upgrades to Kat6550

[Yellow]

Hi
It seems that all of the highly useful posts from a few years ago on the WAD Forum have evaporated and I'd like to ask a familiar question about upgrading components.

I have a KaT6550, and want to upgrade it massively. I have PP signal caps already and decent hook-up wire, but I'd like some more info about various other components that yield massive sonic benefits when upgraded.
I hear a lot about Black Gates, but I never see what type of BG cap and where they benefit the most.....carbon or metal film resistors (AN/Shinkoh/Allen Bradley.....).......PP or Cu PIO signal caps, copper or silver wire.......a million questions......

Any specifics such as R13 was great with such and such, or C7 upgraded with a "xxx" was the best £££ I've ever spent.......

Help please!

Neil.

[Yellow]

.....anyone????

[david]

Hi Yellow,
The place to start is what was offered as the standard WAD upgrade kit:

Cathode bypass caps and coupling caps. Cathode bypass should be Black Gates-K series best or standard (good).

For the coupling caps use your favourite brew: Audio Note Copper were the original WAD upgrade offer, I personally think Mundorf Gold /Silver are the very best, others like Soniqs etc and of course it depends how much you want to pay.

You should certainly upgrade the input cable to Soniqs or something similar from the mouse tail wire supplied.

Resistors to try changing are those around the signal / driver valve carrying the signal input + grid stoppers. I prefer Shinkoh first and Kiwami second.

***************************************

Next up is the main psu caps. Black Gate psu caps come expensive but you can change the one that smooths power for the driver signal valves-100uf electrolytic for a Black Gate wkz. Then chan.ge the main psu electrolytic for good polyprops such as Solens.

That gets you some way towards the spec you heard my KAT34 running KT88s all those years ago, although that used Kiwames throughout and was silver wired.

Biggest bang for buck increase is the mods before the asterisks.
Hope that helps,
David

[John T]

Hi Neil,

Good to see you're still in the land of the living!

I did all the usual "upgrades" to my KAT power amp and the KIT integrated I built for my son. Namely C15,16,17,18 and C9,10 replaced with Blackgates. C11,12,13,14 replaced with Jensen PIO's (I don't like polyprops in this position!). ECF80 heater supply converted to DC. I also had trouble with one of the 6550 wirewound cathode resistors R35,36,37,38 (those awful white ceramic jobbies!) I replaced them with Mills equivalent - from Nick Lucas at Hi-Fi Collective. I also bypassed all the power supply electrolytics with polyprops (.1 and .01uf from RS) in my KAT. Finally, in the KIT I replaced internal co-ax with silver plated copper.

None of the above were done all at one time to my KAT. They were added "bit by bit" to judge "improvements". The Blackgates certainly were money well spent even though they must have taken at least 200 hrs to settle down. The Jensens have also earned their keep!

I must admit in not being totally convinced with the DC supply to the ECF80's and bypassing the power supply capacitors - even though I know others are pleased with these mods. The same can be said with the silver coated co-ax in my son's KIT (my KAT still has the bog standard wire supplied with the kit and we can't hear any difference!)

However, the most immediately noticeable "improvement" was with the Mills resistors. Possibly, because they are non-inductive, there was an immediate improvement to the "top-end".

All the above need a fair bit of time to settle down - in which time you've grown used to the sound and forgotten what the original was like!!! - that's why my son's amp has proved to be a useful bench mark.

Well, there you are Neil, that's my contribution for what it's worth! We all have different experiences with so-called upgrades - I'm sure both system and the room also have their effects. I'm also convinced that once a fair bit of cash has been expended on the purchase and fitting of "quality" components it's easy to convince oneself that there must be a dramatic improvement to the sound! Not always the case methinks?

All the best,

John.

[david]

Hi John,
Yes, I forgot to mention the Mills which I fitted from scratch. And Neil, you may remember the difference between the stock kit and my upgraded one. It was considerable-but cost several hundred pounds taking you close to the type of improvement you might get by buying a WD88 kit instead!

I used my KAT34 as a mobile lab to test everything and learn the results. But now I know 300bs rule!
David

[JerryT]

Hi

I agree with the above. But there is an order in my mind.

I am convinced with the ECF80 DC supply mod using schottky diodes and a CRC bridge. I'd do this soon.

