fdegrove said:HPlugging Cinemag iron now, Steve? Howdy BTW...
Hey there, Frank!
Yeah, I'm plugging CineMag iron now. Their quality's every bit as good as Jensen and their prices are about 20% less. Still have a soft spot for Jensen though. They're good people.
se
Allen Wright's SLCF
Hi,
I am simply curious,why nobody mention this kind of CF?Are there big advantages or it is not worth considering it?And have anybody build a preamp with voltage again,first stage and the second stage with this SLCF?
http://www.vacuumstate.com/schematics/fvp5_rev_1_s.gif
http://www.vacuumstate.com/schematics/fvp5_s.gif
Regards,
Yugovitz
Hi,
I am simply curious,why nobody mention this kind of CF?Are there big advantages or it is not worth considering it?And have anybody build a preamp with voltage again,first stage and the second stage with this SLCF?
http://www.vacuumstate.com/schematics/fvp5_rev_1_s.gif
http://www.vacuumstate.com/schematics/fvp5_s.gif
Regards,
Yugovitz
Hi,
From what I hear the results are heavily dependent on the PS used. IOW it needs something like AW's own superregged (grrrrr...) PS to shine.
OTOH, if I had to use 4 6922s per channel for a preamp I'd be building an Aikido. No doubt in my mind about that.
Cheers, 😉
From what I hear the results are heavily dependent on the PS used. IOW it needs something like AW's own superregged (grrrrr...) PS to shine.
OTOH, if I had to use 4 6922s per channel for a preamp I'd be building an Aikido. No doubt in my mind about that.
Cheers, 😉
Frank,
the diagrams I have attached are AW's designs of MC phono preamps in which the last section is SLCF,using only ONE half of the double triode per channel.BTW it is DC coupled with precedent voltage gain stage.I wondered if anyone have build line amp with one section with voltage gain(it can be any other tube) and another with SLCF. Sorry if there was any missunderstanding Frank!
Regards,
Yugovitz
the diagrams I have attached are AW's designs of MC phono preamps in which the last section is SLCF,using only ONE half of the double triode per channel.BTW it is DC coupled with precedent voltage gain stage.I wondered if anyone have build line amp with one section with voltage gain(it can be any other tube) and another with SLCF. Sorry if there was any missunderstanding Frank!
Regards,
Yugovitz
After a lot of thinking....
I think I’ll keep Brett’s 12B4A preamp. I already have built it and it sounds amazing. The only thing that I’ll do is to place the tubes on a sub-chassis and maybe some o-rings will help more for anti-ringing.
The good thing is that you guys have posted very good ideas over here. Thanks for this. I like very much to try in the future the “tried and tested 6SN7” and the WCF. Also thanks to Eddy who suggested me a cheaper than the S&B passive line transformer (maybe this will be my next project-around 100bucks + a good pot, is a dilemma).
Before I’ll start the rebuilding of the chassis (to add the sub-chassis) I’d like to do some questions.
-If a tube (12B4A) is around 8cm (3”) close to PT is there any possibility for hum?
(I’m planning to change the arrangement of the components, too 🙁 )
-Must I use DC on filaments? Right now I use AC but I have some audible hum. I don’t know if this causes hum. But I’m asking right now before starting to search for other causes. 🙂
-Must I use a better PSU or live this simple Shindo style PSU? Notice that I’d like my project to be simple and easy to build. I know that I can use a better PSU but if a more complicated one doesn’t change a lot the sonic quality of my preamp, I’d like to live it as it is.
-Do I need a ST/BY switch? Or with 5V4 I…already have one?
Thanks again for your help.
I think I’ll keep Brett’s 12B4A preamp. I already have built it and it sounds amazing. The only thing that I’ll do is to place the tubes on a sub-chassis and maybe some o-rings will help more for anti-ringing.
I bought four Tronal and all are microphonic.What kind of 12B4A you own?
The good thing is that you guys have posted very good ideas over here. Thanks for this. I like very much to try in the future the “tried and tested 6SN7” and the WCF. Also thanks to Eddy who suggested me a cheaper than the S&B passive line transformer (maybe this will be my next project-around 100bucks + a good pot, is a dilemma).
Before I’ll start the rebuilding of the chassis (to add the sub-chassis) I’d like to do some questions.
-If a tube (12B4A) is around 8cm (3”) close to PT is there any possibility for hum?
(I’m planning to change the arrangement of the components, too 🙁 )
-Must I use DC on filaments? Right now I use AC but I have some audible hum. I don’t know if this causes hum. But I’m asking right now before starting to search for other causes. 🙂
-Must I use a better PSU or live this simple Shindo style PSU? Notice that I’d like my project to be simple and easy to build. I know that I can use a better PSU but if a more complicated one doesn’t change a lot the sonic quality of my preamp, I’d like to live it as it is.
-Do I need a ST/BY switch? Or with 5V4 I…already have one?
Thanks again for your help.
Steve indicated that they'll custom one up for you. And if you don't go that route, I've found that you can take a really well-balanced input tranny and make it into a phase splitter by putting two precision resistors in series across the secondary and grounding their junction- it worked a charm with the JT11-P1 and some Ampex input trannies I have on hand.
Yes.
Yes.
A good solid regulator will be very much worthwhile.
The tube rectifier will help you with slowing the rise of B+ at startup, but you may still find it useful to have the output shunted to ground until a decent interval after startup (like a minute or two), and arrange to do the same in event of shutdown. Pops and bangs can do bad things to speakers and power amps.
Yes.
A good solid regulator will be very much worthwhile.
