Crowther Audio - Hot Cake Overdrive

Greg · Post by **Greg** » 29 May 2009, 11:42

floris wrote:The gain is mainly set by the ratio of the feedback resistor, between opamp output (pin6) and the opamp minus input (pin2), and the resistor between opamp minus input (pin2) and ground. Google for "non inverting amplifier":
http://en.wikipedia.org/wiki/Operationa ... _amplifier
So:
Make the 100k feedback resistor smaller (R7 in the schematic of analogguru if I'm not mistaken).
Or make P1 drive pot larger.

Changing to a higher pot value won't help because maximum gain is achieved with the Drive pot at zero.

If you want to make the higher Drive settings unavailable, there's a resistor in series with the Drive pot that you can change, or there's the 100K Feedback resistor that floris mentioned.

Alexo · Post by **Alexo** » 03 Jun 2009, 19:22

Hi everybody!

Yet another newbie here, wanting to verify his Hotcake's functionality....

I built this pedal about a month ago based on Analogguru's schematics, combining the 77 and 03. It's basically an 03 with true bypass switching and no buffers or relays. Or a 77 with a (50k) presence pot, if you prefer. I just discovered this site and read through all 12 pages of this incredibly informative thread, but my issue doesn't seem to have been discussed...

My pedal seems to work pretty much as it should, but on the last bit of the drive pot, say between 80 and 100%, it sounds as though an intense low-pass filter is being applied. The tone is very much what you would expect through the rest of the range, and the distortion at this point sounds great (to me, anyway) except that it sounds like it's buried under a pile of blankets. If the selective feedback filter is shunting highs from the fb loop to ground, this shouldn't happen, right?

I know there are some great voicing tweaks floating around here, but I want to be sure that I'm starting on the right page before I dive in.

I used an IC socket and tried the 071 and 741. I prefer the 71 because it has less low-end woofiness when cranked (didn't know about that extra 220k R for the 741 though) and it just sounds a little sweeter to me, with less noise.

I cobbled together a schematic, cut and pasted Analogguru's drawings - for my own personal use, of course. I'm more than happy to post it here if it'll help, but I feel I shouldn't do so without Analogguru's permission - it still bears his copyright!

Greg · Post by **Greg** » 04 Jun 2009, 00:09

That's a characteristic of the Hotcake.

As the Hotcake is opamp distortion, I'm thinking it might be a slew rate issue ?
Different opamps do seem to affect it, but also change the tone elsewhere.

The thing is.. the Hotcake gets a little messy at the extreme of the Gain pot.
Most people just don't turn the Gain right up, but stay in the minimum to maybe 1.00 area on the gain knob.
If you can't stand to have those settings on the pedal, just increase the resistor mentioned above..

Alexo · Post by **Alexo** » 04 Jun 2009, 02:38

Ah ha - thank you very much for that information. Without it, I would have torn this thing apart trying to figure out what I did wrong.

But, like others, I find the transition between overdriven and clean, particularly on sustained notes, to be fairly "crackly" and not what I consider "musical," so I've just been trying to work with the all-out distorted tones it gives - I really do like the touch response and compression this thing gives when it's cranked up, but not the apparent darkness, although a rangemaster in front of it improves things. I guess I'll have to try it in front of some EL84's too...

Looks like the crackling may be another characteristic of this pedal, but I could see it not being an issue for rhythm parts where the notes are choked off before they can decay naturally. I guess, as Ken Fisher may have said, this also wouldn't be noticeable with a cranked amp, but if I'm in a situation where I can crank the amp, I'd rather not use any overdrive pedals at all!

Thanks again!!

9 volt · Post by **9 volt** » 11 Jun 2009, 00:49

Could I use a 709 ic with this layout? Cheers

Post by **modman** » 05 Sep 2009, 08:49

All the information contained in this thread has now been indexed and summarized in the Build Your Own Boutique Clone folder. For troubleshooting and direct links to schematics etc, please check this thread:

Crowther Hot Cake summary

sergedeep · Post by **sergedeep** » 06 Nov 2009, 20:46

How substantial is the difference between the 1977 and 2003 actually? I used to have a 2003 version (until it got stolen), so I know pretty well how that one sounds. I read somewhere that the "2003 is a very glassy fender sounding to my ears - 1977 is much more Marshall smooth sounding (less edgy)" - is the difference really THAT big?

