Silktone Parallel 25w 1x12 Class A Tube Combo Amplifier Ivorytone

A 25 Watt Parallel Single-Ended Tube Amp! 
If it’s not obvious yet, I really like single-ended amps. Their ability to deliver nuance, richness and harmonic texture is unmatched when done well. They offer a different sound quality you simply cannot get from a push-pull amp but single-ended amps to date have been limited mostly to 5-10 watts. I really leaned into this with the design of the original Silktone Amp but I still get one request more than any other: more power.

The easy path would have been a higher powered push-pull version! They’re inherently lower noise, smaller transformers, higher power. It’s just easier and cheaper all around to make a 25W push/pull amp - but what you gain in power you end up losing in sound quality as they also cancel harmonics and introduce crossover distortions I’m not crazy about. I wouldn’t call it worse, just different. I didn’t want that - so I took the hard path. A 25W single-ended amp. I wanted to capture the rich single-ended KT66 tone the Silktone Amp has become known for but expand on it and give it a voice of its own.

Comparing this amp to the Silktone Amp what you’d immediately notice is more volume, more bass, more chime, more texture, more everything. The bass response is insane, it can get super low without saturating or farting out and has such a thick and present delivery of sub harmonics when driven. I love throwing a downtuned guitar or even a bass through it and just letting it rip. The new pine cab makes the upper mids really shine through too, it’s so open and resonant without sacrificing too much focus and sweetness - cuts through a mix like butter. The highs! With the help of the pine cab and bright mode this is our most chimey amp to date but it never gets harsh or piercing. Taking a note from the Micronaut and adding a feedback loop kill switch took this thing even further - it shifts the whole character of the amp to become more open, dirtier and grittier with more touch sensitivity. Mode II plus raw silk is fuzz city, a place I often hang.

From heart-melty jazzy r&b tones, to crunchy hard-rock bangers, to downtuned C-std doomgaze - I use this thing for every variety my tastes require. - Charles Henry

Design Notes

Soursound Transformers - Soursound is quickly developing a reputation for making the best audio transformers on the planet for good reason. I wanted to do this amp in the past but the transformer companies I worked with before wouldn’t take it on. They didn’t want to make a small batch completely original design (since there’s nothing that exists to model it after.) Single-ended output transformers have to be huge compared to a similar power push-pull design. The only thing I could find were HiFI transformers and they sound terrible for guitar. In comes Soursound. I mentioned the idea to Sours - he said “fuck yes!” and then completely knocked it out of the park. All vintage-style paper layer wound, of course.

Pine Cab - The Parallel uses a pine cab to reduce weight and increase live sound resonance and presence, this balances really well with the increased bass response of the new transformer designs and allows for more focus on the upper mids.

Tube Isolation - Speaker cabs vibrate, there’s no getting around it. In a tube combo amp when you start getting into moderate power the vibrations really mess things up, tubes have fragile expanding materials inside and they ring and rattle like crazy with all the vibrations of a combo amp! This is a huge reason head+cab tends to sound so much clearer. I wanted to reduce tube noise as much as possible with this amp so I designed a chassis sub-plate for mounting the tubes - isolated by soft grommets to separate the tubes from the cab vibrations as much as I could. The clarity approaches that of a head now and tube rattle is nearly non-existent!

Low-noise - A lot of care has to be taken in building a quiet single ended amp without killing all the good vibe. Rather than over-filtering the noise with big capacitors we use Hi-Fi grounding techniques, selected parts and big chokes - and carefully hand-wire everything to keep noise to a minimum.

Silktone Speaker - Again the Silktone Ceramic speaker sounded better than anything else tried. With an American style thin seamed cone, British style magnet and vintage style paper voice coil formers this thing never stops sounding awesome. Sweet mids, growly lows and an open delicate top end.

Features & Specs

Mode I & II

1. High amount of negative feedback to make the amp more balanced and clean and controlled for those beautiful silky clean tones, the silktone amp runs this way
2. Kills the negative feedback loop to give the amp more gain and harmonic texture, this lets the power stage behave in its natural state not cancelling out any distortions/harmonics. It’s incredibly lively and responsive compared to mode 1 and can get a lot more gritty.

EQ Modes

• Chiffon - Allows use of finely tuned treble, mid and bass controls to shape the amp however you’d like. The range of the knobs offer extremely useful variations. Treble never gets too grating, mid can go from full scoop to fat searing lead, bass can be dialed back to tighten your tone or pushed to really move some air.
• Bright - Same as Chiffon but brings some more chime to the top end.
• Raw Silk - Bypasses the EQ controls for a huge gain boost and reveals the natural tone of the amp.

Reverb

• Dwell - Controls the amount of signal going into the reverb tank. Lower settings offer a subtle plate-like reverb to nicely enrich and fatten your tone while higher settings can take you to drip-drip splashy surf land.
• Mix - Controls the amount of signal after the reverb tank mixed in with the clean.

Attenuator: 25W to 1W reactive load, super transparent so it only changes volume and not tone.
Tubes: 1 x 12AX7, 2 x 12AT7, 2 x KT66, 1 x 5AR4
Size: 21.25” x 18.5” x 10.75” @ 45 lbs