18W Baby Bluesbreaker build | Warehouse Guitar Speakers

18W Baby Bluesbreaker build

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Wm Anderson
10/31/2018 12:06pm

Itching to do a fall project, I’m thinking about a BBB (Baby Bluesbreaker) with 2x10!!

I like this Mojotone cabinet:
https://www.mojotone.com/Cabinets_x/Cabinets_xx/Front-Mount-British-18-W...

Mainly because the Mojotone cabinet is for 1x12, I will build the cabinet and 18W myself, get the Top Mount Faceplates from Mojotone, and fit it with 2x10” speakers.

Searching previous threads point to ET65 & Reaper paired or Green Beret alone for an 18W. So, in 10” I’m thinking Green Berets, or should I include ET10 or Retro 10 or something else in the mix?

VAUGHN SKOW
10/31/2018 4:18pm

Such a cool project!
The pair of GBs would be the most authentic (Brit) sounding, with a pronounced midrange throatyness ... but you might want to make one a Ret 10 if you want to add a good bit more bottom end and a little more sparkle ... and head a little away from the mid focus.

Narcoleptigon_47048
10/31/2018 10:08pm

And in case you aren't yet aware, I just learned that the old US made 6B5Q (EL84) I assume your amp will be designed for were actually beam tetrodes like the 5881 or KT66 used in JTM45's, rather than the European EL84 or Russian 7189 pentodes. Somewhat of a fine point, but beam tetrodes generate a lower 3rd harmonic level, as well as less harmonic "swirl" (possibly from the aligned grids?), which should make it sound technically more like a JTM45. It may be worth sourcing a pair of NOS GE or Sylvania 6BQ5 for ~$100. The US made RCA "black plate" 6BQ5 were supposedly "harder" sounding. Anything made B4 the late 60's is apparently the best quality, and should last much longer than most current production tubes.

Wm Anderson
11/01/2018 1:21pm

Vaughn, thx for the input.

Narcoleptigon, based on your tip, I'll do some research and look into it.

Narcoleptigon_47048
11/01/2018 7:04pm

In fact, you could source some US made 5W 6AQ5 tubes really cheap for a "JTM8" (8W). Check the 6AQ5 Wiki for details. This dude makes great little amps from a police radio that has a major JTM vibe: https://www.youtube.com/watch?v=GDell9SHE-A

Sounds just like mini KT66 tubes to me. I love the sound of that thing. Not sure if it's a SS rec and has a choke. A simple resistor can be used in the PT to simulate tube rec sag if you want. London Power makes an adjustable "SUS" kit you might like, as well as some other interesting kits. The "GMX" kit (transconductance multiplier) can make the amp sound "bigger" without increasing power, and can transparently increase the output by as much as ~4x without affecting the power tube/OT/speaker interaction.

VAUGHN SKOW
11/03/2018 8:54pm

I like the idea of going with the old US-made 6BQ5 valves ... they ARE quite readily available at a fair price ... but be sure to check out this:
https://wgsusa.com/blog/when-working-el846bq5-tube-amps-you-must-know-ab...

Narcoleptigon_47048
11/04/2018 4:08am

Thanks Vaughn, and that blog could save a nice set of tubes.

Wm Anderson
11/09/2018 4:51pm

OK, so I need opinions/alternatives/suggestions to this dimensional issue I've uncovered with the build.

Jumping right to the issue, this cabinet by design is 20(H) x 24(W) x 9(D), see the issue yet?

Well, the 18W chassis are 6.5" deep, meaning that if the front and rear panels are 1/2" that totals 7.5" leaving a 1.5" gap to deal with. In a discussion with Mojotone, "Yeah, that's just the way it is, didn't you notice the shadow in the picture? There's a gap in the rear."

The options:

1) Make the cabinet depth 7.5", could be a little tipsy?
2) Add a 1.5" frame/window at the rear that will get covered with tolex. Yeah, the rear chassis panel will sit in 2" instead of 1/2"
3) Cut the 18W chassis in a strategic spot and weld in an additional 1.5" making it 8" wide.

Hmm, WWYD?

Considering that for the most part I won't find myself dealing with the rear, I'm thinking option 2...

Oh yeah, regarding the blog on 6BQ5 and pin 1: The first tube amp I built was Knight-Kit KM-15 in 1966, and the kit had been around for a few years. Anyway, reviewing the schematic it shows the connection was at pin 2. So, by 1960 it was known by Allied, or they just got lucky!!

Narcoleptigon_47048
11/11/2018 6:02am

If you won't be needing to access the rear panel regularly, why not just leave the 1.5" gap? It will allow more heat to escape and won't have much affect on the sound of the open back cab. In other words: DON'T mind the gap...hehe.