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Old 31st March 2006, 12:48 AM   #1
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Default Is this practical

I am building the enclosed amp in a mono configuration. I plan on using
Plitron Out put iron . I would also like to use Plitron chokes in the power supply however the cost is $225 a pop. Is this practical when using a Hammond power xformer that only costs $40.00 (270ex)

is it worth the expense or does the cheap powerxformer negate any benefits?

thanks
J
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Old 31st March 2006, 12:58 AM   #2
hacknet is offline hacknet  Singapore
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you should get a good power transformer. imo, this is where the magic happens : )
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Old 31st March 2006, 01:00 AM   #3
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Default I figured

I figured as much , the good plitron available is not centered taped
so i would have to use a tube bridge recdtifier(four tubes for each amp)

thanks j


If I did use a powertransformer with no center tap and I utilized a 4 tube bridge , could I use the same CLC filter values as in the stereo version attached above?
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Old 31st March 2006, 01:24 AM   #4
arnoldc is offline arnoldc  Philippines
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Ideally you all want the good stuff, but in my case I'd buy the "best" output transformer I can afford.

Good power transformers can be had cheap. They're not that difficult to make compared to output transformers. My transformer winder was the contractor for Xerox when they were still doing business in the Philippines.

Here's what my amps has:

45 amp - Tamura F-475 output transformers, Tamura choke (because it came part of the output transformer deal), custom power transformer, custom second choke.

2A3 amp - MagneQuest DS-025 output transformer, Hammond 300 series power transformer, Hammond choke.

Exception:

10Y/50/300B amp - Hammond 1628 output transformer (old, bought from a friend), Lundahl 1648 power transformer, custom choke.

Quote:
I would also like to use Plitron chokes in the power supply however the cost is $225 a pop.


Quote:
Is this practical when using a Hammond power xformer that only costs $40.00 (270ex)
There have been reports about 270 series overheating. In fact Jim Hagerman changed from the 270 to 370 series to address this issue. The custom transformers I had made are cooler than the Hammonds.

Quote:
If I did use a powertransformer with no center tap and I utilized a 4 tube bridge , could I use the same CLC filter values as in the stereo version attached above?
My Lundahl does not have a center tap and I used a hybrid configuration - 5AR4 + FR107
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Old 31st March 2006, 02:46 AM   #5
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Default B+

arnoldc what is the B+ with the hybrid rectifier and the Lundahl 1648 xformer
And do you use CLC filter with C= 100uf? before and after choke like on the Lundahl website?



ty J
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Old 31st March 2006, 03:48 AM   #6
arnoldc is offline arnoldc  Philippines
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Hi J,

With 0-350V from the Lundahl, 5U4G + FR107, I have 10uF (make sure you don't exceed the maximum capacitance for the tube rectifier) - 10H choke, 100uF I get 380V feeding a 417A driver (10mA) and 10Y (28mA)
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Old 31st March 2006, 04:42 AM   #7
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Quote:
is it worth the expense or does the cheap powerxformer negate any benefits?
I don't think the power transformer is important, as long as it's able to provide the required voltages at the required current, with low winding resistance, good insulation, reasonably high inductance and it doesn't get hot. An electrostatic shield would also be nice.

The power transformer certainly does not need to have a wide frequency response; in fact that would be a detriment, because it would tend to carry the mains-borne noise through to the secondary. Toroid design isn't as suitable as E-I for power transformers.

Quote:
I figured as much , the good plitron available is not centered taped so i would have to use a tube bridge recdtifier(four tubes for each amp)
If you insist on using Plitron for the power tranny, and its secondary is not centre-tapped, then you don't have to use four tube rectifiers. Instead, you can use a hybrid tubes-and-SS Graetz bridge. The negative-going diodes in the bridge are SS and the positive-going diodes are tubes. This arrangement is as noiseless as a tubes-only rectifier and it doesn't lose as much voltage, nor does it have such a high internal resistance.
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Old 31st March 2006, 05:25 AM   #8
arnoldc is offline arnoldc  Philippines
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Quote:
SS Graetz bridge
Here - http://homepages.ihug.co.nz/~rwillis...rectifier.html

And the discussion about its PSUD simulation here - http://forum.duncanamps.com/viewtopi...1366153603097d
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Old 31st March 2006, 11:53 AM   #9
EC8010 is offline EC8010  United Kingdom
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Quote:
Originally posted by ray_moth
I don't think the power transformer is important, as long as it's able to provide the required voltages at the required current, with low winding resistance, good insulation, reasonably high inductance and it doesn't get hot. An electrostatic shield would also be nice.
And, as ray_moth says, a toroid will couple mains-borne noise into your electronics. It's the output transformer that's the difficult thing to get right.
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Old 31st March 2006, 04:08 PM   #10
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Default done

defiinately using plitron output iron.I think I am going to use Hammond 300 series as arnoldc sugests. not sure about B +
voltage yet . looking in to it (using Tj meshplates) 300 or 350
Not sure about the Lundahl 1648 at 380 VB +


thanks
j

and I think the Plitron chokes are out at 225 usd a pop
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