The Marco-boy main system, as of August 2020

[Marco]

try these they are a step above in my opinion https://theartofsound.net/forum/show...-Tung-Sol-6F8G

Problem is, Jamie, she needs 4!

...and also, physically, the glass envelope of those valves is too bulbous for them to fit side by side, where they need to go, as there isn't much room.

Marco.

[Marco]

Which we did today and the answer is 12uF



The next big question, is what will you replace it with?

Lol, thanks for that, mate. Could you email me all the pics you took today of the above? If you haven't already got my addy, then PM me for it.

As for what to replace them with... I'm currently considering various options and will report back later!

Marco.

[Wakefield Turntables]

Hi guys,

Firstly, the glass is defo grey, not a black of any description!

And yes, both are VT-229s, so military spec 6SL7GTs. One is badged as Raytheon, and the other as National Union. The internal construction of both valves is identical. It's my understanding that Raytheon (once a huge electronics and vacuum tube producing company) had some of their tubes rebranded under different names, one of which was National Union. So essentially they are Raytheons.

The key factors in terms of how good they sound is that they are a very closely matched pair, indeed one valve is fully balanced, and that they are 1940s vintage. That last bit is CRUCIAL, in terms of ascertaining if the ones you've had, Andy, were the same. IME, even one or two years of age difference can have a significant impact on matters.

Therefore, 1950s, 60s, 70s or later ones, all sound quite different, with the earlier varieties invariably always being best. Therefore, ONLY if yours were 1940s vintage and grey-glass can you say you've heard the same valves... I also like red-base 5691s, but unlike you they aren't my favourite 6SL7.

As I've said before, mate, results are totally dependent on the circuit used, and we've already identified in a previous discussion we had about 5691s, with your Croft needing modified by Alan before it could take them, and mine not, so clearly our amps react differently to the valves used, therefore proving that it's pointless compiling lists of 'The best 6SL7s', in a sense that it will apply universally or be definitive, which of course for reasons stated it can't.

In that respect, unfortunately, there is no 'one size fits all' valve, of any description, but nonetheless that doesn't stop you or I recommending specific ones, and it being interesting (and also potentially beneficial) to others

Marco.

No arguments with those statements, it's fun messing about with stuff innit!!

[Wakefield Turntables]

Lol, thanks for that, mate. Could you email me all the pics you took today of the above? If you haven't already got my addy, then PM me for it.

As for what to replace them with... I'm currently considering various options and will report back later!

Marco.

I added a pair of Duelund 0.01uF tinner copper bypass caps. They sound bloody lovely.

[Marco]

The ones I'm replacing though, Andy, as 12uF, and I can't get Duelunds in that value.

Marco.

[Wakefield Turntables]

The ones I'm replacing though, Andy, as 12uF, and I can't get Duelunds in that value.

Marco.

Yep, you can keep the 12uF in situ if you like. I seem to remember you saying you really liked the noise they produced. The bypass caps keep the uF value at 12uf (well 12.001 uf) but you get to experience the Duelund flavour! Have a look at post 60, that's what I used. https://theartofsound.net/forum/show...lestion+ditton I also used Janzten Audio Silver Z Cap 2% to recap the XO's. The caps are worth more than the speakers but they sound very good.

[User211]

The ones I'm replacing though, Andy, as 12uF, and I can't get Duelunds in that value.

Marco.

I use both Dueland and Jupiter copper foil output caps in the output stage of my DAC.

.47 uF Dueland versus 2.2uF Jupiter.

The Jupiter's sound better generally. Smoother and warmer. The Dueland's appear more accurate and possibly a smidge faster.

That might purely be due to capacitance values rather than actual real differences in construction. The capacitance value of the Jupiter's means better bass extension, which may account for the marginal, and I do mean marginal perception of warmth.

That said the character traits of a few of the triodes I use in that output stage work better with the Duelands. But they are in the minority.

As bypass caps some pussy (non man like, small) value of either will probably be fine.

[Marco]

Yep, you can keep the 12uF in situ if you like. I seem to remember you saying you really liked the noise they produced. The bypass caps keep the uF value at 12uf (well 12.001 uf) but you get to experience the Duelund flavour! Have a look at post 60, that's what I used. https://theartofsound.net/forum/show...lestion+ditton I also used Janzten Audio Silver Z Cap 2% to recap the XO's. The caps are worth more than the speakers but they sound very good.

Ah yes, Andy, interesting idea...I hadn't considered bypass caps. The lower capacitance value of such would certainly reduce costs when choosing 'exotic' replacements!

Are you saying that you used the Z-Caps to replace the original 12uF ones, then bypassed them with Duelunds? If not, I'm unsure what you mean.

Marco.

[Marco]

I use both Dueland and Jupiter copper foil output caps in the output stage of my DAC.

.47 uF Dueland versus 2.2uF Jupiter.

The Jupiter's sound better generally. Smoother and warmer. The Dueland's appear more accurate and possibly a smidge faster.

That might purely be due to capacitance values rather than actual real differences in construction. The capacitance value of the Jupiter's means better bass extension, which may account for the marginal, and I do mean marginal perception of warmth.

That said the character traits of a few of the triodes I use in that output stage work better with the Duelands. But they are in the minority.

As bypass caps some pussy (non man like, small) value of either will probably be fine.

Thanks, Justers, that's also very useful info

Marco.

[Marco]

Also, Andy, how did you work out the value of the bypass caps as optimally being 0.01uF?

Marco.