Baja Presence and Resonance 091118

bajaman · Post by **bajaman** » 09 Nov 2018, 08:23

Here is a little circuit I just designed to emulate the presence and resonance controls in a typical tube amplifier driving a speaker cabinet.
A typical tube amplifier reacts with the loudspeaker load quite differently to a solid state amplifier - it puts extra power into the speaker at resonance and due to rising voice coil inductance at higher frequencies it puts out a progressively louder response as the frequency rises, solid state amplifiers do not do this and consequently lack the bottom end "balls" and top end "sizzle".
This little circuit aims to rectify that solid state amplifier "flat" sound - it is best used as the last effect in the chain before the solid state amplifier input socket, or in the effects loop etc. it can also be used directly in to a mixer or daw to give more tube amplifier type characteristics.
When the two spst switches are open the response is totally flat allowing the user to hear the difference when either the resonance or presence tone filters are bypassed - of course these can be separate toggle switches or a single dpst switch or even a footswitch - the choice is yours

When the switches are closed and both potentiometers are set to minimum, there is a slight boost at 100hz of about +2dB and a gradual rise from 1kHz to 10kHz of +3dB.
When both potentiometers are set to maximum, the resonant peak rises a further 4.5dB, and the presence rises a further 10dB. The resonance control should be a linear type and the presence a reverse log for the best operation contour - if you cannot find a reverse log pot then a linear will work, but most of the additional boost will be in the final 5 or so degrees of rotation.
The graphs show (both potentiometers) the full boost, minimum boost and flat conditions.
Enjoy and as always , your comments are most welcome.
cheers
bajaman

swt · Post by **swt** » 10 Nov 2018, 19:19

Wow this is definitely useful. Will try it. Thanks a lot?!

bajaman · Post by **bajaman** » 10 Nov 2018, 22:09

a small update that has a higher Q resonant peak and increased range on resonant peak level.
cheers
bajaman

note: the schematic is shown in the bypassed condition - please close either or both switches for presence and resonance boost effects. I added the 1M resistors to reduce any dc offset when switches are activated. The 10uf capacitor should ideally be a bipolar type (two back to back negative terminal 22uf polarised capacitors in series could be used - this would give 11uf which is close enough

)

illus1on7 · Post by **illus1on7** » 26 Nov 2018, 10:38

Hi,
Little confused. how about the speaker response load sim compared to this
Thankx

temol · Post by **temol** » 10 Dec 2018, 17:56

hi bajaman,

is there any easy way to make frequency of the resonant peak adjustable?

T.

temol · Post by **temol** » 12 Dec 2018, 22:20

Here's my quick recording. File on Soundcloud:

In action - Baja UBS, Baja P&R.

#1 - UBS, 4x12 V30 Mesa IR.
#2 - UBS through P&R (knobs @noon), 4x12 V30 Mesa IR.
#3 - UBS through P&R (R knob @ 4 o'clock, P knob @ 3 o'clock), 4x12 V30 Mesa IR.

T.

bajaman · Post by **bajaman** » 12 Dec 2018, 23:07

Thanks Temol

bmxguitarsbmx · Post by **bmxguitarsbmx** » 14 Dec 2018, 18:44

Nice work Bajaman! I don't know of anything like this on the market.
Thanks for the great clips Temol!

temol · Post by **temol** » 14 Dec 2018, 22:34

I think there is something similar - check the Amptweaker Depth Finder.

T.

bmxguitarsbmx · Post by **bmxguitarsbmx** » 15 Dec 2018, 06:39

James Brown is the F'n Man!
Here is an interview if anyone is interested:

temol · Post by **temol** » 17 Dec 2018, 08:10

bmxguitarsbmx - thanks for the link to the interview.

And here is my version of the P&R. It fits into 1590B. Maybe I should work on it again and try to squeeze the board into 1590a. Smd maybe...
I'm working on a graphic for the enclosure.

T.

blackboarcult · Post by **blackboarcult** » 10 Jan 2019, 13:30

Here's the layout I did a while ago.

