|
|
Post by Auf Kiltre on Aug 30, 2022 14:32:48 GMT -5
But in practice have any of you had experience running an 8 ohm combo amp into a 16 ohm speaker? Any issues?
I have a Princeton Reverb II which is an 8 ohm out running an 8 ohm Celestion Blue. Works/worked spectacularly for decades. I also have an Egnater 112 with a 16 ohm Celestion G12H30 Anniversary that I run my VHT Special 6 head through using the 16 ohm out. I'd like to swap speakers.
I hooked the 16 ohm cab to the PRII's 8 ohm out and it sounds pretty good. I didn't notice any less output, if anything it sounds bigger. Probably the closed back cab talking there. All this because I'm considering moving the Princeton Reverb II and will likely never need much more than the Special 6 with a Blue in the cab.
Thoughts/experiences?
|
|
|
|
Post by Leftee on Aug 30, 2022 14:34:37 GMT -5
It probably would not cause any issues.
|
|
|
|
Post by Auf Kiltre on Aug 30, 2022 14:42:24 GMT -5
The one thing I have to consider is if the 16 ohm speaker might diminish the value of the amp. I don't want to sell the amp with the blue installed (some might be skiddish about the 15 watt speaker in a 20 watt combo though that has not been an issue through many years gigging). Plus I really want the speaker. I also don't want to buy a replacement speaker/break it in just to sell the amp. Decisions, decisions.
|
|
pdf64
Wholenote
Posts: 557
|
Post by pdf64 on Aug 30, 2022 14:50:08 GMT -5
A key thing is how the amp, ie the power amp section, gets used.
If just at low power output in a domestic setting, then it really doesn’t matter.
Cranked, eg with a loud band, is another matter.
Worst of all being cranked into an attenuator.
And every model amp is really a different scenario.
Overdriving into a load impedance much higher than the amp was intended for will reduce stress on the output valve anodes but increase it on screen grids.
Most likely things will be fine though, but there’s no guarantees.
|
|
|
|
Post by Auf Kiltre on Aug 30, 2022 15:19:55 GMT -5
All food for thought. Maybe I should just buy a replacement speaker for the amp and sell the G12H30, should I decide to move the amp. My guess is I'll fall in love with the amp all over again and keep it, lol.
|
|
|
|
Post by Leftee on Aug 30, 2022 17:32:33 GMT -5
Forego the speaker and sell the amp without. It would be cheaper to ship.
Speakers are no big deal.
|
|
|
|
Post by cedarchoper58 on Sept 9, 2022 16:20:35 GMT -5
I have run a ultimate Attenuator on my BF 67 Pro reverb cranked for 15 years. The Attenuator uses a 30ohm load and reamps. I have had no issues at all
|
|
DrKev
Wholenote
It's just a guitar, it's not rocket science.
Posts: 418
|
Post by DrKev on Sept 10, 2022 4:36:16 GMT -5
I run my Mesa Express 5:25 with an 8 ohm speaker on the 4 ohm out, which is the same direction mismatch as you're doing, Kilter. Mesa specifically say it's OK to do so, and even say that going the other direction (4 ohm speaker on the 8 ohm out) is fine but they warn it may reduce tube life a little. They say there is a slight change in feel, though I really don't notice. I measured a 2 dB drop in output compared to perfectly matched output and load, which is minimal.
|
|
pdf64
Wholenote
Posts: 557
|
Post by pdf64 on Sept 10, 2022 9:57:46 GMT -5
Amps with beam pentodes (eg 6V6, 6L6) tend to accommodate load impedances both higher and lower than that intended better than suppressor grid pentodes (eg EL34, EL84). The latter can be protected from the stress caused by high load impedance by restricting screen grid current somehow. Rather than a low resistance choke, the Mesa 5:25 has a 5k6 HT dropper between its reservoir and screen grid supply nodes. A consequence of that approach is that similar to a 5E3 tweed Deluxe, the amp’s audio power output will become somewhat more saggier and constricted than would otherwise be the case. But that may not be a bad thing, eg marketing could spin it as having a vintage type feel  In regard of a Pro Reverb (intended for a 4ohm load) being overdriven into a 30ohm load, I think the output valve’s screen grid resistors will probably significantly exceed their 1W dissipation rating. I suggest to uprate them to 1k 2W or more, and, to protect the transformers in case an output valve shorts, add a fast acting HT fuse. |
|
|
|
Post by cedarchoper58 on Sept 15, 2022 17:41:55 GMT -5
In regard of a Pro Reverb (intended for a 4ohm load) being overdriven into a 30ohm load, I think the output valve’s screen grid resistors will probably significantly exceed their 1W dissipation rating. I suggest to uprate them to 1k 2W or more, and, to protect the transformers in case an output valve shorts, add a fast acting HT fuse. Like i said i have been giggin it for 15+ years with the UA 30 ohm load cranked on 7 with a tube screamer pushing it harder with no issues only replacing tubes |
|
|
|
Post by Leftee on Sept 18, 2022 17:15:37 GMT -5
Auf KiltreHow's the new (to you) speaker in the PRII treating you?
|
|
|
|
Post by Auf Kiltre on Sept 18, 2022 17:44:52 GMT -5
Auf Kiltre How's the new (to you) speaker in the PRII treating you? I think it is a really good match for the amp. I wish I had more opportunity to use it. My wife will be away for a week in October, think I'll rattle the walls a bit. |
|
