Switching on OT input impedance

[daveyajd]

Hello all,
I am going to be getting my PT and OT from MPS https://www.musicalpowersupplies.com/ and the OT comes with both 6.6k and 8k input impedance. Since this is an EL84 amp can I set these up on a switch to go between the two? What should I expect sound wise and is it worth it? Is it really just as easy as using a DPDT On-On with the OT going to the top and bottom lugs and the center lugs going to the tubes? Thanks for any “input”. 😀


Aaron

[sluckey]

That will work. Don't know if it's worth it. I'm kinda skeptical. I'd just pick the 8K leads and tape off the 6.6K leads.

[daveyajd]

I figured that the difference would probably be negligible. Thank you.


Aaron

[pdf64]

Plus there spikes of several kV at the plates of overdriven, inductively loaded power tubes. So any switches insulation would really need to be rated for that (good luck sourcing one).
Though I concede that regular dpdt switches get used for triode/pentode switching and seem to survive.

[Tbone55]

The amp I'm currently building has an OT transformer with dual impedance, 5k and 2.5k that's made to work with either 6V6 or EL34. I sourced a regular DPDT on-on mini-switch for this, nothing rating for voltage spikes as mentioned. I am new to building amps so I don't want to be giving advice on this. What I know is that the I've seen amps built like mine and the switch used doesn't appear to be anything special. I also couldn't offer an opinion on whether or not you'll hear any differences with the power tubes you'd be using. Personally, I think the difference is something that the speaker will have a big effect on. The same tube used with different speakers will sound different and if you play with the capacitor values for the first pre-amp section that will change the sound as well, all things being equal. Does your circuit have different bias resistors to work with the impedance switching?

 

[daveyajd]

 Does your circuit have different bias resistors to work with the impedance switching?

No, nothing like that. It is just a Matchless Lightning build. I figured that those impedances were so close it would probably be pointless. Seems to be easy enough that I may try it out on a switch without drilling out the chassis. Just for my own education. Thanks.