832 TWEEKS

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Nick
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#181

Post by Nick »

Maybe, but I bet the 300b will sound better with a CCS in the CF load.
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Mike H
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#182

Post by Mike H »

Sez you :lol:

I baggsy choke


12AT7 aka ECC81, does seem a mite under-run for one of them.

ECC83, OK

.
 
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Nick
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#183

Post by Nick »

Ahh, well, maybe so, but I was talking about better than a resistor. Using a choke in the circuit Phil gets a bit trickier. Could do it though. move the cap from before the 300b to before the pentode.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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Mike H
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#184

Post by Mike H »

Shure nuff I was messing about :D

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pre65
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#185

Post by pre65 »

Nick wrote:Yep, it does seem a bit of a odd place to be if the valve you have matches the curves. Not sure it would be my choice of a op point.

Using a CCS could work out well in this case. I would suggest setting the CCS for 4ma and changing the cathode resistor to 620R. Should give you about 200v on the anode, I would connect to the top the CCS to the B+ on the output transfomer and ignore any decoupling so you have the most voltage to play with.
I'd forgotten about this vital bit of info, now that GM70 is singing again this better be my next little project. It will be good to hear 832a (and QQV07'50) again after a reasonably long absence.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
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pre65
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#186

Post by pre65 »

I have started to tidy up what was left of the original wiring, as this was my first home build the standard was pretty disgusting !

With only using half of the 12AT7 and a simple phase splitter there will be less to wire up anyway.

I noticed I had also put in two 12AT7 grid leak resistors (1M and 100K) but as that gave 91K it was not a problem. The earthing arrangements will be tidied up and simplified a bit, the old bits of bus bar will go and full star earthing employed.

Not much time to play today but might get a chance to do some more tonight.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
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Mike H
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#187

Post by Mike H »

I remember that, about the 91k. Assuming it's the same


 
 
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pre65
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#188

Post by pre65 »

It lives again !

It sounded a bit "sharp" with the 12AT7 (ECC81) so I have put in the ECC82 that Andrew I gave me to try eons ago. It was to lower the gain a bit.

Now I remember why I like it !! :wink: :lol:
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
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pre65
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#189

Post by pre65 »

As it has been a while since I posted a picture of this amp (my first scratch build) I have a picture of it. Mainly for the benefit of newer members.

It has top and bottom "legs" which make it a doddle to work on. :wink:

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

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
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Mike H
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#190

Post by Mike H »

I've seen that, it's actually quite clever
 
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Dave the bass
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#191

Post by Dave the bass »

Shoddy.

DTB
"The fat bourgeois and his doppelganger"
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Mike H
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#192

Post by Mike H »

That means he likes it. :D

Na na na-na na


 
 
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Dave the bass
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#193

Post by Dave the bass »

Mike H wrote:That means he likes it. :D

Na na na-na na


Bah! Rumbled!

DTB
"The fat bourgeois and his doppelganger"
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pre65
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#194

Post by pre65 »

I took the 832a amp to Thomas's place yesterday where the Essex/nearly Suffolk/Beds/Kent brigade had a mini fest.

After the event DTB was quizzing me about how the 832a grounded grid was wired up.

Doing some research this morning it seems I was in error, so now the grid is grounded and no 1K or 390K in the way.

Thanks Dave for noticing that faux pax on my behalf, and it actually seems to sound a tad better now as well. :D
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
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Dave the bass
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#195

Post by Dave the bass »

No prob's.

I love picking holes in your constructions! :lol:

DTB
"The fat bourgeois and his doppelganger"
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