Hi !
I was navigating across a member's website and found this interesting preamp :
http://ptsoundlab.free.fr/sectubes/preamps/vtv6sn7line/vtv6sn7line.htm
I would like to hear your comments about it. Should I bother building this one ? Which tube brand do you recommend ? My electronic parts supplier is able to provide me tubes for about 25$CAN each but he cannot tell me from which manufacturer they'll come from. This is of course inacceptable.
One final question : Would it be possible with some modifications to add output for headphones ? Schematics ?
Thanks for your help !
I was navigating across a member's website and found this interesting preamp :
http://ptsoundlab.free.fr/sectubes/preamps/vtv6sn7line/vtv6sn7line.htm
I would like to hear your comments about it. Should I bother building this one ? Which tube brand do you recommend ? My electronic parts supplier is able to provide me tubes for about 25$CAN each but he cannot tell me from which manufacturer they'll come from. This is of course inacceptable.
One final question : Would it be possible with some modifications to add output for headphones ? Schematics ?
Thanks for your help !
Hello,
at this time, only Sovtek make very good 6SN7 (and for low price), I buy all my tubes in Germany www.tube-town.de (very good price and service, I recommend it, contact Dirk the boss of my share), the best shop for europeans.
For you it is certainly more easy to buy in USA http://store.yahoo.com/thetubestore/sovtek6sn7.html
Cordially.
Pascal.
at this time, only Sovtek make very good 6SN7 (and for low price), I buy all my tubes in Germany www.tube-town.de (very good price and service, I recommend it, contact Dirk the boss of my share), the best shop for europeans.
For you it is certainly more easy to buy in USA http://store.yahoo.com/thetubestore/sovtek6sn7.html
Cordially.
Pascal.
Like everything else in life, the Circuit has its pluses and minuses.
Pluses:
6SN7 is a good sounding pre-amp tube.
The output Z is under 400 ohms
Power supply with CLCRC should be quiet
Tube rectifier will be quiet and slow turn on.
Very Conservative bias currents on tube sections
5 and 8 ma respectively. Tube life should be good.
DC filament supply.
Good Voltage swings of +-100v max.
Minuses.
Low Z in of about 100k may affect high frequency response at some pot settings.
Higher gain than I like in a line amp. About 24 db.
Bypassed cathode resistor adds unwanted gain and probably increases distortion.
Cathode followers do not have the best sonic reputation, especially at only 8 ma current.
For best sound, both tube sections should have about 15 ma current each. Running the grounded cathode at only 18% of its static dissipation and 25% of its current capability will increase distortion.
Will be very sensitive to parts quality.
IMHO, it should sound good.
Should you build one? That's for you to decide.
Will I build one. No. I think I could do better with the same tubes.
HTH
Doug
Pluses:
6SN7 is a good sounding pre-amp tube.
The output Z is under 400 ohms
Power supply with CLCRC should be quiet
Tube rectifier will be quiet and slow turn on.
Very Conservative bias currents on tube sections
5 and 8 ma respectively. Tube life should be good.
DC filament supply.
Good Voltage swings of +-100v max.
Minuses.
Low Z in of about 100k may affect high frequency response at some pot settings.
Higher gain than I like in a line amp. About 24 db.
Bypassed cathode resistor adds unwanted gain and probably increases distortion.
Cathode followers do not have the best sonic reputation, especially at only 8 ma current.
For best sound, both tube sections should have about 15 ma current each. Running the grounded cathode at only 18% of its static dissipation and 25% of its current capability will increase distortion.
Will be very sensitive to parts quality.
IMHO, it should sound good.
Should you build one? That's for you to decide.
Will I build one. No. I think I could do better with the same tubes.
HTH
Doug
If you do a search you will find an excellent schematic for the 5692/6SN7 that Frank has done. I personally use this line stage and can attest to its sonic quality. I do recommend using VR tube regulation. I have had good luck with both the 6SN7 tubes and 5692 in this circuit.
I purchase both used 6SN7 tubes and 5692's off Ebay and have had excellent results. I am a firm believer in the sonic quality of the older tubes vers the current production. Just my .02
Joe
I purchase both used 6SN7 tubes and 5692's off Ebay and have had excellent results. I am a firm believer in the sonic quality of the older tubes vers the current production. Just my .02
Joe
Thanks a lot !
