Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ed_Chambley on June 23, 2012, 08:06:21 pm

Title: NFB Question on Multi-tap OT
Post by: Ed_Chambley on June 23, 2012, 08:06:21 pm

I am finishing up a build and I cannot remember which tap one is supposed to connect the NFB to.  I have a 2-4-8 ohm using separate jacks.  Does it matter?  Will any jack suffice?

Title: Re: NFB Question on Multi-tap OT
Post by: sluckey on June 23, 2012, 08:23:00 pm

The higher Z taps will send a larger NFB signal.

Title: Re: NFB Question on Multi-tap OT
Post by: HotBluePlates on June 23, 2012, 08:26:42 pm

What is the build?

Title: Re: NFB Question on Multi-tap OT
Post by: Ed_Chambley on June 23, 2012, 09:39:39 pm

I am finally wiring up the Princeton Ab1164 with vary bias and dual bias with a dual intensity pot, adjustable NFB, Mid control, switchable inputs for tele and humbuckers.  Brownface with tweed cabinet. 2 10's paper cones, 1.51 15 watts each.  One is ribbed and the other is smooth.  Deluxe Blackface PT and Mercury OT Deluxe with multi-tap.  I can send this baby to a separate cab with 2 12's silver bell and blue pups and I have 2 12" small cabs I made from some of the blond tolex doug discounted.  I have a Celestian v-30, 15 ohms in one and a 4 ohm Celestian alnico blue in the other.

I told you I was going crazy on this build.  I hope it all works out.  I have planned a lot, but I know if I get in trouble, yu felllers will give me a hand.  I still gotta wire it up. but all that is left is the tonestack.

BTW, I am using 7c5 with amphenol sockets.  I got some Bugle Boys for it.  Well not new, but NOS.

Oh I forgot, I have a switchable Rectifier.  I made one of those that has 6 diodes and 6 resisters and 6 caps.  I have got to figure out the correct resistor to keep the B+ voltage the same as it is Bias Vary Tremolo.  That is the easy part.  The hard part is getting that MV Steve posted and the dual bias working.   I think I understand it tho.

The SS rectifier should give me the country spank on call and I am trying a 39K input at V1, but I have a switch for 68K as well.  This thing has stuff all over it.  From the front it looks like a brownface in a tweed cabinet.

This is the first amp where I built the chassis and cab.  Like I have said before, I was a machinist before becoming a Graphic Designer.  Metal is no problem.  I just cannot believe my finger joints came out so well and everything fits.

Thanks for asking as you can tell, I am a little excited.

Title: Re: NFB Question on Multi-tap OT
Post by: Ed_Chambley on June 23, 2012, 09:40:41 pm

Quote from: sluckey on June 23, 2012, 08:23:00 pm

The higher Z taps will send a larger NFB signal.

8 ohms it is.  Thanks Steve.