etheory ePreamp001 - 2-stage pre based on Tamas BigFetBloke

[etheory]

Awesome, make sure you let me know how you go!

 

[kato]

Thanks for the interest.

BigFetBloak is surprisingly simple and easy-to-build. I rarely can stuff on the same day I etch, but I took a parts inventory and discovered I had everything except the power transistors and 22Ω 1w resistors, so I stuffed what I had. Mouser order will have to wait so I'll report back when it's finished.

 

[opacheco]

Hi there!.....

....This was also my first "complex" PCB manufacturing exercise - where I decided that using a vendor to do the boards was my best bet for speed and even price......

I need to do some PCB like these for my own projects; Could you share the Vendor PCB contact information please?

Thanks
Opacheco.

 

[etheory]

I need to do some PCB like these for my own projects; Could you share the Vendor PCB contact information please?
Thanks
Opacheco.

Hi there,
I ended up using seeed studio: https://www.seeedstudio.com/fusion_pcb.html

 

[My3gger]

I know this is an old topic, but just a quick FYI.

I revisited this after my original failure with the BigFetBlokes drawing too much current at +-15V and found the rather obvious issue.

I once read on the original Tamas BigFetBloke thread to make the current-setting resistor, which replaces the 1.1mA regulating diode originally specced as a 1N5298 (D7 on schematic), 15K or 18K.
Which is what I originally tried.
Unfortunately this makes the stand-by power about 1W, which put my original power supply under too much strain to sustain clean power.

After some quick simulation, I found setting D7 to a 24K or 25K resistor puts 1.1-1.3mA though the current source Q3, making everything run nicely from +-15V rails.

For +-24V rails, I'd recommend around 42K.

This drastically reduces PSU requirements with no effect on measured sound/frequency response/distortion etc. etc.

The amp still runs class A with this biasing and retains the original beautiful sound.
Q4 consumes around 210mW and Q5 around 100mW, and you can drive 600R with ease.

enjoy!

BigFetBlokes are around for quite long time, some information is probably lost now.
I made a few of them point to point because they are so simple whole preamp with two takes very little space, since it is fet input they were built with Hamptone JFP on pcb.
IIRC there were two schematics of BigFetBloke, second rewised replaced diode with resistor, iirc it was the same reason you found out. This is what i used and sounded very, very nice.
Don't recall excessive heat on any of this two, despite getting heatsink just in case.