Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: robrob on March 02, 2019, 01:05:11 pm

Title: Single Channel, No Reverb, No tremolo AB763 Amp Design
Post by: robrob on March 02, 2019, 01:05:11 pm

I know this has been done before but here's my take on an easy to build, normal channel only, no reverb, no tremolo AB763 amplifier. There is a 2x6L6 and 2x6V6 version along with a 1 watt micro version that uses the AB763 preamp and phase inverter but feeds a single 12AU7 push-pull power tube.

https://robrobinette.com/RR763_BLACKVIBE.htm (https://robrobinette.com/RR763_BLACKVIBE.htm)
The webpage explains my design decisions and fully documents the amps.

(https://robrobinette.com/images/Guitar/AB763_Models/RR763_BLACKVIBE/RR763_BLACKVIBE_Schematic_small.png)

(https://robrobinette.com/images/Guitar/AB763_Models/RR763_BLACKVIBE/RR763_BLACKVIBE_Layout_small.png)

(https://robrobinette.com/images/Guitar/AB763_Models/RR763_BLACKVIBE/RR763_BLACKVIBE_MICRO_Layout_small.png)

Title: Re: Single Channel, No Reverb, No tremolo AB763 Amp Design
Post by: tubenit on March 02, 2019, 02:10:20 pm

Thank you for sharing this! 

With respect, Tubenit

Title: Re: Single Channel, No Reverb, No tremolo AB763 Amp Design
Post by: pdf64 on March 03, 2019, 08:34:55 am

Note that it may be beneficial to connect the PT HT CT wire directly to the reservoir cap's negative terminal, thereby avoiding the heavy ripple current in that circuit contaminating other 0V returns. See section 15.3 of http://www.valvewizard.co.uk/Grounding.pdf
Specifically -

Quote

To minimise the interaction of ripple current with the rest of the circuit, the transformer-rectifier-reservoir must be treated as a single, selfcontained circuit block.

Title: Re: Single Channel, No Reverb, No tremolo AB763 Amp Design
Post by: robrob on March 03, 2019, 11:04:19 am

Thank you for that suggestion, I'll make that change pdf64.

Title: Re: Single Channel, No Reverb, No tremolo AB763 Amp Design
Post by: vampwizzard on March 03, 2019, 03:41:57 pm

Id love to hear any sound samples on these if theyve been built. Thanks for more great info!

Title: Re: Single Channel, No Reverb, No tremolo AB763 Amp Design
Post by: ALBATROS1234 on March 04, 2019, 09:59:52 pm

good one, i like it. been planning on building a micro type but was thinking of using a 6sn7 instead of 12au7 but i have a couple other tubes i may try 6BL7, 6BX7 and/or 12BH7. i like the idea of the above mentioned 6 volt tube because they are octal.

Title: Re: Single Channel, No Reverb, No tremolo AB763 Amp Design
Post by: Papa Jim on March 04, 2019, 10:22:46 pm

My 5F2 princeton was built into a chassis that had extra sockets, pots, and switches. I have the trannys for the scaled back AB763.  I may just use that princeton build and convert it into this amp. The preamp is very similar just a different tone stack, and bright switch basicly. The extra sockets were left in the chassis. I may just do it.