Little Bastard 30 - zero mid or treble

[birdxofxprey]

Hello TB brothers and sisters,

I recently acquired a used little bastard 30. After a week or so of testing, I find that the mid and table eq knobs do nothing.

The eq is passive, so with master volume up and all the eq at zero, theres no sound. Turn up the bass, and you hear it fine. But turn up the mid or treble - nothing, except very a faint clicking noise).

Im new to tube amps so I have no idea whats going on. Other than this issue the LB 30 seems to work fine.

Thanks for any advice!

 

[Wasnex]

My guess is you have a mk2 and it's behaving normally for the version. Not necessarily normal for a tube amp. Different amp models tend to have quite a bit of variance in their personality, and IME some of the Ashdown tone stacks are quirky.

The circuit varies across different production runs. I have a mk1 and mk2. The voicing and way the tone controls work is significantly different. The mk2 preamp always remains clean and has big lows and highs, with a considerable mid scoop. The mk1 tone is more even and midrangy and the preamp is easy to push into drive territory.

The order of the tone controls from left to right on the original LB30 is Mid, Bass, Treble. The order on the mk2 is Bass, Mid, Treble. The mk2 also has a choke on top of the chassis. See the shiny object on the bottom ride side of this image. Shine a light through the right side of the front panel and you should see the choke.

No choke in this image of a mk1.

The mid control barely does anything on the mk2, but it depend on the position of one of the switches. In one position the mid control makes subtle changes. In the other position I can't hear any audible impact if the bass and treble are not pretty much all the way off.

To see if the controls are working, turn all of the tone controls all the way down. Turn one control up, if it increase the volume, it's working. The bass control will be more bassy, the mid control will be fairly full range with lean lows, the treble will also probably be fairly full range. It's been awhile since I played with these amps, so my memory is not fresh. If I remember correctly, even with the bass and treble off, the mid control hardly does anything.

The tone controls on the mk1 have more impact than the mk2, but they are not completely intuitive or very powerful. Turning up the tone controls on my mk1 beyond a certain range pushes the preamp into drive. FYI, these amps have no gain control and the volume control is after the tone stack.

 

[birdxofxprey]

Thanks! Ill take a look inside when I get home later today.

 

[Wasnex]

I originally bought the Mk2 as I wanted to see how closely the LB30 was voiced to my Small Block 427. The voicing of the mk2 is drastically different and I noted how ineffectual the tone controls seemed. I initially assumed something was wrong with the amp and started poking around. I also bought a mk1, which is voiced quite a bit closer to the 427.

I can't say for sure this is accurate:

The right is from the original LB30 schematic. The middle is what I think the mk2 tone stack looks like. The left is my documentation of the changes.

IMHO the original is sort of a variant of a Fender tone stack. It has some added components to create the Bass Shift and Mid Shift circuits.

Many of the component values are changed in the mk2. This alone would modify the voicing and the way the tone controls respond. I also think they mk2 essentially deletes C15 and then adds a capacitor on the lower left side of the circuit. I labeled the new capacitor C15.

Changing the placement of the capacitor seems to make the circuit behave a little bit like a Hiwatt tone stack, although it's not voiced like a Hiwatt. Seems like the Mid control becomes the Bass control and the Bass control becomes the Mid control. The roles of the toggles are also reversed.

Toggling the Mid Shift on the mk2 does seem to have an audible impact on the tone and the way the Mid control works. I don't hear any impact from toggling the Low Freq control. I believe it changes the frequency of the LF cutt off, but both options seem to be too low to be audible

 

[birdxofxprey]

Looked inside the amp.

Ive definitely got the mk2, no choke. On mine the bright and mid freq switches do nothing to affect the tone and they dont affect the treble and mid knob function (or lack of it) - they just do nothing.

But, it seems this may be normal for the LB 30.

It actually sounds very good; I have it connected to my Subway 215 at present and it shakes the house. Truly surprising how insanely loud it can get.

Thanks for the expert assistance, much appreciated!

 

[GrowlerBox]

Looked inside the amp.

Ive definitely got the mk2, no choke. On mine the bright and mid freq switches do nothing to affect the tone and they dont affect the treble and mid knob function (or lack of it) - they just do nothing.

But, it seems this may be normal for the LB 30.

It actually sounds very good; I have it connected to my Subway 215 at present and it shakes the house. Truly surprising how insanely loud it can get.

Thanks for the expert assistance, much appreciated!

Mark 2 has the choke, Mark 1 has no choke and Mid Bass Treble EQ dial arrangement. I have a Chinese Mark 1 as well; it passes some sound when all the EQ dials are zeroed, although not much.