The tube rectifier will help you with slowing the rise of B+ at startup, but you may still find it useful to have the output shunted to ground until a decent interval after startup (like a minute or two), and arrange to do the same in event of shutdown. Pops and bangs can do bad things to speakers and power amps.
planet10 said:
Couldn't tell ya. I don't know what would make for a suitable phase splitter for a PP amp. Give 'em a call or drop 'em an EMail. http://www.cinemag.biz
se
Hi,
Tronal....That's one of the brand names used by a Brussels based tube vendor...Hard to tell what the 12B4As are without having a closer look at them.
Mine are all RCA.
When it comes to US made tubes my motto is "In RCA We Trust".
Yeah...My mistake, Yugo...I had been browsing the rest of the schematics on Allen's site si I had his "all tube" linestage in mind when posting.
Something a mute swithc takes care of elegantly and with no sound degrading add-ons whatsoever. All it takes is the habit to sequence the switch according to usage. (IOW adopt a Pavlovian reflex 🙂 )
Works for me anyway....
As for the 12B4A preamp:
DC heaters would be wisest.
Tubes far enough away from any magntic fields (xfromer and AC carrying wires)
Some modicum of mechanical damping of the tube carrying board; rubber grommets work small miracles already, can be helpful to mount the powerxformer on too.
Cheers, 😉
Tronal....That's one of the brand names used by a Brussels based tube vendor...Hard to tell what the 12B4As are without having a closer look at them.
Mine are all RCA.
When it comes to US made tubes my motto is "In RCA We Trust".
Yeah...My mistake, Yugo...I had been browsing the rest of the schematics on Allen's site si I had his "all tube" linestage in mind when posting.
Something a mute swithc takes care of elegantly and with no sound degrading add-ons whatsoever. All it takes is the habit to sequence the switch according to usage. (IOW adopt a Pavlovian reflex 🙂 )
Works for me anyway....
As for the 12B4A preamp:
DC heaters would be wisest.
Tubes far enough away from any magntic fields (xfromer and AC carrying wires)
Some modicum of mechanical damping of the tube carrying board; rubber grommets work small miracles already, can be helpful to mount the powerxformer on too.
Cheers, 😉
I'll try to post a pic to have a look.
Any source to find RCA 12B4A?
Ok.But...can I have 6,3Vdc from the 6,3Vac winding? Or I need more voltage?
6.3V will be fine for the 12B4 since it has a centre tapped 12.6V heater (i.e. it allows a 6.3V connection option)
Hi,
Not easily.
Why not use a dedicated heater xformer?
If you have a 15VAC xformer of sufficient current for instance you could use a FWB, filter that and feed something like a 7812 to end up with 12VDC.
Less current circulating means less EMF which makes layout that little bit easier.
Having a dedicated heater xformer also avoids capacitvie coupling
through neighbouring windings, another plus.
Microphony isn't normally brand related.
Don't forget the 12B4As were never constructed with microphony in mind in the first place. It was mainly a tube for TV service.
Mine were bought from Antique Electronic Supply years ago.
Other than that, just ask a few dealers and see what they can offer?
Cheers, 😉
Not easily.
Why not use a dedicated heater xformer?
If you have a 15VAC xformer of sufficient current for instance you could use a FWB, filter that and feed something like a 7812 to end up with 12VDC.
Less current circulating means less EMF which makes layout that little bit easier.
Having a dedicated heater xformer also avoids capacitvie coupling
through neighbouring windings, another plus.
Microphony isn't normally brand related.
Don't forget the 12B4As were never constructed with microphony in mind in the first place. It was mainly a tube for TV service.
Mine were bought from Antique Electronic Supply years ago.
Other than that, just ask a few dealers and see what they can offer?
Cheers, 😉
Hey-Hey!!!,
I do like active loads. Properly used, they make things like cathode impedances a bit less important. They also allow things like simpler PS design. Single stage of L-C for instance.
I like the Red LED's to bias the cathodes with. You are limited to ~20 mA of current though...20 mA for a 12B4 is enough. I found a bit of improvement going to +15 mA from ~8.
The gird leak 1m is redudundant. The volume pot serves this duty, and better due to its lower R-value. Why load the circuit further I say.
This is how I'd do it:
http://audioroundtable.com/GroupBuild/messages/568.html
regards,
Douglas
If you want to get really nuts, I have done somthing similar with a valve active load. Sound is excellent, and I have not taken it out of service long enough to perform measurements on it for things like output Z and such.
I do like active loads. Properly used, they make things like cathode impedances a bit less important. They also allow things like simpler PS design. Single stage of L-C for instance.
I like the Red LED's to bias the cathodes with. You are limited to ~20 mA of current though...20 mA for a 12B4 is enough. I found a bit of improvement going to +15 mA from ~8.
The gird leak 1m is redudundant. The volume pot serves this duty, and better due to its lower R-value. Why load the circuit further I say.
This is how I'd do it:
http://audioroundtable.com/GroupBuild/messages/568.html
regards,
Douglas
If you want to get really nuts, I have done somthing similar with a valve active load. Sound is excellent, and I have not taken it out of service long enough to perform measurements on it for things like output Z and such.
The Guinever linestage is being done with 5687's in its first rendering. It's really a simple design. It is not sruprising that somebody else would have arrived at the same conclusion.
As to active loads with valves, it's really quite simple. I can't post any schematic 'cause I don't have a scanner or software. I may also attempt to apply it to a commercial design....
Keep all the paths high impedance. The design follows more or less by common sense.
regards,
Douglas
As to active loads with valves, it's really quite simple. I can't post any schematic 'cause I don't have a scanner or software. I may also attempt to apply it to a commercial design....
Keep all the paths high impedance. The design follows more or less by common sense.
regards,
Douglas
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