Diplomat - Matchless DC30's EF86 Channel

[vigilante398]

Quick clarification. Based on an earlier post in this thread, the Diplomat could be used as a pre-amp in an fx loop of an amp? Or also into the front of an amp but will have lots of output available?

Yup, can be used in either case. I personally like running it in front of the amp as a clean boost as it pushes my amp into a really neat overdrive, but it can also be used into an FX return to bypass your amp's preamp and go straight into the power amp.

 

[joelorigo]

Thanks!

 

[Dysvalence]

I personally like running it in front of the amp as a clean boost as it pushes my amp into a really neat overdrive

Does the SMPS provide enough current to run another tube or two?

 

[vigilante398]

Does the SMPS provide enough current to run another tube or two?

Yup, it absolutely does.

 

[zgrav]

Assembled mine yesterday using a tube sourced from ebay. No problems following the parts on the PCB and it sounds nice. Very transparent and the options from the tone control are really nice. Putting it at the end of the effects in front of my practice amp right now, but will try switching it to the front too.

 

[MichaelW]

@vigilante398 is there a significant difference between how the Diplomat sounds with the stepped tone rotary and the Echo Foxtrot with the tone pot?

 

[vigilante398]

@vigilante398 is there a significant difference between how the Diplomat sounds with the stepped tone rotary and the Echo Foxtrot with the tone pot?

Kind of? They both use EF86 at the same voltage so the inherent tone is similar, but there are some differences.

• Echo Foxtrot's tone control is cut only, so even fully cranked it can be a little dark for some uses. Diplomat's rotary tone control can get much brighter and I find it to have a more "focused" sound.
• Diplomat is biased a little hotter so it has more gain on tap
• The circuit Echo Foxtrot was based on was largely designed for bass use and modified slightly to be more suitable for guitar, whereas Diplomat is based on the Matchless DC-30 which is a guitar amp, and some additional tone settings were added to make it work for bass.

 

[MichaelW]

Kind of? They both use EF86 at the same voltage so the inherent tone is similar, but there are some differences.

• Echo Foxtrot's tone control is cut only, so even fully cranked it can be a little dark for some uses. Diplomat's rotary tone control can get much brighter and I find it to have a more "focused" sound.
• Diplomat is biased a little hotter so it has more gain on tap
• The circuit Echo Foxtrot was based on was largely designed for bass use and modified slightly to be more suitable for guitar, whereas Diplomat is based on the Matchless DC-30 which is a guitar amp, and some additional tone settings were added to make it work for bass.

Damn, I guess I'm gonna have to order one.........

 

[MichaelW]

Damn, I guess I'm gonna have to order one.........

Done!

 

[zgrav]

Damn, I guess I'm gonna have to order one.........

Of course you must! Thanks to Nathan there is a new category of DIY pedals to enrich the build collection. So much better than the starved voltage tube amp projects that have popped up over the years.

 

[zgrav]

Playing through the Diplomat into an amp really shows off its dynamic range. I think that is a significant part of what comes across as "transparency". I get why it works at the beginning of the pedal chain since adding other pedals into the mix quickly shows how much compression they bring to the signal chain even for nice growly overdrives. Even then, a bit more dynamic range survives to add shimmer to your modulation based pedals.

 

[caspercody]

Curious, why was R21 (470K) added to your build? I do not see it in the schematic I see online for this channel.

 

[vigilante398]

Curious, why was R21 (470K) added to your build? I do not see it in the schematic I see online for this channel.

R21 was added as a level-dropping resistor on the output, as without it the level is HOT. You're welcome to jumper it to compare, but you'll find unity gain to be right around 8:00 on the level control, which makes it hard to use in a lot of applications.

On the other hand, if you're running straight from this pedal into a power amp, you may want to jumper R21.

 

[Betty Wont]

Just finished mine. It sounds great and it is a very satisfying layout to build. Mine starts to break up after noon on the volume and with the tone and volume all the way up it is a really chunky bass drive.

 

[Smrtokvitek]

As I am scouting for components, I have noticed a 10uF cap for SMPS output filtering rated for 250V, which seems quite risky. I understand it is probably due to the space limit (height), but I would rather use anything rated 300V or more. Is there enough space for a 21mm capacitor in the 125B enclosure? Do you have any experience using lower values, such as 4u7?
And a little note, both C1 and C2 should be low ESR. It may work even if they are not but it will decrease their life.

 

[Betty Wont]

As I am scouting for components, I have noticed a 10uF cap for SMPS output filtering rated for 250V, which seems quite risky. I understand it is probably due to the space limit (height), but I would rather use anything rated 300V or more. Is there enough space for a 21mm capacitor in the 125B enclosure? Do you have any experience using lower values, such as 4u7?
And a little note, both C1 and C2 should be low ESR. It may work even if they are not but it will decrease their life.

I use a 10x20mm 450v 10uf and there is plenty of room.

 

[vigilante398]

As I am scouting for components, I have noticed a 10uF cap for SMPS output filtering rated for 250V, which seems quite risky.

Risky in what way? 400V capacitors fit there just fine, I use 250V because the SMPS is regulated and does not spike above its set value like an AC-fed power transformer-based power section would. At my day job we use capacitors rated for a minimum of double the expected voltage, but as hobbyists we don't need to be as careful. I have been using 250V caps in my builds for years and have yet to run into problems.

 

[Betty Wont]

I’ve decided my favorite tone setting is #2 the 680pf cap. Because that one costs $3 each

 

[MichaelW]

Just painted my enclosure today.....and waiting for some of those $3 caps to arrive from AES heh.

 

[MichaelW]

@vigilante398 Any issues using 5M6 resistors in place of the 5M1's?