I think I found Frank's preamp :
http://www.diyaudio.com/forums/showthread.php?postid=235666#post235666
Is that right ?
However, I would like to use 5U4G rectifier in the Power Supply. Since I'm a completely noob in PSU (and audio gear) design, a little hand would be appreciated.
I tried to play a bit with Duncan'S PSUD II but I can't achieve nice results since I don't really know what I'm doing... Only trials and errors.
I think I found Frank's preamp :
http://www.diyaudio.com/forums/showthread.php?postid=235666#post235666
Is that right ?
However, I would like to use 5U4G rectifier in the Power Supply. Since I'm a completely noob in PSU (and audio gear) design, a little hand would be appreciated.
I tried to play a bit with Duncan'S PSUD II but I can't achieve nice results since I don't really know what I'm doing... Only trials and errors.
Looks like you found Frank's line stage all right. I'm not versed in using Duncans power supply progran so I can't help. There are others that are very well versed on the program that can help. A 5U4 will work but it seems kinda like overkill to me since the current required by this design is small. Personally I like the sound of a tube rectifier over the silicone rival. Once you get the power supply figured out you can rest easy knowing that this design is tried and true. With a good regulated supply it will easily surpass anything that you can buy in my opinion.
Joe
Joe
Hi,
There actually is a mistake in that diagram, the value of the coupling cap between the two stages should be 0.33µF, not 0.033µF as stated.
Maybe this was corrected later on, I haven't checked.
You can but as Joe says, it's a bit of a waste.
I'm not versed with PSUD either but it's not hard to build a basic PS as long as you have enough volts to start with...
Have you decided on the powerxformer yet or is that still open?
No idea it was actually that good...Thanks, Joe.
What version did you actually build in the end?
Cheers,
There actually is a mistake in that diagram, the value of the coupling cap between the two stages should be 0.33µF, not 0.033µF as stated.
Maybe this was corrected later on, I haven't checked.
You can but as Joe says, it's a bit of a waste.
I'm not versed with PSUD either but it's not hard to build a basic PS as long as you have enough volts to start with...
Have you decided on the powerxformer yet or is that still open?
No idea it was actually that good...Thanks, Joe.
What version did you actually build in the end?
Cheers,
Hi Frank
Actually I started out with a VR90 and VR150 for each channel and liked that. I ended up with a second version that included a regulated supply that you designed. Unfortunately I cannot find the link to it or I would post it.
Like I said earlier and I believe others have also mentioned a lot is to be gained sonically by a well designed power supply. I could be wrong but I seem to favor a larger transformer capable of higher voltage and amp rating.
I have build a number of line stages since I joined this group. I have build several 6sn7 designs as well as 5687's and 12B4's, #27's, #37's, and a humming #26. If i had to choose a favorite it would be between the 12B4 and the 6SN7/5692. The #26 holds promise but I seem to be lacking patience.
Sorry about rambling on...
Joe
Actually I started out with a VR90 and VR150 for each channel and liked that. I ended up with a second version that included a regulated supply that you designed. Unfortunately I cannot find the link to it or I would post it.
Like I said earlier and I believe others have also mentioned a lot is to be gained sonically by a well designed power supply. I could be wrong but I seem to favor a larger transformer capable of higher voltage and amp rating.
I have build a number of line stages since I joined this group. I have build several 6sn7 designs as well as 5687's and 12B4's, #27's, #37's, and a humming #26. If i had to choose a favorite it would be between the 12B4 and the 6SN7/5692. The #26 holds promise but I seem to be lacking patience.
Sorry about rambling on...
Joe
Hi Joe,
I suppose this is the one you mean?
250VDC REG.
So do I in general...A well designed powerxformer is very important to me.
It seems to rank among the favourites for linestage duties.
Triode Dick at http://www.vt52.com/ has even build a little gallery around it.
Look under Tubeinfo, UX226 gallery.
BTW, did you know that the 12B4A is a direct descendent of the 2A3?
That a trioded 6BQ5 is almost the same as a 12B4A (curveswise)?
That one of my favourite mini amps is the VTL 15/15 AKA Tiny Tott which uses 6BQ5s in triode mode?
