I have bought 2 transformator (each 2 A) i use mount pcb transformator.I use it for back to back system to get a best with minimum result. However,i'm eager to build using tube rectifier but i don't have CT in transformator (because i use back to back transformator the output of the trafo is 0-220 without centertap).If i use fullwave rectifier, i should build a "virtual ground".
So,i use bridge diode rectifier
I will try to build the best PSU for this tube with a very small ripple.Maybe i will add some zener diode to smooth the ripple. And use some transistor to provide some current.
How about the heater supply?Is it worth if i use only AC without regulator?How about a DC for the heater?
In 12au7 i have some choice to decide which voltage of the heater should i use 6/12v?What is the different between that?
regards
---------
TomZ
So,i use bridge diode rectifier
I will try to build the best PSU for this tube with a very small ripple.Maybe i will add some zener diode to smooth the ripple. And use some transistor to provide some current.
How about the heater supply?Is it worth if i use only AC without regulator?How about a DC for the heater?
In 12au7 i have some choice to decide which voltage of the heater should i use 6/12v?What is the different between that?
regards
---------
TomZ
i'm going to say some stuff now
which others may disagree with:
AC heaters will be fine for THIS linestage
i have had no problems with 6.3V AC heaters
solid state rectification will be fine
use ultra fast recovery diodes
like uf4007 or whatever
you will still be pleased
and save some money
regulators and valve rectifiers sound different
whether better depends upon your preferences
dave dove
which others may disagree with:
AC heaters will be fine for THIS linestage
i have had no problems with 6.3V AC heaters
solid state rectification will be fine
use ultra fast recovery diodes
like uf4007 or whatever
you will still be pleased
and save some money
regulators and valve rectifiers sound different
whether better depends upon your preferences
dave dove
Hi,dave dove!This is my project report to build this simple preamp:
1.Finally i use this configuration for my PSU: 22uF-->100r-->100uF-->100r-->220uF+220k parallel as a bleeder.
I got a a very smooth ripple.My mains supply is 220v.I use back to back sytem using 2 transformator (each 2 ampere).I do some test and get only 207VAC after back to back.After through bridge rectifier,it should be 293VDC.
My question is, in the SJS's website this 12au7 preamp only need 280VDC not 293VDC,so,how to drop the voltage until 280VDC?Should i use voltage divider?
Or, use 293VDC as a supply but do some changes in Rplate's value?How to calculate this Rplate's value?
Need ur help please!
regards
-------
TomZ
1.Finally i use this configuration for my PSU: 22uF-->100r-->100uF-->100r-->220uF+220k parallel as a bleeder.
I got a a very smooth ripple.My mains supply is 220v.I use back to back sytem using 2 transformator (each 2 ampere).I do some test and get only 207VAC after back to back.After through bridge rectifier,it should be 293VDC.
My question is, in the SJS's website this 12au7 preamp only need 280VDC not 293VDC,so,how to drop the voltage until 280VDC?Should i use voltage divider?
Or, use 293VDC as a supply but do some changes in Rplate's value?How to calculate this Rplate's value?
Need ur help please!
regards
-------
TomZ
Attachments
thomgun
the bleeder resistor does not go into psud
if you right click that
select change
select constant current
set to 20mA
you now have 280V
if you change C2 to 20uf watch the rise time/line
it will shift to the left
this indicates a faster psu
you still have enough smoothing
and it's cheaper too
when are you going to build it?
dave dove
the bleeder resistor does not go into psud
if you right click that
select change
select constant current
set to 20mA
you now have 280V
if you change C2 to 20uf watch the rise time/line
it will shift to the left
this indicates a faster psu
you still have enough smoothing
and it's cheaper too
when are you going to build it?
dave dove
Hi,
I,m a newbie too!! 'vef got an Eico HF-12 Integrated amp and it has a12au7(it's the version1) preamp at Valve2. an au7 has an amplification factor of about 40. If you can accomplish the power supply with a few resistors and capacitors you might even be able to run it at tour house line of 220. Mine runs at 185vB+. The two sections are connected in series to get the gain so you would need two of them for 2 channel. If you use Mullards the sound is especially sweet. I've never heard this in combination with a solid state power amp though. If you need the tone controls look at the eico HF-81 schematic for the values. Actually the HF-81 would be the best place to look since it's 2 channel and has all the information in one spot. You should be able to find a free one at:
http://users.rcn.com/fiddler.interport/HF81.HTM
click on the schematic button
Remember you only need the valve 2, from the volume control to the place where the tape monitor jack connects for a preamp.
steve
I,m a newbie too!! 'vef got an Eico HF-12 Integrated amp and it has a12au7(it's the version1) preamp at Valve2. an au7 has an amplification factor of about 40. If you can accomplish the power supply with a few resistors and capacitors you might even be able to run it at tour house line of 220. Mine runs at 185vB+. The two sections are connected in series to get the gain so you would need two of them for 2 channel. If you use Mullards the sound is especially sweet. I've never heard this in combination with a solid state power amp though. If you need the tone controls look at the eico HF-81 schematic for the values. Actually the HF-81 would be the best place to look since it's 2 channel and has all the information in one spot. You should be able to find a free one at:
http://users.rcn.com/fiddler.interport/HF81.HTM
click on the schematic button
Remember you only need the valve 2, from the volume control to the place where the tape monitor jack connects for a preamp.
steve
My progress report to build this tube line preamp:
I still do some changes on the PCB because i use a small chassis. I wouldn't put the transformator and the tube outside the chassis, that's why i try to reduce the size of the PCB.
Here is the PCB. Please take a look at my pcb:
Regards
----------
TomZ
Tube Preamp 12au7 board:
I still do some changes on the PCB because i use a small chassis. I wouldn't put the transformator and the tube outside the chassis, that's why i try to reduce the size of the PCB.
Here is the PCB. Please take a look at my pcb:
Regards
----------
TomZ
Tube Preamp 12au7 board:
Attachments
thomgun
your pcbs all look OK
but i have never used pcb
i cannot comment on your DC heaters
i've never bothered with them
a cheap choke will be worse than resistor
i have tried hammond 157g 30H 40mA
and they do work ok
i don't know if you can get them
but
your power supply looks fast enough to me
when are you going to build it? ;-)
dave dove
your pcbs all look OK
but i have never used pcb
i cannot comment on your DC heaters
i've never bothered with them
a cheap choke will be worse than resistor
i have tried hammond 157g 30H 40mA
and they do work ok
i don't know if you can get them
but
your power supply looks fast enough to me
when are you going to build it? ;-)
dave dove
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