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Old 6th August 2010, 07:33 PM   #291
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Quote:
Originally Posted by tangmonster View Post
200V Ac will give 282V dc That is still a 82V drop.

I think you can safely drop the 200Vac to 180Vac(254Vdc)


With 9Vac my lm317 is sitting at 75C which is too high. Using a 6.7c/w heatsink.


Long story short I will need to get a different transformer......

170Vac and 7Vac should do nicely

For now I am going to experiment with a 10ohm 50W resistor on the primary of the transformer to drop input and output voltages

170Vac and 7Vac should do nicely
anyone else just have finished his PS and have the same problems?
After this Im a little bit unshure what PT Ive to buy.
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Old 7th August 2010, 08:54 AM   #292
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Last night I experimented with putting a 60W light bulb in series with my transformer primary to drop the secondary voltages on both my 230V and 9V secondaries.

Even on 7.6V ac the 6.3V lm317 circuit did not work. I was only able to get out about 4.5V DC max.
I am going to do some more experimenting but it seems that it might need 8V AC minimum to be able to function. And with 9V the lm317 was hitting 75C in temp so I don't know?

What is the total current is drawn by the 4 heaters?


I will let you guys know as soon as I finish my testing today.
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Old 7th August 2010, 09:22 AM   #293
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Originally Posted by tangmonster View Post
What is the total current is drawn by the 4 heaters?

every tube heater current is about 320mA, tl. +/- 1,3A
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Old 7th August 2010, 12:10 PM   #294
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I got mine running!

I dropped my input voltage a bit with a 150ohm resistor on the primarty of the transformer.

measurements:

AC input to powersupply

220V ac

8.5V ac

DC Voltage measurement over first 220uF 400V cap 265Vdc

i put my 220R 5W resistor back

DC voltage measurement over second 220uF 400V cap 249Vdc

voltage measurement over 2 x 4700uF 16V capacitors 8.5V dc ,the 8.5V seems a bit low. not entirely shure why this is ,but i will have to measure this with an oscilloscope to see how it varies.

6.3V is steady.
200V output is steady

all temperatures are in die low 40C

I am listening to The wailers - babylon by bus.

Sounds awesome!
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Old 7th August 2010, 12:15 PM   #295
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Very well balanced!
On my previous el cheapo dj mixing phono preamp I had to set the treble and bass up to get this correct tone. now it just sounds correct the way i like it.


Will a 10k ohm potentiometer be to high of a load for this preamp?
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Old 7th August 2010, 02:50 PM   #296
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Hi tangmonster!
Do you finis Phono?? and test it?
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update 06/14/2013 :http://www.audiodesignguide.com/DAC32/index2.html
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Old 7th August 2010, 02:55 PM   #297
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Tangmonster you can use 10K volume if you have high input impedience amplifier but to get best from this GREAT preamp use 50k or best 100k. Use switched attenuator with tantalum of caddock resistors or DACT attenuator... And with valve or very high quality Mosfet amplifier.
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Old 8th August 2010, 08:26 AM   #298
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Yes quanghao

Its working!

Thanks deej49. I am currently building a class a amplifier based on the krell ksa 50 design. This preamp will be used on it.
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Old 8th August 2010, 08:48 AM   #299
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Quote:
Originally Posted by tangmonster View Post
Yes quanghao

Its working!

Thanks deej49. I am currently building a class a amplifier based on the krell ksa 50 design. This preamp will be used on it.
Hi! What your test it??
And can you show me the sound it?? please
I want se your advance!
Thanks!
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Old 8th August 2010, 09:05 AM   #300
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Default 100K volume.

I cannot state strong enough that 50% of sound quality will be lost with even a high quality Alps volume control. Even the Audio Note for US$100 is poor compared to DACT or a set of switched resistors. Over 20 years we have carried out 100 blindfold tests.

DACT is best and worth saving for.

I have finished building my Phono preamp but I have a strange fault in one channel and even though I have 40 years experience in design of valve I cannot yet find the fault. One channel has higher gain by 20% but when I put my finger on top of R43 the gain becomes same as other channel. I have changed everything except the valve socket. I have used ONLY the very best components.

So I have not yet listened but the RIAA accuruacy is very good. Square wave perform also good.
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