Crowther Audio - Hot Cake Overdrive  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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markm
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Post by markm »

Wanted to show this to all here;
http://image.blog.livedoor.jp/mse_drive ... daedfa.JPG
Anybody think this is the real deal?
UPDATE SEPT 5 2009. modman wrote: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
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Crowther_Hotcake-2003.gif

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theblackman
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Post by theblackman »

isn't the shortcake on that matsumin site really the hotcake? I have found a few layouts etc for the hotcake on some japanese sites...

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Post by bajaman »

Hi markm
I've repaired afew over the years, but I have never seen one with a transistor in it. :wink:
Cheers
Steve

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theblackman
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Post by theblackman »

i think that's a mod one of the japanese guys did

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theblackman
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Post by theblackman »

here is all the info i have found on the net about the hotcake. it took learning two non native languages to find this so i hope you like it haha.

http://rapidshare.com/files/40721155/hotcake.zip

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Post by analogguru »

That´s not really much. I also found:

this

enjoy,
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Post by theblackman »

haha, thanks but that one has a transistor too :D .. there must be a few different versions around.

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Post by analogguru »

haha, thanks but that one has a transistor too ...
yes, but as you can see here on the 77-reissue:
http://www.geocities.jp/fenderlead2/attach.htm

it is not assembled on the main board it is mounted on a separate switchboard.
there must be a few different versions around.
There have been. Even on the pcb-layout is space for such a transistor, but it may have been assembled only on few units (without big success).

But bajaman is the expert, I believe he he is the one who has seen the most of this units.

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Post by bajaman »

Hi guys
Yes, there are many versions - blackberry etc. and now a double Hotcake with a master volume control, BUT as far as my experience with them is concerned, there are basically two types (incidentally that 77 reissue on the Japanese site is not even remotely similar to his original design - if it ever was original??)
The very early 77 units used a 741 type opamp (no, I don't remember who it was made by!) and a switch between the two extreme positions shown on analogguru's drawing instead of the later presence control. It also had a two stage high frequency rolloff - 10k and 12n, similar to the rolloff on the BSIABII or STM Runoffgroove hf rolloff filters, instead of the single 10k and 22n filter in the 2003 model.
The transistor is used for the relay and bypass board in the 2003 model, BUT the 77 model did not have as sophisticated a bypass. It used a 120k resistor and simple shorting switch from the bottom of the drive pot, 1k, 470p, 12n, 12n, and bottom of the level pot, to earth. When the switch is open all the foregoing components were lifted by the 120k resitor - hey presto bypass mode. when the switch is closed: bingo, tons of boost :wink:
Another minor detail, which has a subtle effect on the sound of the original 77, was the addition of a 220k resistor from the inverting input of the 741 to the half rail bias supply.
Personally, I prefer the sound of the 77 model - more mushy like a Marshall. The 2003 model has a more sparkly Fender sound, because of the better top end response obtained with the TL071.
I have played around a lot with this circuit years ago - a NE5534 sounds nice in there too - but consumes a lot more current from the
battery :wink:
I'm sure analogguru will get around to sketching the 77 original version eventually, but i think he is a bit overloaded with stuff at present - stay tuned :wink:
Cheers
Steve

ps: I have verified both models :shock: :lol: :lol: :lol:

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Post by bajaman »

Hi analogguru
I know it may seem strange BUT the presence control was DEFINATELY a 22k linear pot in the 2003 model I had opened up on my workbench.
The pots he is using are OMEG type and the gutshots show the different colour wafer (lighter colour) than the two 50k types.
Further clarification - Paul Crowther's 77 model used a 50k log pot for the drive control - this worked backward (just like ZVEX) (the pot that is :lol: :lol: ). Anyway that is probably why he is now using OMEG pots - must have had a few complaints :wink: - the OMEG drive pot is of course a reverse 50k log pot, so it increases the gain as you turn it clockwise :) .
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Steve

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Post by kagaxdx »

I know it may seem strange BUT the presence control was DEFINATELY a 22k linear pot in the 2003 model I had opened up on my workbench
Hi Steve, have you measured or checked the printed value on this presence pot?

