18Watt.com

JP77 wrote: ↑

Tue 01/12/21 4:45 pm

I'm seeing rectifier circuit on some of the diagrams vs a tube. Is there a benefit there other than cost?

Use only the latest docs. That's the only true representation of the circuit. ZP doesn't care for rectifier tubes so much, and a 100 ohm sag resistor gives about the same effect as an ez81 rectifier tube. Less money and more reliable.

I'm having some difficulty trying to narrow down which is the latest TMB schematic/layout. It all looks like it is from 200x. If that's the latest available, that's cool. I'll figure it out and work in the latest grounding schemes.

Does the 18watt crowd have a favorite chassis for a head build?

JP77 wrote: ↑

Wed 01/13/21 2:47 am

I'm having some difficulty trying to narrow down which is the latest TMB schematic/layout. It all looks like it is from 200x. If that's the latest available, that's cool. I'll figure it out and work in the latest grounding schemes.

Does the 18watt crowd have a favorite chassis for a head build?

The top of the page, where it says "newest version" in huge letters

viewtopic.php?f=25&t=24430

That's from 2020.

Was looking over that schematic just now. Wondering if you've detected any issues resulting from driving the tone stack with the anode, rather than from a cathode follower. Have you run this in a simulator or swept it to see how much it varies from the original Marshall design?

That’s interesting,i’ve Been looking at the hiwatt custom 20 preamp and that tonestack is driven by the plate and I was wondering the difference.

I seem to remember reading that cathode drive prevents the volume from changing so much when the stack is adjusted. Don't know how significant this is in the real world though.

TriodeLuvr wrote: ↑

Wed 01/13/21 12:13 pm

Was looking over that schematic just now. Wondering if you've detected any issues resulting from driving the tone stack with the anode, rather than from a cathode follower. Have you run this in a simulator or swept it to see how much it varies from the original Marshall design?

I've built plenty of them, and they're great amps. It was designed by Zaphod_Phil, who is an EE and professional amp builder/designer, as well as a founding member of this site.

This is not an "original Marshall design." It's an original ZP design, with the 18W power section.

lol, for that matter, there aren't many "original" Marshall designs either; they stole most of them.

Thanks,
Josh

JMPGuitars wrote: ↑

Wed 01/13/21 8:04 am

JP77 wrote: ↑

Wed 01/13/21 2:47 am

I'm having some difficulty trying to narrow down which is the latest TMB schematic/layout. It all looks like it is from 200x. If that's the latest available, that's cool. I'll figure it out and work in the latest grounding schemes.

Does the 18watt crowd have a favorite chassis for a head build?

The top of the page, where it says "newest version" in huge letters

viewtopic.php?f=25&t=24430

That's from 2020.

I'm still leaning toward a two channel build.

No preferred chassis? I was considering picking up the chassis from GDS along with the transformers unless there is a better chassis.

JP77 wrote: ↑

Wed 01/13/21 1:18 pm

I'm still leaning toward a two channel build.

The "Modern Classic" series is probably the safest bet for a two channel version.

I have my own chassis made, there are plenty of good options from popular suppliers. The GDS transformers are great.