Questions about solidstate ohm miss-matching

ragingben

Hey guys quick question:

I have a solid state head, 8 ohm. I know this is fine running into a 16 ohm cab, but what will the effect be compared to an 8 ohm cab? Online I've read "more bass response, quieter" but that is hard to get an idea of how much either of these things will affect sound.

I have a 112 16 ohm V30 cab. Theoretically if I were running a 112 V30 8 ohm cab would I notice much difference in sound?

ICBM

If anything with higher impedance you will get *less* bass response, not more - if there's any difference at all - and less volume. How much less depends on the amp design - there's no exact rule but you will lose between 30% and 50% of the power when running into double the impedance. That's nowhere near 30-50% less volume though, it's just slightly less.

If you swapped your speaker to an 8-ohm one you would get a *little* extra volume and punch, but not much. If you want a noticeably bigger sound you'd be better with a different speaker type as well, something with inherently more bass response than the V30… like a G12K-100, or a Classic Lead.

ragingben

Thanks ICBM, that's interesting. I was mainly concerned because I didn't want to have less volume available than I could have, you never know when you might need it!

My other amp has a 8-16 ohm output (Hughes and Kettner Tubemesiter 36), I guess if I got say a 8 ohm 112 I couldn't use the 8 ohm and 16 ohm cabs in parallel as it would only be 5.3 ohm, and in series 24 ohm. So I would be best buying a 212 8ohm to have a bit more umph that I could use with both amps?

ICBM

5.33 ohms from an 8-ohm valve amp is safe, in almost all cases. Valve amps don't usually mind a slightly lower impedance - all it does is wear the valves slightly faster, and it would really only make a difference if you were really thrashing the amp.

You can't safely run that load from a solid-state amp with an 8-ohm minimum load if you're running it up full though - it's the opposite from valve amps.

So ideally you need either another 16-ohm cab to make a total of 8, which is safe with either amp, or a single cab of either impedance if you just want to run one cab. The volume differences due to the impedance are probably less important than the type and number of speakers.

ragingben

ICBM said:

You can't safely run that load from a solid-state amp with an 8-ohm minimum load if you're running it up full though - it's the opposite from valve amps.

Just to clarify - I shouldn't be thrashing the 8 ohm ss amp into the 16 ohm cab? I used it at about 3/4 volume.

Good advice on the 2nd 16 ohm cab, hadn't thought of that!

ragingben

ICBM said:

5.33 ohms from an 8-ohm valve amp is safe, in almost all cases.

I don't doubt this, but I do doubt my amp I would be using it with - the Tubemeister. Had a bit of trouble with it and H&K so I wouldn't want want to risk anything with it even if it was a 0.01% chance of failure.

The solid state amp is the AMT Stonehead I received yesterday - I'm going to do a review of it to post here once I've gigged it a few times and just wanted to check the 16/8 ohm think before ragging it all out or a long time.

ICBM

ragingben said:

Just to clarify - I shouldn't be thrashing the 8 ohm ss amp into the 16 ohm cab? I used it at about 3/4 volume.

It makes no difference - it's actually less stressful for a solid-state amp to be run into a slightly higher impedance.

I always try to do this when I'm working on amps which will get maximum abuse - like rehearsal studio gear - change speakers if necessary to make sure it will usually or always be operating at double the minimum impedance, which noticeably helps the reliability.

I've been interested in the Stonehead for a while too - let us know how it works out .

ragingben

Phew! Thanks for clarifying ICBM!

I will definitely do as there is minimal info out there and no manual. First impressions are very good - it's small enough to fit in a back pack, flexible enough to not need most of my board, loud enough for small gigs and rehearsals, and very very warm. The clean channel got a comment from out drummer last night which is a rare thing indeed! I don't think I'm going to put everything up for sale or anything silly like that, but I am considering recording our EP with it mid Jan, which will be mainly clean and crunch.

ThePrettyDamned

Lovely. How does it do lower gain crunch, and insane infinite amounts of gain?

Glad you like it. I suspect I'll own one myself someday

ragingben

So far I would say it does both of those well, especially higher gain. It was quite noisey with high gain though to be honest so probably put a gate in the loop. So far I'm thinking it's decent at everything but maybe not king of anything. But... So far I love it and I can guarantee due to size and weight it is going to be used a lot. The reason I'm going to record with it is because it sounds very different to my valve gear, which is a little generic sounding to be honest.

ThePrettyDamned

Jack of all trades, master of none that fits in a backpack and costs less than 500 sheets still sounds really impressive.

Keep us updated on how you go!