What is the best ohm setting to run your amp at?

butterguitar · 10-12-2009, 06:09 PM

^^topic.

I got the Bugera 1990 head and a crate cab that are selectable for ohms. They can go from 4, 6 or 16 ohms. What is the best ohm rate to set my set up at? Will the 16 ohm, sound better and make the amp work less hard, or will the 4 ohm be my best bet?

What ohm setting would be the best for tone?

bro blue · 10-12-2009, 09:10 PM

If you have a transformer that runs on 16 ohms and you use a lower setting, you are not getting the full potential out of it. If you can set both the head and cab at 16 ohms, then use that setting.

Jesstaa · 10-12-2009, 11:05 PM

The best setting to run your head at, is the setting your cab is at.
That's it, as far as I know and from what I've heard off the really experienced guys on the forum, there is no difference.

American Viking · 10-13-2009, 02:36 AM

Impedance matching is the proper relationship of electrical current flow and resistance. This is to ensure the life of your amplifier, it doesn't really affect tone. Make sure it is always matched or the amplifier could blow.

Frankie · 10-13-2009, 10:59 AM

Yeah, the whole, "My transformer is 16 ohms so the 4 ohm setting only uses 1/4 of the windings," isn't really a valid point. Your amp will work best if matched to the cabinet, and by work best, I mean won't blow the OT or fuses.

bro blue · 10-14-2009, 12:35 AM

Of course you should always match impedance, but to not use the 16 ohm setting on the head is to use less of the transformer's output, which does affect tone. The OP said both head and cab are selectable, so he should use the 16 ohm setting on both.

***Adwex*** · 10-14-2009, 01:36 PM

Quote:

Originally Posted by Frankie

Yeah, the whole, "My transformer is 16 ohms so the 4 ohm setting only uses 1/4 of the windings," isn't really a valid point. .....

Well, the jury is still out on that issue. Personally, I tried both 4 and 16, and I didn't notice any difference, but I only tried 4 for a minute or so. I was looking for a dramatic difference, and there wasn't any, so I went back to 16 and left it there forever. There may be a very subtle difference in tone or response/feel, but I didn't give it enough time to experience it.

Frankie · 10-14-2009, 03:17 PM

I think you guys hear a tonal difference more due to the way the negative feedback loop is wired vs. the way the OT is performing. Not sure on the new Marshalls, but old ones had it wired to the speaker jack. The lower you set the impedance, the less negative feedback you got, so the more powertube distortion happened.

Wilder Amplification · 10-17-2009, 11:30 AM

I call BS on this "you're not using the full potential of the transformer" nonsense.

If the transformer were not wired for 8 and 16 ohms and you only had a 4 ohm tap, you would think "Oh I'm using the full winding so that means I'm using the full potential...blah blah blah", yet it would be the same exact thing as running on the 4 ohm tap of your multitap transformer.

The whole entire reason for even having a multitap output transformer is to allow you to match the load that the power valves see...PERIOD! You want the valves to see the same exact load no matter what cab config you're running and that is done through multitap OTs.

Here's the skinny -

4 Ohm Cab - 4 Ohm Setting
8 Ohm Cab - 8 Ohm Setting
16 Ohm Cab - 16 Ohm Setting

Two 4 Ohm Cabs - Don't even try it
Two 8 Ohm Cabs - 4 Ohm Setting
Two 16 Ohm Cabs - 8 Ohm Setting

If you run a 100 watt head and you pull either the two outer or two inner valves out to set it up as a 50 watt -

4 Ohm Cab - Don't even try it
8 Ohm Cab - 4 Ohm Setting
16 Ohm Cab - 8 Ohm Setting

Two 4 or Two 8 Ohm Cabs - Don't even try it
Two 16 Ohm Cabs - 4 Ohm Setting

The trick with this trick of the trade is to double the load on the valves in 50 watt mode since two valves by themselves need double the load of having two valves paralled on each side of the OT like a 100 watter has. Some other stuff about flyback voltage comes into play here but to keep it simple we won't get into that.

Also I agree with Frankie on the tonal difference you hear having to do with the negative feedback loop and nothing to do with the OT secondary. Some amps had it permanently wired to the 8 ohm tap while others wired it to the speaker jack so that it ended up being on whatever tap you were switched to. This will greatly affect the response of the power amp.

To add to his post, the other tonal difference you'll hear is if you're trying the different settings on the same cab due to impedance mismatch.

However...not everything that sounds "cool" is good for your gear.

MartyStrat54 · 11-05-2009, 09:27 PM

"However...not everything that sounds "cool" is good for your gear." by JW

Yeah, like plugging into a Variac at 85 volts.

I run my TSL122 at 4 ohms (two, 8 ohm speakers wired in parallel). It was my main gigging amp until I got the 602's. I really can't tell any difference between a 100 watt amp running at 4 ohms versus a 100 watt head (TSL100) running at 16 ohms. If there is a difference, it mixes in with the amps overall sound. Plus, you have to consider that each amp may sound different. In my case, different NOS tubes in the pre and power sections of all of my amps.

