Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: CordovaNate on September 14, 2019, 10:50:23 pm

Title: Look what I did to my Hoffman PR...and I have a question re OT w/ 4&8 ohm taps
Post by: CordovaNate on September 14, 2019, 10:50:23 pm

I built a head cabinet for my PR...because I built a 2x10 cabinet out of curiosity.  Nothing exotic, but I'm very happy with it.

Speaker cabinet has 2 WGS Veteran 10's in it at 8 ohms each, wired in parallel for a 4 ohm load.  Currently I'm using a Mojotone 8 ohm OT.  I've ordered a ClassicTone 40-18045 OT (8.5k primary, 4 & 8 ohm secondary) and I don't know how to wire the two speaker jacks at the rear of the chassis.  Do both speaker jacks need to be Switchcraft type 12A shorting jacks?  Only one of them is of that type right now.

Link to 15-20 add'l pics stored at google photos if anyone wants to see more. https://photos.app.goo.gl/Pdypi25Rwt1uhUvb6

Thanks


 

Title: Re: Look what I did to my Hoffman PR...and I have a question re OT w/ 4&8 ohm taps
Post by: sluckey on September 14, 2019, 11:04:29 pm

If you want to have one 4Ω jack and one 8Ω jack, just use the two jacks you have, but do not connect the shorting switch lug to anything.

Title: Re: Look what I did to my Hoffman PR...and I have a question re OT w/ 4&8 ohm taps
Post by: CordovaNate on September 14, 2019, 11:09:06 pm

I can do that!  Thank you!

Now I'm wondering if this complicates the NFB.

Title: Re: Look what I did to my Hoffman PR...and I have a question re OT w/ 4&8 ohm taps
Post by: sluckey on September 15, 2019, 08:46:12 am

Leave the NFB wire connected to the 8Ω jack. NFB circuit don't care which speaker jack you use.

Title: Re: Look what I did to my Hoffman PR...and I have a question re OT w/ 4&8 ohm taps
Post by: CordovaNate on September 15, 2019, 11:17:25 am

NFB don't know jack, and neither do I!
Thanks again,
Nate