Nice Preamp

[Kipper4]

How do i get a DR Z Maz 18 in a Stomp?
I was thinking a fet amp followed by an op amp gain stage.
With an amazing tone stack. Capable of clean and overdiriven sounds.
for the Amazine tone stack i was thinking a variation fo the baxandall inbetween the fet stage and op amp. Maybe between dual op amp stages.
volume control on fet stage, master on the op amp
kind of use the fet to overdrive the op amp instead of using a clipping amp approach.
Do you think i'm taking the right approach?

[Kipper4]

OH yer i forgot to add for less than 20$ usd.

[Kipper4]

Has anyone made the ROG Fetzer?
or any cab sims that ressemble fenders or DR Z.
Has anyone designed any cab sims here?

[Mark Hammer]

I would think one starts with listening to the Maz 18 preamp output through somethng other than the remainder of the circuit and the speaker/can it comes with.  That's not to take anything away from the front end of the amp itself, but one needs to know what aspects of the tone to attribute to what.

[Kipper4]

Well i'm doing my best to establish what it is that players like about the maz and what makes it differant to other amps
heres a starter article
http://uniqueguitar.blogspot.co.uk/2012/01/dr-z.html

i also have a part (hand drawn) schmatic if anyone want to have a look. Its a bit pointless me looking i dont know enough about enough.
It's rumoured to be derived from a hammond reverb amp
Theres a discussion over on the other forum too.

[Kipper4]

Heres an idea i've had to get this project moving.
Its my previous design witha tone control bolted on between stages.
I've increased the gain on the second op amp stage to compensate for the drop in volume from the Baxanadall i've heard about.
I will be breadboarding it but meantime if you can see anything that will make it fail please feel free to chime in and stop me.
The only thing i can think of is maybe i'll have to connect pin 5 to bias (4.5V) instead of going to ground. Or will that make the bright fail.
I remember being told also to connect the ground connection on the bottom of the tone stack to Bias (4.- you get the picture) instead of Ground.
Thanks for any help you can give.


Heres the schemo
https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#f:BlackHead%201.jpg

[Kipper4]

After breadboarding it i've made a few changes.
I did connect pin 5 to 4.5v too.
I took the switch out for the bright but left the cap in so it's permanantly wired in.
changed the 100k and 1m resistors on the second opamp feedback loop for smaller values 1k and 10k so i have the same amount of gain but less noise. I heard the higher the value the more noise is introduced. so i thought it wise to change it.
It gets a bit crunchy in the top of the volume.
i might have to make it and tweek it on the stripboard.
The pots are on order for the tone stack.

[psychedelicfish]

Schematic error! The input of the second op amp is grounded, and your bright switch won't do anything

[Kipper4]

Thanks for the response Fish.
I get where your coming from the second op amp now goes to Bias (4.5V) this became apparent on the bread board and i've drawn the bright mod all wrong too i'll have to retry it thanks for the help

[Kipper4]

I made it on a perfboard today.
I've had to make some adjustments to get it going but i'm learning
i couldnt make the baxandall tone stack work between the op amps.
It would work but only when all the tone controls where biased together. Totally wierd. I didnt expect that at all.
it was like it was working like a voltage divider and if it wasnt set within a certain range of each pot then it wouldnt work and it most certainly didnt work as a tone stack even when the circuit did work.
So i had to put it in after the second op amp and make sure there is enough gain in the circuit to over ride any drop from the tone stack.
It works really well as a tone stack now and another thing i didnt expect was that when all 3 pots are turned down the volume dies totally too.

would you suggest i put the tone stacks ground connection to Vref (Bias 4.5v) to make it an active one instead?
if its even possible?
and would this stop the pots tuned down from making the output volume fade out?

i made the first op amp with a gain of around 6 and the second with a gain of 11 by my rough calculations.
it took some experimenting with gain of 1st stage againsgt the 2nd stage to get it to go a bit crunchy and overdriven when the volume is maxed on guitar and pre amp.
luckily or sensibly i put sockets in the prototype for the resistors so i could play with the op amps gains.
i'm reasonably happy with it although it might be a bit noisy. I'm just going to test it with my interface and see how it records.
If its still noisy then can i couple/decouple the circuit somehow to eliminate the noise?

Thanks for any help you can give
Rich

heres the latest Schemo

https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#f:Black%20Head%20II.jpg

[Kipper4]

It's not really that noisy.
However
when i roll back the volume on the guitar. it starts to get hummy.
Is this because the impedances ( input/output )are not right somehow?
its nothing like as loud as i thought too. works great with an amp more than loud enough.
Stick it on the line in on the audio interface and its way to quite to record alone.
my goal was to make a styled preamp that would record directly to the line in.
i have a schematic for a direct record board/headphones out board that i used with my 1 watt amp would this circuit on the output bring it up to level to play well with a line in ?
heres the scematic for it ?
  https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#f:Deacy%20direct%20record.jpg

thanks for any help you can give.