My experience is much the same as yours. Almost all the tonal changes come from the mid dial, and only the “bass shift” switch does anything discernible to the tone, and mostly in the mid range (I leave them all down, which seems to be off). The treble control adds noise if it’s turned up but not a whole lot else (I dial it back until the hiss stops). The bass dial perhaps does slightly more, but the vast majority of its effect occurs across a very small sweep of the dial. It seems to be something like a Fender tone stack within these limitations, in that flat is bass and treble set quite low and mid set quite high.

Fortunately, the fundamental tone of the thing is really pleasant, and I usually play it just plugged straight in to the front (I play my solid states with compression, some saturation and HPF always on). Anything in front of it detracts from the tone, although a little reverb and/or delay in the effects loop livens it up nicely if you play in an otherwise dead room. The natural compression and saturation of the amp are spot on for my tastes.

 

[Nuage420]

I don't remember if it was on the FB group or here on TB but the Original LB30 design was confirmed to be based off the fender tone stack.

 

[GrowlerBox]

I don't remember if it was on the FB group or here on TB but the Original LB30 design was confirmed to be based off the fender tone stack.

“Based on” sounds right, albeit pretty loosely, if my Chinese-made example is representative.

 

[Nuage420]

“Based on” sounds right, albeit pretty loosely, if my Chinese-made example is representative.

I'm referring to the OG UK custom shop build. I'm hazy on who confirmed it but I want to say it was Mr Gooday in a comment section or thread many moons ago.

 

[Relsom]

I'll have to check my CTM 30. I never knew there were 2 generations of the LB30, so I'm guessing it would be the same about the CTM-30. It's been a while since I've used it, but I recall it was Bass, Mid, Treble. ....and made in PRC.

 

[Wasnex]

I'm referring to the OG UK custom shop build. I'm hazy on who confirmed it but I want to say it was Mr Gooday in a comment section or thread many moons ago.

FYI my Mk2 is a UK custom shop build.

 

[Nuage420]

FYI min Mk2 is a UK custom shop build.

Then the one he's talking about must be as well. It's the one I sold him.

 

[Wasnex]

I never knew there were 2 generations of the LB30, so I'm guessing it would be the same about the CTM-30.

Supposedly there was some sort of litigation with the James Dean estate over the use of the name LB. Per Ashdown the CTM 30 is the same amp. I haven't ever compared first run LB30 to CTM 30s, so I can't say how strictly they match.

I am certain there have been at least two generations LB30 and CTM 30. There may have more distinctly different production runs. Based on my experience I wouldn't be surprised if there is some circuit variation between each production run.

Perhaps the legal issues with the Dean estate have been resolved as the MK2 LB30 was released quite some time after I read about the legal issues.

My impression is the UK Custom Shop basically uses up residual parts from earlier production runs. Additional components must be either adapted or fabricated to make complete amps. They basically seem to be cobbling together old and new. I believe in some instances they may also repurpose parts from other amplifier models. Pretty sure many of the Custom Shop amps are not strict replicas of the original amps.


AFAIK, the chrome front panel is the primary part of the mk2 LB30 that was left over from the original LB30 production run. Much of the rest of the mk2 had to be remade. The main circuit cards is obviously different and is embossed Mk2. I originally thought perhaps the tone stack capacitor that I think been relocated in the circuit was accidental (I.E. a mistake). However, the circuit card is labeled with component values and many of them are different. This suggest intentional changes, but the circuit functionality is extremely limited IMHO.

The headcases are different dimensions. The original has a vent over the output tubes; the mk2 does not. Also per the images I posted above, it looks like different transformers were used, and the mk2 adds a choke in the power supply PI filter in place of couple of resistor. AFAIK the choke helps regulate the voltage a bit, which I believe is probably why the mk2 preamp has more clean headroom...there may be other reasons as well.

 

[Wasnex]

Then the one he's talking about must be as well. It's the one I sold him.

So I was right in my first post .

My guess is you have a mk2 and it's behaving normally for the version.

 

[Wasnex]

Fortunately, the fundamental tone of the thing is really pleasant

Totally agree. MY LB30s sound very different from each other, but both sound great.

I also have a CTM 30 Little Stubby. The voicing is fairly similar to the mk1 LB30 but not exactly the same. The LB30 has a bit bigger low end and is more vintagey sounding when pushed (bloomy and loose). The Little Stubby is leaner had more modern sounding.

The tone stack in the mk1 is capable of a wider variety of sounds, but I really like the functionality of the Little Stubby tone stack.