EL34 / KT66 SET

What people are working on at the moment
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pre65
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#136

Post by pre65 »

Paul Barker wrote:yes, as long as you have a cathode bypass capacitor.
Oh yes, I have a cathode bypass cap.

Thanks Paul, that makes things a tad more simple.

Mike has re-jigged some component values for me (thanks Mike :wink:) because the choke is not the same as before, but still 48ma ish through the interstage or OPT depending which is connected.
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#137

Post by Mike H »

Don't believe we was last here 2 years ago :shock:
 
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pre65
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#138

Post by pre65 »

Mike H wrote:Don't believe we was last here 2 years ago :shock:

Tempus fugit. :wink:
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#139

Post by Mike H »

He does, he does
 
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#140

Post by Paul Barker »

pre65 wrote: 48ma ish through the interstage or OPT depending which is connected.
This sets you up good for the 600 ohm secondary.

were you to use the 200 ohm secondary option then to exactly balance the dc flux you would have to use 25mA driver, though this is quite possible say with the 6V6 or EL84. It is however a redesign of this other amp.

So I would go with 600 ohm if I were you.
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pre65
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#141

Post by pre65 »

600 ohms it is then. :)

The valve bases are in, heaters and input lead connected and boards fixed in position.

That's all for today, got a few vital bits coming from RS tomorrow.

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#142

Post by pre65 »

I've come to a stop now, can't do any more till the RS package is delivered.

Once these amps are finished they can be tested in the system with the BIG 5K Hammond OPT, and if all is well I can then start to modify the 833a amps to cathode drive. :D
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#143

Post by Mike H »

Hello where did those bits of wood come from?
 
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#144

Post by IslandPink »

Mike H wrote:Hello where did those bits of wood come from?
I think they came from a tree, Mike :D
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#145

Post by pre65 »

Mike H wrote:Hello where did those bits of wood come from?
I think it was from an old display wall unit I broke up.
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#146

Post by pre65 »

My RS parcel came late afternoon. I think everything is wired up now, but I won't test it tonight. I'll do a final check of all the joints in the morning then try plugging it in.
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#147

Post by pre65 »

I did my visual checks this morning, everything seemed OK so I plugged them in.

No sound. :( :?

After some checks with the DMM, and guided by a faint whiff of overheated component, I traced the fault to the anode CCS on the gain section of 6DN7. They had both been used on another amp (can't remember which one), but I was surprised both had expired.

Anyway, two new ones were fitted and wired up and now they both work. Just listening to Auberge as the first test track and sounds good. HT is a bit low, but I started with a 1uf first cap and I will try a 1.5uf next when I can get hold of a pair.


So, now they are up and running it's time for major surgery on 833a. 8)


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#148 Re: EL34 / KT66 SET

Post by pre65 »

Just to show that my KT66 (as a triode) SET monoblocks, designed by Mike H (to my requirements) and using a 6DN7 to drive the KT66, are alive and well. :D

Today I'm using them as normal amps, but they also have been used to drive the mighty 833a.


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The only thing necessary for the triumph of evil is for good men to do nothing.

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#149 Re: EL34 / KT66 SET

Post by IslandPink »

Nice ! - good to see again.
"Once you find out ... the Circumstances ; then you can go out"
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