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You like the sound, that’s all that’s important. ~ If you hear a mechanical flubbing sound from the speaker, back off the EQ or volume as you are pushing the speakers too hard. The bias and balance controls on the back are a good feature.

My worst experience was bringing home a cab that reeked of animal urine and cigarette smoke. I tried everything to rid the smell to no avail. It was deep in the wood. In the end, I chucked it in the bin. It taught me a lesson. Do a smell test before buying.

Ideally, you want a cab that matches the sensitivity, etc. of the one that you have. That way one won’t be louder than the other. If you don’t add a second cab, it helps to elevate the combo closer to ear level. Try the height of an extension cab. This allows you to monitor and sound better.

The Peavey Combo 115 is a workhorse amp. I’ve even seen them supplied \as backline rentals. The amp is 210W with the combo speaker, 300W when an external 4 ohm cab is connected.

Depends how big the pub is and the room acoustics. PF-50T, a 50W tube amp is nice. The more speakers the more volume. For a solid state amp, you might want at least 200W.

I’ve purchased PTFE lubes from box box hardware stores. Graphite is good. I also use Big Bends Nut Sauce on tuners. It works well on nuts. The key is very little lubricant is needed, use it sparingly. Closed tuners have a small oiling hole on them. Many don’t realize what that port is for.

A torpedo box. https://www.two-notes.com/en/

There are some basic things that you can try. Put a patch cable or short instrument cable between the effect send and return. See what happens. Test the power amp by plugging a preamp into the line in jack. If you don’t have a pre-amp, try plugging your bass directly into the line-in jack. It may or may not work depending on the signal strength from the bass. This is for your tech in case they don’t have a schematic. As a start…. There are some minor resistor changes in the later revisions listed in a table. There are also test point voltage references to read when examining the amp. The amp has a few interconnect cables. These should all be inspected and reseated. Clean if oxidized. The jack shunts should all be cleaned with Deoxit. https://ampeg.com/support/files/Schematics/S Series/SVT-200T, 350T/SVT200T_350T Schematics_PL.pdf

Sometimes the headstock has a thin piece of laminated material on the top. You won’t know till you start working. I agree, sanding would be best. Use a sanding block to maintain a flat surface. I use 3mm thick hard rubber that I purchased from an auto-body supply shop. It’s used for fine sanding finishes. Another option is a good hand scraper. Be careful not to round over the edges. Nothing is ever as simple as it first appears.

It would be best to have a dual channel amp. That way you can EQ each channel to suit the tone that you want for each pickup. A dual input amp would mix the pickups at the input. Billy talks a bit about his bass here. They are tracking into a Neve 1073 clone made by BAE (Mark the guitar player’s company).

Both the 20T and 50T are reported to record well in a studio. The PF-50T offers more tonal variation and more headroom. With a PF-20T, you can compensate for that with DAW plugins. Both have the same basic James tone circuit for bass and treble. When I play through an amp, I look for it to inspire me while I’m playing. I like the sound to be there at that point. So for me, the tone out of the speaker is important. The speaker cabinet is important. Both the Ampeg 12 and 15 cabs are good products, it comes down to personal taste. It helps to raise the cabinet close to ear level for better monitoring. How you mic the cabinet is also important, close or a few feet away. If close, where on the speaker should the mic be placed. Which mic to use. A lot to work out to optimize your sound. Some helpful information here: https://www.talkbass.com/wiki/tips-tricks-and-modifications/#23-miking-a-cabinet Others have mentioned mixing a DI with a mic’ed cab. When doing this it’s important to ensure that the two tracks are time aligned to avoid cancellation of parts of the signals. This isn’t a big deal to do in the DAW. DI has advantages in that it can compensate for low frequency roll-off that. mic may have. Not all mics used to capture bass have roll-off issues. A mic’ed cab sound with some air between the speaker and the mic also has its advantages. There are always pros and cons to consider and there is no right or wrong answer. Bottom line, get the amp that you can best afford and make the most of it.

