Biasing the 25W Archon Combo (USA)

[Prina]

Yesterday, after a year of owning it, I wanted to check what the preamp tubes are; they're the ubiquitous JJ ECC83S.

While the protective grill was off, probably the first time ever for this 2019 amp as everything inside looks brand new, playing around with the bias seemed the thing to do. The adjustment port isn't the usual place or documented anywhere that I was aware of; it's behind the grill and recessed about an inch under the jack between the 5881 power tubes. Use a long thin flathead screwdriver to avoid the hot 5881's.

I also checked with PTC about the bias range:
Thank you for reaching out to PRS Guitars. We recommend a bias of around 30mV however you can go down to 25, wouldn't recommend going much outside of that range.
That's where it had been set, likely at the factory and although it seemed to sound a bit better at 31mV it's going back to 30mV.

And a final comment: these amps are a steal in the $500-mid 600 range. Nearly mil-spec PCB with chassis mounted pots and tubes with lots of USA hand wiring:

 

[DreamTheaterRules]

Yesterday, after a year of owning it, I wanted to check what the preamp tubes were, they're the ubiquitous JJ ECC83S.

While the protective grill was off, probably the first time ever for this 2019 amp as everything inside looks brand new, playing around with the bias seemed the thing to do. The adjustment port isn't the usual place or documented anywhere that I was aware of; it's behind the grill and recessed about an inch under the jack between the 5881 power tubes. Use a long thin flathead screwdriver to avoid the hot 5881's.

I also checked with PTC about the bias range:
Thank you for reaching out to PRS Guitars. We recommend a bias of around 30mV however you can go down to 25, wouldn't recommend going much outside of that range.
That's where it had been set, likely at the factory and although it seemed to sound a bit better at 31mV it's going back to 30mV.

And a final comment: these amps are a steal in the $500-mid 600 range. Nearly mil-spec PCB with chassis mounted pots and tubes with lots of USA hand wiring:

Yeah, it’s pretty crazy. Dr. Z Miini Z used goes for 50% more. Maz 8, double easily. Many other 18 watt range amps sell for double the price. Mesa Mark V 25 combo, triple the price. The 25 watt Archon combo is A STEAL!

 

[Dennyz]

Installed a set of JJs 5881 (biased at 31mV) and a Creamback M65 on mine.

That amp is a piece of art. The circuit and wiring is very Soldano-ish.

Considering converting mine to a head format. It became my #1 amp.

 

[Prina]

Installed a set of JJs 5881 (biased at 31mV) and a Creamback M65 on mine.

That amp is a piece of art. The circuit and wiring is very Soldano-ish.

Bet the Creamback sounds awesome; I've heard great things about them.

Agree with the Soldano looks comparison. I've been comparing the clean channel to a JTM45 and will check out the Soldano models some more on the Fractal FM9.

 

[Dennyz]

Bet the Creamback sounds awesome; I've heard great things about them.

Agree with the Soldano looks comparison. I've been comparing the clean channel to a JTM45 and will check out the Soldano models some more on the Fractal FM9.

The amp came with a 16 ohm chinese Greenback which sounded incredible but i had to crank the bass and depth knob to "simulate" the thump and tone of a 4x12/2x12 closed back. With the Creamback M65 (8 ohm, UK made) i have almost the same tone but darker, bigger sounding, with less of that vocal midrange crunch of the GB but not that far. With the Creamback i have the bass and depth set to 7/10. A very robust sounding speaker with a hint of thar pappery Greenback tone.

I think that with this particular amp, the V-Type could be the perfect speaker. Its optimized for 1x12 open back construction.

The clean is very neutral sounding. With the bright cap off is dark-ish with no spike on any frecuency. Perfect for pedals. Bright cap on and it gets fendery. Perfect for a Tubescreamer boosting it or humbuckers played clean. My Prs Custom 22 and my Les Paul with PAFs loves it.

Its an incredible amp, very responsive at pick attack, pickups, guitars and how you set the Eq and Gain. A plethora of tone.

I would describe it like this...
Clean channel: neutral/Fender
Gain channel: Bogner Uberschall-Marshally high gain/Mesa Rectifier-ish

 

[S2C22]

Yesterday, after a year of owning it, I wanted to check what the preamp tubes are; they're the ubiquitous JJ ECC83S.

While the protective grill was off, probably the first time ever for this 2019 amp as everything inside looks brand new, playing around with the bias seemed the thing to do. The adjustment port isn't the usual place or documented anywhere that I was aware of; it's behind the grill and recessed about an inch under the jack between the 5881 power tubes. Use a long thin flathead screwdriver to avoid the hot 5881's.

I also checked with PTC about the bias range:
Thank you for reaching out to PRS Guitars. We recommend a bias of around 30mV however you can go down to 25, wouldn't recommend going much outside of that range.
That's where it had been set, likely at the factory and although it seemed to sound a bit better at 31mV it's going back to 30mV.

And a final comment: these amps are a steal in the $500-mid 600 range. Nearly mil-spec PCB with chassis mounted pots and tubes with lots of USA hand wiring:

I would leave it where it sounds best. Nobody checks or factors in the Plate Voltage on these, or check. Manufacturers are always going to go with the coldest setting possible to extend tube life, when biasing it slightly warmer, (and closer to where it SHOULD be), isn't going to be life and death.

My Archon 50 MKII came from the factory at 24mA. The Plate Voltage is 440, which equates to less than 50% dissipation. That's CRAZY cold, and holding the amp back from its full potential. It's like putting training wheels on it. I biased mine at 34mA, which is closer to 60%. In vintage amps that rely more on Power Tube distortion, people would shoot for 70%. You want a cleaner power section for a high gainer, since it's gain is primarily preamp, so I split the difference. But 50% is too cold, and robs warmth and punch.

 

[Prina]

Agreed that 24mA is really cold for a 50W.

For mine, which only gets cranked when it's running thru the Suhr RL box, sometime I'll check it on the clean channel -> load box which relies much more on power amp distortion for crunch. Too bad PRS doesn't publish plate voltage since it's a hassle to slide the chassis out.

 

[S2C22]

Agreed that 24mA is really cold for a 50W.

For mine, which only gets cranked when it's running thru the Suhr RL box, sometime I'll check it on the clean channel -> load box which relies much more on power amp distortion for crunch. Too bad PRS doesn't publish plate voltage since it's a hassle to slide the chassis out.

I just use a Eurotubes Pro One bias probe. Pretty painless, no poking around.