freestompboxes.org

Hi folks
Here is my take on the Bogner Uberschall preamp frequency characteristics - once again 9v friendly - just a gain and level control - put it in front of any clean Fender type amp and experience the midrange snarl of the Uberschall
I was a bit shocked when I noticed the need for a 22n high frequency capacitor at the first gain stage input and also the large 39n capacitor in the feedback loop of the third stage, however these values were necessary to match the individual tube gain stage frequency response characteristics of the actual Bogner Uberschall amplifier. I have not come across such a mid heavy design by other designers such as Diezel, Soldano or even Marshall - the Bogner amplifier really does have a very unique voicing
Even with such a large amount of high frequency rolloff, I was pleasantly surprised with the sound of the finished pedal - although very different to the recent Baja VH4 sound which is almost hifi in comparison - this pedal snarls and demands to be played LOUD!
Anyway - once again - vero layouts and pcb layouts are most welcome. I always build as insert components for these prototype designs so often I have components stacked or crossing each other, however I always build directly from my published schematic.
have fun
bajaman

It's getting more and more interesting Can you design circuit without seeing schematic of the amp? Just by hearing?

T.

temol wrote:It's getting more and more interesting Can you design circuit without seeing schematic of the amp? Just by hearing?

T.

Tomasz
afaik, Bajaman like our comrade trueVAL
circuit simulation based, compare with real schemo and build his own, his style

the different
Bajaman build this project for simplicity, because he build this and theother to use in front fender amp
trueVAL make design for complete pedal from scratch, just to emulate and use as preamp

but, we wait confirmation from Baja himself.

maybe, if you send real schemo of your dream amp, Baja can help you make that in a box

and yes, their ear, imagination and logic make me (and maybe you) jealous
everybody can build anything, but everybody can't design anything as pioneer

I'm amazed how many different sounds you can achieve out of basically the same topology. And also how easy it is to mod these circuits to suit my own gear and taste. It's a real lesson for me into feedback networks as well. From my limited time playing with these circuits I have noticed that most components are actually not set in stone. There a tweekers paradise. Thanks again Bajaman.
Regards Johno

I just ordered a bunch of TL064s from Small Bear. Should've ordered more...

Thanks again Bajaman! (Still working on the Highway 1 vero build!)

Well, another one added to my "to build" list

JOHNO wrote:I'm amazed how many different sounds you can achieve out of basically the same topology. And also how easy it is to mod these circuits to suit my own gear and taste. It's a real lesson for me into feedback networks as well. From my limited time playing with these circuits I have noticed that most components are actually not set in stone. There a tweekers paradise. Thanks again Bajaman.
Regards Johno

Well funnily enough, the VH4, Ubershal, SLO, HBE and AFD amps are all 4x 12ax7 gain stage +cathode follower. It's all in the tone shaping and interstage gain...

Not with coffee now
but, here the 2SK117 perf plan, with errrmm 90degree. cause its easy to bend
you can edit the etch pdf with gimp to mods to any curve you want

hint :
use either C2A or C2B, not both.
rock it before box, then install CLR. Wire that via hole nearest too make clean-ish

Again, Viva Bajaman!

here are some quick and dirty pics of a 1kHz sine wave at medium clip and hard clip cheers
bajaman

my quote
regards

Nice job there Bajaman, the UBS sounds crisp and has lots of emphasis on the mids

Here's a layout for it. Consider it verified, I've built it. Now I just need to box it properly...

My version of the UBS. There is a place for a tone stack bypass switch in the bottom right corner of the pcb (switch is not mounted now, it's jumpered). Some jumpers, some zero Ohm resistors.


T.

Nice jobs, guys!
I like the veroboard layout, but I would like to have the tonestack, too.
Is there someway to add it with that vero layout?

Ichabod_Crane wrote:Nice jobs, guys!
I like the veroboard layout, but I would like to have the tonestack, too.
Is there someway to add it with that vero layout?

There are two options to do that, either re-draw a vero layout integrating a tonestack or adding a daughterboard with the desired tone stack.

Which tone stack would you like to see there Ichabod ?

temol wrote:My version of the UBS. There is a place for a tone stack bypass switch in the bottom right corner of the pcb (switch is not mounted now, it's jumpered). Some jumpers, some zero Ohm resistors.
[ Image ][ Image ]

T.

Amazing!

Any layout to share with us, plz..?

CheapChip - sure, but you have to wait a bit. I have couple other projects on my desk that I'd like to finish.

T.

Thanks Temol!

No problem: I have some projects to build, among many other things to do too.
Anyway, your layout seems to be so cool: I'd like to add it to my to-do list...

Let me know when it is possible for you!

Cheers.

My small contribution, I do not know if it can be appreciated. Have good fun.

Anyway to get more gain out of this?

I believe raising any of the four IC 2k7 feedback resistors will raise the gain. However it will do so mainly for the specific frequency band manipulated by that IC.
Maybe raising all four resistors by the same amount would hence achieve an overall higher gain ?

Putting a bigger gain pot could help too, though I'm not sure for this circuit.

I'd be interested too in the answer from someone more knowledgeable than I am