BAJA MDR overdrive pedal 9v 060218 [documentation]

[temol]

Bajaman - can you suggest one universal tone stack for all of your recent hi-gain circuits?

T.

[temol]

So far I've breadboarded UBS, MDR, EVH and ENG. I like them all Had some oscillation issues with ENG.
SLO and VH4 next in line. Here's a short recording of a DI track played through each preamp:


T.

[marcao_cfh]

Thanks a lot for this clip! I decided to go first with the UBS thanks to your demo.

[temol]

Thanks a lot for this clip! I decided to go first with the UBS thanks to your demo.

Please note - there is a speaker cabinet impulse response added to each track (Engl 4x12 loaded with V30 speakers). Your setup may sound a bit different.

T.

[Optical]

So far I've breadboarded UBS, MDR, EVH and ENG. I like them all Had some oscillation issues with ENG.
SLO and VH4 next in line. Here's a short recording of a DI track played through each preamp.

T.

Good work. Did you have any tone stack after the circuit?

Lasse really needs to sort us all a new DI track

[temol]

Good work. Did you have any tone stack after the circuit?

Lasse really needs to sort us all a new DI track

Exactly.. we need a new DI track

Each preamp had a tone stack. I'm not sure which one I used in UBS (probably the one from MDR or ENG).


T.

[jhergonz]

Which Engl would you like to see ?

Engl Savage (Blackmore)

T.

I have schematics for powerball and fireball, how could I send it to you???

[bajaman]

Which Engl would you like to see ?

Engl Savage (Blackmore)

T.

I have schematics for powerball and fireball, how could I send it to you???

i already have those schematics thank you.
bajaman

[jhergonz]

Which Engl would you like to see ?

Engl Savage (Blackmore)

T.

I have schematics for powerball and fireball, how could I send it to you???

i already have those schematics thank you.
bajaman

I think you already have all the Tube amplifiers's schematics that are available in the internet , i think I will just wait for your next creation ... BTW, why didn't you use inverting input of the OPAMP?

[jhergonz]

Here is the latest in the series - the Mesa Dual Rectifier high gain channel.
Not built yet but should work fine
have fun
cheers
bajaman

Baja MDR overdrive pedal 9v 060218.GIF

on what version of Dual Rectifier is this based? Mark 1 or Mark 2

[Ichabod_Crane]

[...]
the Mesa Dual Rectifier high gain channel.
[...]
bajaman

Baja MDR overdrive pedal 9v 060218.GIF

[Ichabod_Crane]

Excuse me, I was wondering... If it's based on the high gain channel of the Dual Rectifier, could it have even that sort of voicing switch (Vintage, Raw and Modern)? Or it is too much tricky?

[Groovenut]

Baja,

Maybe a silly question, but how are you accounting for the asymmetric clipping in early gain stages of the real amp?

Thanks!

[jhergonz]

Hi Mr. Bajaman,

I'am not an engineer or some sort, but I'am eager to learn from the schematics that I found. That is why I have this question for you. Hope I'm not wasting your precious time.
Why did you choose to connect some of the components to "VBIAS" instead of "GROUND"? is there an advantage in choosing this method?

[sixthfloor]

Excuse me, I was wondering... If it's based on the high gain channel of the Dual Rectifier, could it have even that sort of voicing switch (Vintage, Raw and Modern)? Or it is too much tricky?

The voicing of the Rectifier is part of the EQ section of the circuit. If you compare the EQ section proposed by Bajaman with the schematic of a Rectifier you can tweak it to your liking, there's little difficulty to that

EDIT : After a more in depth search, the voicing also affects other sections of the amp. Hence only changing the EQ section as I suggested would not be faithfull to the original Rectifier.
More information in this very useful article : https://warpedmusician.wordpress.com/20 ... d-voicing/

[Ichabod_Crane]

Thank you, very interesting article.
It seems to me a bit tricky to include the voicing section. Perhaps a daughterboard. Or maybe just a Presence pot.
Any ideas? Just to see what we can do.

