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Let's talk about the Ashdown Little Bastard
- Thread starter Joris 55
- Start date
Try turning the Bass control down more. Your amp appears to be a Mk1, so essentially it has a tricked out Fender tone stack. Nominal flat is with the Mid control near max and Bass and Treble near minimum.
The reason to use the LB30 for the recording session is because you like the way it sounds. If the Genzler fits the project better, use the Genzler. It's no big deal either way IMHO.
Mid near max with bass and treble near minimum is where I was playing it. Yea, I need to record with it and compare it with the Genzler. People have great things to say about the Genzler DI as well, which has been working great for me.
I've had both the Magellan and now on my second LB... And my handbox with 3tube pre. My take is for a class D light weight the Magellan comes closest to capturing true tube magic and harmonics. But, the tubes still do it better.
@GroovyBaby I almost PMed you immediately to buy that and have you ship it straight to Sushibox so he can mod it like my last LB for cab less recording. But man, I recommend you keep it and be the one to send it to him or have someone do the mod.
What’s that run? And where are they? Shipping ain’t cheap these days.
He's a pedal builder here on TB. I paid the shipping both ways and a labor fee. Can't really say what it was as it was not something he advertised to do, it was something I asked if he could and would do. All I know is he put a resistive load in to keep the transitor happy and allow for me to go DI into my interface without a cab hooked up. Since I have the 550 to push my ashdown stack I want another LB30 for my studio.
I don't see 'em popping up very often, happy hunting!
Been looking at pics of the circuit boards, trying to locate where I can adjust the bias on the EL84's, going to do some tube rolling, and does anyone know what the {ma} setting should be, I am guessing 20-25
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I could be wrong, but I believe the LB30 is cathode biased. I don’t know if you can manually adjust if.
This. No need to adjust bias, but I believe all tubes need to be matched.
This amp is cathode biased, each output tube has a network with two resistors and a bypass capacitor on the cathode.
Cathode network circled in red:
I believe the individual cathode networks reduces the impact of mistmatched tubes, which reduces hum. My vintage Vox AC30 shares a single cathode network across all 4 tubes.
I took these readings on my Mk1 LB30.
Output tubes are Ruby EL84 rated PC24 TC2800
Plate = 329V
Cathode = 10.5V to 11.5V
Effective Plate = Average 318V
Total Cathode Resistance = 320 Ohms
Calculated Cathode Current range = 32.8-35.9mA
85% dissipation = 32.1mA
90% dissipation = 34mA
95% dissipation = 35.8mA
I set up my amps on a variac with an ammeter. The Mk1 idles at 0.92A (total current), 120V
These dissipation ratings are based on the effective plate voltage and the 12W plate dissipation rating of the tube type. It's fairly easy to do the calculations, but I use this webpage: Tube Bias Calc (robrobinette.com)
The hottest tube is running right at the limit (95%). 35.8mA is the cathode current, which is split to the plate and screen grid. So, the actual plate current should be running slightly under 35.8mA. If you want the actual plate current, measure the voltage drop across the screen resistors, calculate the screen current and subtract from the cathode current.
Some people actually like biasing this type of circuit considerably over 100%. So although the tubes in the Mk1 may be a bit worn, I am not too concerned. I have a fresh set of JJ EL84s.
In order to change the bias, you change the resistance in the cathode networks. Reducing the resistance will result in higher tube current.
My Mk2 idles at 0.84mA, so my guess is the tubes are running a bit cooler. I have not documented the operating voltages in the Mk2. I believe all of the tubes are JJs.
Looks like a Mk2. Tone control order is Bass, Mid, Treble. The order on the Mk1 is Mid, Bass, Treble.
My Mk2 sounds considerably different than my Mk1. My Mk2 has much bigger lows and more headroom in the preamp. It's also more mid scooped and the Mid control does not really do much.
I poked around inside my Mk2 and it looks like the tone stack is closer to a Hiwatt than Fender, one of the capacitors appears to be connected in a different way, AFAIK this actually reverses the function of the Mid and Bass circuits. This relates to both the rotary controls and the toggles. Although the Bass and Mid controls are in a different order, they are cross connected with flying leads to the original position on the circuits.
The Bass and Mid switches are also connected to their original positions, but notice they are relabeled. I believe Low Freq changes the HPF frequency, but it's so low that I can't really hear the change. I believe Mid Freq changes the depth of the mid scoop. In one position the Mid control has a small impact. In the other position, it's hard to hear any impact from adjusting the Mid control.
I believe the extra headroom in the preamp is due to the added choke in the power supply.
I'm curious if your Mk2 works the same way.
You hit everything on the head man. I noticed all the same. Very noticable difference and controls are friendlier to adjustment.
BassTheWorld posted a review for the Ashdown LB-30 2.N:
Lots of great info in this thread. Just got an Ashdown MAG 410t cab so I can be ready to jump on a Little Bastard as soon as I see one in the classifieds (little stubby is out of my reasonable range, considering other stuff at that price). The MK1 and MK2 stuff is really interesting.
