Search found 90 matches

by Badside
Thu May 06, 2021 4:47 pm
Forum: Marshall Discussion
Topic: Marshall Standby switch deletion and bias tap design
Replies: 25
Views: 3969

Re: Marshall Standby switch deletion and bias tap design

The preamp and phase inverter filter caps in marshalls are only rated for 350v to 500v (depending on the amp). In many cases you risk blowing these caps unless you use the standby switch. For example, a 100JH has 600VDC across the standby switch, while the phase inverter cap is only rated for 450v....
by Badside
Wed Feb 01, 2017 7:32 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Re: Demo of my cathode-biased tube-rectified 6V6 Plexi

Reverb should go through some kind of effects loop, I use an interrupt type passive loop to drive reverb and delay. Sounds good. It is going through a loop (a slightly modified version of the one in Merlin's book). Reverb sounds perfect, but 15W means not a lot of headroom so reverb gets compressed...
by Badside
Wed Feb 01, 2017 7:30 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Re: Demo of my cathode-biased tube-rectified 6V6 Plexi

Littlewyan wrote:Is that 56K on the 16Ohm tap?

The amp sounds good!
56k on the 8 ohm tap

Thanks
by Badside
Wed Feb 01, 2017 2:56 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Re: Demo of my cathode-biased tube-rectified 6V6 Plexi

Newer demo with more tweaks (including the smaller NFB resistor)

https://www.youtube.com/watch?v=3bWiXUqG_5A&t=361s

Starting to sound pretty good IMHO
Having never owned an amp that made less than 50W before (save for my 8W JCM8 which is more of a toy), it takes some adaptation
by Badside
Mon Jan 30, 2017 1:41 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Re: Demo of my cathode-biased tube-rectified 6V6 Plexi

Ah cool glad you sorted it. Does the presence control work well? If not you might want to consider changing the NFB resistor to 82K as at the moment you don't have much feedback with that 100K. Sounds good though :). I struggle to get a clean tone with my 20W Master Volume amp when the gain and mas...
by Badside
Sun Jan 29, 2017 4:36 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Re: Demo of my cathode-biased tube-rectified 6V6 Plexi

Ah cool glad you sorted it. Does the presence control work well? If not you might want to consider changing the NFB resistor to 82K as at the moment you don't have much feedback with that 100K. Sounds good though :). I struggle to get a clean tone with my 20W Master Volume amp when the gain and mas...
by Badside
Fri Jan 27, 2017 4:01 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Re: Demo of my cathode-biased tube-rectified 6V6 Plexi

Changing the voltage divider to 470k/22k pretty much fixed the loop's volume drop. Also, swapped a smaller coupling cap in the lead channel (0.0033uF), and experimented with a 12AY7 for more clean range

https://www.youtube.com/watch?v=Jn6mz9ROHDY
by Badside
Wed Jan 25, 2017 9:28 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Re: Demo of my cathode-biased tube-rectified 6V6 Plexi

Nice amp man :). Good tone. I've never seen a low power switch like that before, thats pretty cool! Maybe try changing it to a triode/pentode switch so it keeps the distortion at a lower volume. It will change the tone but you might like it. With regards to the Effects Loop, try setting it up how S...
by Badside
Wed Jan 25, 2017 8:58 pm
Forum: Marshall Discussion
Topic: Demo of my cathode-biased tube-rectified 6V6 Plexi
Replies: 11
Views: 2723

Demo of my cathode-biased tube-rectified 6V6 Plexi

https://www.youtube.com/watch?v=tF9a8yhygy4 I did a complete video log of the build if anyone is curious. It's built entirely from scratch: https://www.youtube.com/playlist?list=PLqC_WjyYCKZHSq071HgWoueuDdyoHHHWm There's a schematic and description on my website of what it WILL be when it's complete...
by Badside
Fri Oct 07, 2016 12:21 pm
Forum: Marshall Discussion
Topic: kt66 in a stock 18watt?
Replies: 7
Views: 1503

Re: kt66 in a stock 18watt?

6V6 yes, KT66 no
by Badside
Tue Oct 04, 2016 12:44 pm
Forum: Vox/Hiwatt Discussion
Topic: Morgan AC20 layout or schematic
Replies: 12
Views: 11078

Re: Morgan AC20 layout or schematic

Interesting. So my analysis wasn't too far off. The EF86 is not triode-strapped (that didn't make much sense too, but I'm no EF86 specialist), and the switch also switches B+ (turning off the unused tube, and sending the signal through the same coupling caps, which explains why the coupling cap sele...
by Badside
Thu Sep 29, 2016 2:54 pm
Forum: Vox/Hiwatt Discussion
Topic: Morgan AC20 layout or schematic
Replies: 12
Views: 11078

Re: Morgan AC20 layout or schematic

If you MUST copy that amp, there are some very clear gut shots if you Google for it, you can clearly make out the circuit and read most cap and resistor values. Looks like a pretty basic AC15-type circuit, with a switch to select an EF86 or 12AX7 preamp tube, and a neat little VVR control on its own...
by Badside
Tue Sep 27, 2016 11:11 am
Forum: Marshall Discussion
Topic: Anderton '64 reissue JTM145 - any info?
Replies: 442
Views: 117662

Re: Anderton '64 reissue JTM145 - any info?

So did anyone ever figure out how the JTM145 offers two volume knobs? It sounds QUITE different from the JTM1, I doubt it's just a JTM1 with a full tone stack. Here's my theory: one of the designers gave some clues about the JTM1 and JCM1 on another forum, and one trick they used on the JCM1 is to h...
by Badside
Sun Sep 25, 2016 12:53 pm
Forum: Technical Discussion
Topic: Calling Supro experts: which version of the 1624T to build?
Replies: 4
Views: 2174

Re: Calling Supro experts: which version of the 1624T to build?

I guess I figured out why the change in tremolo circuit: the original one had the Intensity control as a plate load, aka it had B+ on it. It'll work (Alpha 24mm pots are rated for 500V), but it's not ideal.

So I guess I'll stick with the 2 triode tremolo (which keeps DC off the pots)
by Badside
Fri Sep 23, 2016 4:57 pm
Forum: Technical Discussion
Topic: Calling Supro experts: which version of the 1624T to build?
Replies: 4
Views: 2174

Re: Calling Supro experts: which version of the 1624T to build?

No expert by any means but always on the edge of getting one of Ken's 24 kits to see what tones would/could be available. Not sure how close it is to a dual tone http://tubeamplifierparts.com/amp-kits/supro-amp-kits.html#! D It's pretty much exactly a 60's Dual Tone (the 2nd schematic I shared): ht...