basstone

Changing the bridge saddle material changes to tonal qualities of the sound so maybe worth experimenting with that. Even string balance does rely on good contact between the saddle and the pickup. Check that the saddle cavity is clean and the bottom of the saddle is smooth and flat. Better even pressure can also be achieved by chamfering the bottom edge of the saddle resulting in a smaller but higher pressure contact. It might also be worth swapping out just the pickup, they generally all have a mini jack connector for the preamp, so long as the thickness is similar it's a quick and easy job.

I'll be there all being well 🙂

The Mackie amp kit replaces the original DSP with analog circuitry, which although easier to modify is still not straightforward! Picking up a pre-crossover signal from the preamp should however be fairly straightforward, retaining the input and tone controls and hopefully at a suitable signal level to feed the main LF power amp then feed the existing passive crossover. Another possibility may be to feed the full bandwidth signal to both amps and split the passive crossover for the 2 inputs! I have no immediate plans to try any of this out as I'm already on the same Icepower route as this original project (based mainly on the fact it is already proven in several good bass amps - my own GK SB500 included). I just thought as I came across it, it could be interesting as potentially there is less work involved than developing a preamp and phase splitter required to drive the Icepower modules.

I suspected that would probably be the case. If I have time I could measure the actual crossover frequency response when I get the parts to repair the speaker. I can't find the schematic for this analog preamp and surface mount boards are tricky at best to modify but it could be possible to feed a full range signal to the LF amp and retain the passive crossover.

My own active BC12 cab project has also been stalled due to other priorities and my repair business is now starting to pick up again and one of the items brought in last week for repair was a Mackie TH-12A active speaker. Why is this of any interest or relevance? I found that the DSP input module had failed and being SMT and not repairable I my only realistic option was to buy a complete upgrade kit for £139 plus £6.99 postage. This kit includes all the electronics ready assembled including; balanced input board with level control, 3 way parametric equaliser with bypass switch, active crossover, input EMC filter, SMPSU and dual amp module with 300W class D LF amp and 50W HF amp. The PSU and power amp are mounted on an alloy heatsink/ mounting bracket and the preamp boards stack on 4 spacers. All Fairly lightweight and compact. It would just need an input panel and mounting inside the cab. I wonder how well the active crossover would match the BC12 design? An alternative would be to use just the LF 300W amp with full range input and use the existing passive crossover design. Here is the link to the supplier: https://sbsav.co.uk/shop/59588-mackie-thump-th-12a-digital-to-analog-rework-kit.html Any thoughts?

Mine should be the same assuming the Marshall combo is still for sale. Maybe even have the amp fitted in my BCv3 cab by then

Thank you Mike for all your work on this and making the only decision possible. Looking forward to resuming on the other side of this, meantime everyone stay safe. Good opportunity to polish up the bass chops and learn some new parts.

I think postponement is the best option, looking at what has happened in Italy and Spain. You can have this virus and be spreading it to others for 5 days before you even get any symptoms. It would be difficult to keep all the basses and gear clean throughout the day not to mention sharing the food. Happy to help cover costs if applicable.

Yes it was faulty power valves. One eventually shorted completely and totally destroyed the protection fuse and its holder in the cathode circuit of the valve. There is a lot of stored energy in the HT power supply so thankfully the fuse did it's job and no other components were damaged. A new set of power valves, a new fuse holder and fuse and all up and running with the bias nice and steady on both valves. It's a nice touch on the CTM to use the VU meter to set the bias which can be done separately for each valve.

Yes, I had exactly the same problem. I even tried negative numbers and 0. nothing worked, so I phoned instead and spoke to a very helpful Dave Green. I think that the 4 digit CTM serial numbers relate to manufacturing sequence- first 2 digits, year of manufacture - third and fourth digit.

Indeed, funnily enough I also have a 1960's Reslo ribbon mic that was used with my Father's Ferrograph series 6 tape recorder 🙂

Having checked out the SVT with the cab, I thought it would be interesting to try out this. It is a General Electric PA amplifier, made in 1935. 4 KT66 cathode biased output valves and rated very conservatively at 30W. It was my first amp when I started playing well over 40 years ago! My father had just bought a TV and cycle shop business and we found this old (even then) amp languishing in the loft. It needed a good service, jack connectors adding for input and output and a matching transformer for the 100v line output. It weighs nearly as much as the SVT and back in the day was paired with a massive 1 x 12" cab with a slate baffle from an old billiard table with 1 1/4" chipboard for the rest of the cab and a pine frame around the front, painted gloss purple! The cab is long gone but I still have the amp and it still works. The valves are all original except for the driver. I've changed a couple of leaky caps and added some new smoothing caps to help the originals. It's not as loud as the SVT but has a smooth slightly compressed sound. A peek inside for the tech minded. Very neat and easy to work on.

I just had to see how my cab sounded with the SVT classic amp that I just repaired for a client, and what better way to demo the amp. It almost looks made for the amp to sit on when on its side. I needed to add the 1 x 15" polytone cab to get the 4ohm load for the amp. Imagine 2 Basschat cabs stacked with the SVT (top cab with horn rotated 90 degrees and bottom with low pass filter and no horn?). It would make a great looking and great sounding rig! Needless to say it did sound great, a nice rounded full tone but with plenty of definition. Shame about the weight (of the SVT that is :-)) but great valve tone is never going to be lightweight.

There is not much out there that is. It will be interesting to see if modding the tone stack on the Ashdown to the later spec makes much difference.

I have used Ashdown gear for many years as well as repairing them in my amp tech business. Ashdown have always provided excellent support both with information, schematics and spare parts. The amps are well made and easy to work on not to mention sounding great to me!

which wire you connect to + or - will in practice only really matter if you connect more than one cab up to the amp. If you do connect 2 cabs together and mysteriously loose loads of bottom end then you will know the speakers are out of phase. Although most “vintage” amps and cabs used TS 1/4” jacks for speaker connections, I’m not a great fan as it is possible with metal bodied jack socket designs to short out the amp output whilst inserting / removing the jack with the amp switched on..

Cover has arrived from Roqsolid. Only took a week from placing the order 🙂. Now when's my next gig.... Here's the link again for anyone interested in ordering one. https://amplifiercoversonline.com/tinyurls/6 Remember to use the discount code "basschat" to get free delivery.

My G K cabs have an aluminium grille which has folded flanges on all sides. These make it rigid and space the grill off the baffle without the need for a frame. The grille is also fixed from the sides of the cab giving a really clean look. It would be more expensive to get made for sure, but just a thought?

Just popped the template with 150mm round cutout for the handle in the post to Roqsolid 🙂