basstone

You're welcome Matt.

Sorry I won't be able to make it this year as I'm away that week. Gutted!

On the amp front, I've used a Gallien Krueger MB500 for several years, now. Very light (3Kg) and compact giving 300W into 8 ohms. I use it with a GK 210 neo cab most of the time. The cab is probably still too heavy for you but the MB500 would work well with a BF cab I think!

From the picture, I suspect that this is a dual gang 20K pot(C taper) and a single gang 10K (B taper). That makes some sense as often variable frequency middle controls use a dual gang pot for the sweep and a single gang for the level.

Does anyone out there have a schematic or even a simple wiring diagram showing how the controls connect to the board? The 3 sig and ground is probably fairly straightforward but for the middle frequency with 3 sig plus bias it is not obvious how to add this in. Maybe someone with an SR Ibanez with mid sweep could trace it out. It would be a really good asset for the Ibanez owners on the forum. As for the connectors, they are readily available from multiple sources including: https://www.ebay.co.uk/itm/134781932915?var=434274031445 It pays to get the correct wire size and a good crimping tool to make reliable professional quality pin connections.

The cap in question is the dc blocking capacitor in the power amp feedback ensuring that the power amp has unity gain at dc. If this fails any small dc offset in the circuit will be amplified and presented to the output. It will depend on the particular amp design and is not a common failure but worth checking!

A small DC offset will not significantly affect amp headroom but is not desirable as it will increase the possibility of noise and hum on the output as well as a small increase in heat dissipation and a thump or click when the amp is switched on and off or the speaker connected. Also worrying is the possibility of a leaky capacitor in the feedback circuit which if left will gradually allow the DC offset to increase to the point where the amp and or speaker will be fried through thermal overload - I know from personal experience! Glad to hear it's now fixed and sounding better.

As already noted, it's quite likely that a pot connection has made an unintentional contact with the screening foil. I always put an insulating layer of clear plastic sheet between the foil screen and the pots to avoid the possibility of this happening. Screening foil is far more effective than conductive paint in my experience and well worth another go.

It's hard to tell the quality of these enclosed barrel jack sockets. Switchcraft branded should be as good as any available. I've replaced quite a few including Warwick basses. 27 years is good going and the new replacement will not likely last as long! You can't open them up to inspect or repair them and peering inside with a torch, it looks like the contacts are very narrow and likely loose their springiness over time which results in intermittent connection. Access to the barrel securing nut is usually the biggest issue, finding a suitable spanner the correct size that you can actually get in the control cavity. Make sure the soldered connections are good and some insulating sleeving is a good idea which also provides some mechanical strain relief, especially for the wire going directly to the battery clip.

Getting a decent bass monitor level is not easy particularly with acoustic upright where feedback is often an issue even at moderate sound levels. As already noted putting a high pass filter to reduce the bottom octave helps and often cleans the bass sound up nicely as well as allowing the amp and speaker to go to higher volume levels without distress! I tip my floor monitor amp/speaker back about 45 degrees and try to position it pointing directly at my head if possible ( much easier if sitting as I most often do playing electric beetles for jazz and big band). Putting the amp on a speaker stand is a good option but it’s more gear and needs a cab with a pole mount. Using a separate preamp and an active pa speaker is a good option as well. In ears is worth looking at but as well as good earphones you need to get a balanced mix so you can hear the other instruments and the ambient sound. This is fine if you have the luxury of a full pa with everything going through it and either a decent sound engineer or the ability to control your own mix. All this is not often available on smaller gigs! It would be interesting to hear if anyone has tried a simple 2 way mix of di bass and an ambient mic?

Perhaps think about making a switch to a digital mixer and doing either CAT ethernet cable to FOH or even wifi to a tablet etc. There are lots of reasonably priced options about now from Soundcraft, A & H, etc... they have the added advantages of each band member being able to manage their own monitor mix and lots of onboard eq, effects, compression etc. Snakes are big and heavy.