Because I have one schem (will try to up load it) that shows a 50K pot *but* with two 10K resistors, each from outside lugs to the midle one. Wich may end up resulting the pot actually measuring around 20k... :roll:

edit: ooops... it's exactly the same as the one posted by AG...

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Post by bajaman »

Hi Steve, have you measured or checked the printed value on this presence pot?
Yes :) , but that is not to say he didn't use 50k lin at some other time.
Incidentally, the 56n capacitor on the output was DEFINATELY a 47n on earlier 77 units. I think he used what he had at the time, like Jim Marshall with his "plexi" models - if he ran out of one value, he used whatever he had closest - not uncommon :wink:
Cheers
Steve

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Post by bajaman »

Hi friends
Not denying that the Hot Cake is a clever circuit, like most "original" designs, it makes use of a simple trick - in this case it is the frequency selective feedback strung off the output of the op amp ( 10k, 1k, 82n ).
This allows the opamp to clip far more easily on the higher treble frequencies and reduces the closed loop gain progressively at low bass frequencies.
result: plenty of harmonic distortion whilst retaining a tight bottom end :wink:
As the drive control is increased, the sound gets progressively muddier though as the op amp slew rate limits. For this reason, most fans of the Hot Cake use it with low drive settings, and here it provides a pleasing "sparkle' and plenty of boost to the amplifier input when the level control is maxed out :wink: :wink: :wink:
Cheers
Steve

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Post by analogguru »

I'm sure analogguru will get around to sketching the 77 original version eventually, but i think he is a bit overloaded with stuff at present - stay tuned
bajaman is right, occasionally I even have to work to earn a little bit of money. Today I had to repair this "stompbox":
http://aufcrange.au.funpic.de/geschaeft ... ller-y.jpg
after a lovely electrician exchanged accidentally neutral with phase and there were 400V (instead of the normal 230V) on some of the components.... Some of the solidstays relais really exploded, I will post some pictures of the mess....

Sadly there was no correct schematic available. For this reason I had to do some tracing. I dont want to post the corrected schematic cause PT or ZV may be a liitle bit to much confused by the 80 pages.

So stay tuned for another stuff.

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Post by markm »

theblackman wrote:here is all the info i have found on the net about the hotcake. it took learning two non native languages to find this so i hope you like it haha.

http://rapidshare.com/files/40721155/hotcake.zip
That's the same one!

Incredibly interesting stuff fellas. 8)

Andy
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Post by Andy »

analogguru wrote:
I'm sure analogguru will get around to after a lovely electrician exchanged accidentally neutral with phase
OT: I once had the chance to get called after this happened to the sideracks at a local show... All the Behringer stuff survived (mains fuse blew on each) while the TC stuff really got grilled (you could use them as a shaker after that little accident)

Back to topic: The HC is really cool. I found mine oscillating in bypass mode when using a TL071 even with an input buffer. The "relais trick" seems to solve this - I go on with a 741...

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Post by analogguru »

The above schematic (3-knob, 2003) has been updated to the "bajaman"-specs.

Please download again and delete the old file.

analogguru
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Post by modman »

AG,

could you explain the function of the relais in your schematic, it's not in the others and the first time I see one in a stompbox.

but that's just me maybe?
zj
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Post by analogguru »

The relais is the most sophisticated part and idea in the Hotcake. It is a special impuls relais. On impuls switches the relais on, the next impuls switches the relais is off. In the meantime the relais doesn´t draw any current. The problem is only, that you never know in which position is the relais now, without any feedback. For this reason the LED is switched by the relais. The impuls is created by charging/discharging the capacitor in series with the relais coil.

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Post by bajaman »

The relais (relay in English) is an Aromat TQ Series Telcom Single Coil Latching Relay type TQ2-L-5V (5 volt coil)
T-Series relays are widely used in communications, instrumentation
and control interface equipment. They are a miniature printed circuit board device.
They are available from Digikey( part #255-1004-ND ) and are US$3.16 each!
more details are available on the Digikey site.
Paul only started using these relays in 2001 - his earlier hot cakes had the far simpler switching arangement seen elsewhere on the net :wink:

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