Hi, i'm a newbie in tube. Actually, i want to build a preamp to accompany my gainclone chipamps.I need to build a very simple preamp (beginner).I found many schematic, and i'm difficul to choose the best simple preamp.
I have a question:
1.Which is the best;srpp or single ended preamp?what is different between them?
2.Can anyone give me an information about how to build a good power supply for tube preamp?
Actually, i want to use 2 transformator using back to back design(not custom transformator).So,it will produce about 240Vac.But,I'm difficult to find the combination of the CRC filter(CLC filter is expensive for me,especially the price of the choke). I have tried using CRC filter and using 220r&50uF (C-R-C-R-C-R-C-R-C), it's a ver long filter to get a smooth ripple, so it will act like using choke.Can anyone give me another option to build the power supply?:smash(of course with a small ripple & not using choke)
3.Does anybody have a simple preamp schematic?I will build a tube preamp using 12Au7/12Ax7 family.
4.I need to build a preamp which provide a single gain or a gain less than 10.Which design should i build?grounded grid?grounded cathode?cathode follower?
please need ur help to build this simple tube preamp.
regards
----------
TomZ
"Everything must be simple as possible , but not simpler"
Hi TomZ,
What is the purpose of the pre-amp as I don't understand the requirement of unity gain or less then 10??
unity voltage gain would be a cathode follower
grounded grid is not realy an option for an audio pre-amp
I presume this pre-amp will drive a power amp of some sort?
as for psu I'm not so sure you will need all that filtering C>R>C
should be fine.
back to back transformers work ok, or there are dc to dc converters which for low power units such as pre amps would work fine and due to the higher opreation frequency don't require as much filtering and as a bonus if you source one that runs from 12volts your filament supply is already available.
Robert
What is the purpose of the pre-amp as I don't understand the requirement of unity gain or less then 10??
unity voltage gain would be a cathode follower
grounded grid is not realy an option for an audio pre-amp
I presume this pre-amp will drive a power amp of some sort?
as for psu I'm not so sure you will need all that filtering C>R>C
should be fine.
back to back transformers work ok, or there are dc to dc converters which for low power units such as pre amps would work fine and due to the higher opreation frequency don't require as much filtering and as a bonus if you source one that runs from 12volts your filament supply is already available.
Robert
Hi TomZ
check this thread you may find this helpful
http://www.diyaudio.com/forums/showthread.php?s=&threadid=11307[/URL]
check this thread you may find this helpful
http://www.diyaudio.com/forums/showthread.php?s=&threadid=11307[/URL]
The purpose of this preamp is to give my chipamps a valve sound.So, i will get a smooth and warm sound from tube. No, not unity gain. I don't want to build a buffer(unity gain) because it doesn't provide a sufficient gain to make make my chipamps become more dynamic sound.And, my chipamp is non inverted version so i think i don't need to add a buffer.
Yes, i want to use this preamp to drive my Gainclone amplifier.
Do you know the combination of CRC filter?I use 220r and 50uF.
I want to minimize the ripple.
I want to use high voltage tube like 12au7/12ax7 in 150v-250v B+.
I don't need to use a high voltage if i use low voltage tube like 6922/6dj8.But, i want to use 150v B+ as a preamp.
Do u have DC-DC converter schematic?i have tried to use quadupler voltage from 40VAC but the result is very bad ripple.
If i use a switching power supply, there is a high ripple and not continous voltage( because a switching psu is a PWM).
Need ur sugestion to build a valve preamp.
Thx
regards
---------
TomZ
High TomZ
switch modes designed properly should be fairly clean. any way at high frequence it is easier to filter and make clean in a good design.
Ok on power your filter need to know what you are going to use for preamp stage, likely current draw 10ma or so.
Also I see there is a thread on gg preamp, but there is enough discussion on that subject interresting reading. and some circuits are available. but with gg you will need something to buffer the input from the low input z of a gg stage hence the reason i thought gg wouldn't be usable.