A tube amp is designed to produce the same power output on each output transformer tap with a cab that matches the impedance. So a 16 ohm cab on a 16 ohm tap will produce full output power, an 8 ohm cab on an 8 ohm tap should produce the same output power. You might hear differences with 8 and 16 ohm cabs. The speakers are different, the cab designs are also different. One cab may be louder than the other due to sensitivity differences. Even the same speakers can have different specs due to tolerance difference coming off the assembly line. Looking up the Quattro, they say that it can be either 4 or 8 ohms. The same cabinet, with the same speakers, just wired differently internally should sound the same.

Just to be clear. A dummy plug is a standard ¼” plug that is left open. When the plug is inserted into the speaker jack, it reroutes the amp’s output from the 16 ohm to the 8 ohm transformer tap. This allows you to plug in an 8 ohm speaker cab and the impedance between the amp and the speaker cab will be matched. A dummy load is something else.

Since you want to avoid weight, a tube amp sounds like it would be out of the question. They do naturally compress when pushed. Having a tube rectifier helps even more. But a simple way to compress is to mechanically dampen with a sponge mute at the bridge. It worked for James Jamerson. If you have a tweeter turn it down. Again, a mechanical damper, padding placed in front of the tweeter helps. These kind of things are fun to try.

First check that the jack nut is tight. Strain from the cable can bend the tip connection on the jack and make contact with the plug intermittent. The fix is to pull the jack plate and carefully bend the jack’s tip contact inward to make a better contact with the plug when it is inserted. One of these two often works. It is also possible that there is an issue with your instrument wiring or soldering, oxidation on the jack contacts (use deoxit to fix that), even a bad instrument cable. This would require an inspection to properly resolve the issue.

It depends on the pickup. If the four wires can be brought out, the coils can be wired in series, parallel, or anti-parallel (humbucking). Guitar players use switches to select these various options, search for wiring diagrams. Each option is tonally different.

I recall an article a year ago saying that the component and chip manufacturers saw the pandemic as a temporary problem that would go away in a year or two. They didn’t want to build new large scale plants only to have them sit idle when this is over. This decision is proving to be a mistake. Future demand estimates for parts are proving to be beyond expectations. Now companies are building their own plants to meet their own demand. Even Apple is affected and they are pretty good at meeting their needs. I will have to wait three months for a USB-C power supply.

https://electronics-sourcing.com/2021/06/01/navigating-supply-chain-shortages/

Production is shut down in favour of short term higher profit. Asia controls much of the market now and can shut it down in a heartbeat. Manufacturing all over the world needs to be re-established.

Vintage-Blue (http://www.vintage-blue.com) makes a high quality double baffle B-15 cabinet. These DB cabs were used in the earlier revisions. A slightly larger version of the cabinet can be paired with an Ampeg PF-50T if you want to flip it.

According to two emails that I’ve received, retailers are claiming that there will be shortages this Christmas. This isn’t just to boost sales as I’ve seen it beFore in the industry. Some manufacturers have stopped accepting new orders till they get through their backlog. They say that part shortages are to blame.

Excessive weight from a too long speaker cable can be a problem. Speakons offer some strain relief, ¼” plugs are more of a problem although some do offer some relief. A looped speaker cable should have the loop supported to relieve stress on the connectors.

There are those that buy long speaker cables then coil them up and tie them to keep them off the floor. Not the same inductance as a curly instrument cord. Buy just the length that you need, not way longer. If you have a long instrument cord, snake it back and forth on the stage, don’t coil it. It is important not to walk on your cords. It can damage them with time. Also, when winding your cables for storage, use the over-under technique. This prevents twisting.

Cathode bias eliminates one possibility. Something odd is going on then. Carefully recheck the wiring. When soldering on the socket, the rectifier tube should be removed. Check the socket tension, the tube should slip in and out with some resistance. It helps to have a scope to examine what is going on. Test the high voltage AC secondary with the tube removed. Check for the presence of the 5VAC heater. Then check the rectified voltage with the other tubes removed. Be patient. It requires logically checking each step along the pathway.

The uF4007 is fine. UF5408 will work but are harder to fit because of their size. The diode must be located after the bias tap if there is one. I describe it here: https://www.talkbass.com/wiki/technical-amplifier/#39-protecting-the-rectifier-tube-from-flashover