Optimal Umbilical Runs and Connections - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th November 2007, 06:14 AM   #1
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Default Optimal Umbilical Runs and Connections

Not sure if the subject is actually useful here -- I am running an umbilical connection from a PS to an amp. The PS will send a raw DC voltage to the amp where it will be regulated.

The tubes in the amp will be heated with AC. Typically, I build a voltage divider from B+ and connect the heater winding's center tap to bias the heaters up about 40V or so, which seems to work well. So, the question is, should I do the biasing in the PS (which is cLCLC filtered so reasonably quiet on its own, and reasonably well regulated due to the choke input), or is it better to run the center tap all the way to the amp to build the divider off the well regulated B+? Does it even matter?

Finally, any problem with 6.3VAC and ~200VDC in the same ~1m connection?
  Reply With Quote
Old 7th November 2007, 10:57 AM   #2
diyAudio Member
 
Join Date: Sep 2003
Location: London
There are connectors like Speakons with shielded pins, and on the other hand there are XLR types with only one shielded end of a normal cable. If you have any B+ capacitors in the circuit box you'll need a shielded connector there. Obviously has to be shielded at the PSU box.

You probably know this, but just to make sure!!

200vDC allows you to use all kinds of connectors - XLRs, D-connectors, speakon 4 or 8 way etc. Most are specced for 250vDC. Seems to be just a beurocratic decision to state 250v max. since originally these connectors were tested for much higher DC.
  Reply With Quote
Old 7th November 2007, 12:17 PM   #3
diyAudio Member
 
zigzagflux's Avatar
 
Join Date: Oct 2006
Location: Charlotte, NC
I would use Belden 1037A cable, individually shielded twisted pair, good for 600V.

No problem running DC and AC in the same cable. However, I would send 120VAC into the cable, instead of 6.3. Place your filament xfmr inside the amp chassis, not the PS chassis.

This, then answers your last question about how to bias the 6.3V winding.
  Reply With Quote
Old 7th November 2007, 12:43 PM   #4
Sherman is offline Sherman  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Chicago area
You didn't mention if you wanted the ability to unplug the umbilical from the amp and/or power supply but I assume you do. There are lots of choices of connectors to do this from Molex to the Speakon connectors mentioned before. Whichever connector you choose it must of course be keyed. Wouldn't want to plug 200VDC into the wrong thing!

That 200VDC is important in another way. It can really hurt if gets out! Therefore the umbilical should be designed to prevent the possibility of anyone touching a hot pin. My solution it to permanently connect the umbilical to the amp and only have a plug on the PS end. Make the jack on the PS have the **female** connector, no chance of anyone touching a hot pin there. Have the connector coming from the amp be the male end.

I've put AC and DC in the same umbilical successfully. I used shielded twisted pair for the AC and regular teflon insulated 600V non-shielded wire for the DC. It worked fine though if I were to do it again I would do as zigzagflux recommends and run 120VAC through the umbilical rather than high current 6.3VAC.

I've used Molex connectors for this type of thing and they work well but they aren't very attractive. Speakon connectors look much more professional. In lower voltage (but much higher current) chip amps I've even used 5 pin DIN connectors with the female jack on the PS. The wires are thin but with runs of < 1 meter they have worked flawlessly.
__________________
--Sherman
  Reply With Quote
Old 7th November 2007, 03:17 PM   #5
ckniker is offline ckniker  United States
diyAudio Member
 
Join Date: Jul 2007
I have the same exact questions for a Raven-style Line stage preamp that I'm about to implement.

Since 2 of you have suggested running 120VAC through the umbilical (instead of 6.3 VAC) I'll probably go with your suggestions. I'd like to understand why you make these suggestions, however.... (voltage/current drops?)


Additional questions:

I'd need to send B+ (around 125VDC), -12.5 VDC (for cathode CCS bias), ground, and 120 VAC through the umbilical. Does the shield of the umbilical cable become the ground signal? Or should there be a separate wire in the umbilical that is used as the ground signal?

If I'm using a star grounding scheme, do I have all the grounds come together in the PSU box?
Or are there 2 separate star grounds (one in the PSU box and one in the amp box) that are connected together via the ground in the umbilical?

Chris
  Reply With Quote
Old 7th November 2007, 04:13 PM   #6
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I use and recommend CPC connectors for these applications. They are keyed, fairly inexpensive and can handle high voltages and currents.

I like to keep all supplies including filaments in the main supply, and run those to the device being powered. Tightly twist the filament wires and run with everything else in the umbilical. I've been doing this forever and have never had a problem with coupling between supplies.

It would not be a bad idea to interlock the connector so that if it is not connected the power supply cannot operate.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 7th November 2007, 04:14 PM   #7
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Quote:
Originally posted by zigzagflux
No problem running DC and AC in the same cable. However, I would send 120VAC into the cable, instead of 6.3. Place your filament xfmr inside the amp chassis, not the PS chassis.
The whole point of the separate PSU chassis is that I am getting magnetic coupling between the power and output transformer, so I can't put the filament transformer in the same box.

Quote:
Originally posted by ckniker
I have the same exact questions for a Raven-style Line stage preamp that I'm about to implement.
You won't have the same magnetic coupling issues because it is a push-pull design, so no (or at least less) worries about transformers being in the same box.

Quote:
Originally posted by ckniker
Since 2 of you have suggested running 120VAC through the umbilical (instead of 6.3 VAC) I'll probably go with your suggestions. I'd like to understand why you make these suggestions, however.... (voltage/current drops?)
It's because of the lower current that needs to travel through the wire.
  Reply With Quote
Old 7th November 2007, 04:17 PM   #8
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Here is where I get my CPC connectors and pins. Ideal in my mind anyway..

http://www.action-electronics.com/ampcpc.htm

No association, just a very happy customer. This is definitely the best place to get them in small quantities.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 7th November 2007, 04:24 PM   #9
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Quote:
Originally posted by kevinkr
It would not be a bad idea to interlock the connector so that if it is not connected the power supply cannot operate.
So, like a loopback from one otherwise unused pin to another otherwise unused? Doesn't the pin still have high voltage on it, or do you use a relay of some sort?

I am planning to use some 5 pin XLR's here (yes yes, SY, I know all the warnings, but the number of people who will touch this amp is exactly 1 -- it sits in my home office) and I'll use a female jack on the PS and male on the amp for safety.
  Reply With Quote
Old 7th November 2007, 04:37 PM   #10
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Loopback is exactly the right term, and yes it is 120V, these connectors are usually rated for fairly high voltages depending on the one you choose.

These CPC may actually cost less than a 5 pin xlr unless you already have some on hand that is.

edit: typo
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Looking for amp kit that runs on 12V (car battery) maurycy Chip Amps 5 2nd October 2008 08:29 PM
Dynaco ST-120 runs hot bobgroger Solid State 6 15th April 2008 05:20 AM
Neutrik XLR for Umbilical dsavitsk Tubes / Valves 14 17th August 2006 02:20 PM
Umbilical Supplies rtarbell Parts 1 9th March 2006 10:47 PM
BOSOZ's PSU runs very very hot ruangrit Pass Labs 18 5th February 2003 11:45 PM


New To Site? Need Help?

All times are GMT. The time now is 06:44 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2