KiT/KaT6550 and fuse blowing inrush current

[Yellow]

Hi again,

So, if you could somehow measure the sound quality improvement moving to a set of Sowters, would it be the equivalent of say changing some super-cheap signal coupling caps to hi-end Silver Paper-in-Oils? Is it that kind of step change, or more so?

Neil.

[Greg.]

It’s not as simple as that, Neil. A change to coupling caps does not necessarily bring a better sound although they can, but it is more realistic to say they may change the sound to the owners preference.

In contrast, fitting Sowter’s has an overall impact on all of the sound. You should notice (once we’ll run in) more authority to the presentation, more control over sounds, particularly in the deep bass and high treble regions and particularly, a much more transparent and revealing ( you’ll hear more of what is on the recording, particularly micro detail) sound. This brings improved speed and decay on notes (especially in the bass) and high sounds are more realistic such as high hat cymbals. You should also get a more three dimensional sound stage with better separation between voices/instruments.

In my opinion, once Sowter’s or other upgrade output transformers are fitted, it is then the time to start experimenting with coupling caps. Remember, Richard, on his WAD KiT88 fitted Sowter’s and went around the houses trying different coupling caps and finalised with the original orange drops which initially came with the kit. Boutique component options are not always the best choice. As said, they change the sound but do not necessarily improve it. However the variety available does allow us to alter the sound until it fits our ears and we arrive at a sound we like.

[Chris]

Greg the Sowter's upgrade looks like worth considering, was it a straight drop in replacement?

Chris.

[Greg.]

Originally Posted by Chris

Greg the Sowter's upgrade looks like worth considering, was it a straight drop in replacement?

Chris.

Sorry Chris, no. You have the option of surface mount ‘fully shrouded’ or ‘drop through’. Fully shrouded can be used most easily as it requires the chassis to be drilled in four places to mount it simply on the chassis surface. However, in my opinion, it’s the ugly looking option. Drop through requires the existing chassis hole to be opened up and new fixing holes drilled. This looks best (same orientation as original but a bit bigger) to me and what we have in Intenso’s amp. Cutting out the extra metal from the chassis should not be too difficult to do if you have a Dremel or other suitable tools. Importantly, cutting this bigger access for the output Tx’s does not interfere with anything else inside the chassis.

[Chris]

Thanks for that Greg, will have a look around for a suitable tool to cut the chassis, will practice a few times on some scrap metal. Also the wiring up of the Tx’s is that similar to the original or are they different coloured wires?

Chris.

[Greg.]

I believe if you choose Sowter UO82, looking at their current spec, there are some differences to wire colours. My advise would be to phone Sowter in the first instant and discuss with them what you want to do. Since the Tx’s were fitted to Intenso’s amp, Sowter have made changes to their products and other models are now available for 6550 and KT88 valves. Sowter have always been very amenable to discussing customer needs and advising on the best way forward and I have no doubt they will still be familiar with the original WAD KiT/KaT 6550.

[Chris]

Thanks again Greg for your very informative and helpful advice.

Chris.

[Greg.]

I hope you get a good result, Chris. Maybe if you do this upgrade you could record it here for the interest of others.

I should emphasise that the KiT/KaT 6550 is now an old amp and other areas would benefit from attention. A typical example is contained within this thread.

http://www.world-designs.co.uk/forum...ead.php?t=7785

The quality of the original PSU electrolytic caps (1 - 5) were pretty poor in the first place (also used in the WAD 2A3 PSE, and probably other amps), so if you still have those fitted, they need replacement pronto. The replacements I did for Intenso recently was well timed as the originals were showing signs of bulging (one particularly badly) and the newly fitted Mundorf are, to my understanding making a very big difference and improvement to the sound. Of course, the original upgrade as suggested by WAD at the time in the DIY supplement is a very good idea, albeit, you might want to use something other than paper in oil coupling caps (such as polypropylene) and Blackgates are now almost unobtainium, but other makes come close. If you like paper in oil, Jensen are good, readily available and can be bought directly from the manufacturer which I previously found cost saving.

I consider the WAD KiT/KaT 6550 one of the finest amps WAD ever produced, and that includes the original 300B PP circa 1995. If you have a 6550, it is well worth persevering with. An absolute classic still capable of providing a sound quality that will better or match anything currently on the High Street available for several thousands of pounds.

[Intenso]

I can only echo what Greg has stated and since we replaced the electrolytic caps to the Mundorfs this 6550 amp has really started to sing. I can't imagine I will ever need another amp...