Sparky Mark

I wonder if the difference in heft (apologies for introducing the "H word") that several bassists hear is down to high pass filtering used in more modern amplifier designs? Maybe old designs didn't have any HPF implemented so produced a big fat output but ran out of headroom sooner? Newer designs might be able to get louder but at the expense of big, deep low end? I realise speakers actually make the sound but hope you know what I mean.

Is there actually a difference in the electrical signal sent to the speaker from a class D amp when compared to a class AB amp?

That really surprises me. The D800 and D800+ get almost universal praise both here and on Talkbass.

I think it's also important to know how to sculpt "your sound" with any amplifier's EQ section. I prefer a boost around 100Hz, some cut around 340Hz and a boost around 1.2 to 1.5kHz. If I can control those areas I can nearly always get a decent tone from an amp. Use your ears not your eyes; everything might end up at noon (nominally flat) but some systems (full signal chain including fingers thru to speaker cab) may need a kick in certain frequencies. I always got the impression that Shuttles were intrinsically very clean but could be EQ'd to almost any tone due to the highly flexible EQ section. I'm sure I've blamed amps for being poor in the past because I wasn't familiar with what I needed to do EQ wise.

As you previously advised, you bought your old combo second-hand over 5 years ago so now it might just not be worth throwing big money at it. You can easily determine if the combo speaker is okay buy connecting it to another amp. The CMD121H is an excellent combo so I'd look out for a good condition used Little Mark head of any type (they'll all fit) to swap into the combo chassis.

There's definitely a difference between how a LM2 and a class AB LM3 sound with both filters off and all EQ at noon. In my experience there's less of a difference between class AB and class D versions of the LM3. I think possible changes to the HPF, preamp board and limiter from LM2 to LM3 may be more significant than the power amp topology.

The 600 watts refers to the maximum mains input power requirement, not the amp's speaker output power. It makes sense that with class D being more efficient than class AB it would require less input power as less is being lost as heat.

If you can see the two aluminium heatsinks through both sets of side vent slots then you have class AB (below). If you only see one aluminium heatsink then you have class D.

I wouldn't get hung up about the class of the power amp. All LM heads sound very similar due to the common pre amp section. The LM2 sounds as good as any Markbass head IMO and if you can live without the adjustable DI or need massive power then it's a winner even now.

Oh, yes the LM800 is ckass D.

There are no Markbass reliability issues that are different to any other manufacturer. Electronics of any type will eventually fail, the same as any mechanical system. If you bought a 15 year old car you might expect more problems due to wear and tear. There's no way of knowing how well or badly an amp has been used, so cosmetic condition is probably the only available indication.

You're welcome. I think that they are as reliable as any other quality brand, just be aware that a good amp may well have seen plenty of gigs in 14+ years. If you can find a lightly used/ home studio example it could well last several more years. A repair by a Markbass authorised tech will probably cost around £200 even if they keep the parts so may not be worth doing.

The LM2 will be quite old as they stopped making them around 2008. All LM2 had a class AB power amp. For three to four years of production its replacement, the LM3, also used a class AB power amp, but from around 2012 all LM3 have a class D power amp. A good condition LM2 is an excellent amp that can be found second-hand for £200ish.

Another 4003S?

And the verdict is......?

Strange to think that depending on your definition of "vintage" the Precision Lyte (1989-95) now qualifies as a vintage instrument. My example is all original and being a Fender nerd I'd never change the electronics. I actually like the original pre amp on these; the bass and treble cut/boost being much more subtle than most. The approximate 7lbs weight will possibly make this my old age bass alongside my Mustang.

If we're allowing PJ as options then I'll suggest the 90s Japanese Precision Lyte. It's lighter and smaller bodied than a standard P and has a slim J like neck.

This is spot on. There's not many manufacturers of anything that publish full design schematics that would allow others to copy their products or elements thereof. Electronic components and printed circuit boards are relatively low cost but the labour time/cost of properly diagnosing faults and then swapping out the correct part(s) is the expensive bit. We shouldn't forget that the repair tech needs to make a living too, so there is profit to include also. I would estimate to open up, diagnose, dis-assemble, replace failed part/assembly then test, re-assemble, pack and return even the simplest job would take between one and two hours labour. Add modest material costs and profit and it's not hard to see where £200 comes from for an out of warranty repair. No one is making a killing fixing old amplifiers.