#1
Hi everyone!

Here's the deal: I bought a Marshall 1960, which usually can be set to 8ohms mono or 4/16 ohms stereo (correct me if I'm wrong). The thing is: the guy who sold me had swapped the T75s (16 ohms each) for 8 ohms V30s. Now the cab can only be run on 8 ohms mono while on stereo mode is 2 ohms.
Here's the problem now - I am about to build a rack system to play live with my band, but as you guys know, most tube power amps are better suited for stereo operation. It'd be folly to spend hundreds of dollars on a tube power amp and then use only one channel.

The question: is there any way to set my cab's wiring so that I could, with four 8 ohms speakers, have a 4, 8 or 16 ohms impedance in stereo mode? If not, I'll probably buy a Velocity 300 or a Matrix GT800FX to pair with my SansAmp PSA 1.1, sice those can be bridged... But I think I want a tube power amp... but not with a 2 ohms cabinet

Thanks in advance!
#2
Quote by Kivenkantaja
but as you guys know, most tube power amps are better suited for stereo operation. It'd be folly to spend hundreds of dollars on a tube power amp and then use only one channel.
Do you even monoblock?

Unless you want to use both channels to amplify two different signals, and you don't seem like you want that, get a mono tube power amp.
Or a tube power amp you can bridge.
And it's not like tube power amps will not have 2ohm outputs.
Well the ones used for guitar application will most likely not but I don't really see why you would get a power amp designed for that, I recon you'd be paying a lot of money for a very little to non existent improvement when you could achieve the same result with whatever good quality power amp.

Seriously, the fact that "most tube power amps are better suited for stereo operation" is plain false.
If you insist in getting a stereo power amp and using both channels to amplify the same signal with both channels you're wasting the second channel.

If you wanna amplify two different signals and you happen to get a stereo power amp that doesn't have 2ohm outputs, wire two speakers in series and two in parallel to get an 8ohm mono and two 4/16ohm stereo inputs.
Name's Luca.

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#3
I think you are confused about terminology and/or what he ohms of your cab actually are or I just don't get your explanation of the problem. If you have 4 speakers each rated at 8 ohms and the total mono impedance of the cab is 8 ohms then that means your speakers are wired in series parallel like this



If the cabinet was set to operate in stereo it would split the two series sections apart and you would end up with 2 16 ohm inputs or you could have two sets of speakers wired in parallel giving you 2 4 ohm inputs.

To get 2 ohms from your cabinet you would have to wire all 4 speakers in parallel but that would not give you stereo, it would be mono just like your 8 ohms is mono.

If your problem is that you have a stereo amp and you want to use one cab for both channels of your stereo amp then you can rewire your cab to have 2 separate inputs in either 4 ohm or 16 ohm so as long as your stereo amp is happy to run in one of those two impedance ratings you should be fine. You don't need to jump the two channels of the amp and run it at 2 ohms.
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Last edited by CorduroyEW at May 15, 2014,
#4
Well, I'm just quoting what the guy who sold it told me... The right input would be mono 8 ohms, both would be 2 ohms in stereo. At the time it didn't matter because I was using it with a 6505 112 acting as a head... Here in Europe those tube monoblocs are very difficult to come by, like the Carvin TS100 or the Peavey Classic 120. Those would be my first choices but I can't seem to find nearby. I've been using a friend's solid state 100 watts combo as a poweramp (with the sansamp preamp) for rehearsals and it just hasn't got the power, as it starts to clip badly before getting to decent live levels. I need more power lol!

About the terminology thing, well, it maybe that I'm a portuguese guy that's probably getting a little bit lost in translation

Thanks for the replies!
Last edited by Kivenkantaja at May 15, 2014,
#5
Wire as above for a proper 8 ohm load. I don't understand the whole stereo thing or why anyone would run stereo into a single cab. The only reason I would choose to run stereo is when running two cabs on either side of the stage for sweep effects like chorus/delay. I don't know any current players who do this. For stereo they run direct from Multi-effects to the house sound.
"Your sound is in your hands as much as anything. It's the way you pick, and the way you hold the guitar, more than it is the amp or the guitar you use." -- Stevie Ray Vaughan

"Anybody can play. The note is only 20 percent. The attitude of the motherfucker who plays it is 80 percent." -- Miles Davis

Guthrie on tone: https://www.youtube.com/watch?v=zmohdG9lLqY
#6
The numbers you were given don't add up so you must have been given bad information. You can have 8 ohms split to 4 or 8 split to 16. If the cab is ever running at 2 ohms then the 2 ohms would have to be in MONO and stereo would be running at 4 ohms.
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#7
Quote by Kivenkantaja
Here in Europe those tube monoblocs are very difficult to come by, like the Carvin TS100 or the Peavey Classic 120.
The TS100 is actually a stereo amp :P
Quote by Kivenkantaja
I've been using a friend's solid state 100 watts combo as a poweramp (with the sansamp preamp) for rehearsals and it just hasn't got the power,
Then you need a good power amp.
The problem probably lies in the fact that the people who assign power ratings to guitar amps are more or less making them up in most cases.
A solid state guitar amp rated at 100w may as well have a generously rated 80w peak power amp, while a carvin TS100 actually seem to put up around 100w RMS @ around 0.something% THD, which is a lot more.
Plus it's a tube power amp so you wouldn't really even bother bringing it to 10% THD unless you want pristine clean stuff - but I'm guessing you wouldn't be using a guitar amp at all if that's was the case.
Quote by Kivenkantaja
as it starts to clip badly before getting to decent live levels.
Decent line levels?
TS, check your terminology.
A line level doesn't really have a lot to do with what we're talking about.

Anyway, since you're having doubts about the input impedances of your cab, grab a multimeter and whatever cable with jack leads at both ends.
Set your multimeter to 20kOhm or 2kOhm if you have that too, plug the cable in the each cab's input, put one of the multimeter leads on the jack's shield and the other one on the tip - the input impedance of your cab is the nearest higher power of 2 (2, 4, 8, 16...).

Now that we solved the cab issue, let's just keep the amp thing in the other thread for the sake of clarity.
Name's Luca.

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Clue: amplifiers amplify so don't turn it on if you need quiet.
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#8
Live levels, not line levels. By that I meant decent volume (and definition) for band rehearsals
#9
Aww, sorry.
Well we got that too, so let's go to the other thread now
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.