AB763 take two

[nateflanigan]

After my first try spiraled into a rabbit hole of problems I decided to start over.  This attempt is much much neater, I've been playing the amp all night and I think I got it this time.  I gotta sit with it a while, and A/B it with a friends DRRI, try it with the band etc before I really feel comfortable saying there's no issues.  Here's a few pics...

[mresistor]

Pretty sweet looking lil amp. I like how you've routed the filament wires. I'll bet it sounds nice. 

Is the reverb and vibrato working well? I sure like the bias vary vibes better than the roach circuit.

[eleventeen]

Nice! From the perspective of the first pix it looks longer than a Twin Reverb! I had to count your output tubes!

So you have the footswitch jacks combo'ed into a stereo 1/4"?

[nateflanigan]

Thank you, vibe and verb are working nicely as of this moment.  I never cared much about tremelo until I heard the bias circuit, I love the way it fades in.

So you have the footswitch jacks combo'ed into a stereo 1/4"?

Yes I do.  My footswitch has a TRS plug, so I went with it.

I think once I'm really comfortable with the idea that it actually works I'll try some mods on the normal channel.

 

[Fresh_Start]

Nate - well done!  Your lead dress looks really good.  I like the heater wiring too.  :glasses9:

What's up with the two terminal strips on the input end of the chassis and between V2 and the board?  Just curious.

Cheers,

Chip

[nateflanigan]

Thanks so much Chip!

This is the first time I've tried running the heater wires that way, I wish I could remember who's post I got the idea from.  Was it something you said?  I really prefer doing it that way.

The two terminal strips hold the 68k input resistors.  I know bazillions of amps across the world have them soldered directly to the jack or the tube itself but I've broken the legs off more than once moving the wires around so I thought I'd try something more secure.  It also set up a convenient spot to ground the shield of the input lead.

[nateflanigan]

This afternoon I had the opportunity to sit down and compare my hoffman DR with an original '65 DR and a DRRI at a friends studio.  We used the same speaker when comparing the amps to slim down some the variables (an old mojotone that's in the vintage fender).  All the amps sounded good and they were all reasonably close to one another, but the differences weren't subtle.  I'm happy to say the hoffman kicked ass.  Clean, the hoffman had an overall richer tone than both of the fenders which was nice but the '65 had sort of softer highs than mine which we liked.  The hoffman was also a good bit louder and generally bigger sounding, overall we preferred my amp.  Cranked, the DRRI really didn't hold up, it sounded like a distortion pedal compared to the two.  The hoffman sounds awesome overdriven but we both liked the '65 a little better.  They both seemed to have the same sweet spot but the hoffman was more saturated where as the '65 stayed a little more dynamic.  Maybe if we could have swapped tubes and matched plate dissipations and what not they'd be closer.  Either way I'm really happy with the amp.   

[LooseChange]

I like to hear these types of comparisons. But always to many uncontrollable variables.

One big difference between the two is the tremolo type which effects the overall gain when not engaged. The DRRI has the tremolo roach which sucks some gain out of the circuit even when off.