually like using them (and vintage RCAs in general), in key areas of the Croft's phono stage.

They have a nicely open, punchy and dynamic sound, and not in any way thin-toned [as is often their criticism] when used in the right circuit, and which doesn't need the rather 'plump' bass enhancement of 'phat' sounding tubes. When tube rolling, and subsequently optimising the sound, it's all about successfully combining 'flavours'!

Anyway, here are the little 'tall-bottled' bastards...







Nicely constructed... Look at those nice fat shiny pins!

Oh, and as an aside, this is a rather interesting site, detailing the history of many different valves, but this bit is involving 6SL7s and their history, which folks here using them should read: http://vinylsavor.blogspot.com/2016/...onth-6sl7.html



Marco.

[Marco]

Ok, so now that the Lentek's been modded, and sounding STUNNING [more on that later], it's time to start on my valve headphone amp! Firstly, just to remind folks what the internals look like again:





So... To begin with, I've sourced some quality NOS Melz tubes (including some as spares), to replace the, no doubt, modern Chinese one that'll be in it above: https://www.ebay.com/itm/6N16B-V-602...72.m2749.l2649

Secondly, I've just bought a rather nice NOS 50K Alps Black Beauty pot, originally intended for use in a McIntosh amp, which (with some jiggery pokery to the PCB, moving some caps around, etc, which Anthony will be doing) will replace the existing cheap pot:









I was originally going to fit a stepped attenuator, but decided to go down a different route for this project.

I've always liked the Alps BBs, which have a very detailed and musical sound, perhaps not quite as 'upfront' or transparent as the likes of the DACT stepped attenuator in the Croft, but it will compliment the sonic signature of this headphone amp nicely - and NOS Alps BBs (highly-regarded but long discontinued) are pretty rare these days!

Anyway, that's stage 1 and 2 of the mods, which I'll analyse separately first before starting on any alterations to caps or resistors, with the aim in the end of creating a 'giant killing' headphone amp, which majors on the highest SPPV!

Marco.