Tubes are fun, aren't they?
Cheers,
I suppose this is the one you mean?
250VDC REG.
So do I in general...A well designed powerxformer is very important to me.
It seems to rank among the favourites for linestage duties.
Triode Dick at http://www.vt52.com/ has even build a little gallery around it.
Look under Tubeinfo, UX226 gallery.
BTW, did you know that the 12B4A is a direct descendent of the 2A3?
That a trioded 6BQ5 is almost the same as a 12B4A (curveswise)?
That one of my favourite mini amps is the VTL 15/15 AKA Tiny Tott which uses 6BQ5s in triode mode?
Tubes are fun, aren't they?
Cheers,
Hi !
First of all, thank you for your comments !
Everything concerning the PSU is still open as long as the parts are easily obtainable and not too expensive (i.e. Hammond)
I'm completely convinced about the preamp but the PSU is still giving me headache. I would really use the 5u4g for two reasons : I have some on hand and they're sooo nice. Even if it means an additional 3A 5V tranny.
Since I know next to nothing about PSU design, your experience would be greatly appreciated !
Have a nice day !
First of all, thank you for your comments !
Everything concerning the PSU is still open as long as the parts are easily obtainable and not too expensive (i.e. Hammond)
I'm completely convinced about the preamp but the PSU is still giving me headache. I would really use the 5u4g for two reasons : I have some on hand and they're sooo nice. Even if it means an additional 3A 5V tranny.
Since I know next to nothing about PSU design, your experience would be greatly appreciated !
Have a nice day !
Hi Frank
Yes, thats the right regulator circuit. Yes, tubes are fun and can provide a lot of pleasure but caution must be excercised at all times when building/working on them.
Elkaid
I figured that you probably owned several 5u4's. Mine are sitting in the bottom of a box waiting usage on a power amplifier. The point that I am also trying to make is the fact that a transformer with a smaller 5volt supply would cost less and the additional money could be implemented elseware in the power supply. The cost of a 5Y3 is very small and it would provide more than adequate rectification in this circuit. Hammond is a good choice for a power transformer as are some older NOS transformers. I would scout Ebay looking for transformers first and then purchase one from Hammond if you couldn't find what you needed in the used department. I can only provide suggestions but you will have to figure the route to travel.
How about some help from someone well versed in the Duncan power supply program so Elkaid can get a good start?
Granted there are people out there like Frank, and Sy, and Brett just to name a few that don't need to rely on a program to design a good power supply. They are a group that have lived and breathed tubes all of their lives. One can only imagine the patience that is required of them when they go into detail in the explanation of a circuit. My hat if off to you gentlemen.
Maybe all of us could help give Elkaid the help he needs here?
Joe
Yes, thats the right regulator circuit. Yes, tubes are fun and can provide a lot of pleasure but caution must be excercised at all times when building/working on them.
Elkaid
I figured that you probably owned several 5u4's. Mine are sitting in the bottom of a box waiting usage on a power amplifier. The point that I am also trying to make is the fact that a transformer with a smaller 5volt supply would cost less and the additional money could be implemented elseware in the power supply. The cost of a 5Y3 is very small and it would provide more than adequate rectification in this circuit. Hammond is a good choice for a power transformer as are some older NOS transformers. I would scout Ebay looking for transformers first and then purchase one from Hammond if you couldn't find what you needed in the used department. I can only provide suggestions but you will have to figure the route to travel.
How about some help from someone well versed in the Duncan power supply program so Elkaid can get a good start?
Granted there are people out there like Frank, and Sy, and Brett just to name a few that don't need to rely on a program to design a good power supply. They are a group that have lived and breathed tubes all of their lives. One can only imagine the patience that is required of them when they go into detail in the explanation of a circuit. My hat if off to you gentlemen.
Maybe all of us could help give Elkaid the help he needs here?
Joe
Well, I'm probably useless since I preach the virtues of solid state supplies! Were it my preamp (and this is what I do in my preamp), I'd use silicon rectification, an active regulator for preregulation (a 317 with a HV bipolar transistor setting Vin for it), then RC decoupling.
