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george craig
Guest
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 Posted:
Thu Dec 09, 2004 6:16 am Post subject:
Re: latest 845 |
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"Adam Stouffer" <adam_stouffer@hotmail.com> wrote in message
news:HZMtd.3704$xa6.193@trnddc09...
| Quote: | Don Pearce wrote:
Having grounded the centre tap of the output valves heater winding,
the circuit will operate. I hesitate to say work, because this is one
of the most benightedly awful amplifier circuits I have ever seen. In
fact, I would call it an effects box rather than an amplifier.
Better?
Tough crowd :)
Adam
I would wire up the driver on the bench and check the Peak to Peak output
and distortion level....choke loading the driver may be necessary....GC |
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Patrick Turner
Guest
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| Posted:
Thu Dec 09, 2004 2:18 pm Post subject:
Re: latest 845 |
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Don Pearce wrote:
| Quote: | On Wed, 8 Dec 2004 14:35:41 +0100, "Ronald" <ln.emoh@sebut.oremilac
wrote:
Hi Pearce ,
I have plenty of clues about all sorts of things. And yes, I know what
I would do with that centre tap. But that is hardly the point is it?
I think that's exactly the point since Adam asked for it .....
The way you put it might smell like starting a flame war , as we
sadly used to here ......
Ronald .
OK - I will spell it out. The circuit will not work, because the
centre tap of the output valves heater winding needs to be grounded.
Having grounded the centre tap of the output valves heater winding,
the circuit will operate. I hesitate to say work, because this is one
of the most benightedly awful amplifier circuits I have ever seen. In
fact, I would call it an effects box rather than an amplifier.
Better?
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Well, we needn't reply to you then.
Patrick Turner.
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Don Pearce
Guest
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| Posted:
Thu Dec 09, 2004 2:18 pm Post subject:
Re: latest 845 |
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On Thu, 09 Dec 2004 23:53:43 +1100, Patrick Turner
<info@turneraudio.com.au> wrote:
| Quote: |
Don Pearce wrote:
On Wed, 8 Dec 2004 14:35:41 +0100, "Ronald" <ln.emoh@sebut.oremilac
wrote:
Hi Pearce ,
I have plenty of clues about all sorts of things. And yes, I know what
I would do with that centre tap. But that is hardly the point is it?
I think that's exactly the point since Adam asked for it .....
The way you put it might smell like starting a flame war , as we
sadly used to here ......
Ronald .
OK - I will spell it out. The circuit will not work, because the
centre tap of the output valves heater winding needs to be grounded.
Having grounded the centre tap of the output valves heater winding,
the circuit will operate. I hesitate to say work, because this is one
of the most benightedly awful amplifier circuits I have ever seen. In
fact, I would call it an effects box rather than an amplifier.
Better?
Well, we needn't reply to you then.
|
He said, by way of reply.
d
Pearce Consulting
http://www.pearce.uk.com |
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Patrick Turner
Guest
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| Posted:
Thu Dec 09, 2004 2:18 pm Post subject:
Re: latest 845 |
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Iain M Churches wrote:
| Quote: | "Patrick Turner" <info@turneraudio.com.au> wrote in message
news:41B71029.8FC10079@turneraudio.com.au...
Ronald wrote:
Hi Pearce ,
I have plenty of clues about all sorts of things. And yes, I know what
I would do with that centre tap. But that is hardly the point is it?
I think that's exactly the point since Adam asked for it .....
The way you put it might smell like starting a flame war , as we
sadly used to here ......
Ronald .
I cannot view the circuit in question since I have lousy service from my
ISP.
Care to send the schematic in a package of about 200 kB?
pdf, jpg, or gif please.
info@turneraudio.com.au
Patrick Turner
The same goes for me. I wouild very much like to see the schematic.
Please send to
tael@kolumbus.fi
Cordially,
Iain
|
Tnx again for the copies of the schematic.
The guy who said it wouldn't work because the cathodes were not connected
hasn't been around tubes very long.
Let's leave him alone, and hope that understanding comes one day....
From what I see of the schematic, the general idea is fine.
Why not cathode bias instaed of fixed bias?
I have found fixed bias in SET or SEUL amps to be less DC stable than
cathode bias, where the cathode R regulates the bias voltage.
OK, there is the issue of the electrolytic bypass cap for the Rk,
but modern types are pretty good, and if about 3,300 uF is used,
or say 2 x 1,000 uF in parallel, with some 4 uF uF of MKP plastic cap,
the bypassing can't be worse than the bypass caps of the power supply, also
in series with the load and the tube.
The 6AH4 seems able to provide the necessary triode grunt for the
drive; there is no grid current in the 845, a blessing really.
Tyhe 2H of the 6AH4 should cancel the 2H of the 845 perhaps quite well.
But you could also bypass the Rk of the 6AH4, and thus lower the driver Ro,
extend the bandwidth a little, and produce slightly more 2H in the driver,
thus maybe get less 2H overall due to cancelation.
But since the po from an 845 is considerable, the thd should be low
at the region where one normally listens.
Patrick Turner. |
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Tim Williams
Guest
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| Posted:
Thu Dec 09, 2004 10:18 pm Post subject:
Re: latest 845 |
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"Don Pearce" <donald@pearce.uk.com> wrote in message
news:41be4b39.15268078@212.159.2.87...
| Quote: | Well, we needn't reply to you then.
He said, by way of reply.
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He's the same way with Phalluson. Which reminds me, you can join him in the
k-file. *plink*
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms |
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