NFB loop original

[llemtt]

Has anyone ever seen an original, HAD made, NFB implementation with values other than the "standard" 10M+10M+0.047uF+10M+10M?

Teo

[phsyconoodler]

You can use the amp without it at all and it just lowers the headroom and makes the amp more touch sensitive.That can be good or bad.
Try lower values.They all have a different vibe up to a point and then they just don't do much at all.
The correct name for this feedback is 'local feedback' and not 'negative feedback',as it injects it into V1 and not at the phase inverter.There are lots of ways to alter the tones in the dumble and the local and negative feedback areas are good places to play with.
I like to use a switch to switch the local feedback in or out.

[martin manning]

The correct name for this feedback is 'local feedback' and not 'negative feedback',as it injects it into V1 and not at the phase inverter.

Not to 'jack the thread, but strictly speaking it is "local negative feedback," no? Local negative feedback as opposed to "global negative feedback" from the OT secondary.

MPM

[jelle]

I am assuming you are speaking about the second gain stage here. In the pics I have seen there was no LNFB or the 10M+10M+0.047uF+10M+10M configuration. I have seen 22M's instead of 2x 10M.

I have even seen 10M + 10M + 10M + 10M + 0.047uF.

The return of the Dumbleator was 22M (or 10M + 10M) and 0.22uF.

There may be more but I haven't seen it.

Jelle

[Fischerman]

Yes, it is local negative feedback.

Try lower values.They all have a different vibe up to a point and then they just don't do much at all.

I think it's the other way around...higher value resistors will have less and less effect until the circuit makes no difference...lower values will have a more pronounced effect until it 'chokes' the stage too much.

Also, IIRC the local NFB on the Return stage in the D'Lator uses different values than the local NFB on V1b.

[ic-racer]

I am assuming you are speaking about the second gain stage here. In the pics I have seen there was no LNFB or the 10M+10M+0.047uF+10M+10M configuration. I have seen 22M's instead of 2x 10M.

I have even seen 10M + 10M + 10M + 10M + 0.047uF.

The return of the Dumbleator was 22M (or 10M + 10M) and 0.22uF.

There may be more but I haven't seen it.

Jelle

Not challenging you, just curious, did you see pictures or real amps with 22m instead of 2x10m? And in your experience (or anyone else), do you think there is any difference?
Thanks.

[glasman]

Glaswerks have been using a dual setup for a few years. In the up position it is 44M total and in the down position it is 22M, with center being out of the circuit.

I have always found the 22M setting to be interesting depending on the sound I am looking for.....


Gary

[glasman]

Normally HAD used 10M resistors, I don't remember ever seeing pics with 22M, but I have not seen every Dumble every built either.


Gary

[dogears]

I have a pic of an HRM with lnfb on the V1. There is one orange drop cap and one resistor on each side. You can't see the bands, but I'd assume it is a 22M on each side for a total of 44M.

This HRM had other wacky values fwiw. It is not like HRM 101.

[phsyconoodler]

I do know that it's local 'negative' feedback.And sorry about not being clearer about the effect of the resistors.Of course as the values go up the effect gets to be less pronounced.
I like the sound with them out altogether.Very fluid transistion to overdrive.
I lifted the negative feedback(global) on a two rock reverb signature and it became a monster rock machine.Too much for the jazz player that was looking for a bit of clean boost!

[llemtt]

I have a pic of an HRM with lnfb on the V1. There is one orange drop cap and one resistor on each side. You can't see the bands, but I'd assume it is a 22M on each side for a total of 44M.

What do you think about them being 10M on each side?

Teo

[glasman]

I have a pic of an HRM with lnfb on the V1. There is one orange drop cap and one resistor on each side. You can't see the bands, but I'd assume it is a 22M on each side for a total of 44M.

What do you think about them being 10M on each side?

Teo

I would doubt it, the reason is that with two 10Megs you would severely restrict the gain of V1B. As the HRM input trim circuit knocks down the signal even more, I doubt that there would be sufficient drive for the HRM.

I wil have to try it later today. My amps are setup to use either 22M or 44M and I will try it in 22M with the POStack enabled.

Gary

[jelle]

Without a 100k trimmer (or 220K trimmer) I do not care for it. Just like you said, Gary, not enough gain.

jelle

[glasman]

Without a 100k trimmer (or 220K trimmer) I do not care for it. Just like you said, Gary, not enough gain.

jelle

Yup, that 100K trimmer will help a lot and the 220K might even be better.

The 20Meg really flattens the BW out a lot, but it also tends to compress a bit (or a lot more). Of course it is just another color in my box of Crayolas . You saw the GW at the NT amp fest. Lots of colors in the box.

[jelle]

That 100W Glaswerks was great! Nice job, Gary.