100w 2nd Gen. ODS build

[dbharris]

Hi Dan,

One other item to keep in the back of your mind is the global negative feedback resistor. I don't think you can see the value on the images Max linked to for the 100W ODRS amps. Typically you would increase that resistor for a 100W versus a 50W. I didn't do the math, but maybe something like 1K or 1.2K if you feel the amp needs a little bit of a wake up. Again, I wouldn't mess with that until you have gotten to know this amp for a while.

-Dan

[martin manning]

Typically you would increase that resistor for a 100W versus a 50W.

In theory it should be larger by a factor of 1.414 for a 100W vs. a 50W, assuming the same speaker impedance. That puts the same feedback voltage at the PI tail.

[DSull89]

Thanks for the advice! I appreciate the helpful dialogue of this forum. Is the GNFB resistor the 820R next to the 100R Accent/NFB shunt?

[martin manning]

Yes, the 820 and the 100 make a voltage divider.

[DSull89]

Made a little more progress…

[martin manning]

Get the right size parts!

[DSull89]

I will admit, fumbling with those 1000uf’s was a nightmare. Lol. I had tried finding the small can ones but never could. Guess I’ll do some more hunting.

[dbharris]

This is what I would get:

https://www.mouser.com/ProductDetail/Ni ... eiEg%3D%3D

[DSull89]

Thanks, guys! Just ordered the radial’s from mouser. Thanks for the recommendation, Dan!
-Dan

[DSull89]

Hey everybody, been away for a bit but will be resuming my build tonight. I have a cabinet question. I got an Eminence PF-350 for pretty cheap and want to know which style 1x12 cab would be best suited for a 2nd Gen. I've read a lot about the ported Carlton cab that many prefer for a 1x12 EV style speaker setup but this speaker seems to be a different animal spec wise, mainly the 4" voicecoil. Any and all input is much appreciated.
Thanks,
Dan

[DSull89]

So I’m at the point where I’m going to start wiring everything into the chassis, but the fit of my relay supply transformer is kinda tight. Is the bobbin pressing against the chassis wall going to be enough of a problem that I should move my mounting holes?

[martin manning]

The problem is the 1A transformer is oversized. Can you ovalize the holes (round file) just enough to straighten out the core and eliminate any pressure on the coil? 166G6B, 6.3V CT, 0.6A would be a better fit, 2" mounting centers, 1.38" wide across the coils.

[DSull89]

I think I’m gonna just drill some new holes as these mounting holes aren’t lining up for this transformer anyway. Thanks for the reply, Martin! Always appreciated!
-Dan

[DSull89]

I didn’t see your transformer recommendation in your original post, Martin. Wasn’t ignoring you or your advice. I got the 166JA12 because, if I understand correctly, the stock 2nd Gen supply board isn’t a voltage doubler. If that’s incorrect, please correct me. I’m pretty new to this stuff, the ODS is far more complicated than the other builds I’ve done. Again, I appreciate the advice.
-Dan

[martin manning]

No worries. It is a doubler, turning 6.3VAC into (6.3VAC*1.414-0.7)*2 = 16.4VDC. It's unregulated, and that's why it has the 56R feeding the 3rd cap. I convinced Marc aka Raoul Duke to add a regulator to that board. The Triad F-313X is still available, and it's cheap!

See here for the reg mod: https://ampgarage.com/forum/viewtopic.p ... 80#p462380