As for psu filter you need to compromise assuming 10ma current draw you issues here is how much voltage can you afford to loose in the filter? at 10ma you will get 1 volt drop per 100ohms of series resistance in the series r. I think this needs to be maybe be 2k2r to 4k7 improve ripple.
if you like there is a link for psu design which is very helpful?
and suitable switch mode kit is available locally for about $30AUD.
check out some of the links and threads many schematics, the dificult question is which one. for me as I hadn't done any thing with valves in a long time I bought a kit from a local supplier jaycar electronics maybe not the best but it got me interrested.
Robert
switch modes designed properly should be fairly clean. any way at high frequence it is easier to filter and make clean in a good design.
Ok on power your filter need to know what you are going to use for preamp stage, likely current draw 10ma or so.
Also I see there is a thread on gg preamp, but there is enough discussion on that subject interresting reading. and some circuits are available. but with gg you will need something to buffer the input from the low input z of a gg stage hence the reason i thought gg wouldn't be usable.
As for psu filter you need to compromise assuming 10ma current draw you issues here is how much voltage can you afford to loose in the filter? at 10ma you will get 1 volt drop per 100ohms of series resistance in the series r. I think this needs to be maybe be 2k2r to 4k7 improve ripple.
if you like there is a link for psu design which is very helpful?
and suitable switch mode kit is available locally for about $30AUD.
check out some of the links and threads many schematics, the dificult question is which one. for me as I hadn't done any thing with valves in a long time I bought a kit from a local supplier jaycar electronics maybe not the best but it got me interrested.
Robert
Hi Thomgun_lc,
Tag along here and you'll pick up on some things:
http://www.diyaudio.com/forums/showthread.php?goto=newpost&threadid=59170
Enjoy
Tag along here and you'll pick up on some things:
http://www.diyaudio.com/forums/showthread.php?goto=newpost&threadid=59170
Enjoy
I'm sory for a newbie question about this tube preamp. But, i really confused to decided which schematic should i used.I found many schematic but still don't know which preamp should i build.
When i read an article about single ended preamp (using 1 tube for 2 channel), they said that a very simple design could make some tube noise which can decrease the detail of chipamp.Is it true?
I need some preamp schematic using 12au7/12ax7 family.Because i can found this tube very easy.
If i use 2 tube for 2 channel, i need to match both tube, is it true?
I only can find used tube, because the price are very low.
i try to build a swicth mode power supply from 12vdc-250vdc, but i have a problem with a step-up transformator.I must wind the transformator.The SMPS works in 33khz, is it ok?
The other option is to use back to back transformator which very simple and cheap but i still do some trial&error to find the best CRC filter combination.
I really need to build this simple preamp to give a total gain (preamp+gainclone) over 100x.With this total gain, i will get a "punchy"sound but warm&smooth.
I have tried to combine my gainclone chipamps with my friend's tube preamp and the sound was great,more dynamic but smooth & have a good imaging with a natural distortion.
regards
---------
TomZ
Hi TomZ,
don't worry we were all newbe's at some time, i'm still a newbe.
simple well too simple could have poor performance and cause distortions you don't want, if you think about it you want to colour the sound but you don't want to make it bad.
do you have a circuit for your friends pre amp? if you like that sound it would be a good starting point.
33khz is fine it will need to provide 10 to 20ma current and 250vdc is fine for 12ax7
what is your local supply volts/frequency?? 120vac or 240vac 50 or 60hz?
If transformer is cheap maybe seconday 12.6vac (can use for 12ax7 filaments) at 0.5amp and a smaller rated 240 to 18v. If you feed 12.6vac into 18volt winding you should get 160vac if you bridge rectify that you end up with about 225vdc in the same way a 15v primary fed with 12.6vac should yeild 270vdc. no load!
given you want to use C>R>C filter maybe
secondary 12.6 into 15 to 240 for HT supply!
