I have a set of Fostex Pm-2 monitors ... they are loud , clear and transparent ....
after i started reading these forums .. i got psyched up to build a tube - preamp , to give my ipod a signal boost and to sweeten that sterile sound the monitors make !
i originally thought the "foreplay preamp" was the go .. but i cant find any schematics (obviously its copyright)
then i heard something about the "wright - 11 " something or other
the i heard about some aikido pre amp
and then there is some guy "FRED" that has his design.
but i cant for the life of me find ... a schematic
which do you guys recommend ? for hifi applications that doesnt colour the sound tooo much , but just gives it nice touch.
and a schematic if possible!
cheers
CM
after i started reading these forums .. i got psyched up to build a tube - preamp , to give my ipod a signal boost and to sweeten that sterile sound the monitors make !
i originally thought the "foreplay preamp" was the go .. but i cant find any schematics (obviously its copyright)
then i heard something about the "wright - 11 " something or other
the i heard about some aikido pre amp
and then there is some guy "FRED" that has his design.
but i cant for the life of me find ... a schematic
which do you guys recommend ? for hifi applications that doesnt colour the sound tooo much , but just gives it nice touch.
and a schematic if possible!
cheers
CM
just use a basic voltage amplifier stage, its the best sounding by far.
use ecc82, 6922, or 6sn7
check the ratings, 300 volts psu.
make anode resistors around 3x the rp,
can't recall cathode resistor, 1meg input grid resistor, or 470k, same at output, 2uf coupling capacitor.
that's it, and it sounds great
CLClC supply, use hammonds say, either ez81 rectifier or bridge.
dc heaters, CLC filter.
one of the best you will find or hear. others will disagree with tubes, but they are common and do sound fine.
afterwards, you can try output transformer, and a battery bias.
check on the
'read it'
section on the lhs here@
http://www.sjselectroacoustics.co.uk/
lots of info there, get you going, superb design
use ecc82, 6922, or 6sn7
check the ratings, 300 volts psu.
make anode resistors around 3x the rp,
can't recall cathode resistor, 1meg input grid resistor, or 470k, same at output, 2uf coupling capacitor.
that's it, and it sounds great
CLClC supply, use hammonds say, either ez81 rectifier or bridge.
dc heaters, CLC filter.
one of the best you will find or hear. others will disagree with tubes, but they are common and do sound fine.
afterwards, you can try output transformer, and a battery bias.
check on the
'read it'
section on the lhs here@
http://www.sjselectroacoustics.co.uk/
lots of info there, get you going, superb design
cm_ls1 said:
Hi,
An I-pod driving a valve pre-amp ? what is the world coming to ?
/sreten.Edit : Seriously speaking, the PM2's don't look too bad.
As a studio monitor they are likely to lack baffle step compensation.
The best way of driving them from a portable headphone out is
via a pair of decent signal transformers + a dual gang volume pot.
You could add a passive BSC circuit to sweeten the PM2's.
http://sound.westhost.com/bafflestep.htm
/sreten.i was wondering what chassis to use for the pre-amp , i found this hdd enclosure at work ( i was only a "dummy case" with no parts inside , made from brushed aluminium and a white plastic top , there is a pinhole led light on the front , and a mount for a fan at the back , it also well ventilated underneath.
its 160mm square , and around 35cm height.
i might attempt an aikido set up , from all reviews it seems like a great pre-amp , it says that it works with various power supplies , can someone point me in the right direction on what psu and rectifier to use ( do i need a rectifier?) , is the a brand and model you could suggest , and maybe a website that sells them ?
i was going to use 9 pin triodes , 12au7 or something similar ?
thanks !
CM
its 160mm square , and around 35cm height.
An externally hosted image should be here but it was not working when we last tested it.
i might attempt an aikido set up , from all reviews it seems like a great pre-amp , it says that it works with various power supplies , can someone point me in the right direction on what psu and rectifier to use ( do i need a rectifier?) , is the a brand and model you could suggest , and maybe a website that sells them ?
i was going to use 9 pin triodes , 12au7 or something similar ?
thanks !
