Mojo Wired Board for Blackheart BH5H

[The Boathouse]

Hey,

I'm mulling over the idea of doing the Mojo mod on my Blackheart head that'll switch the head from a PCB to a wired board with a tube rectifier. My concern, primarily, and why I haven't already done this mod, is that it substitutes a standby switch for the pentode/triode switch. I'm assuming, then, that the amp will run at 5 watts ALL the time. I'm mildly concerned about that, as the 5 watt setting actually has less headroom than the 3 watt, which is something I'm still wrapping my brain around. The 5 watt just has this absurd level of breakup early on in the knob, which is fine for when I'm playing with drive, but I'm all about the cleans on that head. The 3 watt cleans are absolutely sparkling, and I'd like to preserve those. I've had limited run-ins with tube rects, and I'm unsure where I stand on the matter. My few experiences have been much higher wattage, as well, so I feel my knowledge of them may not translate to low wattage amplifiers. Will the decreased headroom of the 5 watt stage remain? Or will this board alteration calm down the 5 watt setting of the amp?

[patrickhowell]

Hey,

I'm mulling over the idea of doing the Mojo mod on my Blackheart head that'll switch the head from a PCB to a wired board with a tube rectifier. My concern, primarily, and why I haven't already done this mod, is that it substitutes a standby switch for the pentode/triode switch. I'm assuming, then, that the amp will run at 5 watts ALL the time. I'm mildly concerned about that, as the 5 watt setting actually has less headroom than the 3 watt, which is something I'm still wrapping my brain around. The 5 watt just has this absurd level of breakup early on in the knob, which is fine for when I'm playing with drive, but I'm all about the cleans on that head. The 3 watt cleans are absolutely sparkling, and I'd like to preserve those. I've had limited run-ins with tube rects, and I'm unsure where I stand on the matter. My few experiences have been much higher wattage, as well, so I feel my knowledge of them may not translate to low wattage amplifiers. Will the decreased headroom of the 5 watt stage remain? Or will this board alteration calm down the 5 watt setting of the amp?

The overall tone will probably be much better with the handwired board, but you are going to lose a lot of clean volume. What preamp tube do you have in your BH right now? If you haven't tried anything besides a 12AX7, then you are really missing out. (If you haven't already upgraded your power tube, this is a good time for that too). 12AX7's have the most gain of any preamp tube, so if you want more clean headroom, I'd recommend a 12AT7 (aka ECC81), or even better a 5751 if you can find one. JJ generally makes the best current production tubes, and their ECC81 is what I use in my VJ. You should be able to find one between $10 and $15 no problem. If you want to try a 5751, you'll have to get a NOS tube, since I don't think anyone makes them currently, and that will run you about $20. Here's a quick list of some preamp tubes and their gain values:

100% - 12AX7 (ECC83)
70% - 5751
60% - 12AT7 (ECC81)
45% - 12AY7
20% - 12AU7 (ECC82)

Also, if you switch over to a tube rectifier, you aren't going to be getting any of the "sag" that people usually associate with a tube rectifier because the blackheart is a single-ended amp and it always draws the same current from the rectifier. However, what you ARE going to get with a tube rectifier is less efficient conversion of AC to DC current, which will give you a lower voltage inside your amp, and therefore EARLIER breakup, which you already said you don't want. On the other hand, if you lower your gain by switching out the 12AX7 in your preamp, you will be fine, and personally, I think that early breakup in the power tube is great, even in "clean" tones.

[The Boathouse]

Ah thanks man! I had been mulling over trying out the 12at7 change for a while. I'm not opposed to minimal breakup early on, I just rarely have a need for really balls out overdrive. A little shimmer on the edges never hurt, and if the tone is greatly improved, then I'm totally game. I put a JJ in for my powertube a while back, and that was a huge step forward. I was wondering about the "sag", but it wasn't too big a factor for me. Thanks for all the info! I'll post once I finish the work with my findings.

[patrickhowell]

Ah thanks man! I had been mulling over trying out the 12at7 change for a while. I'm not opposed to minimal breakup early on, I just rarely have a need for really balls out overdrive. A little shimmer on the edges never hurt, and if the tone is greatly improved, then I'm totally game. I put a JJ in for my powertube a while back, and that was a huge step forward. I was wondering about the "sag", but it wasn't too big a factor for me. Thanks for all the info! I'll post once I finish the work with my findings.

Yeah, if you want really heavy overdrive, I really think that power tube distortion is going to sound better than preamp gain. I have a JJ 12AT7 in my Valve Junior, and it still sounds really heavy turned up loud, and I like the mix of pre/power distortion better. Plus, I get a lot more clean headroom than with the 12AX7 I had in before.

[themeanmeanmen]

I play really loud ugly music. If I do any of these mods, will I lose any of that nasty tone I like?

The reason I am asking is because the idea of the triple bypass switch mod caught my eye.
But when I watched a youtube video of the guy playin hendrix songs, I thought, "well that sounds like a hendrix song exactly." But I don't play for the Hendrix sound. You know what I mean?

Let me know if you guys are still on this thread.

cheers,
Pat

www.myspace.com/themeanmeanmen