Novar Spud :: A $200 sweep tube Spud with PCB

[smoking-amp]

Here is another little trick.

I put Novar pc mount sockets on Pete Millett's 9 pin Noval prototyping boards. Then I made the Noval sockets it came with (specify un-attached) into an adapter using 40 mil Keystone 1405- 1/2/3 pins (Mouser has these). Now it works for Noval or Novar, and it provides convenient scope probe clip-on contacts for Noval tubes:

Since Novar fits too, I may make some Novar to Novar socket adapters also using the 40 mil pins (just like the Noval adapter shown), then I'll have convenient scope probe clip-ons for Novar too.

 

[tomchr]

That's a pretty neat trick.

 

[smoking-amp]

OT: More little tricks

I used Octal Wafer plugs ( Ebay) to make adapters for 7 pin B7G and 8 pin sub-mini tubes. I used a 7 pin PC tube socket, and an old Augat 8 pin Teflon round IC socket for each. The 7 pin PC sockets fit perfectly into the Octal Wafer pins. The Augat IC socket required wire spreaders to fit the Octal Wafer pins. The gray Octal relay sockets make for cheap wired prototyping bases. I also put some looped copper wire scope clip-on contacts around the sockets.

 

[tomchr]

I generally use a piece of scrap PCB with some tube socket mounting holes and turret strips for prototyping. It's not pretty but it does the job until I lay out a PCB.

Tom

 

[pluplog]

Putting together a tube amplifier for the first time, I couldn't have picked a better one to go with. The documentation was easy to follow. I also got to learn some CAD and had a nice chassis design cut out by the guys at Landfall. Some photos:

Very happy DIYer

Thanks Tom!

 

[tomchr]

Nicely done! I like the blue-on-silver look. Thanks for sharing. I'd be interested in your listening impressions as well.

Tom

 

[dolphin123]

Who wants?

An externally hosted image should be here but it was not working when we last tested it.

 

[pluplog]

Nicely done! I like the blue-on-silver look. Thanks for sharing. I'd be interested in your listening impressions as well.

Tom

Thanks Tom. As far as listening goes, these run together with a pair of OB Betsy's... I've been playing tunes all day long while I sit in my study, and I am reluctant to move They are really really sweet!

 

[tomchr]

Who wants?

Somebody in the Swap Meet perhaps?

Tom

 

[Natural Sound]

Antek is out of AS-1T250 for the next six weeks. I have a little time to work on work on my Novar Spud (6LR8) project. I was wondering if any of the Edcor "Tube Power" transformers would be a suitable replacement.


EDCOR - XPWR Series Tube Power Transformers

 

[poseidonsvoice]

NS,

I quote from Tom’s website:

The toroidal transformers by Antek Inc. are very hard to beat when it comes to good performance for little money. If you’re planning to use the 6GF7A, I recommend getting the AS-1T200 for a rectified B+ of 250 V. If you’re using the 6KY8 or 6LR8, I recommend the AS-1T250 for a 300 V B+. The Edcor XPWR050 is a strong candidate as well and would result in a 300 V B+.

Best,
Anand

 

[tomchr]

Thanks Anand!

Note that the XPWR050 is available with international primary (120/240 V) for an additional $3. That's a nice option for those overseas.

Tom

 

[Natural Sound]

NS,

I quote from Tom’s website:



Best,
Anand

Thanks I missed that. I was looking at the design documentation PDF and there is no mention of it there.


The bad news is that the XPWR050 has an EIGHT week lead time. Oh well, guess I'll get my order placed and work on something else.

 

[poseidonsvoice]

NS,

Mind you Edcor’s estimate is their worst case scenario. I ordered a pair of autoformers from them recently and despite the Internet quote of 6 weeks, the product arrived at my doorstep in 10 days.

So a phone call may help to clarify.

That being said I am biased towards transformer designs that allow for an electrostatic shield as well a magnetic band or steel housing which the Antek most certainly offers.

And if you want to go all out, then order a custom power toroid from “Toroidy” in Poland, with all the bells and whistles your diy heart desires, just pony up the $$$ .

Best,
Anand.

 

[tomchr]

I've only ordered once from Edcor, so my experience may not be representative. I think they quoted 6-8 week lead time (even over the phone). They shipped in two weeks. They seem to be an under-promise, over-deliver type place. Their CXSE25-5K OPT is a nice OPT. I just wish it had 4 Ω and 8 Ω taps.

You can also toss John an email at Antek. Maybe he can give you an update on the lead time.

Tom

 

[poseidonsvoice]

Indeed! I have only good things to say about Edcor! Their level of communication is excellent...only topped by a few like Neurochrome etc

Best,
Anand

 

[Natural Sound]

You can also toss John an email at Antek. Maybe he can give you an update on the lead time.

Tom

It was John that told me 6 weeks.

 

[kengler13]

I finally have gotten around to putting my Novar Spud together.

Unfortunately I have a 60hz hum that I can't seem to get rid of. Hum does not change with volume adjustment. Removed inputs and binding posts from chassis with no difference. Tried multiple grounding locations with no change. If I remove source and short inputs there is no hum. Unsure what else to do at this point. 3rd photo of layout is before I finished wiring the outputs, I can upload a current photo when I get home, but the -'s are connected and ground to the pcb as per the schematic.

 

[tomchr]

If the hum goes away when you short the inputs, the hum does not come from the amp.

I suspect you have a ground loop between the source and the amp. You can break that with a line transformer. You can also try a ground lifting circuit. I'm normally not a fan of those, but they can at least help you debug the issue.

If you have a 2-pin IEC cable (i.e. one with the ground missing) or one of the 3-pin to 2-pin adapters (ground cheaters) you can try that first. You can find the adapters at your local hardware store. If this removes the hum, we can work out a more permanent solution.

I do like that you've used grommets where the wires go through the chassis. Nice work.

Tom

 

[wcakey]

Voltage too low across 6 & 8

I finally got this amp built and am excited to hear it. However, I have a problem.


I have not hooked it up to speakers or input nor inserted the tubes. Running the fist tests as you suggest in your build guide, I get an appropriate voltage value across R24 and desired voltages across pins 4&5 on both TU1 and TU2. However, I do not get B+ level voltages across pins 6 & 8 on either tube. I get something on the order of 5 V.


Where should I look first to figure out what is causing the problem?


Thanks