Recent Posts

51

Tube Amp Building - Tweaks - Repairs / Re: Laney Amp - 220V to 120V

« Last post by SEL49 on January 21, 2026, 07:03:56 pm »

Remove the jumper between 0 and 120. Put a jumper between 0 and 0. Put a second jumper between 120 and 120.

52

Tube Amp Building - Tweaks - Repairs / Laney Amp - 220V to 120V

« Last post by Joe6v6 on January 21, 2026, 06:48:46 pm »

Can anyone see what needs to be done to wire this for 120 volt operation? Its set at 220v now as it came from the other side of the pond. The Brown & Blue wires go to the 4 prong switch.  .   Thanks for any info.  .   Joe

53

Tube Amp Building - Tweaks - Repairs / Re: Fender Blues Deville - Low Volume on Both Channels

« Last post by Grantorino on January 21, 2026, 03:13:37 pm »

Thanks for your reply tubeswell.

Thankfully this amp is sorted now.

There were many issues, including mis-wired CP leads from the power components (wired in the 240 V configuration, not 230 V), burnt out resistors, broken solder pads, failing caps, broken input jacks, mis-wired speakers and two dead speakers.

The issues seems to have arisen from work done on the amplifier, rather than the original design.

Two Jensen speakers have just been fitted - killer amp!

54

Tube Amp Building - Tweaks - Repairs / Re: Fender Blues Deville - Low Volume on Both Channels

« Last post by tubeswell on January 21, 2026, 01:55:42 pm »

The low voltage +/- power supply for the channel relays/opamps etc is quite possibly the culprit- especially if someone already had to replace the 5W resistors previously. Some broken component powered from that supply could be causing the problem.


The issues with these amps are well documented on the inter webs.

55

Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by shooter on January 21, 2026, 12:22:38 pm »

in the mid 20th century iron was cheap, like Leo, less parts, less cost, more $$'s


I built 2 using I.T. for the PI, one got a round of thumbs up from the guitarists

56

Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by dogburn on January 21, 2026, 11:12:59 am »

Oddly enough, my first ever amp (way back in high school) was a Fender Musicmaster Bass amp - it was most likely the 6AQ5 version. I had no clue at all about amps, tubes or anything, just that I needed an amp for my bass (my first guitar of any kind). I ended up selling the amp after a few years because I needed something louder (got a Peavey TKO). Seeing the Musicmaster amp has gone up in value, I wish I'd kept it.

It appears the Musicmaster has an interstage transformer for the phase inverter - anybody know why they did that rather than use a tube? Could you easily substitute a tube PI there?

57

Introduce Yourself / Re: I'm new here, questions about Vox 1964 JMI AC10

« Last post by EL34 on January 21, 2026, 11:02:07 am »

You are posting the wrong board

The correct board link is listed above

58

Introduce Yourself / I'm new here, questions about Vox 1964 JMI AC10

« Last post by EL34 on January 21, 2026, 10:48:38 am »

Welcome to the Hoffman Amps forum

There are many different boards on this forum for different topics.

The Tube Amp Building - Tweaks - Repairs board is where you can post amp questions.

That board is listed here.
https://el34world.com/Forum/index.php?board=13.0

Thanks,
Doug Hoffman

59

Introduce Yourself / I'm new here, questions about Vox 1964 JMI AC10

« Last post by actenner on January 21, 2026, 10:48:38 am »

Hi. Brand new here. I'm not an amp builder, and barely know enough beyond biasing my Marshall DSL 100. I love the tone of the 64' Vox AC-10 in this video:
Listen from 5:25 minute mark to 5:55 and then from 22:00 minute mark to 22:31 for reference. Can anyone direct me to the section of the site where people know the inner workings of these JMI era AC-10's?

And where I might find information about trying to build one based schematics here or elsewhere. I could never afford one of these old ones, but maybe with the help from my friend who's an electrical engineer, I could start somewhere. I love the articulation and spank of this amp.

Have people here replicated this older circuit? I really want one of these. Much thanks.

60

Tube Amp Building - Tweaks - Repairs / Blues Jr Hoffman Circuit Adding Reverb

« Last post by ALK2MT on January 21, 2026, 10:42:26 am »

I have a question about connecting the solid state reverb circuit back into the Blues Jr Hoffman circuit. I am wanting some expertise on modding the circuit. Could I just attach the reverb circuit back in on either side of R18 like the original circuit? How do I delete meat control as well.

Thank you!

Alex