Orange Amp OR120 Boost Circuit Question

[silverfox]

I'm trying to understand how this circuit works. What is confusing at the moment is the Lead-Lag relationship created by the inductors and capacitors. While I believe it must be some sort of filter circuit, it seems to me the signal at the cathode will be out of phase with the input at the grid?Or are the resistors shifting the phase relationship back to equal with the grid input. How does this circuit work.

silverfox.

[PRR]

> signal at the cathode will be out of phase with the input at the grid?

Cathode and grid are IN-phase.

But that is not the point. Signal isn't coming-around from cathode to grid. There is a Ground there. The draftsman happened to use the same ground triangle for two different things: grid-leak and tank ground. But you can draw them properly (separately).

That wire coming down from top could be trivial or could be a Major Player.

[shooter]

I re-sketched it - for my benefit, my guess, if you dial the pot, you dial the tubes gain?
and As PRR pointed out, the cathode wire *might* be interesting

[2deaf]

The gain of V2A is going to depend on the total impedance of the combination of R44, L1, and C30 at any given setting at any given frequency (if we ignore that connection of the cathode to some unknown entity).  On paper it looks like L1 is a waste of time and money, but I don't have a 2mH choke to try it out for sure.

At full boost, it looks like V2A would have very similar gain and frequency response to a 1K cathode resister bypassed by a 0.47uf capacitor.  As you turn the boost control down, the gain decreases and the frequency response flattens out.

[TubeGeek]

I am building this circuit in my current project.  I am very curious how this works and sounds too.

The cathode connects to a presence control...see attached schematic


I am using a Hammond 1535B choke with an inductance of 2.5mH +/-5%.  DC resistance of 9 ohms.  160 mA max DC current. I'm hoping it's right for the job.


https://www.hammfg.com/electronics/transformers/choke/1531-1535

[PRR]

> it looks like L1 is a waste

2mH and 0.47uFd resonates (band pass) at 5,436Hz.

The real effect is that boost does not continue to rise above the guitar band; it slopes-off high frequencies to avoid super-sonic troubles like oscillation and radio reception.

With a spread-out layout, it might be possible to omit the coil and have "the same effect". Or it could annoy the cat while mangling your fine tones, or drive your power stage into putt-putt mode.

That Hammond will work. Cost is no big deal. Mouser has small stock.

[silverfox]

PRR: That wire coming down from top could be trivial or could be a Major Player.Oh boy! Hadn't considered the FB circuit would be important. And then after I cut it out of the drawing I forgot about it...

TubeGeek: I am building this circuit in my current project.  I am very curious how this works and sounds too. Yeah I know. I didn't want to slide your forum topic so I just started this one.

TG- If you've ever heard of or listened to Rob Chappers, "Monkey Lord", in his early days he was an Orange Rocker Reverb Fan-Tester-Etc. I really like the sound he got out of that amp. The new Dual Terror I think it's called, sounds okay but in general I'm finding there is something about the bass on the newer models that has a sort of resonance to it I don't like. Sort of like it's being played in a large pipe. In the mid 70's I first heard an Orange, probably the OR120 and that rocked. And recently I played an older one in GC and that sounded just great. I'll be real curious to hear how your amp turns out. I will say the Weber schematics have these little tweaks in them that seem to be quite beneficial in the end.

silverfox.

[TubeGeek]

PRR: That wire coming down from top could be trivial or could be a Major Player.Oh boy! Hadn't considered the FB circuit would be important. And then after I cut it out of the drawing I forgot about it...

TubeGeek: I am building this circuit in my current project.  I am very curious how this works and sounds too. Yeah I know. I didn't want to slide your forum topic so I just started this one.

TG- If you've ever heard of or listened to Rob Chappers, "Monkey Lord", in his early days he was an Orange Rocker Reverb Fan-Tester-Etc. I really like the sound he got out of that amp. The new Dual Terror I think it's called, sounds okay but in general I'm finding there is something about the bass on the newer models that has a sort of resonance to it I don't like. Sort of like it's being played in a large pipe. In the mid 70's I first heard an Orange, probably the OR120 and that rocked. And recently I played an older one in GC and that sounded just great. I'll be real curious to hear how your amp turns out. I will say the Weber schematics have these little tweaks in them that seem to be quite beneficial in the end.

silverfox.

I figured you were watching my orange project thread and I am glad cause I was more than likely going to ask this question after it was built.


The new orange certainly is different than vintage designs.  I have been referencing several different takes on this amp and I keep coming back to weber's design because it basically has all the right things done to it from what I have learned so far.  I am basically starting with my own tweaked version of Weber's layout.  I should make some progress on it this weekend and report back Sunday if I have the energy.