Rexton's Valve System - Upgrade Blog

[Wakefield Turntables]

New toys, a pair of matched 6SU7GTY. OK so they don't come from the 1940's but the 1950's. Should still be a bloody good valve, I love Tung Sol valves and Tung-Sol previously held the position of my Reference valve before the 6591's came about. They should be here back end of December, would be nice to have before Xmas but in no hurry either way!

s-l1600.jpg

s-l1601.jpg

[Wakefield Turntables]

Just a quick pic of the RCA 6SL7GT's in the Croft Preamp. I had now't to do so I thought I'd share this.

[Wakefield Turntables]

JR149's. I've been buggering around with a pair for years and this time I decided to get them finished.


These speakers can benefit from have some slight modifications. Most Mk 1 speakers will be approaching over 40 years of age and most of the capacitors and resistors will have started to deteriorate and be out of specification. My own pair of Mk 1 JR149 had several resistors and capacitors which had gone 10-20% out of specified values. It's been widely accepted that some of the designs in the speakers were made for money saving, but overall the speaker has many excellent design features, these include :-
⦁ An extrinisic speaker cross (XO) over which contains a damping ring to minimise vibrations from the speaker drivers, or extrinsic vibrations outside the speaker cabinet getting into the XO.
⦁ A central rod was used in the speaker cabinet which when tightened increased the rigidity of the speaker cabinet.
⦁ The cabinet was made from rolled metal which was cheap and also had a greater rigidity than it's peer's designs.
⦁ The speakers had no binding posts. Attaching speaker cable was attached straight onto the XO with a simple screw and washer design.

The JR 149 mk 1 also had many areas which could (and should) have been improved. These include :-

⦁ Removing the intrinsic tinned copper wire and replacing with high purity oxygen free copper.
⦁ Removing the instrinsic plugs which attach the SP1032 tweeter to the cross over, this can be converted into a straight run of copper wire from the SP1032 to the XO.
⦁ Re-capping the XO with new caps and 1% tolerance Takman resistors.
⦁ Removing the plastic connector which attached the instrinsic wiring of the driver units to the XO. This can be bypassed by soldering straight on the XO. This bypasses the Nickel plated pins.
⦁ Replacing the speaker wire binding screws and washers with pure copper alternatives. This gets rid of the Nickel versions supplied and improved signal transmission by using a better conductor.
⦁ Replacing the plastazote speaker gaskets. EVA speaker gaskets are used instead which gives better damping for the speaker driver units.
⦁ The speakers feet can be replaced with materials which offer betting damping properties. EVA or Sorbothane can be used.

I'll post some pics eventually.

[Wakefield Turntables]

Pt VIII - A cheap version of the ls3/5a - The JR 149

I've had 3 pairs of these and have never been happy with them until I got the early Mk1 version. These little speakers are supposed to be one of the best LS3/5A variants. I picked this pair up several years ago and until now have never really done much with them until now!

Here's a tale of two halfs. Both speakers have had the XO cover fully stripped down to bare metal and primed. No respray yet. The right hand speaker has had both top and bottom panels stripped with the veneer repaired. The screws on this speaker have been ultrasonicially cleaned and hand polished. The left speaker shows you how the right speaker used to look.




Here we can see the veneer repaired, hand polished and then re-varnished. The other is still to do.






The XO, an early mk 1 version, note, no fuse! The caps had drifted massively from spec, sometimes between 10-20% from supposed value. The resistors fared a little better but still quite some way off. The caps were eventually replaced and the resistors got changed over to 1% tolerance Takman's 1W.




This picture shows the bases fully restored. The XO bases had a full respray and several coats of lacquer. I replaced the old feet with new EVA replacements. The original stickers managed to be saved. The aluminium circular retaining nut was again ultrasonically cleaned and hand polished, it came up a treat.



Old speaker gaskets removed. I remade the gaskets with medium density EVA which gives better damping qualities. These gaskets were retained.



The original "hook" strips were removed from both speaker cabinets and given a good clean. I stripped off all the old glue and applied fresh, strong, double sided tape. I cleaned off the 40 year old glue from the speaker cabinet (not shown in this photo).



I'll post some more pics at some time!

[Wakefield Turntables]

Cheapy power amplifier from eBay (I borrowed this image) and a fully refurbished pair of JR149's making a very very nice sound. How the hell does something costing <£30 sound this good?

s-l1600.jpg

More photos' tomorrow.

[Marco]

Just a quick pic of the RCA 6SL7GT's in the Croft Preamp. I had now't to do so I thought I'd share this.

How are they sounding?

Marco.

[Wakefield Turntables]

Have a look at post #54; they rated very highly.

[Marco]

Interesting... I concur with most of your observations, but not really the negatives, although no valve is perfect. Also, as ever, these things are very much system and equipment dependent

Btw, just a small tip for future... If you want to link to a specific post on a thread, click on the post number (where the hash symbol is), then copy the resulting URL, and paste that, which when clicked on by someone, will take them directly to that post

Marco

[Filterlab]

Sorted the link for you Rexton.

[Wakefield Turntables]

IMF speakers in the house, well the listening room. I finally scratched an itch that I'd had for quite some time and managed to get a half decent pair of Super Compact Mk II's. I can smell a resto/mod project ahoy! So far so good, they work! More when I get some time.