CM
i was hoping to fit everything in the chassis .. but i might have to use a second one as the PSU, as was advised , lucky we have another 2 or 3 at work.
so i physically wouldnt fit
this is how i pictured it...
so i physically wouldnt fit
this is how i pictured it...
An externally hosted image should be here but it was not working when we last tested it.
I built one per the schematic you posted and it was ok. I added VR regulators and it improved the sound. To be honest the Aikido will blow it clean out of the water without a problem. Its your money and time. My opinion it to skip the 5687 and purchase some Aikido boards from Bas and have something that performs well the first time out.
All of the information that you ever wanted to know about Aikido can be found here:
www.tubecad.com
Blank boards can be purchased here:
http://glass-ware.stores.yahoo.net/newhardware.html
No, I haven't built one yet.
www.tubecad.com
Blank boards can be purchased here:
http://glass-ware.stores.yahoo.net/newhardware.html
No, I haven't built one yet.
ok , it looks like im going to order the aikido pcb board ( i wouldve liked to hand wire everything) but as a first project i suppose it will be easier !
now , should i order the 9pin or octal board ? (which tubes would you guys recommend ?)
and what power supply ? 300-0-300 ? 12v dc , or should i go ac filament ? whats recommended for better results ? is there psu's that have both ?, most that ive seen have 6v and 5v @ 3a or something.
please enlighten me !
now , should i order the 9pin or octal board ? (which tubes would you guys recommend ?)
and what power supply ? 300-0-300 ? 12v dc , or should i go ac filament ? whats recommended for better results ? is there psu's that have both ?, most that ive seen have 6v and 5v @ 3a or something.
please enlighten me !
cm_ls1
Since I have built a number of the 9 pin such as the 6FQ7/5687 combination and 6922/5687, and 6N1p/5687 and also the octal
6SN7/6SN7. I have also built several hand wired Aikido's.
I would highly suggest the 9 pin model first. I would suggest that you follow the Aikido thread from the start and take some notes.
The thread will show you how to wire the Aikido and how to inject some B+ into the heater scheme. You will find that power supply design does effect the possible hum you may get from the Aikido so I would follow the thread suggestions closely. As Mr. tubelab has stated the Aikido boards are also available at glassware.
I have used both the octal and the nine pin as sold here by our own "Bas" and they work great. I also have the octal board from
glassware and it is a great board at a higher cost and more flexability. I have also build hand wired units as stated above.
You can build the Aikido with a board or without but I suggest as a first time project that you purchase a board.
Since I have built a number of the 9 pin such as the 6FQ7/5687 combination and 6922/5687, and 6N1p/5687 and also the octal
6SN7/6SN7. I have also built several hand wired Aikido's.
I would highly suggest the 9 pin model first. I would suggest that you follow the Aikido thread from the start and take some notes.
The thread will show you how to wire the Aikido and how to inject some B+ into the heater scheme. You will find that power supply design does effect the possible hum you may get from the Aikido so I would follow the thread suggestions closely. As Mr. tubelab has stated the Aikido boards are also available at glassware.
I have used both the octal and the nine pin as sold here by our own "Bas" and they work great. I also have the octal board from
glassware and it is a great board at a higher cost and more flexability. I have also build hand wired units as stated above.
You can build the Aikido with a board or without but I suggest as a first time project that you purchase a board.
ok ive ordered the aikido PCB ... he dropped it off in the post as he was leaving to go to the airport , he will be away for a month (lucky me ) , and at the discounted rate.
Now what power supply should i buy for this , i know they say this preamp is not really psu specific, but help me out here -
i found these local suppliers that sell a transformer ( 300v , with 6.3v , and 5v outputs) , from what i understand , the 300v goes to a rectifier , something like a Gz30 or a Gz32 tube , which is connected with the 5v supply ... from there i have to pick out some chokes 30h ? and some capacitiors (electrolytic ?) ... from there that should be my B+ voltage ( does the b+ voltage i aim to acheive have to do with the tubes i want to use ?) for both channels.
