AC or DC heathing?

[GoranB]

Hello GoranB,
$0.02 worth.
I have used several versions of all the above.
First with any AC, DC or regulated DC I would use a GE Sensing inrush limiter. I do not recall the part number it starts out cold at 120 or so ohms cold and reduces to 8 or 9 ohms hot. This goes in series with the transformer primary. I have never had any issues with the LM 317 or 1085 type devices, by the time the heaters are hot the heat sinks attached to the adjustable regulators are still cold. Fixed regulators 7812 or 7806 work as well. Non-regulated power supplies also work, the voltage is adjusted under test by adding series resistors.
Take it apart and play with it.
DT
All just for fun!

Thanks for Your reply
Im in that point that I dont know any new method to improve the sound of my setup. As Im using the PF99 SE A class like an output stage (no gain) i need a more gain from preamp. The PCC88 has amplification factor of 33.
I want to try a line gain stage with ECC83 or 12AX7 with amp. fact 100. I dont know if that tube is even ever used to amplify an output of CD player. Because of big amp. factor the hum and noise should be on higher level. In that sence im trying to find out if DC heathing will help to reduce the noise.

 

[GoranB]

I buffer my LM317T with a 2N3055. It sounds fine and only drops about .15 V between cold and hot, once it's warmed up, it doesn't change.

It's a real life saver if you can't find an AC filament transformer for an odd voltage.

In my case im using a separate filament transformer just for gain stage PCC88, I need more gain, and in this moment i have only 12AX7 with amp. factor 100. Im not sure if it will be noiseless with AC heathing. Maybe it will be good to try the DC heathing in case of 12AX7.

 

[AllenB]

I have used current regulated DC in a phono stage/pre-amp with good results. As far as I can tell, apart from hum it's about noise. Whichever you use, you should treat your wiring to reduce RF and magnetic/capacitive coupling. This should give you the results you seek.

 

[GoranB]

I have two ressistors of 220R from filament to ground. With PC88 there is no noise. If that will be the same with 12AX7 ill be very happy

 

[DualTriode]

Hello ,
For simple fast and easy plus quality use this one. It has the common mode choke for RF. I used this one for 307A heaters.
Regulated DC filament supply
For fast and easy, I use this one on the bench.
http://www.kele.com/WorkArea/DownloadAsset.aspx?id=7343
Switch mode may also work!
If you want a Quality buildable line stage with gain try the Aikido.
Take it apart and play with it.
DT
All just for fun!

 

[ihear21khz]

In my case im using a separate filament transformer just for gain stage PCC88, I need more gain, and in this moment i have only 12AX7 with amp. factor 100. Im not sure if it will be noiseless with AC heathing. Maybe it will be good to try the DC heathing in case of 12AX7.

Yes, the use of a separate transformer is very good. Use a split bobbin type or conventional EI core with a shield/screen between Primary and Secondary if you haven't already done so. I suggest using LM series regulators in preference over the LT series as it would be easier to control. And yes, forget AC heating.

 

[GoranB]

Yes, the use of a separate transformer is very good. Use a split bobbin type or conventional EI core with a shield/screen between Primary and Secondary if you haven't already done so. I suggest using LM series regulators in preference over the LT series as it would be easier to control. And yes, forget AC heating.

Thanks for reply.
I wanted to use LM317T but someone suggested that it wont work.

BTW, can You really hear the 21KHz?
I can hear only 13KHz

 

[GoranB]

Hello ,
For simple fast and easy plus quality use this one. It has the common mode choke for RF. I used this one for 307A heaters.
Regulated DC filament supply
For fast and easy, I use this one on the bench.
http://www.kele.com/WorkArea/DownloadAsset.aspx?id=7343
Switch mode may also work!
If you want a Quality buildable line stage with gain try the Aikido.
Take it apart and play with it.
DT
All just for fun!

Thanks, i like when members are posting circuits which can help.
I will try to implement some of these circuits with 12AX7

 

[GoranB]

Yes, the use of a separate transformer is very good. Use a split bobbin type or conventional EI core with a shield/screen between Primary and Secondary if you haven't already done so. I suggest using LM series regulators in preference over the LT series as it would be easier to control. And yes, forget AC heating.

Does LM317T needs an heatsink? It can run without heatsink up to 1A as I know. Filaments for PCC88 is abot 300mA.