Really you need to decide on a circuit before you get into psu design, shouldn't need matched tubes, same type/make should be fine, if second hand thats different need to have similar attributes.
Robert
don't worry we were all newbe's at some time, i'm still a newbe.
simple well too simple could have poor performance and cause distortions you don't want, if you think about it you want to colour the sound but you don't want to make it bad.
do you have a circuit for your friends pre amp? if you like that sound it would be a good starting point.
33khz is fine it will need to provide 10 to 20ma current and 250vdc is fine for 12ax7
what is your local supply volts/frequency?? 120vac or 240vac 50 or 60hz?
If transformer is cheap maybe seconday 12.6vac (can use for 12ax7 filaments) at 0.5amp and a smaller rated 240 to 18v. If you feed 12.6vac into 18volt winding you should get 160vac if you bridge rectify that you end up with about 225vdc in the same way a 15v primary fed with 12.6vac should yeild 270vdc. no load!
given you want to use C>R>C filter maybe
secondary 12.6 into 15 to 240 for HT supply!
Really you need to decide on a circuit before you get into psu design, shouldn't need matched tubes, same type/make should be fine, if second hand thats different need to have similar attributes.
Robert
Tom, I will send you a schematic using 12AX7. I know there are people who likes to add 2nd harmonic distortion to colour the sound. IMO, if you want to colour the sound you should find other ways instead of adding distortion. But the tube can indeed create sounstage (seems 2nd haromincs have something to do with soundstage )
CDP + GC --> Probably not enough gain to boost the details.
CDP + SRPP 6SN7 + GC --> Better dynamic, more detail, more soundstage, MORE distortion --> I prefer CDP + GC
CDP + CF 6SN7 --> No comment, I prefer the two above
CDP + Opamp pres + GC --> prefer CDP + GC
CDP + 3 BJT buffer + IGC --> suggested
But what is an amp!? Only class-A amps can properly "colour" the sound. With non-class-A amps, everything can be handled in the speaker section
)CDP + GC --> Probably not enough gain to boost the details.
CDP + SRPP 6SN7 + GC --> Better dynamic, more detail, more soundstage, MORE distortion --> I prefer CDP + GC
CDP + CF 6SN7 --> No comment, I prefer the two above
CDP + Opamp pres + GC --> prefer CDP + GC
CDP + 3 BJT buffer + IGC --> suggested
But what is an amp!? Only class-A amps can properly "colour" the sound. With non-class-A amps, everything can be handled in the speaker section
my first scratchbuild linestage was this:
http://www.users.globalnet.co.uk/~valveamp/
build whatever power supply you like
you can always improve it/change it later
ecc83/12ax7 has a lot of gain for a linestage
ecc82/12au7 sounds quite nice in this
and you could use just 1 valve
most of the valves in the list are easily available
and then by changing a couple resistors you can try something else
this is a really good introduction to valves
dave dove
http://www.users.globalnet.co.uk/~valveamp/
build whatever power supply you like
you can always improve it/change it later
ecc83/12ax7 has a lot of gain for a linestage
ecc82/12au7 sounds quite nice in this
and you could use just 1 valve
most of the valves in the list are easily available
and then by changing a couple resistors you can try something else
this is a really good introduction to valves
dave dove
The inter-section capacitances are low enough that you'll only see crosstalk at very high frequecies, and even then, not that much. This will probably not be your limitation on separation.
If you're using the tube as a cathode follower, there's even less of an issue since both plates are at AC ground.
And if you use a tube from the ECC88 family, there's even a handy shield between the sections.
If you're using the tube as a cathode follower, there's even less of an issue since both plates are at AC ground.
And if you use a tube from the ECC88 family, there's even a handy shield between the sections.
"Does anyone have a simple tube preamp schematic?like cathode follower?"
http://www.joeltunnah.com
Look at the 12AZ7 buffer project.
Joel
http://www.joeltunnah.com
Look at the 12AZ7 buffer project.