As to the VTV circuit itself, it looks pretty straightforward. I'd strongly disagree about the need to run higher currents. Premium tubes aren't cheap or easy to get, so lifetime is a real consideration. With 8 ma, the CF will drive any reasonable length of cable one is likely to find in a home setup to a bandwidth approaching the AM band. I do agree that there's more gain here than you need (a gain of 5 or so is sufficient for the vast majority of applications), so losing the cathode bypass cap is a good idea- lower distortion with no source impedance penalties.
Always keep in mind that you don't need more than 2-3 volts out of this circuit. And I'm a fan of the red base 5692s.
6SN7 linestage WIP
Hi Elkaid
You may like to have look at The Blue Velvet Line Pre-Amplifier by Dick Olsher and Kara Chaffee. I've just finished bread-boarding one channel and hope to do some serious listenigs this week.
Hi Elkaid
You may like to have look at The Blue Velvet Line Pre-Amplifier by Dick Olsher and Kara Chaffee. I've just finished bread-boarding one channel and hope to do some serious listenigs this week.
Uhhh... Sorry
It seems that it makes almost unanimity that schematic described here http://www.diyaudio.com/forums/showthread.php?postid=235666#post235666 is a superb project. (Thanks everyone for your suggestion !)
As for the Power Supply, I would really really like to use those gorgeous 5U4G rectifier...
On a side note, I hope you didn't get offended by my post. It's just that I have this project in my head for far too long Your help is very appreciated and you can be certain that it's not taken for granted !
And oh, by the way, concerning the headphones, I'm looking for Sennheiser HD-590 (120ohms)
http://www.sennheiser.com/sennheiser/icm_eng.nsf/root/04486
Regards,
It seems that it makes almost unanimity that schematic described here http://www.diyaudio.com/forums/showthread.php?postid=235666#post235666 is a superb project. (Thanks everyone for your suggestion !)
As for the Power Supply, I would really really like to use those gorgeous 5U4G rectifier...
On a side note, I hope you didn't get offended by my post. It's just that I have this project in my head for far too long
Your help is very appreciated and you can be certain that it's not taken for granted !And oh, by the way, concerning the headphones, I'm looking for Sennheiser HD-590 (120ohms)
http://www.sennheiser.com/sennheiser/icm_eng.nsf/root/04486
Regards,
Hi,
I could have guessed....
Anyway, even though the B+ says 250VDC on the schematic it also uses a tubed voltage regulator that's going to eat at least 50VDC in order for it to work properly.
So, if we have the 5U4 with a 250V CT xformer and a cap input filter (AKA CLC) we can have about 330VDC after the cap, add a choke with a DCR of about 300R followed by another filter cap and perhaps a pi filter (AKA CRC) to lower the B+ and ripple to desired levels and we can feed the regulator and come out with a superdeluxe 250VDC with some voltage margin in case you want to recycle it for another project.
Behind the reg we can put some more capacitance, BGs, PIOs or MKPs that we tweak for best sonic results.
No big deal, just letting you know what you're punishing yourself with...
Of course not.
Assuming the 120 Ohm is the impedance of the cans it looks as if the CF may run into trouble there.
If you want a preamp that can drive virtually anything bar a dead short I usually recommend a SRPP coupled to a WCF: the SRPP has all the gain and linearity you'll ever need and the WCF has the muscle of a mini-amp.
Since neither topology has good PSSR they both require a well designed, preferably well regulated PS and it requires two twin triode per channel iso one single tube.
BTW, as good 6SN7s are getting scarcer as we type, why not build a heater supply that can cater for both the 6SN7 and 12SN7 just by the flick of a switch for instance?
More later,
I could have guessed....
Anyway, even though the B+ says 250VDC on the schematic it also uses a tubed voltage regulator that's going to eat at least 50VDC in order for it to work properly.
So, if we have the 5U4 with a 250V CT xformer and a cap input filter (AKA CLC) we can have about 330VDC after the cap, add a choke with a DCR of about 300R followed by another filter cap and perhaps a pi filter (AKA CRC) to lower the B+ and ripple to desired levels and we can feed the regulator and come out with a superdeluxe 250VDC with some voltage margin in case you want to recycle it for another project.
Behind the reg we can put some more capacitance, BGs, PIOs or MKPs that we tweak for best sonic results.
No big deal, just letting you know what you're punishing yourself with...