 

[ihear21khz]

Thanks for reply.
I wanted to use LM317T but someone suggested that it wont work.

BTW, can You really hear the 21KHz?
I can hear only 13KHz

Is this because of the issue of in-rush current? I have not had problems with in-rush current shutting down 317 reg to a heater supply. Try it first. If you have a problem, then switch to an LT. 317s are cheap and cheerful so if it goes bang, just chuck them away. Anyway it has been a while since I used 3 legged regulators for heater supplies. I have used dedicated SMPSs for many years now.

As of a year ago, I could hear up to 21khz (maybe a bit less now). I am also irritated by ultrasonic bug repelling devices. This is not necessarily an asset!!

I always heat-sink regulators even if these are operating well below their design limits.

 

[GoranB]

Is this because of the issue of in-rush current? I have not had problems with in-rush current shutting down 317 reg to a heater supply. Try it first. If you have a problem, then switch to an LT. 317s are cheap and cheerful so if it goes bang, just chuck them away. Anyway it has been a while since I used 3 legged regulators for heater supplies. I have used dedicated SMPSs for many years now.

As of a year ago, I could hear up to 21khz (maybe a bit less now). I am also irritated by ultrasonic bug repelling devices. This is not necessarily an asset!!

I always heat-sink regulators even if these are operating well below their design limits.

The heating terminals in tubes has very low impedance. It can make a problem for LM to start. (its a suggestion for some of the members here).

You are really blessed if You can hear up to 20KHz. I cant even imagine how music will sound in so wide spectrum.

 

[ihear21khz]

By the way, you can use LT regulators if you prefer. Just read up on the application notes on how to best use them.

 

[DualTriode]

Hello GoranB,
While you are considering hum and noise also consider regulating the High Voltage “B+” supply. A sort of resent project I built a tube headphone amplifier. The goal was not to hear any noise (hum, buzz or hiss) with the headphones on my head. Heaters, B+ everything was regulated there was no audible noise.
I also support separate heater and B+ transformers. Keep the diode noise sources separate!
Take a look at the Salas HV shunt regulator here on DIYAudio.
DT
All just for fun!

 

[GoranB]

Hello GoranB,
While you are considering hum and noise also consider regulating the High Voltage “B+” supply. A sort of resent project I built a tube headphone amplifier. The goal was not to hear any noise (hum, buzz or hiss) with the headphones on my head. Heaters, B+ everything was regulated there was no audible noise.
I also support separate heater and B+ transformers. Keep the diode noise sources separate!
Take a look at the Salas HV shunt regulator here on DIYAudio.
DT
All just for fun!

Good suggestion. I have never tried B+ regulated. I also like to use a separate power transformers for the each chanell of my preamplifier.
Till now the best improvement in sound I achieved using the red-led for biasing the catode of gain stage. I dont know if some of You have an experience with red-leds biasing.

 

[Gluca]

I only use RED leds ...

(my hearing falls after 13kHz ... but ... look at this link)

 

[GoranB]

I only use RED leds ...

(my hearing falls after 13kHz ... but ... look at this link)

Same with me 13Khz
We are missing the harmonics of all those instruments on the link you sent.

 

[DualTriode]

Hello GoranB,
Never red LED’s only green.
I have not built large power output tube amps. I have built small up to 2-3 maybe 4 watt output single end power amplifiers. I have built more than I can now recall line stages. The biggest improvement if you can call it that is from regulated B+ power supplies. There is a much more solid response or slam when the voltage does not sag on the transient peaks.
Speakers are another off topic and can make a huge difference.
For even more sneak in 500 watts of SS.
DT
All just for fun!

 

[Gluca]

GoranB .. you (I) can still hear 2nd and 3rd harmonics of the highest piano key.

 

[GoranB]

Hello GoranB,
Never red LED’s only green.
I have not built large power output tube amps. I have built small up to 2-3 maybe 4 watt output single end power amplifiers. I have built more than I can now recall line stages. The biggest improvement if you can call it that is from regulated B+ power supplies. There is a much more solid response or slam when the voltage does not sag on the transient peaks.
Speakers are another off topic and can make a huge difference.
For even more sneak in 500 watts of SS.
DT
All just for fun!

Green led's add more noise then red ones. About regulated PS i will try and i hope it will improve sound.

 

[GoranB]

GoranB .. you (I) can still hear 2nd and 3rd harmonics of the highest piano key.

That's really good for Us