vintage hifi

[barry robin]

good call, going with roy. so, are the boards already stuffed or will you have to break out the soldering kit?

[Fran]

Definitely will be soldering up myself! Have a reputation to live up to!

It'll take a couple of weeks for the stuff to get here - he doesn't hold the choke in Stock so has to get it in. His kit seems to be very well regarded, and from reading around should give me what I want. The sound from it at the moment is pretty good but it's a little bit too smooth, it could do with a little bit more clarity. It's not like it's muffled or anything but just a tad extra would mean the sweetness is kept but with the clarity and openness we all want.

I replaced the bias caps and added in some extra capacitance on the power supply and the bass is noticeably tighter - which means that's the way to go.

I hope to have a new 6sn7 preamp built for it by the time the parts arrive from roy.

Fran

[barry robin]

you wrote: "I hope to have a new 6sn7 preamp built for it by the time the parts arrive from roy".

going with octals, are we? nice! you might remenber that my preamp was a Mapletree-only with 12SN7 octals instead-and valve recfitied. it gave a full sound that ran a bit on the warmish side. the valve rectifcation did soften things up a tad, so if your looking for something tighter sounding, you might want to lose that; on the other hand, you might want go hog-wild and try building a hybrid with the octal top end and SS power, like Audio Research does.

-b

[Fran]

Well, heres the beauty of the thing..... its going to be set up with a 6X5 for calive rectification, but I also have some of those stealth diodes that I will make up a little adaptor for - so I can pull the valve and insert SS rectifier instead. Try the different flavours!

I plan on doing the same thing with the dynaco. You can actually do this with any valve amp, but you need to make sure that the caps after the rectifier can take the higher voltage that SS rectifiers will give. Also, the valve rectifer means a slow start up - easier on the valves, as they get to heat up before seeing the full voltage whereas the SS is almost instant.

Its a suck 'em and see story. BTW, I see from the datasheet that the 12SN7 is exactly the same as the 6SN7 only that one uses 12V heaters and the other 6V. So they should sound pretty similar. The one I'm building is the Broskie aikido - do you know what topology the mapletree one uses (?SRPP)?

I have all my pieces laid out for the pre, its a tight enough fit in the case I'm using, but should all be OK. Its all built but needs to be put into the case and prettified.

Fran

[barry robin]

that SS adapter thingie sounds pretty damn neat. let me know how it goes-i might have to try it myself. as to the mapletree, i have the Octal 6 that is switchable between CF and SRPP and passive too.

you're right about the 12SN7 being simply double the 6SN7. but for some reason, the 12SN7's go for half the price! here's the review and specs:

http://webcache.googleusercontent.com/s ... google.com

-b

[Fran]

The beauty of the aikido is that it would be a very easy switch to using 12sn7 tubes - 2 jumpers and good to go.


Speaking of which, I saw that x-music had kt66 valves for the very good price of 30 quid for a matched pair - genelex gold lions no less. The guy tells me that new sensor who owns a lot of the valve names like sovtek, mullard etc did a deal with Marshall amps and that's how they have such a good deal.

I fitted them first thing when I got home and biased them up and they sound Bloody great. Not as syrupy as the El34 and much better tighter bass. Still as listenable......

[barry robin]

i seem to remember that Mapletree offers, on some models, an built-in internal A/B valve switch for just that purpose.

-b

[Fran]

Those mapletree kits are seriously good value....


so the new pre is up and running and sounding good - great depth but soundstage might not be as wide. Needs time though......

now all I need is the kit to rebuild the dynaco?!

[barry robin]

pics? and nerdy spec stuff too, please.

[Fran]

There was a bit of buzz from the preamp that I've mostly sorted now. At the very highest volume, its still there and I know whats causing it..... the whole thing being in a small case doesn't help. All the usual audiophilia stuff, silver in teflon wire, stepped pot, yada yada yada.

Sound really opened up after it being on for a while. Bass is very grippy and clean. Very happy with this build. I'm a bit sorry I didn't put it in a bigger case. That would have allowed greater separation between transformers and circuit etc etc.

Fran