This project began well over a year ago, transforming and shape-shifting along the way. Ultimately we ended up with “Hi Gain #3” in all of its distorted glory. This custom build features four EL34 power tubes pushing 100 watts with four 12AX7 tubes in the pre-amp and driver positions. This one ended up in the hands of my long time friend, and the biggest Neurosis fan I know, Jason Friedman.
The original concept was a modified circuit based on old Laney designs but has since become something completely different. The input feeds two cascaded gain stages with their own level controls labeled “Drive” for the first, and “Gain” for the second. There is a voicing switch over the Drive control which simultaneously increases distortion and tightens bass. Signal then goes through an active tone stack featuring Treble, Mid and Bass controls. The active tone stack offers a unique tone over the classic cathode follower driven stack, in which the tone controls adjust the gain of each band. This gives the player a little more versatility in the character of note break-up and attack.
Next the signal feeds two paralleled gain stages for a smooth transition from overdrive to distortion, while keeping noise at a reasonable level. The phase inverter circuit is almost verbatim from the classic “long-tailed pair” design with the inclusion of a post-phase inverter “Volume” control. This type of master volume is much, much more suitable to controlling the perceived volume of your amplifier than older, typical circuits. It is a whole lot easier to get that “cranked” tone at lower volumes with this control.
The power amp circuit is derived from classic Marshall and Hiwatt circuits with typical ammendments for reliability and longevity. I omitted the ubiquitous “Presence” control and opted for a “Resonance” style control labeled on #3 as “Room”. Since the aim of the game was modern high gain tones, albeit with plenty of classic influence, the Room control is useful in squeezing out chest-thumping bass that modern metal guitar tone requires. Although I outfitted the amp with EL34 power tubes they can easily be swapped for 6L6s, KT66s, KT77s, 6550s, Kt88s, etc etc. Even a rugged set of 6V6s will sound great in this amp for a little less power output. Almost every custom Steamboat Amp, and this one included, comes with bias monitoring jacks and adjustment so that the user can easily swap and replace tubes as necessary, avoiding those
often costly visits to the ol Tech.
Besides the bias monitoring bank on the back panel, the player can switch from 100 watt to 50 watt power settings. The bias and plate-to-plate impedence do shift slightly from one setting to the other but will not do any harm to the amp. 4/8/16 ohm switchable paralleled output jacks allow maximum versatility for speaker cabinet selection as well as two line outs for driving secondary slaves or recording devices.
All of this was built in a 17.5″x6.5″x2.5″(!!!) enclosure. As you can see from the gut shots the chassis is jam packed, yet noise and thermal management is perfectly under control, thanks to attention to detail and a smart grouding scheme. The head cabinet is vented at the top and almost all of the heat rises straight up out of the amplifier.
We had some fun at the studio recording some silly heavy metal riffs… check ’em out –
Hi Gain #3
Track 1
Track 2
Track 3
Clip 1 played by Jason Friedman, Clips 2 and 3 played by Harrison Jacob
EDIT 4-10-11: I lost my hosting for these clips and they are now MIA, I will try to get them back up ASAP
Next up … Custom 18 watt, the Steamroller 300, and more!
