Bohemia Build Report and Demo

[jjjimi84]

Here is my Bohemia built inside of a tayda yellow enclosure with a purple dinosaur. I originally filmed the intro video back in October and finally finished it with my new camera and new lights! This is going to be the new format for a little while until I really narrow down the best format for us DIYers.

 

[BuddytheReow]

Looks great! Hand painted I’m guessing?

 

[p_wats]

That looks awesome! Did you do the painting?

 

[cooder]

Spot on Dan! Why do the two ceramic disc caps have sharpie markings on them? Did you measure them specifically to match the value or something?

 

[jjjimi84]

Looks great! Hand painted I’m guessing?

Yep, hand painted with testors acrylic.

That looks awesome! Did you do the painting?

Thank you and yes I did. It took two days as I outlined the dinosaur and then filled in everything with white paint and let it dry overnight. Next day was all of the purple and fine line work.

 

[jjjimi84]

Spot on Dan! Why do the two ceramic disc caps have sharpie markings on them? Did you measure them specifically to match the value or something?

Nothing special about them, they just came out of a batch of caps I have had for ten plus years.

 

[p_wats]

Yep, hand painted with testors acrylic.



Thank you and yes I did. It took two days as I outlined the dinosaur and then filled in everything with white paint and let it dry overnight. Next day was all of the purple and fine line work.

Awesome. Inspiring stuff.

 

[Chuck D. Bones]

Great demo, Man!

Love the paint job.

 

[jjjimi84]

Great demo, Man!

Love the paint job.

Thank you, I am struggling with trying to show off tones, talk about the circuit, talk about painting and keep it under 10 minutes.

Have you looked at this circuit at all? I was dreaming up some mod ideas like putting the boost on a switch and then adjusting the gain on q2 and q3 with a pot. Might be something in there or maybe I am just nuts and tired.

 

[Danbieranowski]

Beautiful!

 

[Chuck D. Bones]

You could put a stomp switch in series with the GAIN control. GAIN has about a 20dB range.

The obvious place to put another Gain control is between C8 & R12. We'll call that new control DRIVE. An A1M pot, with a treble bleed would do the trick. Bump C8 up to 680pF to keep the low-end roll-off the same. Put a resistor between the bottom of DRIVE and ground because there's no point in dialing the DRIVE down to zero. Take a look at the Covert and you'll see what I'm talking about.

A less obvious place to put a DRIVE control would be to make R8 an A1M pot with 22K in series. The big difference is if the DRIVE control is after the 2nd stage (Q2 & Q3), the 2nd stage will saturate easily. With the DRIVE control in place of R8, the 2nd stage won't saturate if GAIN & DRIVE are set below noon. The 3rd stage (D4 & Q5) has a ton of gain and is gonna saturate unless you pull everything, including the guitar volume, way down.

I considered putting the MID and BASS controls in for about 5 sec, but those controls don't do much so I think Catalinbread did the right thing hard-wiring them. One could mess will the values in the Tone Stack, using the Tone Stack Calculator for guidance.

C14 and C15 are WAY bigger than they need to be. They could both be 100nF and it would sound the same.

Have you tried running this on 18V? C17 needs to be rated for at least 25V to do that.

 

[jjjimi84]

You could put a stomp switch in series with the GAIN control. GAIN has about a 20dB range.

The obvious place to put another Gain control is between C8 & R12. We'll call that new control DRIVE. An A1M pot, with a treble bleed would do the trick. Bump C8 up to 680pF to keep the low-end roll-off the same. Put a resistor between the bottom of DRIVE and ground because there's no point in dialing the DRIVE down to zero. Take a look at the Covert and you'll see what I'm talking about.

A less obvious place to put a DRIVE control would be to make R8 an A1M pot with 22K in series. The big difference is if the DRIVE control is after the 2nd stage (Q2 & Q3), the 2nd stage will saturate easily. With the DRIVE control in place of R8, the 2nd stage won't saturate if GAIN & DRIVE are set below noon. The 3rd stage (D4 & Q5) has a ton of gain and is gonna saturate unless you pull everything, including the guitar volume, way down.

I considered putting the MID and BASS controls in for about 5 sec, but those controls don't do much so I think Catalinbread did the right thing hard-wiring them. One could mess will the values in the Tone Stack, using the Tone Stack Calculator for guidance.

C14 and C15 are WAY bigger than they need to be. They could both be 100nF and it would sound the same.

Have you tried running this on 18V? C17 needs to be rated for at least 25V to do that.

I just ordered another board and am going to give these a shot. I haven’t ran it at 18v, I have to see what I put in there and give it a shot.