Point-to-point SLO preamp build w/ relay switching
Moderators: pompeiisneaks, Colossal
Point-to-point SLO preamp build w/ relay switching
Wanted to share my latest project - SLO preamp with relay switching instead of LDRs. I challenged myself to put it together in a relatively small enclosure (250 x 180 x 80mm) and wire the main circuit point-to-point. To make it even more challenging, I designed the layout in three dimensions to optimize signal path and minimize the space. There's a ground bus that everything is connected to. Components are arranged in three Z-layers - bottom layer with power supply components, the layer with components that go from tube sockets to ground, the layer with coupling and grid components. There are also few resistors that go between the top layer and ground bus.
Heaters are powered with 12.6VAC to reduce the current and they are elevated to ~50V. For relay switching I used a relatively simple method. Heater voltage is rectified and regulated to 12V. P-MOSFET is used to drive the multi-colored LED and toggle between two colors designating two main channels. Channels can be switched either using the panel switch or a footswitch.
I intentionally omitted the EQ because I want to use it either with a graphic EQ pedal or connected straight into the interface and have VST EQs applied. It's easy enough to add a shared EQ before the volume pots, slightly more complicated to do dedicated EQs with another DPDT relay.
As far as components go - custom toroidal transformers, alpha pots, russian PIO coupling capacitors, Panasonic HV electrolytics, xicon resistors, miyama switches, JJ tubes, panasonic film 1uF caps for cathodes...
It turned out great. There are no clicks or pops from the relay, voltages are pretty close to the official schematic and noise is very low for a high gain amp. The layout makes it easy to choose between having completely isolated channels or have clean bleed into the overdrive. There doesn't seem to be a big difference but I think I prefer to have them isolated. Connecting two terminals together makes the normal channel always on.
This is how the main module looks assembled. There's one aluminum L profile that holds tube sockets. Using four 50mm hex standoffs I connected two terminal strips with 13 contacts each.
and from the side showing different layers
A few components are mounted directly on the controls
The switching circuit is on a separate terminal strip.
The relay is mounted in a wire-wrap socket soldered directly on the main module
Here's the whole preamp assembled
And from the front. Knob color matches the color of the LED - blue for normal, red for overdrive channel.
The article with more pics and info is here http://diy-fever.com/amps/soldano-preamp-mk2/ will update it with more info and clips soon.
Full sized layout here http://diy-fever.com/wordpress/wp-conte ... out_v5.png
Heaters are powered with 12.6VAC to reduce the current and they are elevated to ~50V. For relay switching I used a relatively simple method. Heater voltage is rectified and regulated to 12V. P-MOSFET is used to drive the multi-colored LED and toggle between two colors designating two main channels. Channels can be switched either using the panel switch or a footswitch.
I intentionally omitted the EQ because I want to use it either with a graphic EQ pedal or connected straight into the interface and have VST EQs applied. It's easy enough to add a shared EQ before the volume pots, slightly more complicated to do dedicated EQs with another DPDT relay.
As far as components go - custom toroidal transformers, alpha pots, russian PIO coupling capacitors, Panasonic HV electrolytics, xicon resistors, miyama switches, JJ tubes, panasonic film 1uF caps for cathodes...
It turned out great. There are no clicks or pops from the relay, voltages are pretty close to the official schematic and noise is very low for a high gain amp. The layout makes it easy to choose between having completely isolated channels or have clean bleed into the overdrive. There doesn't seem to be a big difference but I think I prefer to have them isolated. Connecting two terminals together makes the normal channel always on.
This is how the main module looks assembled. There's one aluminum L profile that holds tube sockets. Using four 50mm hex standoffs I connected two terminal strips with 13 contacts each.
and from the side showing different layers
A few components are mounted directly on the controls
The switching circuit is on a separate terminal strip.
The relay is mounted in a wire-wrap socket soldered directly on the main module
Here's the whole preamp assembled
And from the front. Knob color matches the color of the LED - blue for normal, red for overdrive channel.
The article with more pics and info is here http://diy-fever.com/amps/soldano-preamp-mk2/ will update it with more info and clips soon.
