ampage
Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

 
Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Dumb question about impedance


 
4/1/1999 9:42 AM
Don Symes
email
Dumb question about impedance
In the case of an amp with selectable output impedances and a 4x12 switchable between 16 and 4 ohms:  
 
Is there a discernable sonic difference between matching at 16 and matching at 4?
 
4/1/1999 11:38 AM
Steve Dallman
email

Try it and see. Gerald Weber claims the 4 ohm will be brighter and the 16 ohm will be darker.
 
 
  Thursday
Book Of The Day The Ultimate Tone, Volume III by Kevin O'Connor
Have you ever wondered if there is a better way to build a Bassman, Champ, Plexi, an 800, AC-30, Bulldog or Portaflex? Or you wanted to build an SVT with off-the-shelf parts? How about a master-volume amp that doesn’t change tone with the master setting? Everything you need to know is right here, including: proper grounding techniques, wiring methods, and mechanical considerations. Eighteen chapters cover the “iconic” amps everyone knows and loves, with schematics and layouts for each, along with the technical history of the product. Eyelet-board and chassis-mounted tube socket construction is used throughout, for easy servicing and modding. TUT3 is very accessible even if you cannot fully read a schematic and is a "must have" if you are going to build an amp for your self.

Note: The Ampage Archive is an Amazon Associate site. A small commission is paid to the site owner on any qualified purchase made after clicking an associate link such as the one above.
 
4/1/1999 11:59 AM
Gus
The 16 ohm being "darker" kind of make sense because the signal is using more wire in the amps output transformer (higher inductance). R.G. does this make any sense?
 
4/1/1999 12:47 PM
Steve Dallman
email

That would be right.
 
4/1/1999 2:12 PM
R.G.
Website
email

Maybe a little. Actually, for a well-designed transformer, it probably won't make an audible difference, and it depends on whether there is a separate 16 ohm winding or a tap on a single winding for the different impedances. For poorly designed, cheap guitar output transformers, maybe.  
 
The difference would be in a higher leakage inductance, maybe a touch more self capacitance.  
 
The biggest difference is likely to be that most people use two 8's in series or four 16's in series/parallel to get to 16. Any time you put two speakers in series, they each lower the damping factor from amp to speaker for the other one, so they each have looser, boomier bass. Could be that Gerald heard that.  
 
For a 16ohm speaker on a 16 ohm tap verus a single 8 (or 4) speaker on a matched tap, if the speakers were equally good (an impossibility in the real world, naturally!) the differences should be very hard to hear.
 
4/3/1999 1:49 AM
D.L
email

Um.. You guys.. G. Weber was talking about parallel series and series parallel, two ways to still end up 16 ohms but brighter and darker respectively.. I am still deciding whether or not it is effective myself b.t.w.
 
4/3/1999 1:46 PM
R.G.
Website
email

quote:
"G. Weber was talking about parallel series and series parallel, two ways to still end up 16 ohms but brighter and darker respectively.."
 
Gerald has an occasional lapse.  
 
If you take four identical speakers, and hook them in two series chains, then parallel the chains and run audio through them (this is parallel series, right?) you could use an AC voltmeter to measure the voltage between the middle junctions of both series chains.  
 
If the speakers are identical, the voltage between the middle points must be and will be zero, because identical currents are flowing in each of the two identical paths. Makes no difference whether the speakers are good, bad, inductive, capacitive, resistive, just that they're alike.  
 
If you then connect the middles with an ammeter - yep, no current will flow, because there is no voltage between the two points. It makes no difference whether you connect the two middles (making a series-parallel connection, right?) because no voltage exists between the center points and no current flows.  
 
This is the fundamental theory behind all bridge measurement instruments. Maybe Gerald didn't read that book...
 
   Page 1 of 2 Next> Last Page>>