Ampeg V4 … 2.67ohms

[BassAdder60]

Anyone used the Ampeg V4B head into 2.67ohms instead of 2 or 4 ohms ?

Did you use the 2ohm tapping ?

 

Im tempted to get the V4B again but it must on some gigs run my SVT212AV and SVT112AV ( total 2.67ohms ) 

Edited September 30, 2023 by BassAdder60

[BassmanPaul]

With a tube amp it's best when running a load that matched the tap on the OPT. It's more reliable that way.

[Bill Fitzmaurice]

Valves are the opposite of SS, they work better into a lower impedance than the tap rating. With a 2.67 ohm load use the 4 ohm tap. Realistically it won't make much difference, other than for peace of mind. Where you'd have an issue is using an 8 ohm load on a 2 ohm tap. That could lead to premature output valve replacement.

[BassAdder60]

2 hours ago, Bill Fitzmaurice said:

Valves are the opposite of SS, they work better into a lower impedance than the tap rating. With a 2.67 ohm load use the 4 ohm tap. Realistically it won't make much difference, other than for peace of mind. Where you'd have an issue is using an 8 ohm load on a 2 ohm tap. That could lead to premature output valve replacement.

Thanks Bill 

 

Any damage likely of power tubes and OPT ? 
 

I assume not as you would have said !

 

It wouldn’t be used like this every gig but occasionally when both cabs used. 

[Bill Fitzmaurice]

Back when we didn't know an ohm from a watt we used to run our Fender amps with 4 ohm taps with 1 ohm loads with no ill effect.

[BassmanPaul]

13 hours ago, Bill Fitzmaurice said:

Back when we didn't know an ohm from a watt we used to run our Fender amps with 4 ohm taps with 1 ohm loads with no ill effect.

Well Fender do short circuit the output when no speaker jack is inserted. I still say that the correct tap for the load is best all around. Any thing else I see as abuse. in an emergency you could get away with it and I've done so myself many times. It's not something I recommend as a regular basis.

Edited October 1, 2023 by BassmanPaul

[BassAdder60]

35 minutes ago, BassmanPaul said:

Well Fender do short circuit the output when no speaker jack is inserted. I still say that the correct tap for the load is best all around. Any thing else I see as abuse. in an emergency you could get away with it and I've done so myself many times. It's not something I recommend as a regular basis.

I’m going to run it with just the 4 ohm cab I think .. seems like the better approach 

[Bill Fitzmaurice]

4 hours ago, BassmanPaul said:

Well Fender do short circuit the output when no speaker jack is inserted. I still say that the correct tap for the load is best all around. Any thing else I see as abuse. in an emergency you could get away with it and I've done so myself many times. It's not something I recommend as a regular basis.

Fender shorts the output because that doesn't hurt valves, while running with no load does. Every valve amp should do the same. Using the tap with the same rating is nice when you can do it, but when you can't using the tap that's closest to the load without being lower is perfectly safe. That's again because valves are the opposite of SS. SS is rated for the minimum load impedance, valves are rated for the maximum load impedance.

Quote

I’m going to run it with just the 4 ohm cab I think .. seems like the better approach 

59 years using valve amps tells me otherwise. My first Fender was a '65 Bassman. I bought it new.

[BassAdder60]

54 minutes ago, Bill Fitzmaurice said:

Fender shorts the output because that doesn't hurt valves, while running with no load does. Every valve amp should do the same. Using the tap with the same rating is nice when you can do it, but when you can't using the tap that's closest to the load without being lower is perfectly safe. That's again because valves are the opposite of SS. SS is rated for the minimum load impedance, valves are rated for the maximum load impedance.

59 years using valve amps tells me otherwise. My first Fender was a '65 Bassman. I bought it new.

Thanks Bill .. I’m confident I can use it as you say .. it’s nice to know that’s possible 

[BassmanPaul]

On 01/10/2023 at 16:36, Bill Fitzmaurice said:

My first Fender was a '65 Bassman. I bought it new.

I bought a Blonde Blackface Fender Bassman new with it's matching 2x12. It looked wonderful leaned back on its legs.   It lasted one night and I returned it the next day. The combination was horrible. That was in 1968.  

 

Edit to add : OP you should check for a place to buy 7027 tubes. I don't know what the supply would be like in the UK.

 

Edited October 4, 2023 by BassmanPaul
More to add.

[Bill Fitzmaurice]

For sure the Bassman was a POS. The amp was a slightly modified Bandmaster, the speaker was an un-modified Bandmaster. In '65 there wasn't much else to choose from. The first speakers that managed to handle my Bassman's 50 watts were a pair of Kustom 4x12 columns. 😲 Being 30 years before there was an internet my first exposure to the science of speakers was when I found Olson's 'Acoustical Engineering' at my college library, which prompted me to start designing and building my own speakers in 1969. That Bassman was the last factory made speaker I owned.