[rcustoms]

Mr steve what about splawn amps like quick rod?

[jhergonz]

I'am also curious on how to put those voicing in this circuit. but it requires emulating the poweramp section for the presence pot and the filtering between the 1st and 2nd opamp for the "RAW" voicing.

[sixthfloor]

I've read extensively the article I linked above as well as the following one :
https://warpedmusician.wordpress.com/20 ... -controls/

Here's a recap of my findings :
Modern
- no feedback;
- presence EQ is : 22k-3n-presence pot-ground (that is, pretty traditional in guitar pedals);
- treble cap is 500p;
- high frequencies are filtered in the preamp via the presence pot.
I think Bajaman's design might be closest to this voicing in terms of construction.

Vintage
- feedback, controlled by the presence pot;
- presence EQ is : 22k-3n-ground (fixed filter);
- treble cap is 680p (500//180);
- high frequencies are filtered in the power amp by the presence pot controlling the amount of feedback.

Raw
- feedback, fixed amount;
- presence EQ is : 22k-3n-ground (fixed filter);
- treble cap is 680p;
- presence pot disconnected;
- high frequencies are filtered in both power amp and preamp, in a fixed manner.

So, if we'd like to adapt Bajaman's design to include a voicing control, we would need to implement :
1/ emulating feedback of the high frequencies. Might this be achieved by simply adding a HPF at some point of the circuit to emulate removing more or less highs ? Or can we feedback part of the signal from a part of the circuit close to the output to an earlier stage ?
2/ modding the EQ section to connect/disconnect the presence pot and switch the value of the 680p/500p cap.

I'am also curious on how to put those voicing in this circuit. but it requires emulating the poweramp section for the presence pot and the filtering between the 1st and 2nd opamp for the "RAW" voicing.

Do you mean the RC network around the gain pot is shaping the frequency response ? That's interesting, could you tell us more ? Maybe this would relate to point 1/ I've mentionned ?

[jhergonz]

I've read extensively the article I linked above as well as the following one :
https://warpedmusician.wordpress.com/20 ... -controls/

Here's a recap of my findings :
Modern
- no feedback;
- presence EQ is : 22k-3n-presence pot-ground (that is, pretty traditional in guitar pedals);
- treble cap is 500p;
- high frequencies are filtered in the preamp via the presence pot.
I think Bajaman's design might be closest to this voicing in terms of construction.

Vintage
- feedback, controlled by the presence pot;
- presence EQ is : 22k-3n-ground (fixed filter);
- treble cap is 680p (500//180);
- high frequencies are filtered in the power amp by the presence pot controlling the amount of feedback.

Raw
- feedback, fixed amount;
- presence EQ is : 22k-3n-ground (fixed filter);
- treble cap is 680p;
- presence pot disconnected;
- high frequencies are filtered in both power amp and preamp, in a fixed manner.

So, if we'd like to adapt Bajaman's design to include a voicing control, we would need to implement :
1/ emulating feedback of the high frequencies. Might this be achieved by simply adding a HPF at some point of the circuit to emulate removing more or less highs ? Or can we feedback part of the signal from a part of the circuit close to the output to an earlier stage ?
2/ modding the EQ section to connect/disconnect the presence pot and switch the value of the 680p/500p cap.

I'am also curious on how to put those voicing in this circuit. but it requires emulating the poweramp section for the presence pot and the filtering between the 1st and 2nd opamp for the "RAW" voicing.

Do you mean the RC network around the gain pot is shaping the frequency response ? That's interesting, could you tell us more ? Maybe this would relate to point 1/ I've mentionned ?

you already mentioned how it works, but I think in the RAW mode, the Gain is a little less because of the parallel RC filter before the gain pot in the amp and the Presence filter is not fixed, it is like Modern Version with negative feedback in the power amp without a capacitor to ground.