Voltage VS. Amperage? - 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 1st November 2013, 11:45 PM   #1
diyAudio Member
 
mr2racer's Avatar
 
Join Date: Jul 2009
Default Voltage VS. Amperage?

Hey All,

I understand that actual power is the product of voltage and amperage. And that a tube's limitation is the amount of wattage a tube can dissipate. My question is does the balance of voltage and amperage really matter? I have the impression that higher voltage has better sonic characteristics. But is that in fact true?

The reason I ask is if you have a power supply with a B+ of 185 volts which is shared by both the voltage amplifier and the output tubes it would make the power supply much simpler. And you wouldn't have the resistors in the power supply current path to waste energy.
  Reply With Quote
Old 1st November 2013, 11:53 PM   #2
diyAudio Member
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Send a message via Skype™ to JonSnell Electronic
The reason plate voltages of a particular value is used is purely a design function of the valve chosen. A valve that flashes over at 450v on the plate is the limitation. Some people try to run ECC83 valves with 60volts on the anodes. They have around a 40volt Anode to Cathode voltage drop, so not too good, they prefer 180v on the plate. It is all a matter of maximum dissipation versus maximum voltage ratings.
__________________
www.flyingmole.co.uk For World Wide support for Flying Mole, Class D, Refurbishment and Repairs. www.jonsnell.co.uk
  Reply With Quote
Old 2nd November 2013, 12:13 AM   #3
diyAudio Member
 
mr2racer's Avatar
 
Join Date: Jul 2009
Thanks, maybe I should be more specific. I was thinking of an RH84 using a pair of SV83's and a ECC81. Doesn't damping come into this somewhere?
  Reply With Quote
Old 2nd November 2013, 05:17 AM   #4
diyAudio Member
 
FullRangeMan's Avatar
 
Join Date: Aug 2009
Location: Brazil
Quote:
Originally Posted by mr2racer View Post
And you wouldn't have the resistors in the power supply current path to waste energy.
Sound quality/hi fi is all about energy waste, hence it require Class A circuits in SolidState or Tubes.
__________________
>Never go to a psychiatrist, adopt a cat or dog from the streets. On the streets pets live only two years average.
  Reply With Quote
Old 2nd November 2013, 06:01 PM   #5
diyAudio Member
 
Palustris's Avatar
 
Join Date: Aug 2006
Location: Cape Cod
Quote:
Originally Posted by mr2racer View Post
Thanks, maybe I should be more specific. I was thinking of an RH84 using a pair of SV83's and a ECC81. Doesn't damping come into this somewhere?
Both the SV83 and ECC81 should be run in their respective linear regions. It would be a coincidence if the two tubes were optimised for their best supply voltage and it was the same voltage. OTOH, it is plausible that one could find a supply voltage that would work for both.

Even if you find that both tubes work well with any particular supply voltage, it would be best practice to separate them with a resistor and cap to decouple them. This might not be necessary with two stages of equal current but out of phase signals.
  Reply With Quote
Old 2nd November 2013, 11:24 PM   #6
Merlinb is offline Merlinb  United Kingdom
diyAudio Member
 
Merlinb's Avatar
 
Join Date: May 2006
Location: Lancashire
High voltage designs today are often inherited from old-fashioned design attitudes. Back in the days of tubes it was a lot easier to buy components that could handle high voltages than high currents, so it was common to run your output tubes at the highest voltage you could get away with, but at low current, to get the desired output power.

These days the opposite is true: high current rectifiers and big smoothing capacitors are commonplace, but components with really high voltage ratings tend to be much less common. It is now much easier to run things in the 250-350V range and crank up the current instead, to get the desired power.
  Reply With Quote
Old 3rd November 2013, 07:33 AM   #7
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by mr2racer View Post
I have the impression that higher voltage has better sonic characteristics. But is that in fact true?
Not always. It's often true where (interstage or output) transformers with large step-down ratios are hooked to high-Rp tubes. As the transformer is acting as both impedance converter (and effectively, voltage-to-current converter), it is often appropriate to have high voltage swings (and therefore a high voltage supply on the tube) driving the transformer, so that lower current can be used on the transformer's primary (providing more headroom before saturation).
There are also examples of tubes whose most linear range of operation is situated near the top of their maximum voltage range, but this is far from universal.
Quote:
Originally Posted by mr2racer View Post
...with a B+ of 185 volts which is shared by both the voltage amplifier and the output tubes it would make the power supply much simpler. And you wouldn't have the resistors in the power supply current path to waste energy.
You would still "waste energy" in the plate resistors of the voltage amp sections. In fact, the "drop resistors" from the highest voltages to lower voltage stages keep output voltage swings from section to section more reasonably in accordance with what the input of the next stage wants to see.

Last edited by digitrax; 3rd November 2013 at 07:35 AM.
  Reply With Quote
Old 3rd November 2013, 11:54 AM   #8
Merlinb is offline Merlinb  United Kingdom
diyAudio Member
 
Merlinb's Avatar
 
Join Date: May 2006
Location: Lancashire
Quote:
Originally Posted by digitrax View Post
it is often appropriate to have high voltage swings (and therefore a high voltage supply on the tube) driving the transformer, so that lower current can be used on the transformer's primary (providing more headroom before saturation).
This is back-to-front. It is easier to make a transformer that has a small turns ratio, not a high one. It is primary voltage that leads to saturation, not current. Cheaper, better-quality transformer design is is yet another advantage for lower-voltage, higher-current circuits. The notion that higher voltages lead to better fidelity is a myth that beginners often get saddled with; not sure where it comes from though...
  Reply With Quote
Old 3rd November 2013, 12:04 PM   #9
FoMoCo is offline FoMoCo  United States
diyAudio Member
 
Join Date: Dec 2012
Quote:
Originally Posted by FullRangeMan View Post
Sound quality/hi fi is all about energy waste, hence it require Class A circuits in SolidState or Tubes.
Huh? Isn't that a blanket statement that can't be supported logically?
__________________
Account Deletion Requested: 1/26/2014
  Reply With Quote
Old 3rd November 2013, 02:09 PM   #10
TheGimp is offline TheGimp  United States
diyAudio Member
 
TheGimp's Avatar
 
Join Date: Aug 2009
Location: Johnson City, TN
If you are going to run the preamp/driver tube off the same voltage as the output tube(s), remember to run separate RC fiters for each.

If you power all from the same filter cap output, you will get more hum from the power supply.

You can also get positive feedback (and possibly motorboating) from the output to preamp stage if you have three stages.
  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
Chip amp voltage vs amperage argonrepublic Chip Amps 2 23rd February 2013 07:55 AM
How do I measure amperage? Randallm Power Supplies 15 6th June 2011 08:18 AM
options for high amperage voltage regulation brucegseidner Power Supplies 20 14th December 2010 06:12 PM
amperage and watts rtill Solid State 13 24th January 2008 10:21 AM
need a high amperage, low voltage rectifier... Stuart Easson Parts 5 5th November 2004 06:02 AM


New To Site? Need Help?

All times are GMT. The time now is 02:48 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