1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

a.hun · Post by **a.hun** » Thu Dec 11, 2014 4:49 pm

No need to remove any circuitry to run just two valves. I wouldn't bother doing anything...

Does the impedance selector (marked 'ohms') next to the speaker outputs actually have a 4 ohms setting? (Hard to tell from the pics. on the OFG or the thread I linked to early on.) If so than simply pull out the selector plug and reinsert it pointing at the desired 4 ohm setting.

If there is no 4 ohms setting you are a bit snookered for running an 8 ohms load with two valves pulled, mods or no mods. That would mean no 4 ohm ohm tap on the output transformer. You could run a 16 ohms load with the amp set to 8 ohms, but most bass cabs are 4 or 8 ohms, not 16 ohms.

BTW why are you wanting to run only two valves anyway?

Andy.

Gladmarr · Post by **Gladmarr** » Thu Dec 11, 2014 5:43 pm

The OP doesn't have an OR145, he wants to build a clone, so omitting the parts for the extra EL-34s is totally justified. Since the amp in question doesn't exist yet, there is not presently a speaker impedance switch.

a.hun · Post by **a.hun** » Thu Dec 11, 2014 6:36 pm

Thanks, makes more sense now.

Andy.

Randy Bass · Post by **Randy Bass** » Thu Dec 11, 2014 11:29 pm

a.hun wrote:Thanks, makes more sense now.

Andy.

That's debatable.

Post by **bclaire** » Fri Dec 12, 2014 12:01 am

Randy Bass wrote:
a.hun wrote:Thanks, makes more sense now.

Andy.
That's debatable.

Very much so...

Lemos · Post by **Lemos** » Fri Dec 12, 2014 1:59 am

Hmm... It seems the switch only has an 8, and 16 ohm selection. Do you guys know what would happen if I were to run the circuit at 8 ohms, with 2 EL34's, and how it would be affected- leaving the supporting circuitry for the two tubes I am taking out?

a.hun · Post by **a.hun** » Fri Dec 12, 2014 8:45 am

You're right again guys...

Ho Hum... Zappp!

(Andy has left the thread!)

Andy.

Lemos · Post by **Lemos** » Sun Dec 14, 2014 11:41 pm

Or better yet- if I could run the circuit at 8 Ohms with the supporting circuitry for the two tubes I am taking out, in, as well as possibly adding some more circuitry to support the 8 Ohm load, and how I would go about adding some components to do so?

Post by **bclaire** » Mon Dec 15, 2014 4:35 am

Lemos wrote:Or better yet- if I could run the circuit at 8 Ohms with the supporting circuitry for the two tubes I am taking out, in, as well as possibly adding some more circuitry to support the 8 Ohm load, and how I would go about adding some components to do so?

You need to stop asking questions and just go build the thing. We've answered all of this for you already... but what you're now asking makes no sense. Go build it - then ask questions.

jontheid · Post by **jontheid** » Tue Dec 16, 2014 3:57 am

Lemos - how about you go learn some electronics. Seriously. It will make your life a lot easier, and less dangerous.

I recommend http://www.valvewizard.co.uk/" onclick="window.open(this.href);return false; as a good place to start, the book he sells is very good too.

The same site also gives info on how to build your own ribbon microphones.

Sadly there is no info on thermal management of logs.

Gladmarr · Post by **Gladmarr** » Tue Dec 16, 2014 1:06 pm

Lemos wrote:Or better yet- if I could run the circuit at 8 Ohms with the supporting circuitry for the two tubes I am taking out, in, as well as possibly adding some more circuitry to support the 8 Ohm load, and how I would go about adding some components to do so?

It doesn't work that way. The number of tubes determines the primary-side impedance for the output transformer. That, in turn, determines what needs to appear on the secondary side of the transformer as a load for the tubes to be happy.

Lemos · Post by **Lemos** » Tue Dec 16, 2014 3:32 pm

So I should not be concerned of anything blowing up with two EL34's taken out of the original circuit? I just wanted to make sure I was not running too much power to too small of a limited capacity. I will most certainly check out the website, too broke for books right now!

Gladmarr · Post by **Gladmarr** » Tue Dec 16, 2014 7:46 pm

Lemos wrote:So I should not be concerned of anything blowing up with two EL34's taken out of the original circuit? I just wanted to make sure I was not running too much power to too small of a limited capacity. I will most certainly check out the website, too broke for books right now!

No. The tubes can't be subjected to more power than they need unless something is seriously wrong with the amp. If you're too broke for books, how are you going to afford the parts to make an amp ?

Lemos · Post by **Lemos** » Wed Dec 17, 2014 1:23 am

Barely enough for the amp! This should be my last question: will I need to use a certain type of wires to connect the components, as I have no printed circuit board?

jontheid · Post by **jontheid** » Wed Dec 17, 2014 7:07 pm

Yes. Ones with a metal core.

1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

Re: 1979 Orange OR145 Bass Combo Circuit Schematic/Diagram

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