Blues Briefcase

[zuceno]

By the way, did y'all know about that time Keith electrocuted himself in 1965 playing "The Last Time" in California -- brushed his guitar strings against an ungrounded mic stand, blew him backstage in a flaming blue electric arc, ended the whole show. Almost killed the poor bloke!

Only the good die young!

[crgfrench]

I don't recommend having less than 3/8" for a speaker baffle, and even that is on the thin side. Are you mounting the speaker on the same side as the circuit and transformers?

The good news is, with the tweed and the fur it is 3/8". I'm certain this red crushed velvet fur is growing to contribute meaningfully to a creamy blues tone.

[JMPGuitars]

I'm certain this red crushed velvet fur is growing to contribute meaningfully to a creamy blues tone.

LMAO I agree! Check out this amp mod video I did in 2011: https://youtu.be/_pM1KmdKPHE

[crgfrench]

I'm certain this red crushed velvet fur is growing to contribute meaningfully to a creamy blues tone.

LMAO I agree! Check out this amp mod video I did in 2011: https://youtu.be/_pM1KmdKPHE

OMG That grill cloth! Love it -- nice video Josh, thanks for sharing.

[crgfrench]

I finally installed the sockets onto the chassis,; I only had 4 of this shielded kind and one went missing so I had to order a replacement. So now 2 fully shielded CV4004s and 2 base-shielded EL844s.

Next steps are to wire the board and reinstall it into the chassis, wire the transformers and rectifier diodes.

Screenshot_20190702-135349_Gallery.jpg

[crgfrench]

There is room for another OT in the briefcase so I'm thinking of adding a Classictone 40-18031 or a Hammond 125ESE like this:

20190703_082112.jpg

[crgfrench]

Class AB usually runs cooler than Class A so to complement the single-ended / double-ended switch I might add 2 more brown devils connected via this switch
https://tubedepot.com/products/three-po ... ary-switch
Like this:

20190703_093915.jpg

[crgfrench]

I know, I know, this is so wrong. But I had to translate bias into something normal musicians understand, like Scoville Heat Units.

[JMPGuitars]

Those numbers are way off. SHU: Ghost is 1M, Scorpion is 2M, and the Reaper is 2.2M. If you wanted to go directly from SHU to Ohms, then they'd all be Pepperoncini.

[crgfrench]

Those numbers are way off. SHU: Ghost is 1M, Scorpion is 2M, and the Reaper is 2.2M. If you wanted to go directly from SHU to Ohms, then they'd all be Pepperoncini.

Notice below the switch it's clarified, "SHU x 1,000". Like on a tachometer.

[JMPGuitars]

Notice below the switch it's clarified, "SHU x 1,000". Like on a tachometer.

lol! I didn't see that, but I still think it's funny that they're all really pepperoncini.

[crgfrench]

Assuming we agree that the Trini Scorpion is 1.5 million SHU rather than 2M (I'm referring to the Butch T version not the Moruga), the approximation formula for conversion would be:

Scoville Heat Units = [-9,579 * Ohms] + 3,000,000.

So with no resistor at all we would max out at 3 million SHU, or pepper spray territory.
No amp could get all the way to pure Capsaicin territory.
And any resistor higher than 313 Ohms is a mere Bell Pepper.

Screen Shot 2019-07-03 at 11.16.11 AM.png

[crgfrench]

...they're all really pepperoncini.

This would be true if you thought Ohms=SHU.
That's why you need to use my formula to convert them.

[JMPGuitars]

...they're all really pepperoncini.

This would be true if you thought Ohms=SHU.
That's why you need to use my formula to convert them.

Well, I think if Ohms does not equal SHU then we'll need to setup a board of directors to setup a standard equation we all agree on. This is serious stuff!

[crgfrench]

Ah I finally got the Hakko warmed up again and got my fair share of lead/tin poisoning for the day. I was soldering up a new stompbox -- and there was my Blues Briefcase circuitboard, patiently waiting for its V1 plexi bias resistor and bypass cap to be laid down properly instead of standing up all erect and lonely, the way I botched it at first.

Screenshot_20190722-121557_Gallery.jpg

So a little desoldering surgery and resoldering, now it's a proper piggyback in the middle of the board.

And my "Lil' Hare Pi" [it's a bunny] pedal is coming along nicely too.

Screenshot_20190722-121941_Gallery.jpg

[crgfrench]

Replaced the 125 Ohm 8 Watt bias resistor with a 150 Ohm 12 Watter.

20190725_020602.jpg

[JMPGuitars]

Replaced the 125 Ohm 8 Watt bias resistor with a 150 Ohm 12 Watter.

Those are good resistors. I have the 20W version on my EL34 36W Superlite TMB.

[crgfrench]

There is room for another OT in the briefcase so I'm thinking of adding a Classictone 40-18031 or a Hammond 125ESE like this:
20190703_082112.jpg

...So I'm finally getting back to my briefcase project after it sat on the back burner all summer. I'm just ordering the 125ESE now.
One issue I see with my dual OT concept is: i believe ithe setup in my schematic would result in 2 in-phase signals being combined when the switch is set to the single-ended position. This could be problematic? I'm going to try it anyway unless you guys all think it would blow up my workbench...

EDIT: I meant to say, "I believe it would result in 2 out-of-phase signals going into the same side of the transformer when in SE mode. This could be problematic?"

[geoff 1965]

have a look at this schematic,he has the power section switchable between single end and push/pull with the same OT but LTP but you might be able to improvise!

p18sc02.jpg

[crgfrench]

have a look at this schematic,he has the power section switchable between single end and push/pull with the same OT but LTP but you might be able to improvise!
p18sc02.jpg

Thanks Geoff. The switching on this and on mine is all after the PI so the PI type probably doesn't matter. The ampmaker one is interesting, works by turning off one output tube which would also significantly lower the Wattage. Mine keeps both output tubes running and would keep similar Wattage in double ended or single ended mode.