Then we have the 6.3v , that should connect to the heater of the tubes , i understand that i can use straight ac for these although i risk it having noise / hum ? , dc is better ?
i was thinking of using 6n1p / 6n6p tubes ? any experience with these? alternatively 12ax7 / 12au7 ( although these need 12v heater which can be acheived from a 6.3v supply if i join 4 & 5 together, and use pin 9 ? )
as you can see im am new to this ... but if its ok , i can ask questions each step of the way , and you guys can pull me up if you see anything wrong
Cheers
CM.
here is the transformer
TR C076 - 300 or 330V per side 80mA, 6.3V/5A, 5.0V/3A
but its only 80milliamps is that too small ?
) , and at the discounted rate.Now what power supply should i buy for this , i know they say this preamp is not really psu specific, but help me out here -
i found these local suppliers that sell a transformer ( 300v , with 6.3v , and 5v outputs) , from what i understand , the 300v goes to a rectifier , something like a Gz30 or a Gz32 tube , which is connected with the 5v supply ... from there i have to pick out some chokes 30h ? and some capacitiors (electrolytic ?) ... from there that should be my B+ voltage ( does the b+ voltage i aim to acheive have to do with the tubes i want to use ?) for both channels.
Then we have the 6.3v , that should connect to the heater of the tubes , i understand that i can use straight ac for these although i risk it having noise / hum ? , dc is better ?
i was thinking of using 6n1p / 6n6p tubes ? any experience with these? alternatively 12ax7 / 12au7 ( although these need 12v heater which can be acheived from a 6.3v supply if i join 4 & 5 together, and use pin 9 ? )
as you can see im am new to this ... but if its ok , i can ask questions each step of the way , and you guys can pull me up if you see anything wrong
Cheers
CM.
here is the transformer
TR C076 - 300 or 330V per side 80mA, 6.3V/5A, 5.0V/3A
An externally hosted image should be here but it was not working when we last tested it.
but its only 80milliamps is that too small ?
Yes the HV output of your transformer is connected to the anodes of your rectifier tube, if it is directly heated then connect the appropriate heater voltage to the cathode (follow the pin out for the rectifier you choose).
You need to be careful how much capacitance you connect after your rectifier (look at the datasheets max ratings). You can add much more capacitance than the max ratings specify by putting a choke before the bulk of your capacitance, 30H would do nicely.
The 12A*7 tubes all have 6.3 volt heaters, you just wire each heater in parallel. Running from AC can be fine, you should twist the 2 heater leads tightly togeather though.
You can run from DC too but apparently AC can be very quite too.
80 milliamps is plenty.
Maybe it was just my bad layout but when i built the aikido (P2P) i got a lot of hiss when using higher gain tubes like the 12AX7 in the first position.
The hiss was only acceptable with a 12AU7 for me.... just in case you experience similar problems down the line.
Regards
Craig
You need to be careful how much capacitance you connect after your rectifier (look at the datasheets max ratings). You can add much more capacitance than the max ratings specify by putting a choke before the bulk of your capacitance, 30H would do nicely.
The 12A*7 tubes all have 6.3 volt heaters, you just wire each heater in parallel. Running from AC can be fine, you should twist the 2 heater leads tightly togeather though.
You can run from DC too but apparently AC can be very quite too.
80 milliamps is plenty.
Maybe it was just my bad layout but when i built the aikido (P2P) i got a lot of hiss when using higher gain tubes like the 12AX7 in the first position.
The hiss was only acceptable with a 12AU7 for me.... just in case you experience similar problems down the line
.Regards
Craig
I would suggest going back to the Aikido thread and reading it from start to finish. It lists a transformer model that will be excellent to use. There are no chokes in this supply and none should be needed. The 12AX7 has way too much gain in my opinion to use in the Aikido circuit. I would suggest a 6N1p or 6922 as the first tube and a 5687 in the second slot. You may end up with a very slight hiss but even this beats the heck out of any hum that other circuits will give.
