Is It Worh Modding An Amp

CV4004 are long life Valves. When supplied with very good measurements, these are proven to be very secure Valves that have a very long usage life.

Note: Measurements shown in relation to Factory Spec' are the only description worth taking on board, I have received verbal descriptions and in nearly all cases they are proven to be very unreliable, causing Seller/ Vendor friction when Valves are wanted to be returned. 

Caveat Emptor is ones friend when purchasing Valves.

It could be a case where a 1000hrs are used by the latest owner of the Valves, the Valves are still presenting a very good measurement, this can result in more monies being remunerated than the original purchase.

This is one of the fuels that stoke the Vintage Valve Market and one I know that has benefitted my choices made for Vintage Mullard Valves.

Alternatively at a later date, an Amp' can be brought in for demo' purposes as a Amp' replacement, that has the same Valves used in the Circuit. This indirectly means that Valves already purchased with a recognised high end sonic quality, can be immediately used on the New Amp' to assist with the assessment. If the New Amp is the preferred Amp' the earlier amp' used can be considered for being sold on with original supplied Valves in place.   

Generally, I would say "yes."

We perform mods on amps and speakers, and reserve "parts swaps" to clearly inferior components. By looking at a photo of the back of the unit, does not appear to be the case here. Without the ability to see the inside, it’s difficult to say, but my guess is that they used "good stuff" on the inside as well. Our "modding" goal is not to paint a mustache on the Mona Lisa, but to try to reveal the sound quality the original designer would have produced if they had a) more time, b) more money, c) "newer" thinking, or other constraints.

The most basic, and surprising, upgrade (for me) is cable quality in both signal and power. Sonic improvements are absolutely shocking in some cases. Snipping off spade and lug connectors and direct silver soldering helps, too. (Warning: going to drop an "F-bomb" here). If you haven’t done so, you might try an audiophile FUSE in place of the OEM fuse. You can usually try and return. And, the unit can be returned to "stock" in seconds. Note, that nothing mentioned above changes internal parts or changes the "basic sonic character" of the amp you already like. Just getting things out of the way that degrade its potential.

We have 2 identical amps on hand. One stock, one not-so-stock. The "modded" amp doesn’t just sound better. It sounds like it was built in a different factory at twice the price of the original amp.

The challenge is finding the "right" tech to do the work with experience with the same amp. Might be easier to find the Matco Tool Guy at a Mary Kay convention?

Good luck.

In most cases, it's probably not a good idea. I definitely wouldn't touch it if it were still under warranty. I got a pair of 60's vintage ALTEC 1570B mono blocks and had them modded using Tom Tutay's mods. These mods made a considerable difference and turned old commercial amps into something special in my two-channel system.

@waytoomuchstuff clearly reflected my points of view on what not to do with pure nonsense ESPECIALLY about FUSE so figure out what's gonna happen after "upgrades". 

No