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Knight kb-85

audiofred

audiofred

Active Member
Hello All,
I am going to get back to re-building a Knight KB85 amp. Is it worth the extra time of searching for the original output tubes or just stick some Svetlana
6L6's in there? There were 4- EL37's.
I have a pair of JBL Studio monitors 3-way speakers with the 12" woofer. Would the KB-85 be able to make a nice sound??
Are these JBL's from the ineffecient speaker days, where you needed many many watts to get some SPL's??
And another set of speakers for consideration are a pair of Advent's with a 10 inch woofer, also a 3-way system.
Thanks

Fred
 
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I have a KB-85 awaiting rebuild as well. My solution on the EL37 was to set-up an eBay search. After ~3 years I got (8) EL37's which yielded (6) reasonably close tubes.
 
I also have a KB-85 that luckily came with all of it's EL37s.

I have a friend who has three KB-85s and he been running the Russian 6P3S-E tubes in them and says they sound nearly if not as good as the Mullard EL37s.

They can be bought off of many different vendors at that on-line action place.

If you buy some make sure you get the E variety, they are a sturdier tube than the straight 6P3S.

Cheers

Lar
 
yeah . .. EL37's are pricey . . .

I have a matched pair that came out of a $50 tube caddy . . I want to try a EL37 SE amp eventually . . .

I know EL37 is a 6L6 'variant', but wouldn't you have to re-bias for proper operation ?
 
GordonW said:
Wonder how KT66s would sound in place of these?

Regards,
Gordon.
Click to expand...

If they do it is just barely -

a_knightkit_front.jpg
 
Soundmotor and fellow audio folks,
I wish my KB looked as good as yours. I got mine from the Bay and it was actually two units. I'm restoring the nicer looking amp, using the other as a parts unit and spare iron.
And, Gordon, I think there is an issue with the KT66's drawing a lot more filament current than the 6L6GC's or EL37's. There were some useful threads and googling looking for advantage/disadvantages of 6L6's and KT-88 or KT-66's or even 6550's.
I'll stick with the suggestion from here for some Rusky tubes or maybe JJ Tesla.

Would this amp make my JBL's happy or the Advents I mentioned earlier?? I'm thinking that ineffecient speakers won't let the amp do its thing.
This forum is a great place. "Ya'll" are bringing back wonderful memories from my tube days.

fred
 
audiofred said:
Soundmotor and fellow audio folks, I wish my KB looked as good as yours.
Click to expand...

Not mine, off web.

Mine has the chassis bead-blasted down to bare metal. All the plating is gone. When I got it I believe it had been on the Andrea Doria. It was a rusted mess, missing the front-end PCB, & and a host of other problems. Transformers were OK and have been repainted with matte black epoxy-based. They were actually done in the ADS paint shop and look like L200cc's. This amp is a love/hate project as the KB-85 probably has the worst physical layout of any amplifier I've had. The chassis is weak, perhaps half the gauge of a Dynaco ST70 with it's power transformer ~2X bigger. I take it out of the box periodically, stare at it, and put it away.
 
Well, thanks to this forum and what you folks do here, I quit staring at my KB-85 sitting on the shelf, lonely and cold in the basement.
I ordered and will "shotgun" the resistors. I previously "re-capped" everything. The output tubes were broken from a move 4 yrs ago. So a trip to an auction site and I purchased a set of JJ Tesla 6L6GC's.
I had some rememberances of nice tube stuff about 5 yrs ago with a Fisher 500C and then I wanted to play with an ST70.
It's time to hear tube audio again as a steady diet.

Fred
 
May I keep this thread at the top with one more thought??

Has anybody "suped up" a KB-85??? Solid state the 5AR4's for more B+??
Played with the bias?? change from stock setting increase/decrease? Experiment with a modified class of operation??
Wasted effort??? Keep it stock??
Just loose thoughts rolling around, that's all.

Fred
 
I had one of these once, missing the circuit boards and sold what was left about 10 years ago. Should have kept it of course - something about having to pay bills....:tears:

If I remember correctly, the KB-85 is the Mullard 5-20 circuit, almost exactly out of the Mullard book except for the change to dual rectifiers. I would think that good quality EL-34s would just plug right in. It's fuzzy, but I think there's something about the 6L6 that makes it less than an ideal sub - too much heater current? I'd adjust the B+ voltage to suit the EL34s. I wouldn't change the rectifiers to SS - the 5AR4s in this amp are used well within their limits, almost in what I think is the ideal situation for these. Big stereo amps or tube receivers using one 5AR4 are pushing these a bit too much, at least for long life and low power supply resistance.
 
Hi All,

I went for broke and did a complete restore including re-chroming the chassis on a KB-85 that I got off ebay only to find one of the output transformers is dead. I so want to keep this old boy original. Is there anybody out there that may have a extra OPT for sell or trade or be willing to sell or trade the unit? Any condition just as long as it has a working OPT. Thanks, Stan email: everstan1@bresnan.net
 
can you get the part number off the transformer? if not i believe the transformer might be the same as the 25w basic mono amp.

chris
 
Could you use an EL38 and re-wire as needed? They are cheap enough, but you get an anode cap to deal with.
 
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