Aikido line preamp
Hello fellow diyers
This is another strange problem that I hope someone makes
some light on it.
I built the Aikido with a 9 pin tube board and the supply is about
268 volts. The filaments are heavy regulated, DC, 6.3 V right on the money and the tubes are 6922.
I'm using a toroid and to my desmay when I fired it up I noticed
some oscillation on the output signal, coming from the supply.
This one is 100 uF after the full wave rectifiers, a Hammond choke
and another 100 uF bypassed by a 0.1 uF.
As I said there is an oscillation on the signal and about 100 mV of DC at the output. Scoping it out it seems that
this oscillation comes from the transformer but I'm not sure.
Increasing the amount of filtering reduces the ripple a bit but
not interely.
What wonders me is oscillation + DC and also flutuations on the
signal at the rate of the offset going up and down. I tried a few
things already but it doesn't go away. Everything points to the
transformer I bought specifically for the Aikido.
Any thoughts?
Hello fellow diyers
This is another strange problem that I hope someone makes
some light on it.
I built the Aikido with a 9 pin tube board and the supply is about
268 volts. The filaments are heavy regulated, DC, 6.3 V right on the money and the tubes are 6922.
I'm using a toroid and to my desmay when I fired it up I noticed
some oscillation on the output signal, coming from the supply.
This one is 100 uF after the full wave rectifiers, a Hammond choke
and another 100 uF bypassed by a 0.1 uF.
As I said there is an oscillation on the signal and about 100 mV of DC at the output. Scoping it out it seems that
this oscillation comes from the transformer but I'm not sure.
Increasing the amount of filtering reduces the ripple a bit but
not interely.
What wonders me is oscillation + DC and also flutuations on the
signal at the rate of the offset going up and down. I tried a few
things already but it doesn't go away. Everything points to the
transformer I bought specifically for the Aikido.
Any thoughts?
woo hoo ! came back from work and look what was waiting for me
ok can you guys list your ideal tubes / component specs and brand if you where to build this pre for yourselves-
R1 , R5 , R6 , R7 , R12 , R13 , R14 = 1m
R2 , R4 = 200 - 2k ? (depends on tube)
R3 , R9 , R10 = 100 - 470 ohm (1/2w or higher)
R8 , R11 = 100 - 1k (depends on tube)
R15 = 100k
R16 = R15 x (mu + 2) / (mu - 2) eg. 113k for 6dj8
C1 = 0.1 - 4uf ( exceed B+ )
C2 = 0.1 - 4uf ( exceed B+ )
C3 = 0.1 uf (optional)
C4 = 0.1 uf (optional)
C5 = 1 - 10uf ( must exceed b+ )
C6 = 0.1 uf (exceed b+ )
C7 , C8 , C9 , C10 = 10-100uf (Electrolytic must exceed heater ps voltage)
and what power supply ? b+ ? heaters ?
An externally hosted image should be here but it was not working when we last tested it.
ok can you guys list your ideal tubes / component specs and brand if you where to build this pre for yourselves-
R1 , R5 , R6 , R7 , R12 , R13 , R14 = 1m
R2 , R4 = 200 - 2k ? (depends on tube)
R3 , R9 , R10 = 100 - 470 ohm (1/2w or higher)
R8 , R11 = 100 - 1k (depends on tube)
R15 = 100k
R16 = R15 x (mu + 2) / (mu - 2) eg. 113k for 6dj8
C1 = 0.1 - 4uf ( exceed B+ )
C2 = 0.1 - 4uf ( exceed B+ )
C3 = 0.1 uf (optional)
C4 = 0.1 uf (optional)
C5 = 1 - 10uf ( must exceed b+ )
C6 = 0.1 uf (exceed b+ )
C7 , C8 , C9 , C10 = 10-100uf (Electrolytic must exceed heater ps voltage)
and what power supply ? b+ ? heaters ?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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