Crowther Audio - Hot Cake Overdrive

floris · Post by **floris** » 19 Nov 2008, 16:42

+1 for soulsonic's 741 can layout, thank you.

soulsonic · Post by **soulsonic** » 19 Nov 2008, 20:49

Thanks, guys!

I'll put together a zip package with the pcb artwork, component layout, and a schematic of my version of the circuit. The circuit I used is a kind of blend of the old and new versions with a few little tweaks to a couple component values.

floris · Post by **floris** » 20 Nov 2008, 00:23

@soulsonic: I think the board looks very aesthetically pleasing with all its curved traces. Almost a shame to box it...

Silent Fly · Post by **Silent Fly** » 20 Nov 2008, 10:21

floris wrote:@soulsonic: I think the board looks very aesthetically pleasing with all its curved traces. Almost a shame to box it...

+1

What did you use to design/draw it?

soulsonic · Post by **soulsonic** » 20 Nov 2008, 10:48

Silent Fly wrote:
floris wrote:@soulsonic: I think the board looks very aesthetically pleasing with all its curved traces. Almost a shame to box it...
+1

What did you use to design/draw it?

Eagle!!!

Thanks again!

205 · Post by **205** » 10 Dec 2008, 11:25

bajaman wrote:Hi bluetoad
Did you connect the additional 220k resistor from the inverting input (op amp pin 2) to the half rail voltage point, when trying the 741
Try it
Cheers
Steve

ah my first post!
i just built the Torchy version of the hotcake, sounds great! I want to try to sub the 071 with a 741 but I'm finding it hard to understand where the 220K resistor goes... i understand where pin 2 is but don't understand the "half rail voltage point" part.

i'm still learning, can someone explain this??

great thread by the way!

ryanuk · Post by **ryanuk** » 10 Dec 2008, 12:21

205 wrote:
bajaman wrote:Hi bluetoad
Did you connect the additional 220k resistor from the inverting input (op amp pin 2) to the half rail voltage point, when trying the 741
Try it
Cheers
Steve
ah my first post!
i just built the Torchy version of the hotcake, sounds great! I want to try to sub the 071 with a 741 but I'm finding it hard to understand where the 220K resistor goes... i understand where pin 2 is but don't understand the "half rail voltage point" part.

i'm still learning, can someone explain this??

great thread by the way!

205 - check out analoggurus schematics for the 1977 and 2003 hotcakes. The 220K resistor can be seen on the '77 but not on the '03. For clarity - one side of the 220k goes to pin 2 and the other goes between R2 and R3. R2 and R3 form the voltage divider.

Hope this helps!!

Soulsonic - any chance of posting your schematic for your hotcake project??

205 · Post by **205** » 10 Dec 2008, 12:48

ryanuk wrote:
205 wrote:
bajaman wrote:Hi bluetoad
Did you connect the additional 220k resistor from the inverting input (op amp pin 2) to the half rail voltage point, when trying the 741
Try it
Cheers
Steve
ah my first post!
i just built the Torchy version of the hotcake, sounds great! I want to try to sub the 071 with a 741 but I'm finding it hard to understand where the 220K resistor goes... i understand where pin 2 is but don't understand the "half rail voltage point" part.

i'm still learning, can someone explain this??

great thread by the way!
205 - check out analoggurus schematics for the 1977 and 2003 hotcakes. The 220K resistor can be seen on the '77 but not on the '03. For clarity - one side of the 220k goes to pin 2 and the other goes between R2 and R3. R2 and R3 form the voltage divider.

Hope this helps!!

Soulsonic - any chance of posting your schematic for your hotcake project??

Ryanuk - I did eventually work it out

but thank you very much for your help!

205 · Post by **205** » 11 Dec 2008, 03:41

I thought I'd post my thoughts on the 071 or 741 (with 220k resistor) option, this is on Torchys build.
I must say that their are very minor differences between the two options but out of the two options I prefer the 071, it just sounds a touch warmer to my ears, which kind of goes against the general concensus.
Anyway I'm sure others may hear it differently with different guitar and amps etc. I'm using a 72 Tele Thinline through an ac-15.

