Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Speakz on February 23, 2014, 08:37:11 pm

Title: 3ma or 3mra Pot?
Post by: Speakz on February 23, 2014, 08:37:11 pm
I'm ordering more parts for my build and the parts list says 3ma but there is only CTS 3 mra in the catalog.  Is this the appropriate part for the single channel AB763 Fender?
Thanks
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on February 23, 2014, 09:20:23 pm
3M RA is correct.
Title: Re: 3ma or 3mra Pot?
Post by: tubeswell on February 23, 2014, 11:30:07 pm
Yep you want reverse audio taper for trem speed control pots.
Title: Re: 3ma or 3mra Pot?
Post by: Speakz on February 24, 2014, 01:12:14 pm
Thanks again for the help  :occasion14:
Title: Re: 3ma or 3mra Pot?
Post by: Speakz on February 25, 2014, 09:03:28 am
Another question.  I've been reading one of Gerald Weber's books on amp building and he recommends shielded wire to replace what goes from the two 68k input resistors to the grid of the first input stage and also from the volume control to the grid of the second stage. He recommend low capacitance shielded. 
I only saw shielded wire for reverb tank here in the catalog. 

Thoughts or recommendations on appropriate wire?

Thanks  :icon_biggrin:
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on February 25, 2014, 09:21:14 am
Quote
I only saw shielded wire for reverb tank here in the catalog. 
That's the right stuff. RG-174

I prefer RG-316 because the center conductor has teflon insulation and will not melt when making a solder connection. You have to be careful with the RG-174 because the insulation will melt in a heartbeat. Both cables are the same diameter.
Title: Re: 3ma or 3mra Pot?
Post by: Willabe on April 11, 2014, 05:16:20 pm
Ok, I tried Mouser and Digikey for the RG-316, they say, we no gots.

So where can I get a 50'/100' role of it?


              Brad     :dontknow: 
Title: Re: 3ma or 3mra Pot?
Post by: HotBluePlates on April 11, 2014, 06:22:12 pm
You sure about that? You sometimes have to know there are other ways they have the number indicated...


Newark (http://www.newark.com/thermax/m17-113-rg316/cable-coaxial-rg316-50-ohm-per/dp/21T2403)
Mouser (http://www.mouser.com/_/?keyword=M17-113-RG316)
Digikey (http://www.digikey.com/product-search/en?vendor=624&keywords=135101-03-%20%7C%20135103-03-%20%7C%20135104-03-%20%7C%20135110-03-%20%7C%20135111-03-%20%7C%20255104-03-&lang=en&WT.z_slp_buy=Amphenol-Connex_Fixed-Cables)


I haven't necessarily found the best listing for bulk RG-316 in each case, but you get the idea.
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on April 11, 2014, 07:50:03 pm
eBay has it in the lengths you would want. Buy from US sellers and expect to pay about a dollar/foot. Here's one auction...

     http://www.ebay.com/itm/25-ft-RG316-U-RG-316-Excellent-Quality-Teflon-Coax-USA-SELLER-FREE-SHIPPING-/251460946352?pt=US_Radio_Comm_Coaxial_Cables_Connectors&hash=item3a8c3d89b0 (http://www.ebay.com/itm/25-ft-RG316-U-RG-316-Excellent-Quality-Teflon-Coax-USA-SELLER-FREE-SHIPPING-/251460946352?pt=US_Radio_Comm_Coaxial_Cables_Connectors&hash=item3a8c3d89b0)
Title: Re: 3ma or 3mra Pot?
Post by: jojokeo on April 12, 2014, 11:14:57 am
Is that outer jacket just clear that makes it look like stranded copper in the picture? :dontknow:
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on April 12, 2014, 11:45:53 am
Quote
Is that outer jacket just clear that makes it look like stranded copper in the picture?
yes
Title: Re: 3ma or 3mra Pot?
Post by: Willabe on April 12, 2014, 12:36:08 pm
Thanks you guys.

I'd like to get 25'/50' or so just to have it on hand.

You sure about that? You sometimes have to know there are other ways they have the number indicated...


Sometimes I do pretty good when I do a search for things, other times not so much.


                     Brad     :dontknow:
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on April 12, 2014, 02:31:59 pm
I'd suggest you get about 5 to 10 feet to begin with. It's a little stiffer than the RG-174. You may not like it for that reason. Other than that, it's really high quality stuff. Look at the pics of my Revibe and you can see it being used inside and outside the chassis.

     http://home.comcast.net/~seluckey/amps/revibe/revibe.htm (http://home.comcast.net/~seluckey/amps/revibe/revibe.htm)

I've used way more 174 than 316 but its just because I didn't have any 316 until a few years ago. That tiny center conductor with thin clear plastic insulation is gust too fragile for my liking. You really have to be super careful when soldering to avoid melting it.

The 316 has a larger center conductor of stranded silver plated copper and the PTFE insulation is bullet proof.
Title: Re: 3ma or 3mra Pot?
Post by: Willabe on April 12, 2014, 07:36:18 pm
Ok, good to know. Maybe I'll just get 10'.

I could see being a little stiffer as a good thing in some situations. Might hold it self in place a little better?


                Brad     :icon_biggrin:

Title: Re: 3ma or 3mra Pot?
Post by: Willabe on April 12, 2014, 07:52:01 pm
Which version of Visio are you using?


                  Brad    :think1: 
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on April 12, 2014, 08:00:07 pm
MS Visio Premium 2010
Title: Re: 3ma or 3mra Pot?
Post by: Willabe on April 12, 2014, 08:38:19 pm
Would the lowest/basic version be able to do drawings like yours?


                  Brad     :think1:
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on April 12, 2014, 08:47:00 pm
Maybe. The schematic symbols are part of the engineering stencils included with the Pro and Premium packages. I don't know if the Standard package includes those. You would need to verify by visiting the MS site.

But most of the stuff you see on my layouts is custom stencils that I've created. They're available for download from my website.
Title: Re: 3ma or 3mra Pot?
Post by: Willabe on April 12, 2014, 08:58:14 pm
Ok, thank you.

Express is nice but it's pretty limited. I'd like to step up with something better. What your able to do with Visio is top shelf as far as I'm concerned.

     Brad     :icon_biggrin:
Title: Re: 3ma or 3mra Pot?
Post by: sluckey on April 12, 2014, 09:34:54 pm
I have as much fun with Visio as I do on the workbench. :grin:
Title: Re: 3ma or 3mra Pot?
Post by: Willabe on April 12, 2014, 09:43:11 pm
 :laugh: