133 Dalmeny Drive, Prestons NSW 2170, Australia +612-96074650 & 0412-203382

  JLTi Oppo Player        CD & DVD Player Upgrades        JLTi Tube Amps   

World-Wide Distributors
JLTi BDP Oppo Player
Oppo Level 4 Details
JLTi Phono - Back Again
JLTi EL34 & KT88 Amps
What is Terra Firma?
CD/DVD Upgrades FAQ
Contact Us
Elsinore Speakers DIY
Elsinore Project Kits
JLTi EL34 Wins Shootut
About Joe Rasmussen
JLTi Interconnects
JLTi Review & Comment
Tubes & The Gainclones
DIY Tube Gainclone
Joe's FVP Page
Joe's Equipment Photos
Fletcher-Munson Curves
Joe's Photos
Real Vs False Claims?




We have covered a lot of ground, let us leave the more theoretical behind and deal with more practical matters, like the Power Supply and critical Wiring.

I think it can be appreciated that a circuit diagram only tells so much about wiring and especially the technique that a designer or DIY’ourselfer might employ. Earthing is now taken for granted as very important not just for best sonics but also to keep an amplifier from going unstable. The latter is certainly the case here. A badly wired Gainclone can have all sorts of buzzes and noises, also the heatsink might feel too warm even though there is no signal passing through – most certainly a case of oscillations and watch out for your tweeters!

I certainly have my own ideas, both practical and intuitively. I think in terms of AC and DC currents ALWAYS running in loops, and different loops must not interfere with others. This is difficult to explain in a few words and this won’t be the place.

Critical View of Speaker Return Wiring

Please look carefully at the diagram below. It is critical that the load of the loudspeaker is terminated as shown. I can give you a long and well argued reason for it, but this will have to suffice: All IC amplifiers are internally compensated at a point in its circuit where its gain is produced. Across this gain is a small capacitor and at the point it connects back to acts as a comparator. This 'compares' to something that must be a signal ground. The problem is that the signal ground is usually derived from the negative power supply terminal of the IC. At very high frequencies this can create problems with the return load. The two 1000uF caps should be mounted close to the positive and negative supply terminals and there common (ground or 0V) must be where the speaker's load also returns. If this is not strictly adhered to, then irrespective of what other ground techniques used, you can expect less than optimum stability and other undesirable load/cable sensitivities.

The below suggested wiring diagrams incorporate the above principle. Follow them carefully.

Two Grounds

In our IGC circuits we have TWO Earths, we will call them “S”  for signal and “G” for ground, indeed “G” can also be called Power Supply Ground or “PSG”.

This is how it is applied Single Common Transformer: 

This is how it is applied for Single Common Transformer for Left and Right Channels:


Separate Transformers for Left and Right Channels:

For the NON-tubed version:

The TWO earths can clearly be seen here, they are the two black round pads. It can also plainly be seen that the Power Supply uses “G” but the input Signal uses “S”. They are tied together by a single wire.

Thick lines indicate heavier duty wiring. One that I found particularly critical is the wire from between the two 1000uF electro caps (0V) going back to “G”. Use good quality multi-strand wire with very low inductance.

It is important that IF using the Tube Version, that it too gets its Signal ground from “S”. So in technique in the two versions are much the same:


Re the power transformer, follow the usual recommendations. Some like using separate 160VA toroidals for each channel (but a single 160VA common for both channel does work and I've tried it). You can do that or use a common toroidal for both but may then want to use something like 300VA.

Whatever you do, the Bridge and 1000uF caps must be separate for each channel even if common secondaries used. So the diagram above must be repeated for each channel. My strong recommendation is the 1000uF/50V Panasonic FC cap. The Bridge I used is four 10A 100V Schottky Diodes (in TO-220 packages) and make a discrete Bridge.

Here is my suggested Power Supply – keep in mind I am NOT supplying a PAINT-BY-NUMBERS project, this is for the serious DIY’ourselfer.

Main Power Supply

Note that I use a feature also used in the commercial JLTi Hybrid Tube Integrated Amplifier. When power is connected to the IEC socket the Tube Buffer powers up and stays in Stand-By mode. The Power Switch then only turns On of Off the Gainclone output stage. This so-called ‘Permanent Stand-By Mode’ means that when amp is plugged into AC, make sure that the Power Switch is set to OFF. In this way we avoid rude noises of the Tube Buffer as it stabilizes. 

Tube Buffer Supply:

The 2 x 1000uF/50V may I suggest that you also use the same Panasonic FC caps here. The 1uF/100V must be a suitable film type, NOT an electro. I recommend a 30VA Toroidal Tx, 25V-0V-25V. I use four 1A 1000V FRDs as a discrete Bridge. Together with the Panasonic FC caps, this makes a Split Rail Power Supply, plus 35V and minus 35V.

The Filament Circuit: This can be powered by a small transformer rated no less than 5VA. The 5R6 1W slows down the initial filament current, better for long term life.

The rest should be self-explanatory. Be sure to apply all Power Supply ZERO volts to the “G” ground, and NOT “S” signal ground.

For NON-Tube version IGC, just pare down above.


Join Us On




Send mail to joeras@vacuumstate.com with questions or comments about this web site.
Copyright © 2003-10 Joe Rasmussen & JLTi
Last modified: Monday June 08, 2015

Just had a terrible thought. If "intelligent design" is unscientific, then who will design our audio equipment?