agedhorse

Yes, the amp will drive 250 ohm headphones without any difficulty, but the vast majority of players use lower impedance phones and by far the greatest number of questions (and issues) is with the lower impedance phones. To refresh my memory, I checked the top 30 selling headphones and ~90% were 60 ohms and less. There were just a couple over 100 ohms. Just beware that there are quite a few high impedance phones that do not get as loud at low frequencies, the headphone out will drive some of them beyond their capability without them getting as loud as players expect.

To clarify, a first order filter is 6dB/octave and a second order filter is 12dB/octave.

A tweeter is typically about 10dB more sensitive than the low frequency section, so with the tweeter level control fully up (assuming that's the only attenuation), there will be a 10dB bump in the high end compared with the rest of the speaker's response.

Mid 90's. Be sure that you set your speaker to 8 ohm mode (assuming it's switchable between 4 and 8 ohms) I too would recommend a second speaker identical to your first.

Any electronics before the amp (pedals and active bass for instance) can contribute to a higher than ideal noise floor. If a speaker has a tweeter sensitivity that is significantly higher than the low frequency drivers, this can result in the perception of more hiss than you might otherwise expect. This is common with tweeters turned up to "bite your head off" level that happens with some cabinets. The brighter the tone, the more noise present.

This too is inaccurate and incorrect. Maybe a FEW models of wireless, but certainly not many or great many. Out of the hundreds I have set up, maybe one or two.

That’s not an active bass issue, it’s incompatible wiring/connection with that particular product. I’m not sure why they chose to use a TRS plug on the transmitter, but it’s unusual and maybe even unique. I have worked with hundreds of players, interfacing wireless systems (mostly at the professional level, with pro products by Shure, Sennheiser and Audio Technica) without any problems.

They do? I haven’t seen this to be the case, in 40+ years of being in the business.

Active basses can drive lower impedance loads. This includes long cables because the capacitance reduces impedance (via capacitive reactance) as the cable length grows (for bass guitar it’s typically not a big issue up to about 10M). Most wireless transmitters have an instrument input impedance of around 1M which is compatible with all pickups, active or passive.

Surrey Amps in the UK are qualified to troubleshoot and repair Genz Benz products, I can provide factory support and parts directly to them.

I never suggested he send the amp to the US, I did suggest that he find an experienced, qualified service tech to troubleshoot the actual cause. There’s a lot more than the switches involved in the filter switching. In this series of amp, I have seen maybe 1 or 2 bad in the last 10 years. I’m trying to help by providing good advice.

What is the primary current rating of the transformer? I'm about 99% sure it's well under 250mA full load at 230V, meaning that if there wasn't a problem with the transformer itself before powering it up with the higher value fuse and there was an issue in the circuitry downstream, you now have another problem in addition to the original fault. This is why DIY repairs, and repairs by techs who are under-qualified for the work they are attempting end up the way they do.

I already answered your question on Talkbass.

Did the tech check to be sure that the measured input current was less than the transformer's rated input current x0.65? This would confirm that the load was safe for the transformer.

First of all, that thermal protection isn't going to do much because it's on the outside of all of the wrappers so it will be measuring quite a bit less temperature than what's really present on the coil. The coil can overheat without the core overheating on a small part like that. Is the coil really overheating? Only a proper forensic evaluation (called a transformer "necropsy") will determine the true cause of the fault. The fuse should be slow blow (or time lag) and sized at a minimum of 1.25x the rated continuous primary current. For a toroid, it's possible that the inrush current (which is higher than for an EI transformer) might require an adjustment of this multiplier from 1.25 to 1.5, but this needs to be done after verifying that the transformer is not overloaded. There must be enough primary turns for the core material to prevent magnetic saturation, this design parameter is voltage and frequency dependent. If the transformer saturates, the primary current will be higher as will be the heating effect. Now for the real stuff... do you know what the input current is to the power supply. It looks like a FWB input capacitor filter. The transformer needs to be designed around the derating factor for this particular power supply topology. For this configuration, the rated current of the transformer multiplied by .65 is the usable current for the circuit being powered. It's possible that somebody forgot this when designing the power supply. There's more to solving this problem than replacing a part, you need to know what the maximum current of the circuit is and work backwards with all of the necessary design and derating factors to be sure you have a viable solution.

It's quite different from the ShuttleMax amps and about 1/3 the size. I would expect that you will start seeing Subway products in Europe in the next 3 months or so, we are finally digging ourselves out of backorders and parts sourcing issues. Crazy times we are living in.

Subway D-800 is 800 watts into 2 or 4 ohms, the aux input is suitable for using as a power amp input.

Recent tours with Primus had Les playing a Subway D-800 rig w/ Subway 112 cabinets, slaved for 1600 watts rms into 4 x 112's. I don't know what rig he is using for the new FFFB tour that's going out this spring.

Sometimes, sometimes not. It depends.

We’ve shipped a lot of these amps and haven’t seen any problems. I have no idea what the issue may be.

Probably a good example of two wrongs not making a right...

Sorry guys, that was a horrible typo. It should have been 2 ohm mode not 4 ohm.

Correct, set the amp to 2 ohm mode (NOT 4/8 ohm mode). This is covered in detail in the owner’s manual. This is why we put so much effort into the protection circuits. [edit for bad typo]

Just be sure that the shielding material is bonded to signal ground at the output jack, otherwise it can make things worse.