Any advantage to replacing PS resistors with chokes?
- Thread starter Tubejack
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Grainger49
New member
This is interesting, Bottleheads often replaced one of the power supply resistors with a choke in the FP 2. The Paramour upgrade used a power supply choke. The Paramount uses a choke in the heater supply.
It seems that with fully shunt regulated circuits there is no advantage (Paramount and Eros). But it would be interesting to see if someone tries it in Crack.
It seems that with fully shunt regulated circuits there is no advantage (Paramount and Eros). But it would be interesting to see if someone tries it in Crack.
In a highly modified Crack that I have here, I did indeed use a choke in the power supply (Triad C7X). The Hammond 155H won't work so well, as the Crack draws more than 50ma.
I would suspect that a single Hammond 157L or 158L would do in place of the two 270 ohm resistors. Just double up the power supply caps after the choke. (I haven't tried this, so don't be too shocked if it might be nosier than it should be)
I would suspect that a single Hammond 157L or 158L would do in place of the two 270 ohm resistors. Just double up the power supply caps after the choke. (I haven't tried this, so don't be too shocked if it might be nosier than it should be)
Grainger49
New member
Paul,
Are you suggesting a CLC (doubled) filter or an LC (doubled) filter? I think I remember that the stock filter is CRCRC.
Are you suggesting a CLC (doubled) filter or an LC (doubled) filter? I think I remember that the stock filter is CRCRC.
CLC. Just LC would have tremendous voltage drop.
Was just reading this post, because I'm thinking of replace the first 270R resistor with a Triad choke and before doing so I wanted to review previous posts and see if there was anything on the subject. I already have 1 choke installed in a CRCLC configuration. Since I have a second choke I thought what the help why not use it. From what I gather from the previous posts If I install the second choke in a CLCLC configuration I should at least double the capacitance of the last cap.
Grainger49
New member
There has been discussion back and fourth. I would think that the second resistor replaced with a choke makes it closer to the audio circuit. I think PJ suggests replacing the first resistor. So the Triad for the first one would be a good step.
Grainger49
New member
The biggest improvement in caps is the final cap. Making it a low ESR cap makes an audible difference.
Doubling all the caps in your power supply is not necessarily a good idea.
There is a very nice and simple power supply design application available for free on the net called PSUD2. It lives on a site called duncanamps. You should definitely install it and play with the simulations, if you want to get your power supplies to work properly.
There is a very nice and simple power supply design application available for free on the net called PSUD2. It lives on a site called duncanamps. You should definitely install it and play with the simulations, if you want to get your power supplies to work properly.
I don't know the answer to that one. PSUD2 is a popular program for being so specialized. I suspect that you can find some info at duncanamps and much more by doing google searches.
Other than that you might just start your own journey: [1] why do I want to change the power supply? possible answers to reduce noise, to reduce distortion [2] how is the ps built up right now? all components with necessary values and schematic [3] how does this ps perform in the psud2 simulation? voltages, voltage variation, voltage at startup in various components, currents dto [4] where does the choke fit in and what happens? with all of those steps it helps to check frequently, if the psud2 simulation matches measured performance just to make sure you are using the correct values for components and the correct circuit layout.
It's worthwhile, if you care. If you don't, you might want to ask for advice how to change your power supply rather than swap parts on a whim. The Bottlehead power supplies are pretty good to begin with and you don't want to spend money and effort making them worse.
Other than that you might just start your own journey: [1] why do I want to change the power supply? possible answers to reduce noise, to reduce distortion [2] how is the ps built up right now? all components with necessary values and schematic [3] how does this ps perform in the psud2 simulation? voltages, voltage variation, voltage at startup in various components, currents dto [4] where does the choke fit in and what happens? with all of those steps it helps to check frequently, if the psud2 simulation matches measured performance just to make sure you are using the correct values for components and the correct circuit layout.
It's worthwhile, if you care. If you don't, you might want to ask for advice how to change your power supply rather than swap parts on a whim. The Bottlehead power supplies are pretty good to begin with and you don't want to spend money and effort making them worse.