Thanks to Torchy for the great vero layout!

sopapo1 · Post by **sopapo1** » 29 Dec 2008, 05:45

Hello I have made the torchys version on veroboard but want to have the 77 version on it, with the 741 and the 220k...My question is: The only differences between the 77 version and the 2003 are the opamp, and the 220 k resistor added and the switch instead of the pot for presence? only is different in this three components? or there are more?

I am not very good in electronics,I have see the two schematic but I dont clear my mind on it... I see that 77 schematic have two 12n caps and the 2003 a 22n one...is the same? have the 2003 schematic a 10 K resistor more?

Sorry if I made a stupid question and sorry for my bad english

Thanks for your time
Best regards

JHS · Post by **JHS** » 29 Dec 2008, 09:43

On the 77 the output filter and the coupling cap is a bit different too. The 77-circuit is designed around the 741 IC, the newer circuit for a 071 IC. Both HC sound similar but in nuances different. For me the 77 sounds a bit warmer, darker and more natural (with a strong uA741C, with a weak uA741 and a MA741 it sounds like crap).

My build use the 77 circuit as a base and after the IC the circuit from the 071 with tone control.
Soundwise a 77, but with a flexible tone control.

The filter after the IC and the O-cap can be tuned to taste.

JHS

sopapo1 · Post by **sopapo1** » 29 Dec 2008, 17:51

Thanks for your answer jhs,watching the analogguru schematics, and comparing the 2003 with the 77 I think that
77 version:

- have no zener diode
-no 220 ohm in series with power
-The resistor after the 10u cap before the drive pot is 120 ohm
-220 k between 2 of the opamp and the 1m ressitor and 10 u cap
-in the filter output of the opamp,after the 470 p cap have two 10k with two 12n
-no pot and a switch instead

2003 version:

-zener diode
-220 ohm resistor with the power
-The resistor after the 10u cap before the drive pot is 220 ohm
-no 220 k between 2 opamp leg
-after the 470 pf only a 10k and a 22n cap
-a 22 k pot for presence

is this true? there are more ? or am I wrong?

Somebody knows for sure which changes should I change in the torchy layout to make it a 77?
or am I going mad and the principal change is the 741 and the 220 k and the rest is minor and no have any effect on the sound?

Thanks

scott1568 · Post by **scott1568** » 15 Jan 2009, 02:02

Hi, After reading this entire thread, I am interested in building this pedal.

I was wondering if the layout by Torchy could be posted again, which seems to be a good one. Or, can I use Igloo's veroboard layout?

thanks in advance

Torchy · Post by **Torchy** » 15 Jan 2009, 09:59

https://i197.photobucket.com/albums/aa1 ... e_Vero.gif

scott1568 · Post by **scott1568** » 15 Jan 2009, 16:08

Many thanks!

sadrew · Post by **sadrew** » 16 Jan 2009, 00:04

Hi soulsonic... any chace to share your layout?

I just purchased 2 metal can 741 and i'm looking forward to bake my cakes (one will be for a friend)

scott1568 · Post by **scott1568** » 16 Jan 2009, 00:40

Where did you get the metal can TL071's? Are they THE ones to have?

Another question. I am new to veroboard layouts. Most of it makes sense, but what do the red squares with the red diamonds inside mean?

Greg · Post by **Greg** » 16 Jan 2009, 00:44

scott1568 wrote:Where did you get the metal can TL071's? Are they THE ones to have?

Another question. I am new to veroboard layouts. Most of it makes sense, but what do the red squares with the red diamonds inside mean?

They are circuit breaks on the board.. take a drill and gently twist by hand until you break the copper trace.

The metal cans referred to are 741 not TL071.

soulsonic · Post by **soulsonic** » 16 Jan 2009, 02:24

Okay, here is the files for my Mojo Hotcake with the metal can 741. The .zip file contains the PCB artwork, layout, and schematic of my version of the circuit. The circuit is tweaked a little bit to taste and it's sort of a blending of the '77 and current versions.
Download the package here:
members/soulsonic/Layouts/MojoHotcake.zip

scott1568 · Post by **scott1568** » 16 Jan 2009, 02:47

Thanks Greg and Soulsonic.....

Crowther Audio - Hot Cake Overdrive [traced]