Quad 306 Restoration & Upgrade Kits
**NEW** Not confident soldering components into your amp? No problem as we now offer a full upgrade service. See below for details.
A much under rated little amp, the Quad 306 is a great performer even as standard; punchy and more detailed than a standard 405 to these ears. With a few mods however, it really is a cracking amp. As always, replacing the ageing original electrolytic capacitors improves all areas of the sound. The incredible LME49710 is once again chosen, this time as it is not strictly in the audio path, but is employed as a dc servo to prevent dc voltage on the outputs, because it is a much lower-noise device than the standard TL071; this really sweetens things up, releasing more detail and gaining better definition and control. The Kit 2, fits larger psu smoothing caps for improved bass response and also adds 2.2uF film cap decoupling to the zener diodes supplying the opamps, removing ripple from the opamps supply. Key capacitors in the signal path and bridge are also changed for closer tolerance/better sounding parts. The Kit 3 takes things even further and is the icing on the cake. This replaces the signal path resistors for the fabulous Arcol carbons, which improves detail slightly but adds a wonderfully musical tone to the amp. The opamp supply regulating zener diodes are also decoupled with larger caps, this time 100uF per rail. The gain of the amp is also reduced to ~1.5v for full output, reducing distortion and improving the signal to noise ratio.
The Quad 606 is basically a beefed up, higher power version of this circuit.
Also coming soon: Quad 33 & 34 pre-amp kits and Quad 303 power amp kits.
Quad 306 Kit 1
4 x 6800uF 50v Panasonic smoothing capacitors
2 x 100uF 63v Panasonic FC
2 x LME49710NA Opamps
Instruction Sheet
Kit Price: £27.00 Components Only
Fitting Service Price: £62.00 Includes fitting, testing and insured return UK postage
Quad 306 Kit 2
4 x 10,000uF 50v Panasonic Snap-in Low-ESR
2 x 100uF 63v Panasonic FC
2 x LME49710NA Opamps
4 x 2.2uF Film Decoupling Capacitors for Zener Diodes
6 x 330pF Wima Polypropylene
2 x 180pF 1% Silvered Mica
2 x 47pF 1% Silvered Mica
4 x Binding Posts
Instructions
Kit Price: £65.00 Components Only
Fitting Service Price: £110.00 Includes fitting, testing and insured return UK postage
Quad 306 Kit 3
4 x 10,000uF 50v Panasonic Snap-in Low-ESR
2 x 100uF 63v Panasonic FC
2 x LME49710NA Opamps
4 x 100uF 16v Rubycon ZA Decoupling Capacitors for Zener Diodes
4 x 100nF MMK Film Decoupling for Zener Diodes
6 x 330pF Wima Polypropylene
2 x 180pF 1% Silvered Mica
2 x 47pF 1% Silvered Mica
2 x 330nF Wima MKS4 + 10nF Vishay MKP1837 bypass
10 x Arcol Carbon resistors for signal path
4 x Binding Posts
Instructions
Kit Price: £70.00 Components Only
Fitting Service Price: £130.00 Includes fitting, testing and insured return UK postage
Components and Accessories
LME49710HA TO99 "Tin Hat" - Price: £12.00 each
Binding Post BLACK - Price: £2.50 each - Fits perfectly into original chassis holes
Binding Post RED - Price: £2.50 each - Fits perfectly into original chasssis holes
Amplifier For Sale
This late edition (1994) Quad 306 is cosmetically as good as it gets, and has been fitted with our upgrade kit 1. This involves replacing all of the electrolytic capacitors with new low-esr versions. Not only does this improve reliability, it's also incredibly beneficial to the sound quality. The opamp in the feedback section has also been changed to the fantastic LME49710 which dramatically improved detail, dynamics and stereo imaging whilst removing the grainy sound of the original part.
The output connectors have also been upgraded to proper binding posts to enable the use of spade, banana or bare-wire terminations.
The sound is now highly detailed, very natural and incredibly dynamic. A lack of grain and harshness whilst maintaining a very airy and open sound allow long-term listening with no fatigue.
Quad 306 Upgraded Power Amp: £250