Both of the 602's are running at 8 ohms. Here again, I can't say I can make out any difference. Theoretically, there may be some sort of change to the signal, but I doubt if it is audible.

Yeah, that's why they are called multi-tap OPT's. However, if you read enough threads, you'll see that they aren't used properly all of the time. "POOF!"

Wilder Amplification · 11-05-2009, 09:53 PM

Quote:

Originally Posted by MartyStrat54

"However...not everything that sounds "cool" is good for your gear." by JW

Yeah, like plugging into a Variac at 85 volts.

I run my TSL122 at 4 ohms (two, 8 ohm speakers wired in parallel). It was my main gigging amp until I got the 602's. I really can't tell any difference between a 100 watt amp running at 4 ohms versus a 100 watt head (TSL100) running at 16 ohms. If there is a difference, it mixes in with the amps overall sound. Plus, you have to consider that each amp may sound different. In my case, different NOS tubes in the pre and power sections of all of my amps.

Both of the 602's are running at 8 ohms. Here again, I can't say I can make out any difference. Theoretically, there may be some sort of change to the signal, but I doubt if it is audible.

Yeah, that's why they are called multi-tap OPT's. However, if you read enough threads, you'll see that they aren't used properly all of the time. "POOF!"

My whole thing is...if impedance matching wasn't important on valve amps, why the hell would tranny manufacturers go through the trouble of making multitap transformers? What other possible reason can you think of as to why amp makers would even use them if it weren't important? Tone? HA! Tone wasn't even a consideration back when they started making Marshalls! If it were, there would've DEFINITELY been a LOT more consistancy between circuits, parts used, etc etc...a multitude of other things.

Bottom line...unless you like to blow your shiz and you've got money to throw away, match your impedance. It ain't about tone...this is about electrical parameters that have a definite design limit and will bite you in the ass in the long run if not followed.

MartyStrat54 · 11-05-2009, 10:55 PM

And that's why I have said before that it is imperative that you obtain at least a basic knowledge regarding tube amplifiers. They are basically a piece of test equipment. They have to be hooked up to a load, the load needs to match the OPT setting. Proper use of the On/Standby switch should be observed. Power tubes need to be periodically checked for proper bias. Tubes need to be replaced as required.

If you can't handle this...then stick with a solid state amp.

Wilder Amplification · 11-06-2009, 03:17 AM

Quote:

Originally Posted by martystrat54

and that's why i have said before that it is imperative that you obtain at least a basic knowledge regarding tube amplifiers. They are basically a piece of test equipment. They have to be hooked up to a load, the load needs to match the opt setting. Proper use of the on/standby switch should be observed. Power tubes need to be periodically checked for proper bias. Tubes need to be replaced as required.

If you can't handle this...then stick with a solid state amp.

x100,000,000,000,000,000,000,000,000,000,000,000

el zilcho · 11-11-2009, 08:18 PM

Quote:

Some other stuff about flyback voltage comes into play here but to keep it simple we won't get into that.

I don't know if it's really audible for guitar amps, but in theory you get a little distortion from speakers modulating each other when they are wired in series (in our case the 16ohm setting). Parallel wiring is used in most multiple driver loudspeaker systems to avoid this.

If you short the output of your 16ohm jack and move one of the speakers with your hand, all the other speakers will move. Do the same thing with the 4ohm jack and they won't.

carnada · 11-11-2009, 09:18 PM

hmm hmmmh mhmhmhmhmmhmh

I still dont really get this ohm things lol. I just know if I have to from the 4ohm out of my poweramp to the 4ohm input of the cab, I think

10-12-2009, 06:09 PM	#1 (permalink)
butterguitar Junior Member Join Date: Sep 2009 Location: Las Vegas Posts: 18	What is the best ohm setting to run your amp at? ^^topic. I got the Bugera 1990 head and a crate cab that are selectable for ohms. They can go from 4, 6 or 16 ohms. What is the best ohm rate to set my set up at? Will the 16 ohm, sound better and make the amp work less hard, or will the 4 ohm be my best bet? What ohm setting would be the best for tone? __________________ Bugera 1990 Crate Blue Voodoo Cab w/ Celestion 75's Marshall AVT w/ MC412 Kramer Pacer Epiphone SG Double Neck OLP MM1 Guitar 1987 Yamaha Pacificia

10-12-2009, 09:10 PM	#2 (permalink)
bro blue Senior Member Join Date: Aug 2009 Location: Southern USA Posts: 112	Re: What is the best ohm setting to run your amp at? If you have a transformer that runs on 16 ohms and you use a lower setting, you are not getting the full potential out of it. If you can set both the head and cab at 16 ohms, then use that setting.