Perhaps after replacing the cathode caps with BG and the interstage caps with PIO or whatever you prefer. I'm using the 'more expensive' Jensen Copper in oil that replaced the cheaper Al/tin in oil caps I had before. If I could afford to use the Audionote 'arm, a leg and several internal organs upon death' then I most surely would (but need the lottery to oblige for it to happen in my lifetime!!).

In my particular amp. I found fiddling with circuit wiring to have some effect - pure silver better that that supplied, mostly - different screened cables sounded different but I've returned to shark wire after a number of more expensive options. Resistor changes at this stage were inconsistent in overall effect except for putting good quality 68R 7W balance resistors on the plates of the rectifiers to balance their operation. This definitely improved the clarity as well as reducing the bill for rectifiers that flashed over.

Better PSU caps have a significant effect at this stage. I'm back with Jensen's best electrolytics for the first four and a BG WZ for the fifth (applied to the ECF80 and therefore having the biggest effect was my rationale since I couldn't afford 5). Bypassing the Jensens has a positive effect but I'd wait until after the next stage.

Better valves now make a big difference.

I'm currently using Mullard (yellow label) E80CF, Tung Sol 6550 (replacing Svet KT 88 very successfully), and GE (nos) 5U4GB.

Changing resistors, wiring or by pass caps now can clearly be heard. As can the difference between running in triode, pentode or ultralinear modes. Mine is currently running in triode mode with basically standard wiring and resistors - it was set aside and the bootique resistors and wiring stolen for other projects, then the KAT6550 was reinstated when the mains transformer on the project gave up the ghost. Maybe I'll get around to refitting the 'better bits' - but triode mode pleases me now with sensitive loudspeakers (not built before it was mothballed) and a passive pre amp. I couldn't get on with pentode mode at all .... and UL is fine but not quite as ... I don't know what ...... but just like I preferred Lulu over Dusty over Cilla, it's currently Triode, UL, Pentode.

I've found that after a certain point you are more tuning your amp to the sources and speakers you use than making it better in measurable or absolute terms.

Hope this helps. Trust your ears. If it sounds good to you then it is good. If the TV ever sounds better go to a concert or gig and retune your ears!

Jerry

[Richard]

Originally Posted by david

I used my KAT34 as a mobile lab to test everything and learn the results. But now I know 300bs rule!
David

Hi David,

Are you still using the WAD 300bpp monos?

Rich

[david]

Hi Richard,
I sold my 300b monoblocs and am now (still….) building a 300b stereo WAD clone (actually a pair!). Time is tight so progress is slow!

Most of the learning of good and bad and others’ experience has been carried over into these! As you know I built a Pre 3 which enjoys daily use thru the Kat 34 amp which is still going strong!
David

[Yellow]

Hi everyone

WOW - Seems like the old WAD threads again, and info coming back......great to hear from you all. Yes - I'm still here with my WAD KaT6550 running nicely, but I'd like to upgrade at some point.

I've done my mains cables and that is RFI filtered too. I have Audio Note AN-V interconnect to my pre and after some lobg deliberations, I have attenuated my pre's inputs to cope with the CD's o/p (3V)!!! :-0

Sounds pretty good though normally! But every now and again, I get a crackle from something and when the volume is completely 'zeroed', it makes a weird chirping noise which has only started in the last couple of months.

David - I remember your amp well. I remember thinking it was in a different league so will take on board your comments. Are you still using those caps made from "bee-spit" or whatever it was (Jupiters)?? (They did sound good!!)

I may re-build my pre-amp around my existing case, but I do not have any good circuits that have a highish input sensitivity. In my opinion, 300mV is way too low for a typical 2V+ CD o/p.

Shinkoh's and a sprinkling of Kiwame and Audio-Note resistors is the direction I am heading in - I'd just want to know where to put what to get great result without spending a fortune!

Best wishes,

Neil.

[Richard]

Hi Neil, good to see you here again

Hi David,

A PAIR of 300bpp! I'm impressed. Will you biamp with them or some other reason (they're not really that unreliable )?

Good luck with the build(s) it's a great amp and very easy to tune to taste.

I asked about the monoblocs as I bought a pair a while back and really must have another go with them.

Rich