The Leak Varislope II is one of the most iconic tube preamplifiers of the golden age of British hi-fi, designed to work together with the Leak Stereo 50 power amplifier via the characteristic umbilical cable. In this article, the complete restoration of the Varislope II is documented with a technical and philological approach: chassis cleaning, replacement of out-of-spec components, and recovery of original functionality without altering the design. No spray jobs or improvised fixes, but a serious restoration, with measurements and attention to both safety and the historical value of the unit. If you really want to understand how to bring a Leak preamplifier back to life the right way, here you will find a real and detailed example.

This article can be considered as the conclusion of the one about the restoration of the Leak Stereo 50, to which this preamplifier is connected via an umbilical cable. Click here to read the article on the LEAK Stereo 50.

As happened with the Stereo 50, since it had passed through the hands of the same technician, the Varislope 2 was also greasy and sticky. After removing the tubes, I started here as well by washing the chassis…

Once everything is clean, working becomes much easier. The restoration work was less demanding than on the power amp: here, fortunately, not all resistors were out of tolerance, so I limited myself to replacing the bad ones and all the electrolytic and oil capacitors.

Given what is often said online, I want to clarify that the use of carbon composition resistors is not as essential as some claim. There are people who find units where the old resistors were already replaced with perfectly honest carbon film resistors, and they remove them all to reinstall composition resistors, claiming it is necessary to preserve the “Leak sound”. I am not against using carbon composition resistors, but objectively they are noisy and unstable: they tend to slowly drift in value (usually increasing). Their main advantage today is that they can withstand short peaks of voltage or current much better than other types without failing. But that is all.

In a circuit where there are low-level signals, RIAA networks, filters or even just tube bias networks, finding resistors that within a few years have changed by 20 percent from their original value, or that are already at tolerance limits when new, only causes problems. When someone talks about the “sound of composition resistors”, without realising it, they are saying that after installing them (with imprecise values) the circuit distorted differently than before, certainly more. And we are back to the usual point: some people call a sound with more distortion “beautiful and faithful”.

The same person who removed the “awful” film resistors to reinstall “beautiful and expensive” composition resistors to preserve the LEAK sound then replaced (rightly so) all the original oil capacitors, because they were leaking, with polypropylene ones. So, let us be honest: MAYBE different resistors change the sound by 0.1 percent… while the capacitors change it by at least 50 percent. If one wants to keep the exact original tone, one should look for NOS paper-in-oil capacitors, not polypropylene. So, who are we kidding?

Therefore, if I open an amplifier and find that all the carbon composition resistors are out of spec, as happened with the Stereo 50, I replace them without hesitation with common carbon film resistors: they work perfectly, they are accurate and do not drift over time. In the case of this Varislope, I only replaced the resistors that were out of tolerance and left the others which were still good. I instead replaced the capacitors with excellent NOS film capacitors, not paper-oil, so the sound will be slightly brighter in the high range. Real paper-oil capacitors, the old ones, tend to darken the sound.

Another issue with the Varislope 2 that no one seems to mention is that the RCA input connectors are too close to each other. Even the smallest and cheapest Chinese RCA plugs I could find were too large to fit correctly: as you can see in the photo, they touch each other. Imagine trying to use modern hi-fi RCA connectors which are even larger.

Since I did not want to drill holes or mount connectors randomly, ruining the chassis and the originality of the preamplifier, I made a simple adapter, without frills or unnecessary complications. I know some lovers of fancy snake-skin cables will be horrified, but honestly, just look at the cable that connects the preamp to the power amp. Or look at the cables they used back in the day on these units…