Full sized layout here http://diy-fever.com/wordpress/wp-conte ... out_v5.png
Check out my site with DIY gutars, amps and pedals http://diy-fever.com
Re: Point-to-point SLO preamp build w/ relay switching
Incredible work which I really appreciate since I build preamps into old toasters and space is tight.
Mark
Mark
Re: Point-to-point SLO preamp build w/ relay switching
Fully OCD. I love it.
I build and repair tube amps. http://amps.monkeymatic.com
Re: Point-to-point SLO preamp build w/ relay switching
Awesome
Thanks for sharing
Thanks for sharing
- pompeiisneaks
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Re: Point-to-point SLO preamp build w/ relay switching
HOLY
CRAP
Outstanding work!
~Phil
CRAP
Outstanding work!
~Phil
tUber Nerd!
Re: Point-to-point SLO preamp build w/ relay switching
Thanks everyone!
Adding few quick recordings. The first one is preamp straight into the interface. In reaper I added some EQ, Marshall JTM45 sim and a touch of reverb. The second one is pretty much the same settings but with Timmy overdrive at the front with gain set pretty low and Bass above noon to tighten up the sound.
Cheers
Edit: pompeiisneaks edited and linked the MP3 so it's playable from the site, just add mp3 tags around it by highlighting the link and clicking the "mp3" button in the editor mode.
Adding few quick recordings. The first one is preamp straight into the interface. In reaper I added some EQ, Marshall JTM45 sim and a touch of reverb. The second one is pretty much the same settings but with Timmy overdrive at the front with gain set pretty low and Bass above noon to tighten up the sound.
Cheers
Edit: pompeiisneaks edited and linked the MP3 so it's playable from the site, just add mp3 tags around it by highlighting the link and clicking the "mp3" button in the editor mode.
Check out my site with DIY gutars, amps and pedals http://diy-fever.com
- pompeiisneaks
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Re: Point-to-point SLO preamp build w/ relay switching
Damn sounds good! I edited your post to link the MP3's inline so people can give them a listen right here.
~Phil
~Phil
tUber Nerd!
Re: Point-to-point SLO preamp build w/ relay switching
Thanks, good to know. Here's another one. Timmy OD with gain set pretty low to tighten the bass in front of the SLO (gain at noon). In Reaper I have clean marshall sim (LePou) and two rosen digital impulses panned hard left/right. Could probably tweak the EQ to sound better, but I prefer this to the previous recordings that have a bit of a "digital" quality to them.
Check out my site with DIY gutars, amps and pedals http://diy-fever.com
Re: Point-to-point SLO preamp build w/ relay switching
Super nice PTP, thanks for the documentation. Makes me miss my SLO 100.
Re: Point-to-point SLO preamp build w/ relay switching
Thanks! Few more sounds
My mini telecaster with neck pickup on, crunch channel with a touch of overdrive at the front
Same guitar, similar settings
Another guitar with Dimarzio Fred in the bridge, lead channel with no boost at the front, gain set around noon
One more with ibanez, going after Petrucci's tone. Added V shaped EQ that mimics Mark graphic EQ settings and recto cab impulses. There's a touch of univibe (chorus settings) to fake double tracking.
My mini telecaster with neck pickup on, crunch channel with a touch of overdrive at the front
Same guitar, similar settings
Another guitar with Dimarzio Fred in the bridge, lead channel with no boost at the front, gain set around noon
One more with ibanez, going after Petrucci's tone. Added V shaped EQ that mimics Mark graphic EQ settings and recto cab impulses. There's a touch of univibe (chorus settings) to fake double tracking.
Check out my site with DIY gutars, amps and pedals http://diy-fever.com
- pompeiisneaks
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- Posts: 4222
- Joined: Sat Jan 14, 2017 4:36 pm
- Location: Washington State, USA
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Re: Point-to-point SLO preamp build w/ relay switching
I saw you post that on FB and had someone wanting to have you build them one asap
~Phil
~Phil
tUber Nerd!
Re: Point-to-point SLO preamp build w/ relay switching
Pretty awesome indeed.
He who dies with the most tubes... wins
Re: Point-to-point SLO preamp build w/ relay switching
Wow. Excellent piece of work