10-12-2009, 11:05 PM	#3 (permalink)
Jesstaa Senior Member Join Date: Apr 2009 Location: Gippsland, Vic, Australia. Posts: 801	Re: What is the best ohm setting to run your amp at? The best setting to run your head at, is the setting your cab is at. That's it, as far as I know and from what I've heard off the really experienced guys on the forum, there is no difference. __________________ GEAR LIST Marshall JCM900 4100 (6L6) (1995) Marshall Valvestate 1965A cab (????) Cort VX-2V (2008) TUBES/SPEAKERS Power: Groove Tube 6L6GCB Phase Inverter: Sovtek 7025 Pre: V1 - N.O.S Mullard ECC83. V2 National 12AX7A Speakers: Celestion G10L-35 Marshall forever My tube amp & Real Music appreciation forum

10-13-2009, 02:36 AM	#4 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 1,510	Re: What is the best ohm setting to run your amp at? Impedance matching is the proper relationship of electrical current flow and resistance. This is to ensure the life of your amplifier, it doesn't really affect tone. Make sure it is always matched or the amplifier could blow. __________________ -I'd rather be a good liver than have one...

10-13-2009, 10:59 AM	#5 (permalink)
Frankie Senior Member Join Date: Sep 2007 Location: Clearwater, FL Posts: 362	Re: What is the best ohm setting to run your amp at? Yeah, the whole, "My transformer is 16 ohms so the 4 ohm setting only uses 1/4 of the windings," isn't really a valid point. Your amp will work best if matched to the cabinet, and by work best, I mean won't blow the OT or fuses. __________________ w w w . c o w b o y m a f i a . n e t Myspace.com \| YouTube \| Facebook

10-14-2009, 12:35 AM	#6 (permalink)
bro blue Senior Member Join Date: Aug 2009 Location: Southern USA Posts: 112	Re: What is the best ohm setting to run your amp at? Of course you should always match impedance, but to not use the 16 ohm setting on the head is to use less of the transformer's output, which does affect tone. The OP said both head and cab are selectable, so he should use the 16 ohm setting on both.

10-14-2009, 03:17 PM	#8 (permalink)
Frankie Senior Member Join Date: Sep 2007 Location: Clearwater, FL Posts: 362	Re: What is the best ohm setting to run your amp at? I think you guys hear a tonal difference more due to the way the negative feedback loop is wired vs. the way the OT is performing. Not sure on the new Marshalls, but old ones had it wired to the speaker jack. The lower you set the impedance, the less negative feedback you got, so the more powertube distortion happened. __________________ w w w . c o w b o y m a f i a . n e t Myspace.com \| YouTube \| Facebook

11-05-2009, 09:27 PM	#10 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,583	Re: What is the best ohm setting to run your amp at? "However...not everything that sounds "cool" is good for your gear." by JW Yeah, like plugging into a Variac at 85 volts. I run my TSL122 at 4 ohms (two, 8 ohm speakers wired in parallel). It was my main gigging amp until I got the 602's. I really can't tell any difference between a 100 watt amp running at 4 ohms versus a 100 watt head (TSL100) running at 16 ohms. If there is a difference, it mixes in with the amps overall sound. Plus, you have to consider that each amp may sound different. In my case, different NOS tubes in the pre and power sections of all of my amps. Both of the 602's are running at 8 ohms. Here again, I can't say I can make out any difference. Theoretically, there may be some sort of change to the signal, but I doubt if it is audible. Yeah, that's why they are called multi-tap OPT's. However, if you read enough threads, you'll see that they aren't used properly all of the time. "POOF!" __________________ MARTY 2009 Gibson Explorer-Hell Raising Machine 1989 Fender Strat Plus USA 2008 Fender Tele USA 2004 Schecter Elite w/DiMarzio's TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers. TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends." DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker. Tubes: Let's just say they are NOS that kick ass.

11-05-2009, 10:55 PM	#12 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,583	Re: What is the best ohm setting to run your amp at? And that's why I have said before that it is imperative that you obtain at least a basic knowledge regarding tube amplifiers. They are basically a piece of test equipment. They have to be hooked up to a load, the load needs to match the OPT setting. Proper use of the On/Standby switch should be observed. Power tubes need to be periodically checked for proper bias. Tubes need to be replaced as required. If you can't handle this...then stick with a solid state amp. __________________ MARTY 2009 Gibson Explorer-Hell Raising Machine 1989 Fender Strat Plus USA 2008 Fender Tele USA 2004 Schecter Elite w/DiMarzio's TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers. TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends." DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker. Tubes: Let's just say they are NOS that kick ass.

11-11-2009, 09:18 PM	#15 (permalink)
carnada Senior Member Join Date: Dec 2008 Location: 22 Acacia Avenue Posts: 662	Re: What is the best ohm setting to run your amp at? hmm hmmmh mhmhmhmhmmhmh I still dont really get this ohm things lol. I just know if I have to from the 4ohm out of my poweramp to the 4ohm input of the cab, I think

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