Re: Something is wrong in my calculations !
Konnichiwa,
Here is the answer, verbatim from an answer further up:
In addition, the 1.414 fatcor assumes in essence a zero source and diode impedance and an infinitly large and zero ESR capacitor. As non of these conditions are fulfilled I would suggest modeling the PSU in PSUD which gets jolly close.
My own DHT DC Supply in the works uses a 5R1 / 25W adjustable resistor together with the stated windings to allow the provision of DC to the heaters of 45; 2A3; PX-4; PX-25; RE-604; AD-1; 300B; 6A3/6A5/6B4; 50; 10/10Y/VT25; VT-52.
If you where in addition to provide suitable HT Taps on the mains transformer (I have specified these) you could use a wide range of output Valves, especially if make the output transformers with a 16 (and possibly even 32 Ohm) tap option which allows you to connect an 8 Ohm speaker to the 16 ohm Tap in effect generating an (arguably slightly compromised) 2K5 Transformer and if you have also 4 ohm Taps (and possibly even 2 Ohm) available you could connect an 8 Ohm Speaker to the 4 Ohm Tap genertaing an (arguably slightly compromised) 10K Transformer.
That would then allow you to "drop in" any medium to low Power DHT that takes your fancy.
Sayonara
Konnichiwa,
Antonio Tucci said:KYW,
Something is wrong in my calculations !
considering that the current for the heaters of 300B is 1.2 A (as reported in the data sheet) …
and suppose that I want to have the filament of 300B supplied with 5Vcc in a CLC combination …
with 8Vac on the secondary of the transformer for the heaters, I have,
- After the bridge rectifier and the first capacitor: 8x1.4-1.4 = 9.8
- Reduction produced by the power choke (let say 0.1H, 4A, 0.47 DCR): V=RxI = 0.47x1.2 = 0.56V
- After the choke: 9.9–0.56 = 9.34 Vcc …????
Here is the answer, verbatim from an answer further up:
Kuei Yang Wang said:
In addition, the 1.414 fatcor assumes in essence a zero source and diode impedance and an infinitly large and zero ESR capacitor. As non of these conditions are fulfilled I would suggest modeling the PSU in PSUD which gets jolly close.
My own DHT DC Supply in the works uses a 5R1 / 25W adjustable resistor together with the stated windings to allow the provision of DC to the heaters of 45; 2A3; PX-4; PX-25; RE-604; AD-1; 300B; 6A3/6A5/6B4; 50; 10/10Y/VT25; VT-52.
If you where in addition to provide suitable HT Taps on the mains transformer (I have specified these) you could use a wide range of output Valves, especially if make the output transformers with a 16 (and possibly even 32 Ohm) tap option which allows you to connect an 8 Ohm speaker to the 16 ohm Tap in effect generating an (arguably slightly compromised) 2K5 Transformer and if you have also 4 ohm Taps (and possibly even 2 Ohm) available you could connect an 8 Ohm Speaker to the 4 Ohm Tap genertaing an (arguably slightly compromised) 10K Transformer.
That would then allow you to "drop in" any medium to low Power DHT that takes your fancy.
Sayonara
KYW,
what do you thing about the values 1 uf (C5-6), 40 uF (C3-4) and 100 uF (C1-2) of the capacitors used in the power supply section ... in relation with the values of the reported chokes ?
I'd like to use Solen Fast Metalizzed Polypropylene ...
Somebody told me that I could use a Capacitor with relatively little capacity (i.e. 20-40 uF) and high quality in the last position (C1-2) and a Capacitor with big capacity (i.e. 200 uF) and low quality (also electrolytic) in the sandwitch position (C3-4) ... all this in order to reduce the cost of the power supply section.
what do you thing about the values 1 uf (C5-6), 40 uF (C3-4) and 100 uF (C1-2) of the capacitors used in the power supply section ... in relation with the values of the reported chokes ?
I'd like to use Solen Fast Metalizzed Polypropylene ...
Somebody told me that I could use a Capacitor with relatively little capacity (i.e. 20-40 uF) and high quality in the last position (C1-2) and a Capacitor with big capacity (i.e. 200 uF) and low quality (also electrolytic) in the sandwitch position (C3-4) ... all this in order to reduce the cost of the power supply section.
Konnichiwa,
Looks allright to me. I'd do some detailed modelling in PSUD including step response etc... to be sure.
If you must. I'd probably go for much cheaper and higher quality oil filled MKP Motor run types....
Have a look at the step response of that circuit.... I would instead recommend to use a set of smallish value MKP Cap's with a RC circuit having the lower quality Cap (R can be quite highish), similar principle as "lossy parafeed", to damp resonances caused by insufficient LC Ratio.
Sayonara
Antonio Tucci said:
Looks allright to me. I'd do some detailed modelling in PSUD including step response etc... to be sure.
Antonio Tucci said:
If you must. I'd probably go for much cheaper and higher quality oil filled MKP Motor run types....
