ODS Amps and Tone Shaping

[Structo]

I recently was going over the huge collection of notes I have accumulated over the years from this forum and other sources.
One such note was titled ODS Notes. I can't remember who wrote this but I'm pretty sure it was someone from here. My apologies if you are the author, but feel free to take credit if you are.

In one section it talks about the local feedback loop on V1b and states:
In the Skyliner design the local feedback
loop has been eliminated, possibly to maximize the signal level from the two Clean stages.

I wasn't aware that the Skyliner circuit eliminated this loop.
Is this true?
What affect to the tone could be expected with this LNFB eliminated?

In another section it mentions this:

The earlier amps used 5uF cathode resistor bypass caps instead of the typical 25uF caps used in many Fender designs. By using the smaller caps, there is less of a chance of getting the dreaded "farty" bass response. A further improvement can be achieved by adding a small 1.0uF poly cap in parallel with the 5uF electrolytic cap
(or use a 4uF e-cap if you can get them). Using 5uF Ck caps for all four preamp stages can make the sound a bit bass heavy, so it is suggested that you replace one of the 5uF caps with a 1uF poly cap to keep the bass response under control. You can try using the 1uF poly cap by itself on the second Clean stage or the second OD stage.

I believe I had read something similar before about adding a small poly cap across a bypass cap, making it a bit faster feeling in response.
Also, some builders use all film caps for bypass caps since there are now higher value film caps available these days.
Any idea how having electrolytic caps verses film bypass caps affect the way the amp feels or sounds?
I have seen a few schematics showing a 1uF bypass cap on OD2 in an effort to tame the bass that sometimes is a bit much when all the same bypass caps are used. Such as all 5uF caps.
In fact I believe at one point I did have a 1uF bypass cap on OD2 but later went with all 4.7uF caps.
I can't remember how that worked now.
Any thoughts on this?

In another section it talks about taming some of the high end fizz that plagues some ODS builds.

It says in regards to the series resistor after the OD2 coupling cap:

The series resistance after the OD2 coupling cap has a very drastic effect on the overall sound of the OD section. With no resistance at all, the OD section can sound very harsh and brittle. Adding in a 150k resistance for a 0.01uF coupling cap, or a 330k resistance for a 0.005uF coupling cap seems to work really well in shaving off some of the high frequencies while leaving plenty of definition in the sound. But with the 500k trim pot in there (at least temporarily) you can determine the "sweet spot" for your own amp. Once you find the value you prefer you can hard wire in a fixed resistor (or combination of resistors) for that particular resistance.

Then this about the OD1 coupling:
The series resistance after the OD1 coupling cap has a more subtle effect on the sound of the OD section, and when I dialed it in for the "sweet spot" it worked out to around 105k (very close to the 100k resistor used in both the 70's and 90's designs). However, you are encouraged to try the 500k trim pot here since your own amp may be tuned a bit differently. I noticed that as I set the trimmer to 91k and
82k the sound was a bit brighter, and would improve the blues tones. In seeking an "ultra-smooth" sound, I ended up setting the trimmer to roughly 220k. You may further experiment with small caps in parallel with these trim pots, possibly wired in series with a small trimmer, but I was very impressed with the effect of just the variable resistor. Many people have suggested adding a cap to ground through a variable resistor to remove some of the high frequency content at the end of the OD section, but that arrangement tends to make the sound a bit over-compressed and removes much of the definition of the sound along with the harsher high frequencies.

Anyway, I thought it was some thought provoking commentaries.
My apologies to the author but I did not take note who posted this and also be assured that I am not disparaging this information at all, just wanted to discuss these "tweaks" and whether or not any of you are using any of these values in your ODS amps.

[Structo]

Wow, 114 views and no comments.

[ChrisM]

comment...

Thanks

[dr. who]

I have heard that skyline has "normal 40m lnfb on V1b."

[Pete]

In one section it talks about the local feedback loop on V1b and states:
In the Skyliner design the local feedback loop has been eliminated, possibly to maximize the signal level from the two Clean stages.

I wasn't aware that the Skyliner circuit eliminated this loop.
Is this true?
What affect to the tone could be expected with this LNFB eliminated?

I thought Skyline non HRM would likely have the LNFB, Skyline HRM no LNFB. So perhaps the comment is referring to HRM.
I find the LNFB thins things out a little or put another way: tightens the low end a little. Thus no LNFB sounds a little fatter to me.

[Structo]

Yes, I had considered putting a switch on the LNFB but as it is, my amp is starting to have too many switches back there.
Although I like the versatility, I also like simplicity as well.

[Pete]

double ...

[brewdude]

I have removed the LNFB from my D'Lite. After about 6 months, I tried adding it again and promptly removed it again.

[Structo]

What do you like about not having it?

[brewdude]

To me it felt thin and tight with the LNFB, especially on the clean channel. I have made some other changes as well, but am still not fully satisfied.

[JD0x0]

I have removed the LNFB from my D'Lite. After about 6 months, I tried adding it again and promptly removed it again.

i removed the LNFB from my ceriatone and liked the change alot. fatter tone with a tad more gain

[ampdork]

I have found the lnfb to be mostly useless.
For cleans I have yet to know anyone who likes it.
For non HRM OD's it can be ok but the better ones I have heard are also without it.
At the least I would defeat it for the cleans as I can find little to love about it there...mileage varies of course.

[marcos]

The "ODS Notes" deal with tweaking an amp built off the "70s " schematic
that has been on different sites for some years.You have to look at this schematic to understand the references, I believe it is somewhere in the Dumble files section.
Personally, I have some doubts if an amp with this circuit really exists,
or maybe if there are mistakes in the schematic.
The overdrive section, in particular, seems weird to me, especially regarding the missing series resistors for the OD entrance and the ratio trim pot.
So if you were to build an amp off this schematic, the suggestions for tweaking this circuit would really make sense.

[Max]

I have found the lnfb to be mostly useless.
For cleans I have yet to know anyone who likes it.

Now you have found at least one. My hand is in the air!

Have fun

Max

[markusw]

I have found the lnfb to be mostly useless.
For cleans I have yet to know anyone who likes it.

Now you have found at least one. My hand is in the air!

Have fun

Max

At least for 100k cleans (didn't test w and w/o for 220k/150k cleans) I also clearly prefer it with LNFB, FWIW