Sunn Beta Bass preamp - SUNNβEAM

[storyboardist]

Been wrestling with this off and on (mostly off) for like 2 years. Repeatedly kept screwing up little things, but it's working perfectly now and it sounds awesome. It's the preamp section of the Beta Bass amp in pedal form. On board voltage double/charge pump delivering +/- 15-ish volts, 3-band EQ, lots of headroom and gain on tap.





A few boards are available on my site if anyone wants one.

[Tremster]

Yep. That is a clean and good looking pedal.

[SirEgno]

the beta preamp is one of my favorite.
Nice job.

[matmosphere]

Very nice. Any chance of some kind of sound demo?

[Timko]

Sweet build.  I've been eyeing the matamp build or something like the sunn beta bass. 

[lrgaraujo]

Great job, man! I second that demo request

Looking at the schematic, do you think it could be interesting to separate the gain dual pot into pre'ish and post'ish separate pots?

[nzCdog]

Nice!  PCB and build look great, interested to hear it too

[Isaiah]

Amazing work!
I've been waiting for a Beta Bass PCB for years.
Have the PCBs sold out already? Your site says it's available to backorder.

[rockola]

I dig the "DIGITAL C-MOS TECHNOLOGY" slogan in that oh-so-futuristic (in the 60s) font on the PCB. I used to have a 1980 Rock-Ola 484 jukebox that proudly said "DIGITAL MICROCOMPUTER SOLID STATE MUSIC SYSTEM" on the front glass. That could also go on a suitable PCB...

[storyboardist]

Thanks guys. I'll try and get some sound clips together and make a vid.

Have the PCBs sold out already? Your site says it's available to backorder.

The first run of boards is sold out yes, but I've already ordered more.

Looking at the schematic, do you think it could be interesting to separate the gain dual pot into pre'ish and post'ish separate pots?

The gain control stock gives a great range of gain, so I don't know how useful it would be with separate pots, but it wouldn't hurt to try.

[Isaiah]

Thanks for the reply. I've ordered one.

I noticed you used the Mid circuit from the Beta Lead rather than the Beta Bass.
Was there a reason for this? Does it sound much different (after adjusting capacitor values)?

[storyboardist]

Thanks for the reply. I've ordered one.

I noticed you used the Mid circuit from the Beta Lead rather than the Beta Bass.
Was there a reason for this? Does it sound much different (after adjusting capacitor values)?

Thanks for the order. Should have a new batch of boards in next week and I can get it shipped out to you.

From my understanding the only difference between the Bass and the Lead were 4 cap values. The topography of the two version is the same, at least according the what I read.

[Isaiah]

Thanks for the reply. I've ordered one.

I noticed you used the Mid circuit from the Beta Lead rather than the Beta Bass.
Was there a reason for this? Does it sound much different (after adjusting capacitor values)?

Thanks for the order. Should have a new batch of boards in next week and I can get it shipped out to you.

From my understanding the only difference between the Bass and the Lead were 4 cap values. The topography of the two version is the same, at least according the what I read.

Thanks, looking forward to it!

Sorry, I've looked into this a bit more...
The difference between the Bass and Lead preamps is a handful of caps as you say.
But there are also two different topologies for the Mid circuits. However this doesn't seem to be a difference specifically between Bass and Lead models as I initially thought, but rather it is perhaps that one or the other is a later revision (or incorrect schematic?).


First topology:
https://support.fender.com/hc/en-us/article_attachments/115007663026/Beta_Lead.PDF

https://support.fender.com/hc/en-us/article_attachments/115007663086/Beta_Bass.pdf


Second topology:
http://schems.com/bmampscom/sun/Sunn_Beta_Partial_sm.pdf

[storyboardist]

That's interesting. I'd seen the 2nd pdf before as I originally intended it to be just a Beta Bass board. Then later read on FSB about the 4 cap differences to make the Beat Lead. Never came across the 2nd topography tho. Wonder why they changed it.

[selfdestroyer]

Looks great David. I'll grab a PCB on the next order forsure. This looks like a fun project forsure.