BNAL said:
Well I installed the second Triad choke in the power supply. Damn this amp is getting heavy.
I like the results. There seems, to my ears, to be improved clarity and more definition to the music. Everything seems to have very good impact with and seperation. I was going to replace the electrolytics with film, but think I will save my money for now.
This is such a fun amp that only cost $300 with speedball and I only spent about $60 in parts upgrades, not including tubes. I can't imagine finding a better deal.
I still have a Bottlehead power cord on the way.
I like the results. There seems, to my ears, to be improved clarity and more definition to the music. Everything seems to have very good impact with and seperation. I was going to replace the electrolytics with film, but think I will save my money for now.
This is such a fun amp that only cost $300 with speedball and I only spent about $60 in parts upgrades, not including tubes. I can't imagine finding a better deal.
I still have a Bottlehead power cord on the way.
Am I correct in that at least electrically, the benefit of a choke in the PS is twofold: a) greater isolation of supply-related noise from the output signal, and b) the ability of the inductor to hold electrons in its magnetic field, which would indicate the potential for reserve capacity when the amp "asks" for more juice during a loud transient? The Triad choke is cheap, so I might try one out as well. I have to say, though, the Crack is already near perfection as-is, between the Speedball, good tubes (including the E80cc in the driver's seat) and film capacitors in the output position (previously, large-value electrolytics bypassed with small films - but I've recently given up on using AKG's with this amp and will just stick to Senns).
Grainger49
New member
Well, Brad, your ears are the only two that have to be happy.
Bottlehead is not adverse to chokes in the power supply. It was a frequent, and suggested upgrade for the FP 1 and 2. The Eros PS PCB has spare solder pads for a choke. In that case you have to remove the resistor, of course.
Some of the finest scratch built amps I have ever heard had enough iron to sink a small ship.
The function is several fold. The choke not only drops a little voltage and slows the charging of the next cap creating smoother DC like the resistor. A choke resists rapid current changes through it.
This feature of chokes slows the inrush current at startup. And it feeds back some current when you turn it off. That last bit doesn't harm anything. It just slows the drain of the B+ a little bit.
Chokes pose a high impedance to high frequencies and low impedance to low frequencies. You can see why they are used in crossovers. But in a power supply this characteristic blocks noises that are high frequencies while passing anything DC to low frequency (120 Hz rectified, and lumpy DC). This high frequency noise will pass right through a diode and resistor.
And some day I will sit and do some serious work with PSUD. BTW, it is standard fare for all electrical engineers today, not when I was in school. I was a recruiter at Georgia Tech and UT for Kimberly-Clark. Every applicant had PSUD on their list of skills.
Bottlehead is not adverse to chokes in the power supply. It was a frequent, and suggested upgrade for the FP 1 and 2. The Eros PS PCB has spare solder pads for a choke. In that case you have to remove the resistor, of course.
Some of the finest scratch built amps I have ever heard had enough iron to sink a small ship.
The function is several fold. The choke not only drops a little voltage and slows the charging of the next cap creating smoother DC like the resistor. A choke resists rapid current changes through it.
This feature of chokes slows the inrush current at startup. And it feeds back some current when you turn it off. That last bit doesn't harm anything. It just slows the drain of the B+ a little bit.
Chokes pose a high impedance to high frequencies and low impedance to low frequencies. You can see why they are used in crossovers. But in a power supply this characteristic blocks noises that are high frequencies while passing anything DC to low frequency (120 Hz rectified, and lumpy DC). This high frequency noise will pass right through a diode and resistor.
And some day I will sit and do some serious work with PSUD. BTW, it is standard fare for all electrical engineers today, not when I was in school. I was a recruiter at Georgia Tech and UT for Kimberly-Clark. Every applicant had PSUD on their list of skills.
Chokes are great in power supplies. I never argued against the choke in Brad's amp by the way, but you don't want to increase the size of the capacitors in front of the choke. On the contrary, compared to an RC arrangement you really want smaller capacitors in front of the LC. It has multiple benefits. You can still increase the capactor value towards the end of your filter chain.
