This Week on the Breadboard: MOSFET Driver Redux

[Chuck D. Bones]

Absolutely! That's what I used.

 

[jubal81]

I got this up in the Wish List. Vote and cross your fingers!

 

[cooder]

Last boxing ups of the year, and it's a goodie.... this thing rips!
Cheers @Chuck D. Bones here's my version of the MOSFET Redux, called Cowpoker. And it has some buzz to it indeed, it screams and has a ton of gain available, harmonics pinch easily of the board. Noice one!

Since I allowed for compensation cap (used 33 pF) I tried TL071, CA 3130 and I ended up using a Russian KR1408B supposedly workalike of LM308 chips. All sounded great but the Russian one had maybe a bit less noise on high gain, surprisingly.

 

[Chuck D. Bones]

SWEET! I didn't know they had opamps in Russia. Try an NE5534 if you have one. The LF356 on my breadboard is plenty quiet.

Where did you end up setting the Gain Trim?

 

[cooder]

I do have an 5534 will throw that in. I have the gain trim pretty low, because my age bracket doesn't cope anymore with too much of that gainy stuff... lol... It has plenty of gain as is anyway.
Great sounding for sure.

I got those Russian opamps outta curiosity and have them in some Rat style circuits. Do I hear a difference, I dunno, sounds good though and a bit of exotic fun why not. Love some of the Russiabn tubes. so why not opamps as well when it fits.

 

[cooder]

Just tried the 5534, the Russian chip still has a slight edge, the 5534 had a bit of hi end noise in it. Maybe the Russian chip is not as hi end audio and that might play in favour here? Not a big difference at all bt so far the Russian KR1408B stays.

 

[Chuck D. Bones]

Maybe try a bigger compensation cap on the 5534. Where did you get the YR1408B?

What do you think of the BASS & TREBLE control ranges? Are they OK or would you tune them differently?

 

[cooder]

What size comp cap would you recommend? 100pF?
Bass and treble seems both quite useful, so I find good range in there. Treble below 10 o'clock is a bit dull for me but it's good that it has a wide range, nothing wrong with that.
I got the Russian chips here:
https://www.ebay.com/itm/144257700303?hash=item21966dd1cf:g:YhoAAOSwMNxXVml-

 

[Chuck D. Bones]

100pF is a good start. The other thing to try is a larger feedback cap (C3 on my sch). My gut feel is the NE5534 and LT071 aren't noisier, they just have more bandwidth.

The eBay seller implies they're equivalent to LM308, but without a datasheet, who knows?

 

[cooder]

I just downloaded the data sheet from Russian chip . It does make even less sense than normal to me... lol...
https://pdf1.alldatasheet.com/datasheet-pdf/view/1205140/KWAZAR/KR140UD1408B.html

 

[Chuck D. Bones]

Turns out I had a translated datasheet for that part. Slew rate is 0.05V/μs, which is slow even by LM308 standards. Gain and bandwidth are also low numbers. Explains the "low noise" performance you're observing. If you like the tone, who am I to judge?

 

[cooder]

Thanks for digging those up @Chuck D. Bones !