Joel
Hi TomZ
Try here:
http://www.diyparadise.com/
http://www.diyparadise.com/simplepreamp.html
http://www.diyparadise.com/preamptutorial.html
Good luck
JC
Try here:
http://www.diyparadise.com/
http://www.diyparadise.com/simplepreamp.html
http://www.diyparadise.com/preamptutorial.html
Good luck
JC
Hey-Hey!!!,
Look here:
http://audioroundtable.com/GroupBuild/Projects/
at Guinevere. Gain is only slightly behind a 12AU7. Output Z is less than 200R and it sounds brilliant. Simple L-C power supply. 250VAC to a choke and on to a good cap.
It can be done for less than $200 and it is simple enough for new builders. I penned it and several folks built it right off the 'net. Send a note to the folks who did and I think you'll hear nothing but good stuff.
cheers,
Douglas
Look here:
http://audioroundtable.com/GroupBuild/Projects/
at Guinevere. Gain is only slightly behind a 12AU7. Output Z is less than 200R and it sounds brilliant. Simple L-C power supply. 250VAC to a choke and on to a good cap.
It can be done for less than $200 and it is simple enough for new builders. I penned it and several folks built it right off the 'net. Send a note to the folks who did and I think you'll hear nothing but good stuff.
cheers,
Douglas
I'm using Joel's 6sn7 based pre and think it is pretty nice. It was much better than my vintage tube preamp and better than my ss pre.
Since I had most of the parts around I didn't spend too much either.
I've been impressed with Hey Hey Douglas's designs and would look at it too. Just wish I could get only 4 fets and try a CCS. Mouser has a 50 minimum.
rick
Since I had most of the parts around I didn't spend too much either.
I've been impressed with Hey Hey Douglas's designs and would look at it too. Just wish I could get only 4 fets and try a CCS. Mouser has a 50 minimum.
rick
Hi Bandersnatch!!
Thanks for ur attention.I have seen ur link and found that there is a simple preamp using some CCS.
But, i only have ecc82 tube family.Can i change 5687's tube with ecc82 family?confused:
What is the different between using VAC to heater and using VDC to the heater?Which is better?
To JC_Fardo
I have see ur link and i have build a PCB for that simple preamp.But,i don't use 5687 tube, i change with ecc82/3 family.So, i did some changes on R plate&R cathode value to set the correct bias for ECC82 family.But, i'm worried because it only have one ground for stereo ( i used 1 tube for stereo).How about if i add 10r from signal ground to power ground.Is it the way to avoid crosstalk?
And, i don't have a custom transformator, so i used back to back transformator.
To Joel Tunnah
I only have ECC82/3 tube family, can i substitute that 12az7 with 12ax/au7?Is it an unity gain?like a buffer?
I used back to back transformator, so i don't have center tap (the output pin only 0&220), can i used 6r4 as a rectifier?
Thx
regards
---------
TomZ
Thanks for ur attention.I have seen ur link and found that there is a simple preamp using some CCS.
But, i only have ecc82 tube family.Can i change 5687's tube with ecc82 family?confused:
What is the different between using VAC to heater and using VDC to the heater?Which is better?
To JC_Fardo
I have see ur link and i have build a PCB for that simple preamp.But,i don't use 5687 tube, i change with ecc82/3 family.So, i did some changes on R plate&R cathode value to set the correct bias for ECC82 family.But, i'm worried because it only have one ground for stereo ( i used 1 tube for stereo).How about if i add 10r from signal ground to power ground.Is it the way to avoid crosstalk?
And, i don't have a custom transformator, so i used back to back transformator.
To Joel Tunnah
I only have ECC82/3 tube family, can i substitute that 12az7 with 12ax/au7?Is it an unity gain?like a buffer?
I used back to back transformator, so i don't have center tap (the output pin only 0&220), can i used 6r4 as a rectifier?
Thx
regards
---------
TomZ
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