Monkeymatic Lassen (Supro 24)

[sluckey]

Mine works fine. So do at least two other builds. Put the 270K plate resistor back in. That oscillator needs all the gain it can get.

Use your meter to verify the footswitch jack is indeed isolated from chassis. I can see a fiber bushing on the back side of the jack, but I can only assume there is another bushing on the front?

I would divide and conquer. Disconnect the blue wire from the footswitch jack at the 1M board resistor. Now concentrate on V3B only.

[xtian]

Good advice. Will do tomorrow.

I sat and practiced for a while using the new amp. I'm liking the tone overall, and the twin tone controls work very nicely.

[sluckey]

I see the problem with your tremolo...

[xtian]

I see the problem with your tremolo...

Yuss! Steve for the WIN. Issue solved.

Busy day, but I'll get around to making a video.

PQjxH7Q8TC2hlBAq84e5Mw.jpg

[xtian]

Stand by, please, while we deal with technical...difficulties.

I dimed all the controls and was playing some Hells Bells, man, and ALL was right with the world, until the volume dropped way down.

Now I'm only outputting about 1.5 watts. All voltages measure within spec. I think I half-toasted my 15-watt OT.

[To the line of waiting OTs:] Next!

[xtian]

Well, that was weird. I used the neon bulb test <https://www.premierguitar.com/articles/ ... r-tester-1>. The 15w transformer (that I think I damaged) passes the test, though with a weak flash of the neon bulb. My replacement, a Mesa (Schumacher 562050, for a Boogie Caliber 50, DC-3, Rocket 44, Lonestar Special, Nomad 45) also passes, but with a much brighter flash.

I tacked in the Mesa OT, and I'm back to 12.5 watts clean.

Just for giggles, I resoldered the original OT back in place, and 1.3 watts is the most I can coax out of it.

SO! An OT that passes the neon bulb test, but is FAIL.

[xtian]

New OT works very, very well. The SOUND of this amp with all controls dimed is dead seriously awesome. With this Supro circuit, it being widely associated with Jimmy Page's sound on early Zep albums, I was expecting something a bit gnarly and trashy, like the Silvertone 1484. Not. This has a full bodied, confident anger. There's nothing rattish or shrill. Pick-on-string attack is nicely present.

There is noticeable sag or compression, which gives it a tactile squishiness like leather. Contributors are low(ish) plate voltage (360 plate - 26 cathode = 334), 5Y3 rectifier, low filtering (22/10/10), and small OT.

Amp is interacting really nicely with the Jensen Jet Falcon--this is the one with the green cone, and has a high-mid hump (or lacks the high-mid cut) that most other Jets have.

I'll definitely record something for you tomorrow.

[sluckey]

Those 6973s run pretty hot. That's why I increased the cathode resistor to 470Ω on my amp.

What are the brass colored rivnuts for?

[xtian]

The rivnuts are for mounting the chassis in a 1x12 combo cabinet.

Here is a quick demo. SM57 on center of cone, Jensen Jet Falcon speaker.

Monkeymatic Lassen.mp3

[DenDanger]

Beautiful work, so neat and tidy!
I like the sound of that, nice playing too!
I was hoping the soundclip would go on for a few more minutes.

Denny

[ER]

Hey Xtian-
Cool amp!
I've got an AO-43 OPT if you want it. Shoot me a PM.

I had a baldwin from a leslie tone cab that did the same exact thing, from a scream to a whisper.

[pompeiisneaks]

Sounds great!

I've linked the MP3 here so people can stream it inline in the browser:



If you edit yours, and copy the raw attachment link, and surround it in mp3 bbcode it will do it for you too.

~Phil

[xtian]

I've linked the MP3 here so people can stream it inline in the browser:

Good try, but didn't work...

[pompeiisneaks]

Both yours and mine are working just fine? Maybe you don't have html 5 capabilities on your browser?

~Phil

[pompeiisneaks]

Lookie:

~Phil

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