New Orange OR120 build

[zeppelinofled69]

Managed to scrape together enough parts to do something that another forum member sparked my GAS for...

Started planning this build a long time ago, but never really had the confidence to try it, since the resources available for Orange and Matamp based stuff isn't quite as plentiful as Fender or the like.

Since this one is on the heels of my second Hiwatt DR103 build, you'll see quite a bit of influence from that style of building. I have taken a few liberties with a full star ground setup as well as adapting the power supply to work with the SLO-100 style power transformer I had on hand. Voltages are a little lower than I think they should be, but may be more in line with what they would have looked like when these amps were new back in the 70s.

I am putting a voltage chart here as I think things are OK, but not having another Orange reference to go on, I wanted to make sure with a few more sets of eyes.

B+1 459V
B+2 457V
B+3 363V
B+4 355V

	Pin 1	Pin 2	Pin 3	Pin 4	Pin 5	Pin 6	Pin 7	Pin 8	Pin 9
V1	192.5	0	1.6	Heater	Heater	196	0	1.66	Heater
V2	213.9	0	1.5	Heater	Heater	268.2	31.04	98	Heater
V3	0	Heater	458	456	-44.8	0	Heater	0	N/A
V4	0	Heater	458	456	-44.8	0	Heater	0	N/A
V5	0	Heater	458	456	-44.8	0	Heater	0	N/A
V6	0	Heater	458	456	-44.8	0	Heater	0	N/A

 

[NSB_Chris]

Nice Build! Can you post your schematic?

 

[zeppelinofled69]

Thanks @NSB_Chris

I was working from the attached schematics as well as adapting the Weber 6O100 layout diagram as I went along.

I am working on finishing a layout diagram based on what I built, but it's a slow process for me. When I get it done I'll upload it to this thread.

 

[muscmp]

i have a 76 or80 that was turned into an or120 either at the factory or professionally done. it is a monster and could blow out my windows if i turn it too loud.

good luck on your project!

play muscmp!

 

[NSB_Chris]

Thanks for posting! Can't wait to see how this turns out!

I like trying to analyze schematics of classic amplifiers, so I couldn't resist looking into this. It's dangerous because then I want to build them to see how they sound ... I should make friends with some rich person that has all the originals and a studio large enough to play them in

The OR120 schematic I found is below. Very interesting, but also seems very different than the Weber 60100. The driving stage (V2A) of the DC coupled cathode follower has a huge 390k plate resistor. Really an interesting circuit!

The Weber 60100 circuit seems fundamentally different. The first two gain stages are similar, but it does not have the DC coupled cathode follower. It seems to have a regular gain stage with feedback driving a concertina PI. I would guess both of these would be awesome amps but I would expect them to behave very differently. Weber put a MV in there which is smart as this would be a monster!

 

[zeppelinofled69]

@NSB_Chris

What I find interesting is the Schematic that I posted was supposedly an original circuit trace from an 1970s Orange. I have read that Orange was similar to Hiwatt in that they were changing the circuits on the fly as they made improvements, but yours also being called the Graphic MkII has me confused. I wonder how much different these circuits would sound in practice... and it has my hamster running which as you said... muy dangerous.

I actually got this thing up and running and took it to the band space last night. Wow. It's an absolute monster. I think the most impressive thing about it is the "extra" stuff it seems to get along with the guitar signal. The harmonic content is such that the amp takes high gain pedals like none I have ever heard, and it's knocking the DR103 I just built out of the band space once I get the Orange into a cabinet.

I have it running through a set of JBL E120s in an open back 2x12, and to my surprise it sounds quite good with these speakers. Definitely bright as all get out so I have to use the presence and treble sparingly, but the low end response is incredible and the mids are glorious.

All in all, I am very pleased with how this one turned out and it's close to becoming a favorite of mine... Though I have to admit, now I wonder what the circuit in the diagram you posted sounds like.... Gah.

 

[zeppelinofled69]

I did some more looking at the details across the schematics that are available on the Orange Amp Field Guide, and the schematic that @NSB_Chris posted seems to be the later "post 1972" circuit. I think the one I was working from is the earlier version of the OR120 circuit.