Need PP KT-88 amp design and KT-88 for triode use?

[Norris Wilson]

Hi Everyone,

I have a friend who is wanting to build a quality KT-88 amplifier to use with his Jordan JX92S TL speakers.

He is considering building an Andea Giuffoli PP 20 watt KT-88 design at the below link.

1. Does anyone have any experience with this amplifier?

2. Do you think the 20 watts of class A power will be enough to drive the 88db Jordan TL with enough authority?

3. Are there any other designs that he should be considering to build besides the Andrea Giuffoli design?

4. Do you know which current production KT-88 that would work well strapped in triode mode with excellent sonic results?

Thanks for all of your help.

Norris Wilson



http://www.audiodesignguide.com/my/pp3.html

[timolien]

Interesting design at

Boully KT88 PP



Gert

[richwalters]

[QUOTE]Originally posted by timolien Interesting design at
Boully KT88 PP
[QUOTE]

Better start gettin' used to circuits scribbled on beer mats

richj

[Brett]

1: Yes. Have built variations of this idea, but used parafeed for the IT as I had no SE IT's at the time. I used 6C45 and 8532's as drivers from memory and like the hot and low operating point of the output stage. It's a good little amp. I personally prefer a full differential design though.

2: It measures at about 11WRMS. The 20W number is a 'peak' power. As for it being enough, I dunno, depends on a lot of factors such as room size, listening levels, use of subs etc. I would consider it just enough, in my (very large) room on 104dB/W speakers.

3: Svetlana winged C, though the EH's are getting good reports from friends

[amperex]

The best are same family of tubes called KT90 generation II in triode connection service. The newer production tubes have quality issues.

Another possible option are perhaps the new manufacture Tung-Sol label 6550 tubes just released. A few reviews are stating the tubes are of quality. I would prefer to read a few more reviews before making any commitment. The tubes have a 35-watt plate that requires a look at the plate current in regard to biasing in your proposed circuit.

[richwalters]

Originally posted by amperex
The newer production tubes have quality issues.

Another possible option are perhaps the new manufacture Tung-Sol label 6550 tubes just released.

That's interesting.........In the past I've been scathing about EI KT90 quality.......busted internal welds /shorts etc .....been so bad that I've had to replace all with 88's. Naturally I moaned to the company....but heard nothing.

If the Tungsol coke bottle 6550's have an anode dissip of 35W+ 6W screen diss..is Tungsol are keeping their cards close to their chest in not saying an "A "version equivalent to KT88. To me it seems pointless in producing yet another 6550 gereric...we are flooded with them, if they produced an A version then they would qualify headon for KT 88 competition....yes/or no ?
(By the way where are the Tung's coke bottles made ?)

richj

[Norris Wilson]

I am not sure what plant is making the reissue Tung Sol tubes for Mike Matthews of New Sensor, probably the same people who make the Sovtek 6550's.

http://cgi.ebay.com/ws/eBayISAPI.dll...99238&tc=photo

[amperex]

One audiophile stated the new Tung-Sol 6550 sounded within 90% of the old Tung-Sol. That is a big statement as the older Tung-Sol 6550 black plate is regarded as the best sounding 6550 ever manufactured.

However, I remain guarded.