Now that I am converting to a "Silent Studio", here is another one of my "too many" Tube Amp Heads.

This particular Jet City JCA20H head has a popular Mod - the addition of the Variable Depth Control. This is a potentiometer (knob) installed on the back panel of the amplifier head. It is implemented via a common modification involving the installation of a pot and a capacitor within the amplifier's negative feedback loop.  This control allows users to adjust the low-end response and Bass depth, providing a way to tighten or loosen the low frequencies similarly to how a Presence control adjusts the Treble. Nice enhancement of an already great little Amp. This example has seen light Studio only use and is in excellent functional and cosmetic condition. This JCA20H has a fresh compliment of JJ tubes.

Background:

Mike Soldano is co-founder of Jet City Amplification.  He is the company's lead designer and the mastermind behind its product line, which includes the JCA20H.  Soldano launched Jet City in September 2009 with the company's stated goal to provide boutique-quality tube amplifiers at affordable prices by leveraging Soldano’s decades of design experience.  The JCA20H is explicitly designed by Soldano, utilizing circuits similar to his high-end Soldano Astroverb and SLO amplifiers, but manufactured in China to keep costs down.

From the Manufacture:

Overview

-Pure, simple, and full of tube tone, the Jet City JCA20H delivers from a single-channel amp with absolutely no gimmick features to dilute the all-tube signal path. Elegance of design both inside and out deliver unflinching reliability in an Amp. With full EQ control and separate Preamp and Master volumes, the Jet City JCA20H can deliver spanky cleans through crunchy overdrive.

Specs

--Covering: Black Tolex

Controls:
-- Preamp Gain
-- Bass
-- Middle
-- Treble
-- Master
-- Presence

-- Rear panel mod: Variable Depth Control

Tubes:
-- 3x 12AX7 Preamp
-- 2x EL84 Power

- Rectifier: Solid State
- Cabinetry: Multi-ply, void-free hardwood
- Chassis: 16 gauge, cold-rolled steel
- Output Power: 20 watts into 16 ohm or 2x 8 ohm speaker outputs
- Input Power: Multi-tapped power transformer at 100v/120v/220v/240v and standard IEC connector
- Dimensions (H x D x W): 9 x 9 x 19.5 in.
- Weight: 21.3 lbs.