Built and verified!
Again, I'm a noob to DIYLC, so this could be scaled down if needed, but I adapted it for 5mm pitch terminal blocks, and built as an always on circuit inside a Class D Amp box, coupled with a speaker saturation simulator.
I must say it sounds damn great and has a really nice tube vibe

Cheers

/ZVDW

HEAD · Post by **HEAD** » 12 Jan 2019, 13:19

temol wrote:bmxguitarsbmx - thanks for the link to the interview.

And here is my version of the P&R. It fits into 1590B. Maybe I should work on it again and try to squeeze the board into 1590a. Smd maybe...
I'm working on a graphic for the enclosure.

[ Image ]

T.

Hi Temol,

would you mind to share this layout? Thanks in advance!

KR
Helge

temol · Post by **temol** » 13 Jan 2019, 10:40

Hi Helge,

P@R build doc for download - resonance_presence_build_doc.pdf.

btw - in my opinion, for this type of device, 3pdt is not necessary.

T.

HEAD · Post by **HEAD** » 26 Jan 2019, 18:56

temol wrote:Hi Helge,

P@R build doc for download - resonance_presence_build_doc.pdf.

btw - in my opinion, for this type of device, 3pdt is not necessary.

T.

Thank you Temol! Very much appreciated. Unfortunately is a bit beyond the limitations when using the toner transfer method - at least with my setup. I have trouble with these thin traces and the very small footprint of the pads. :/ No offense!

KR
Helge

temol · Post by **temol** » 28 Jan 2019, 11:09

HEAD wrote: I have trouble with these thin traces and the very small footprint of the pads.

Sorry to hear that. I can widen the tracks and enlarge the pads, but It's not possible to make all the tracks wider. There is some tight places and I'd have to keep current track width. Signal tracks are 16mils wide now - I can make them 20 or 24mils.

T.

HEAD · Post by **HEAD** » 28 Jan 2019, 19:36

temol wrote:
HEAD wrote: I have trouble with these thin traces and the very small footprint of the pads.
Sorry to hear that. I can widen the tracks and enlarge the pads, but It's not possible to make all the tracks wider. There is some tight places and I'd have to keep current track width. Signal tracks are 16mils wide now - I can make them 20 or 24mils.

T.

Hi Temol,

another deep breath, some more patience, a good tea and a lazy sunday I managed to get the transfer done. But it was still quite challenging - especially being super precise with the smalles drill bit I had (0.6mm), because the pads are really small.
But I think other builders would appreciate a layout with bigger pads and fatter traces.

Still not sure if I have every solder joint/trace right - or could you confirm that the resonance pot is rather subtil? It could also be due to the setup I'm using? I'm lacking a transistor amp (irony mode on: poor me) so I use my 2061x diy clone at bed room level. At bed room level the amp is also lacking resonance and the natural presence it has when crank it up more. So I thought trying the BR might be a good idea here.

KR
Helge

bajaman · Post by **bajaman** » 28 Jan 2019, 19:48

Hi all

I finally got around to designing a pcb and built a prototype working unit - the resonance is definitely NOT subtle.
I will post build pictures soon - I do have spare pcbs available - they are designed to fit the standard 1590B enclosure and include board mounted mini potentiometers, neautrik jacks, and dc sockets etc - email me: baja002steve@gmail.com for details if interested.
In the meantime: top and bottom board pictures for your enjoyment

bajaman · Post by **bajaman** » 28 Jan 2019, 23:47

my pcb build pictures

I made a few adjustments to the schematic to place the resonant peak at 130Hz (originally 100hz), also lowered the Q to 2 - this is more realistic for a celestion greenback quad box.
new schematic:

cheers
bajaman

temol · Post by **temol** » 29 Jan 2019, 09:18

Hi Helge.

Sometimes I use even smaller pads.

. For this pcb I would go with 0.8mm drill for most of the holes. Exception - supply pins, potentiometers, wiring, switch solder pads, protection diode. 1mm drill for those listed.
Did you install jumpers / switches? Resonance adjustment is.. normal

not suble.

T.

Baja Presence and Resonance 091118 [documentation]