Of course not.
Assuming the 120 Ohm is the impedance of the cans it looks as if the CF may run into trouble there.
If you want a preamp that can drive virtually anything bar a dead short I usually recommend a SRPP coupled to a WCF: the SRPP has all the gain and linearity you'll ever need and the WCF has the muscle of a mini-amp.
Since neither topology has good PSSR they both require a well designed, preferably well regulated PS and it requires two twin triode per channel iso one single tube.
BTW, as good 6SN7s are getting scarcer as we type, why not build a heater supply that can cater for both the 6SN7 and 12SN7 just by the flick of a switch for instance?
More later,
Hi !!!!
Things are beginning to sounds terribly interesting !
Yup, now we're talking !!!!
I'm ready to the the risk... Least catastrophic than getting married... Well, at least on the financial side.
Really nice idea For the next few hours, I'll try to put on paper (or CAD) what you just suggested. I'm kinda visual guy. 3A 5V windings seems pretty rare on 250VCT xformer (lot of 2A at least from Hammond) so the 5V supply will most likely have its own transformer.
If we go for a universal filament supply, I suppose I should seek for a separate 12.6VCT tranny ? 12SN7 is 12.6V filament isn't it ?
Uhhhhh... can you translate please ? Who do you think I am ? An engineer ?
Finally but not the least... If it's too complicated to add an headphones output, we could always add additional tubes to make some kind of separate headphone amp . Uhhhhh... maybe not... well it's late... maybe not a so good idea after all. Maybe I should consider two separate projects instead.
Thanks a lot !!! I really need some sleep !
Things are beginning to sounds terribly interesting !
Yup, now we're talking !!!!
I'm ready to the the risk... Least catastrophic than getting married...
Well, at least on the financial side.Really nice idea
For the next few hours, I'll try to put on paper (or CAD) what you just suggested. I'm kinda visual guy. 3A 5V windings seems pretty rare on 250VCT xformer (lot of 2A at least from Hammond) so the 5V supply will most likely have its own transformer.If we go for a universal filament supply, I suppose I should seek for a separate 12.6VCT tranny ? 12SN7 is 12.6V filament isn't it ?
Uhhhhh... can you translate please ? Who do you think I am ? An engineer ?
Finally but not the least... If it's too complicated to add an headphones output, we could always add additional tubes to make some kind of separate headphone amp . Uhhhhh... maybe not... well it's late... maybe not a so good idea after all. Maybe I should consider two separate projects instead.
Thanks a lot !!! I really need some sleep !
Hi,
Which is better anyway.
Yes, but...since we want to regulate that as well we'd better pick a common as mud 0-15VAC xformer for that, one per channel if possible or two separate windings at least.
That figures...Engineers usually ask more questions than I've answers for.
I would but there's little point unless you'd build it.
What it boils down to is that if you want to build a preamp that can double as a headphone amp for the Sennheisers then we'd better change the circuit now as it would be more economical IMO.
Talking about engineering, whatever you decide to build I think it's best to think in dual mono constructionwise from just before the regulator downstream to the circuits proper at least.
There's little point in using a regulated PS in common to both stereo channels.
See...That's what I meant with punishment...
It's actually not complicated at all:
All it takes is one more tube per channel, a few caps, a few resistors and a heatersupply for it.
The trick is, both the preamp and the headphoneamp benefit from the choice of topology in one go.
Cheers,
Which is better anyway.
Yes, but...since we want to regulate that as well we'd better pick a common as mud 0-15VAC xformer for that, one per channel if possible or two separate windings at least.
That figures...Engineers usually ask more questions than I've answers for.
I would but there's little point unless you'd build it.
What it boils down to is that if you want to build a preamp that can double as a headphone amp for the Sennheisers then we'd better change the circuit now as it would be more economical IMO.
Talking about engineering, whatever you decide to build I think it's best to think in dual mono constructionwise from just before the regulator downstream to the circuits proper at least.
There's little point in using a regulated PS in common to both stereo channels.
See...That's what I meant with punishment...
It's actually not complicated at all:
All it takes is one more tube per channel, a few caps, a few resistors and a heatersupply for it.
The trick is, both the preamp and the headphoneamp benefit from the choice of topology in one go.
Cheers,
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