5B6 started

[telentubes]

Finally got some time to work on the 5B6. It will be a little while before I can get back to it, but at least I've made some progress.
If anyone notices anything funky, let me know.

There is a section of the main board that is a little cluttered, and I wish I had spread things out a bit, but hopefully there won't be a problem.
I am using the Tino schematic, with just a couple of additions.

I have left some extra room at the end of the main board in case I want to add another filter cap. Any comments or advice there would be appreciated.

[Cliff Schecht]

You'll quickly learn how finicky 6SL7's are if you don't know already. Find a low noise one and it's microphonic, find a low microphonics one and it's noisy as shit. They're a pain but worth it once you find that magic set.

I always plan these builds so that the heater wires are as far away from the signal wires as possible. While this image below is NOT how I wire my 9-pin sockets, it is how I wire my 8-pin sockets. The wires overlap completely when coming off the pins and stay as flat on the chassis as possible. FWIW I wire my 9-pins like Merlin discusses here although I tend to put some heatshrink over the screws if the wire is that close to it to prevent unwanted shorting over time. http://www.valvewizard.co.uk/heater.html

In these tweed builds getting the B+ voltages is critical to getting the sound right. I do whatever I can (Zener or amplified Zener) to get these voltages correct.

[img:600:449]http://www.silvatone.bravepages.com/18% ... rs%201.JPG[/img]

[Blackburn]

I'd be super careful with your lead dress. These octals can turn on you if they are positioned too close to this or that, especially the OT in relation to V1. These amps in PTP do a lot better regarding oscillations, but it may turn out great for you the way it is. Gotta get it built and see. I miss mine...

[telentubes]

Cliff, Did you mean to include a pic of your method of wiring octals. If so, it isn't coming up on my computer. Elevated heater wires has become my preferred method, but I may have to rethink that for this amp.

Bummer about the finicky tubes and lead dress. Might be one reason they aren't in production any more.

Thanks for the tips. I'll plod ahead.

Any thoughts on what level of filtering to use? Fender used 16/16/16/16 caps. Tino uses 20/20/30 caps? I see Mark Fowler used 22/22/47/47caps in his 50 Watt. I've left room for 4 on the board.

[ToneMerc]

Any thoughts on what level of filtering to use? Fender used 16/16/16/16 caps. Tino uses 20/20/30 caps? I see Mark Fowler used 22/22/47/47caps in his 50 Watt. I've left room for 4 on the board.

I used 30-16-16.

https://tubeamparchive.com/download/file.php?id=26956

TM

[Blackburn]

Any thoughts on what level of filtering to use? Fender used 16/16/16/16 caps. Tino uses 20/20/30 caps? I see Mark Fowler used 22/22/47/47caps in his 50 Watt. I've left room for 4 on the board.

I used 30-16-16.

https://tubeamparchive.com/download/file.php?id=26956

TM

Hey TM, sweet build! How do you like it? When I had mine, I used 30uf 30uf 22uf.

Where do you get that real thick buss wire? I've been using 18g, but I want something that will stay absolutely straight.

[ToneMerc]

Where do you get that real thick buss wire? I've been using 18g, but I want something that will stay absolutely straight.

It's 12 x .062 copper tubing that I pick up locally from a mom & pop hardware store.

TM

[Blackburn]

Good to know! Thanks!

[telentubes]

Finished wiring today, but have not double/triple checked with the schematic for errors. I left all the leads full length... just in case.

I also don't have any of the octal preamp tubes yet. Any favorite (affordable) brands and sources?

Thanks.

[ToneMerc]

TT, I would personally remove the "flying leads" style of screen supply wiring and secure those screen resistors with a terminal strip at each tube. That scheme is fine for grid stoppers on pin 5, but I would not use that method for a high voltage feed.

You could just duplicate the original schematic and omit them all together.

TM

[martin manning]

I'm with TM on the screen resistor placement. You have pin 6 open, so you can support the resistors on pins 6 and 4. From there it's easy to connect the supply wire to either pin to run it with or without the screen resistor.

[Colossal]

Very nice build! Clean and neat. Your heater wiring looks like Red Vines. May I eat them? Looking forward to the tone report. If I may ask, what is your PT secondary? Did you use a Bassman type OT?

[Cantplay]

I like to wire heaters for the power tubes out of phase with each other.

This can cancel out some noise.

John

[M Fowler]

Your 5b6 is looking very good.

If I build anymore of these 5b6 amps it will be PTP, it's the only version I've built of the 5b6 that I really enjoy tone wise and stability wise.

Mark

[telentubes]

I will secure the screen resistors, or get rid of them. Thanks for that.

Never heard of running the power tube heaters out of phase to tame hum. I'll keep that in mind.

I did have it in the back of my mind that I could convert this amp to point to point if it didn't work out well. Seems like Mark's PTP has been one of the few without any problems. We'll see how it goes.

The PT is an Edcor, XPWR179-120. Here are the specs...

Power transformer for a 120V, 60Hz. line to 700V (350-0-350) at 200mA center tapped, 6.3V (3.15-0-3.15) at 5A center tapped and 5V at 3A.

The OT is an Allen TO35MT