I'm just trying to decide whether I would make just the 1977 version or both versions (switchable) in one enclosure.

bajaman · Post by **bajaman** » 06 Nov 2009, 23:02

try them both and see

hesunana · Post by **hesunana** » 23 Nov 2009, 23:40

Ok, I finally managed to build my own Hot Cake using Torhcy's layout, but I'm a bit worried about the IC voltages. Is it normal that pin 3 is only at 2,15 volts? According to some posts in this thread it should be 4 volts or even higher.

Here are the complete measurements:

Battery: 9,23V
Zener (8,2V): 8,14V

1: 0,14V
2: 4,49V
3: 2,15V
4: 0V
5: 0,14V
6: 4,48V
7: 8,13V
8: 0V

floris · Post by **floris** » 29 Nov 2009, 22:11

It probably due to the 1M internal resistance of your voltage-meter-device that you're measuring a lower voltage on pin 3. The bias voltage (4.5V) is put on pin 3 via a 1M resistor so the voltage-meter pulls it down. Because the opamp output is still 4.5V (pin 6) its probably working just fine.

hesunana · Post by **hesunana** » 01 Dec 2009, 07:28

Thanks floris, that's probably it. I measured between R2 (82K) and R3 (1M) and got 4,3 volts, which sounds a whole lot better.

Silent Fly · Post by **Silent Fly** » 06 Jan 2010, 09:52

The current version of the Hot Cake has a jumper to select bass or guitar.

I guess it is a matter of changing the input cap - does anybody have more information about it?

Thanks

Greg · Post by **Greg** » 06 Jan 2010, 10:41

Silent Fly wrote:The current version of the Hot Cake has a jumper to select bass or guitar.

I guess it is a matter of changing the input cap - does anybody have more information about it?

Thanks

I thought it had a jumper to choose between standard and Bluesberry version ?

Silent Fly · Post by **Silent Fly** » 06 Jan 2010, 14:52

Greg_G wrote:
Silent Fly wrote:The current version of the Hot Cake has a jumper to select bass or guitar.

I guess it is a matter of changing the input cap - does anybody have more information about it?

Thanks
I thought it had a jumper to choose between standard and Bluesberry version ?

It is possible... do you know how this translates in the schematics?

Greg · Post by **Greg** » 06 Jan 2010, 23:31

Silent Fly wrote:
Greg_G wrote:
Silent Fly wrote:The current version of the Hot Cake has a jumper to select bass or guitar.

I guess it is a matter of changing the input cap - does anybody have more information about it?

Thanks
I thought it had a jumper to choose between standard and Bluesberry version ?
It is possible... do you know how this translates in the schematics?

Sorry.. no.
I also asked the question once and didn't find out.
Having tried a double Hotcake.. which is supposed to contain both circuits, the difference is very subtle.

chromesphere · Post by **chromesphere** » 29 Jan 2010, 01:32

Hi all!

really excited about putting this one together. Just wondering though, does anyone have a PCB layout which includes a square-type of IC instead of the metal can type?

Any help, really appreciated!
CS

imbuedblue · Post by **imbuedblue** » 20 Feb 2010, 22:53

I built a Hot Cake using Torchy's veroboard layout, but for some reason I'm only getting distortion when to gain is set to full. Any help? Thanks.

batteryacidtea · Post by **batteryacidtea** » 21 Feb 2010, 02:35

Maybe you're using a damaged pot for gain, dunno... test it with the multimeter

the3secondrule · Post by **the3secondrule** » 07 Jun 2010, 03:19

Hi,

I have an older hotcake (2003 approx?) that I want to mod to use with Bass - does any one have a schem for the most recent model hotcake (it's apparently internally switchable for bass/guitar, and also standard/bluesberry...)

(it sounds pretty nice on bass as it is - just a little thinner than I would like)

J

KindaFuzzy · Post by **KindaFuzzy** » 17 Jun 2010, 11:09

I baked a little mojo cake last night, very nice. Here's a pic:

Crowther Audio - Hot Cake Overdrive [traced]