Maybe check in with @Wasnex regarding BTA v CTM if you haven’t been able to run through both. Also the full CTM range 15 - 300) definitely are not the same according to Wasnex
Hopefully you can demo one!
We had PM.
I have not played a BTA, but I have been keeping my eyes out for a BTA 400 Mk2. Most of the BTAs I have seen for sale recently have been Custom Shop amps, and I want a Mk2 from the original production run.
AFAIK the CTM 100, 200, and 300 share the same preamp design. I have a CTM 300 and its darker than most tube amps and has stronger mids than most amps with Fender tone stacks. The tone rotaries are extremely interactive and can be frustrating if not confounding. However the preamp is capable of getting a variety of really nice tones, although making adjustments does not always produce the expected results. Not everyone agrees with me, but the low mids of this amp sort of reminds me of my SVTs. This amp has a relatively high gain preamp that drives extremely easy. So it does distortion, but it does not grind like an SVT IMHO.
The original LB30s were from the Dual Tube era. So they have a different preamp and voicing. The CTM30s were said to be the same amps as the LB30 with different cosmetics. I have a Mk1 and Mk2 LB30 and I believe the tones stacks are a bit different due to a change in how one of the capacitors is connected and different component values. I suspect there are some small differences with the CTM 30s as well.
The Mk1 LB30 is closer in sound to older Dual Tube amps. It's not exactly Fendery but it's more in that direction. It's more mid range focused and all three tone controls function in a Fendery way.
The Mk2 is cleaner sounding and has huge lows, glassy highs, and a deeper mid scoop. It's a really nice "bedroom tone," if you know what I mean. The Bass and Treble controls behave as expected but the mid control does little to nothing, depending on how the Mid Freq switch is set. I don't hear any change when I toggle the Low Freq switch. I think it selects two HPF frequencies and both are so low I can't sense the change. The Mk1 and Mk2 are both much brighter than the CTM 300.
I also have a CTM 30 Little Stubby. IMHO this one has the best behaved tone stack across all of the Ashdown tube amps in my collections. It's easy to adjust because it works exactly like I expect. However it's not quite as versatile as most of the other amps. It's voiced similar to the LB30 Mk1, but a bit leaner down low. Both do drive. I would say the LB 30 Mk1 distortion is more vintagey sounding (think late 60s-early 70s). The Little Stubby has a bit more modern distortion sound.
I have not played a CTM 15. There appears to be a new version on the market. The older version has a solid state buffer on the preamp so it's not really all tube. Also I have read multiple comments that suggested it's better for guitar than bass. Weak lows and inadequate clean headroom for bass.