Antonio Tucci said:
Have a look at the step response of that circuit.... I would instead recommend to use a set of smallish value MKP Cap's with a RC circuit having the lower quality Cap (R can be quite highish), similar principle as "lossy parafeed", to damp resonances caused by insufficient LC Ratio.
Sayonara
KYW,
two further questions (the last):
1) Kenvinker wrote ...
2) I included the final version of the schematic ... with the values of the components. Do you have some suggestions, corrections or changes to propose before we start with the prototype ?
P.S.
As to the power stage (300B) we will test the version you proposed (360 Va, 60 mA, 74 Vg ...and no diode on the cathode) too.
KYW ... many many many THANKS for your support .
By by from Italy
two further questions (the last):
1) Kenvinker wrote ...
Why is not possible ?
2) I included the final version of the schematic ... with the values of the components. Do you have some suggestions, corrections or changes to propose before we start with the prototype ?
P.S.
As to the power stage (300B) we will test the version you proposed (360 Va, 60 mA, 74 Vg ...and no diode on the cathode) too.
KYW ... many many many THANKS for your support .
By by from Italy
Konnichiwa,
Well, much is possible. The key difference is that directly heated rectifiers have a Filament arrangement like Directly Heated Triodes. If you want to avoid to overlay 5V extra AC from the heater above the Pulsing 400V or so DC you obtain the HT from a centertap on the Heater winding for the rectifier.
Indirectly Heated Rectifiers have a seperate cathode sleeve. Depending upon the rectifier this cathode sleeve is usually connected to one side of the heater. If you where to use a IDH Rectifier with the centertap designed for a DH Rectifier you would find yourself now with 2.5V AC overlaid AND (more crucial) some DC offset in the transformer core (not one I'd worry about).
In my experience all this is academic, I tend to connect the HT Output to pin 8 for the typhical socketed rectifiers (5U4, 5R4, GZ32/33/34/37) and have yet to encounter problems from it and I tend to be far from alone in this regard.
Looks right to me, except, please DO make the 2K7 resistor in the anode loop of the 6S45 adjustable, around 10K with a 4K7 resistor in series (allows 4k7 - 14k7 adjustment). Given that you use fixed bias on the grid, the 6S45 has rather wide parameter variations in production, you will have to trim these out.
Also, when switching on the Amp first have only the driver stage in place and adjust the Bias to be correct (74V). As you intend to make quite a few Amp's I would suggest to take a handfull of 6S45 and try them all and see what adjustment range you would need for the finished Amplifier and then to fix the value of adjustable resistor and fixed series resistor to suit.
Also, put a grid stopper choke or resistor onto the 6S45.
An anode current meter may be a good idea to allow easy bias setting.
By all means keep space for a diode, it's just that I feel that inserting additional non-linear elements into a non-linear circuit to make it more linear is a bit of a hit/miss game. Make the smallest change to such a circuit if optimised and suddenly you end up with more non-linear circuit than the one without any attempts at linearisation with this methode.
Sayonara
Antonio Tucci said:
Well, much is possible. The key difference is that directly heated rectifiers have a Filament arrangement like Directly Heated Triodes. If you want to avoid to overlay 5V extra AC from the heater above the Pulsing 400V or so DC you obtain the HT from a centertap on the Heater winding for the rectifier.
Indirectly Heated Rectifiers have a seperate cathode sleeve. Depending upon the rectifier this cathode sleeve is usually connected to one side of the heater. If you where to use a IDH Rectifier with the centertap designed for a DH Rectifier you would find yourself now with 2.5V AC overlaid AND (more crucial) some DC offset in the transformer core (not one I'd worry about).
In my experience all this is academic, I tend to connect the HT Output to pin 8 for the typhical socketed rectifiers (5U4, 5R4, GZ32/33/34/37) and have yet to encounter problems from it and I tend to be far from alone in this regard.
Antonio Tucci said:
Looks right to me, except, please DO make the 2K7 resistor in the anode loop of the 6S45 adjustable, around 10K with a 4K7 resistor in series (allows 4k7 - 14k7 adjustment). Given that you use fixed bias on the grid, the 6S45 has rather wide parameter variations in production, you will have to trim these out.
Also, when switching on the Amp first have only the driver stage in place and adjust the Bias to be correct (74V). As you intend to make quite a few Amp's I would suggest to take a handfull of 6S45 and try them all and see what adjustment range you would need for the finished Amplifier and then to fix the value of adjustable resistor and fixed series resistor to suit.
Also, put a grid stopper choke or resistor onto the 6S45.
An anode current meter may be a good idea to allow easy bias setting.
Antonio Tucci said:
By all means keep space for a diode, it's just that I feel that inserting additional non-linear elements into a non-linear circuit to make it more linear is a bit of a hit/miss game. Make the smallest change to such a circuit if optimised and suddenly you end up with more non-linear circuit than the one without any attempts at linearisation with this methode.
Sayonara
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