Kat88 is it any good?? with Klipschorns

[Grog]

hi,
i'm looking for a good valve amp to try with my newly aquired klipschorns.
i've seen a KaT88 for sale at a reasonable price, but i've been reading up about a few problems people have had with this amp.
I don't need huge power (althought he klipsch are 16 ohm i think, so voltage needed)
would i be better off with a secondhand maplin 4-20 (with upgraded optx's)
or a secondhand kel84.
they are all in a similar price point secondhand.
to me the bass is very important, the klipsch have excellent dynamics and depth, i don't want to lose that.
i have no problems at all building my own amp, have scope sig-gen, b&k mic etc

but it seems to be cheaper to buy a secondhand kit. funds are tight, as i've just got the khorns and don't know if i'll like a valve amp.

my system is
downstairs
Khorns
Yamaha DSP-A1
Pioneer DVD575A

upstairs (although i can see this migrating downstairs soon !)
Acoustic precision eikos CD
technics SP10 BBC version. sme s3 arm
Michell Argo / Hera pre
Extensively modified Pioneer A400GTE power amp,
Veritas 40 transmission lines

[alnewall]

Hi Grog, welcome to the forum.
Do you have another name?

I have a Maplin 4-20 somewhere and i suspect that its bass capabilities will not impress you greatly. Even with upgraded transformers, its likely that the kel84 is a nicer amp.

I also use a DVD575a, and have discovered that a separate DAC is well worth the trouble. Though the Pioneer dac is surprisingly good.

[Grog]

my 'real' name's George,
thanks for the advice.
i'm thinking the KAT88 may be the answer, but i hear the opt's are not up to much and the recomended sowter's are £500 ish.

maybe i'd be better saving up and getting a nice 2a3 or 300b kit, shame as i'd have to wait at least 9 months to afford either of these

[pre65]

Hi George-it sometimes helps to indicate your location,there may be local (ish) members with amps who could demo with your speakers.

[Grog]

Hi Philip, i'm in port talbot, south wales.

[Greg.]

Hi George,

I used to have KaT88 which I heavily tweaked following Richard's (moderator here) work. I've now passed onto my son who has had it for several years and remains very happy with it. I never went for the Sowter upgrade as I thought that was a financial step too far. The standard Tx's are not bad and with some tweaking within the chassis the whole amp has a very presentable sound that includes that good deep fast bass typical of KT88's. In your position I would go with this option and not worry about the O/P Tx's at this stage. Upgrading these is very much 'expensive icing on the cake'. I'm sure Richard will chip in on this. His upgrade path and recommendations are still available from him or I can scan and send as it was all published on a previous WAD forum no longer accessable.

Best wishes,

Greg

[Grog]

hi Greg,
if you could scan and send me what you have it would be appreciated.
as you say i think the KaT88 might be the best option, i'm just a bit worried about all the hum/stability problems that people seem to encounter.

[Greg.]

Hi George,

OK, I'll do it if necessary, but all my records are hard copy so it'll take a while to do. I won't forget but lets see if Richard comes back on this first. he is very much the author of the tweaks on this amp and knowing him he'll have plenty digitally stored. I'll ping him with an email/PM. I see he's not visited for a couple of days so he may be away as he usually looks in daily.

Don't worry about the hum and stability issues. Stability was resolved after the initial release of the kit and must of us who had hum got it sorted with very good results.

Best wishes,

Greg

[Richard]

Hi George,

There were indeed a few examples of instability in the first builds of Kit88. I had one of these and worked with Nick Lucas and the designer to resolve it (no choice, mine was humming with red plates!).

In the event, an increase in gridstopper values did the trick. The 6au6 stoppers were increased from 6k8 to 15k and the KT88 stoppers from 1k to 4k7 iirc. Presumably it had been designed and tested with easy load speakers/cables and more reactive loads upset it.

Later changes I made were to lower feedback by 5dB which gave a more open sound in my system. (It also increased the margin of stability by the same dB amount.)

Most folk also changed KT88 bias too (to prevent hot spots on the plates from excessive dissipation) either via the cathode resistors or the fixed bias divider. WAD later incorporated the increased gridstoppers and divider resistors as standard though the circuits I've seen don't show this.

The sound was excellent and the standard TXs were good even though they rang a bit on SW test. Some of us changed to Sowters and these could be run without gridstoppers. My notes include no gridstoppers, changed feedback and bias so probably wouldn't help a lot without the Sowters. Other changes were really just preferred choice of component "flavours".

So, looking back, perhaps it was a design that was a little rushed in bringing to market but it was certainly a very good amp once the niggles were sorted.

Rich

[Ianm2]

I find it strange that noel said it was a gem of an ouput trnasformer, yet rich's findings indicated otherwise.