Alessandro Bluetick Impedance setting - EL34's

glman

Member
Messages
629
Can anyone tell me for certain what the impedance switch on the back of my amp should be set to when using 4 EL34's into a 16 ohm load
and when using 4 6V6 into a 16 ohm load ?

my amp shipped with 4 EL34's and the impedance switch was set to 8 ohms - this could be cause george alessandro was testing it in an 8 Ohm speaker but it could also be cause he knew i was planning to use it with two 8 Ohm Cele blues - = 16 ohms

can I damage the O/T by running the EL34's into a 16 ohm load with the impedance switch set to 16 ohms?
 

rah3

Member
Messages
1,383
Glman,

I was told that the impedance switch should set to the ohms of the speaker load. The jacks on the back of the head are parallel so 2 16 ohm speakers in parallel would be 8 ohms.

I don't believe the EL34 vs 6v6 effects the output tap on the transformer.

BTW - Thanks for sharing all the tube experience in the English. Very helpful.

-RAH3
 

glman

Member
Messages
629
Glman,

I was told that the impedance switch should set to the ohms of the speaker load. The jacks on the back of the head are parallel so 2 16 ohm speakers in parallel would be 8 ohms.

I don't believe the EL34 vs 6v6 effects the output tap on the transformer.

BTW - Thanks for sharing all the tube experience in the English. Very helpful.

-RAH3
always a pleasure to share information that helps others.

your reference to parallel speaker jacks is a bit confusing to me.
i was always under the impression that when plugging two 8 ohm speakers into the speaker jacks on the back of an amp the impedance should be set to 16 ohms as the load doubles 8+8=16 ohms 4+4=8 ohms - the way a speaker cab with 2 speakers is usually wired ( like my vox ) is two 8 ohm speakers with a jumper in between the speakers for a total of 16 ohms
 

rah3

Member
Messages
1,383
Glman,

The load rated in ohms depends on series or parallel connections:

Series is the amps + Positive (tip) being connected to the + Positive connection on the 1st speaker. The - negative connection of the 1st speaker is connected to + Positive connection on the 2nd speaker and - negative is connected to the - sleave on the amp.

Parallel is + Positive to positive on all connections and - Negative to negative on all connections.

2 8 ohm speakers in parallel is a 4 ohm load.
2 8 ohm speakers in series is a 16 ohm load.
2 16 ohm speakers in parallel is a 8 ohm load.
2 16 ohm speakers in series is a 32 ohm load.

Parallel halves the load, series doubles the load.

If you have 2 16 ohm speakers in parallel you have a 8 ohm load. Just as George set it.

-RAH3

http://www.marktaw.com/recording/Electronics/OhmsAmpsandSpeakers.html
 

showman(tx)

Gold Supporting Member
Messages
499
I'm by no means a tech so take this for what it's worth, but I believe you're over-thinking the situation. If it came with 4-EL34's then use the ohm setting that's appropriate for your cab, in your case 16 ohms (2x8 ohm speakers in series). I doubt George anticipated how you were going to wire your cab (it just as easily could have been a 4 ohm cab) and set the ohm switch accordingly, that's why there's a switch ;)

As far as using 6V6's (voltage) or pulling tubes to reduce power (which would impact the ohm rating), I'd call George and ask what tube substitutions are possible and if it would change the ohm rating. I know you sent him an email but I've never had good luck emailing him and I know others call him all the time.

Good luck, beautiful amp!
 

glman

Member
Messages
629
thanx for all the help - I've been playing the amp on the 16 ohm setting as I'm running through the muzzle which is 16 ohms - I'm waiting for him to email me concerning plugging two 8 ohm speakers directly in the head but I suspect that two 8 ohm speakers will equal 16 ohms still - i just want to make sure that changing between tubes doesn't effect the impedance
thanx again guys
 

glman

Member
Messages
629
George alessandro replied - here's what happens.

2 separate 8 ohm speakers is a 4 ohm load - in the head or in the muzzle!!

the impedance switch stays the same between " ANY " octal tubes - there is no compensation necessary - i.e.. when using EL34's into a 16 ohm cab the impedance on the head stays at 16 Ohms
When using 6V6's into a 16 ohm cab - the impedance on the head still stays at 16 Ohms.

the cab is wired parallel -
2 - 16 Ohm speakers = 8 ohms
2 - 8 Ohm speakers = 4 Ohms
2 - 4 Ohm speakers = 2 Ohms - cant be used with alessandro as it only has 4,8,16 Ohms available.

I now realize i need to get a 4 Ohm muzzle for my two 8 Ohm speakers. so I'll just keep using my 16 Ohm Vox cab temporarily till the 4 Ohm muzzle arrives
 

rah3

Member
Messages
1,383
I now realize i need to get a 4 Ohm muzzle for my two 8 Ohm speakers. so I'll just keep using my 16 Ohm Vox cab temporarily till the 4 Ohm muzzle arrives
Glman,
I thought you mentioned that you had 2 16 ohm 1-12 cabs, that would have been 8 ohms. 2 8's is a 4 ohm load. Thats why I bought all, 4 - 8 - 16 ohm, muzzles when I had chance. I bought them all to be able to have the option if I was just bringing a head to session to use it on any cab. I've also read that many prefer the way a multi-ohm head performs in the lowest mode, in this case 4 ohm mode. I have a 2-12 Alessandro cab with 2 8 ohm blues (4 ohms) and the head sounds the best running at 4 ohms.

-RAH3
 

glman

Member
Messages
629
Glman,
I thought you mentioned that you had 2 16 ohm 1-12 cabs, that would have been 8 ohms. 2 8's is a 4 ohm load. Thats why I bought all, 4 - 8 - 16 ohm, muzzles when I had chance. I bought them all to be able to have the option if I was just bringing a head to session to use it on any cab. I've also read that many prefer the way a multi-ohm head performs in the lowest mode, in this case 4 ohm mode. I have a 2-12 Alessandro cab with 2 8 ohm blues (4 ohms) and the head sounds the best running at 4 ohms.

-RAH3
i do have 2 cabs but the speakers are 8 Ohms each - thus 4 Ohms load
but i've got a plan -
I'm getting someone to build me a series box so that i can connect two 8 ohm speakers in series to make up 16 Ohms then I'll just keep my 16 Ohm muzzle and the problem is solved - it's just extra cables but it should work fine
 




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