Bill Fitzmaurice

Most of what makes tubes sound like tubes is compression in the output tubes and output transformer, which you can't really duplicate with anything in the front end, including tubes. Still, if you're going to get any improvement it will be with a good compressor.

No load connected isn't very low impedance, it's very high impedance. It's not quite infinite, as there would be some load provided by the output transformer itself by losses within the windings, but almost. All of the power produced by the tubes still goes into the output transformer primary windings, but with no speaker connected it has no way of flowing out the secondary windings. Bad things ensue. That's also why too high an impedance load can injure both the output transformer and tubes. The power put into the primary windings can't flow out of the secondary windings as easily as they should. SS is the opposite. With no load no current passes, so no harm no foul. With too low a load impedance too much current passes, stressing both the output devices and the power supply.

Valve amps don't have a minimum impedance load, they have a maximum impedance load, the opposite of SS amps.

If I'd used a run of the mill driver as the example invariably someone would have said a better driver would have given a better result. Not that there aren't any drivers better than the 12SW1300 Nd, but they're few and far in between, and aren't going to be found in an off the shelf electric bass cab.

It would, for the reason I already stated, you'd have to find one with linear response from 100w to 300w. Good luck with that quest. Thermal power compression alone will render the simple math null and void. For instance, consider the Beyma 12SW1300 Nd. It's rated at 1200w AES and has 10mm xmax, so on the face of it there's no problem with a 300w input. However, thermal power compression at 100w is 0.25dB, at 300w it's 1dB, so right there the 4.77dB increase you might expect with 300w versus 100w is closer to 4dB. That's with a premium driver, which has much lower than average thermal power compression. There's also mechanical power compression to take into account. With 10mm xmax that won't be much, but the 12SW1300 Nd is hardly a typical driver. Drop that xmax to a more likely to be found 5mm and mechanical compression can be just as significant as thermal.

My hand is raised. If everything about the two amps transfer function was identical then 300w potentially could be 4.77dB louder than 100w. But finding two amps with identical transfer function other than power would be next to impossible, and even if you managed to find them then you'd need to find a speaker with linear output with respect to power input from 100w to 300w. That would be equally as difficult a quest.

It depends on a lot of factors, and no, a 300w valve amp will not necessarily be louder through the same speaker as a 100w valve amp. And there's the rub, there is no direct correlation between watts and perceived loudness.

In most cases separating cabs is a bad idea. The shows why. It's specifically about PA subs, but the same issues apply to bass cabs. http://www.prosoundweb.com/article/in_search_of_the_power_alley/

There are two ways of rating power, RMS watts and everything else. RMS is what's used when you want to give your customer accurate information, anything else is what's used when you don't. RMS watts might not be the best description, as RMS really only properly refers to voltage, but it's worked well enough for nigh on a century, so there's no reason to change it now.

Typically when channels are bridged the minimum acceptable impedance load is doubled. You have two 8 ohm cabs, you have two 8 ohm capable channels, use each cab with one channel. This comes down to the unfortunately seldom debunked notion that more watts equals more output. It doesn't. https://billfitzmaurice.info/forum/viewtopic.php?f=10&t=19292

Try camping/hiking supply stores.

So if you send money for gear and the gear never arrives or it's broken or not as described you're left dangling in the wind. I'd rather the piece of mind with PayPal.

Does Transferwise offer seller protection?

That's when you started to see multi band EQs that were tailored more to either guitar or bass, and more emphasis on over-drive with guitar amps. Major differentiation was most common in SS amps.

Until roughly 1975 the only significant difference between guitar and bass valve amps was that guitar amps had reverb and tremolo, bass amps didn't.

Amps do have voicing, which is a specific frequency response. It can be changed, if you're an expert. If you're not you're about two years away from acquiring the necessary skills at an engineering school. That level of expertise would make going from a single tone control to a 3 band EQ an easy task. Without that expertise, no way.

Sealed cabs have a higher risk of driver damage. For equal output they don't have less excursion, they have more. For equal output they don't draw less power, they draw more. Ported cabs unload well below 100Hz, at least an octave lower on average. If you go low enough sealed has the advantage with respect to both excursion and power for equal output, but that tends to be below 35Hz, where it's of no consequence. High pass filters need not have a higher than 35-40Hz knee frequency for that reason, and their main purpose isn't to reduce low frequency note content, it's to reduce low frequency thump noise.

Cable characteristic impedance is a completely different topic, having no relation to speakers. When you see that a cable is 75 ohm it doesn't mean it measures 75 ohms end to end. The characteristic impedance of a coaxial cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. Since those factors are unaffected by cable length neither is the cable characteristic impedance.

There's no reason to sell the amp. Bridged it will handle a minimum load of 4 ohms. Minimum means that's the lowest value you may use, not the highest, nor the exact load you may use. Perhaps this will help: https://billfitzmaurice.info/forum/viewtopic.php?f=10&t=19292 BTW, there's no such term as ohmage. The term you should be using is impedance. Ohmage is the made up word used by those unaware that ohms are use not only to measure impedance but also its components, resistance, capacitive reactance and inductive reactance, either separately or in combination.

If you're in the UK both fuses should be 4 ampere, if the purpose of the second fuse is to be a replacement spare. If the reason for having two fuses is to give the user the correct fuse for their supply voltage then they would be 4 amp and 8 amp. The truth of the matter should be revealed in the owner's manual.

They're not different, or at least they shouldn't be. The back panel shows two values, one for 110v operation, one for 220v.

Sure, this for instance, but it's a PA top, where 8s are appropriate. I wouldn't use them for bass, as they're not cost effective.

If loudspeaker software modeling software showed that it made a significant improvement over the original driver it could be worth it. If you can't confirm it first then just tossing in a driver based on watts and ohms alone would be a very unwise move.

PIxie dust.

Now you've got it. 😀