I can't remember, it's been a long time since I worked on that amp. It might not have had a center tap on the transformer?
It's to make a full wave bridge, so doesn't apply to the OP.
If I could make a general comment about desired B+, anything less than 400VDC is perfectly fine, as long as the power supply electrolytics have at least a 450VDC rating. Stephe's recommendation of 350VDC is a good conservative number, and her layout preserving as much of the B+ as possible for the driving stage is important. Really, anything that you can get from that mains transformer will work fine. Power varies with the square of voltage, but linearity is best with lower voltage, higher idling current - there's no "ideal" until you define the word.
Everyone seems to have missed Tim Robbin's mixed rectifier solution - very very elegant.
All good fortune,
Chris
If I could make a general comment about desired B+, anything less than 400VDC is perfectly fine, as long as the power supply electrolytics have at least a 450VDC rating. Stephe's recommendation of 350VDC is a good conservative number, and her layout preserving as much of the B+ as possible for the driving stage is important. Really, anything that you can get from that mains transformer will work fine. Power varies with the square of voltage, but linearity is best with lower voltage, higher idling current - there's no "ideal" until you define the word.
Everyone seems to have missed Tim Robbin's mixed rectifier solution - very very elegant.
All good fortune,
Chris
Hereby defined as the "middle of the road" approach as a starting point, not perfection.
Never heard of it. Link please?
I totally missed that link. Sorry. So to be clear, we are talking about this SS-tube hybrid "bridging" option (diagram below)? Increasing rectifier tube life? Plus being able to use a 10uF first cap instead of the smallish specified 5uF too? Not sure I understand the highlighted warning - something like the heavy duty (3A) 1N5408 instead to be on the safe side with the diodes?
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My suggestion was related to the relatively low current capability of a 5U4C given the likely load current. So it may be a way to still use the 5U4C and keep within tube ratings.
The caution comment relates to having a cursory view that this configuration gets you a 140% rating increase.
The caution comment relates to having a cursory view that this configuration gets you a 140% rating increase.
Seems like 1N5408 (3A) ought to more than do it. Those are big.
Do I have this straight?
Do I have this straight?
- "Soft" turn-on delays B+ due to the indirectly heated 5Ц4С.
- Solid state diodes and the bridged configuration double the rated current capability for the 5Ц4С rectifier tube.
- Increases rating for first cap from 5uF to 10uF.
- Increases rectifier tube life vs. no diodes.
- Tube rectifier has the dominant influence on the rectified current, including relatively soft turn-off characteristic vs. pure solid-state rectification. In other words, "The tube rectifier isn't going to introduce switching noise that SS diodes can introduce."
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$10.16 each * 3, plus tax, plus shipping. Nooooo ... those are expensive little doo dads.
It finally got here. The chassis is ok. The output transformers are small 0.913kg/2lb models. Other more expensive versions of the kit come with bigger ones. The power transformer seems decent. It came with a pair of PSvane EL34 output tubes, a Soviet-era 5Ц4С rectifier, and Soviet-era 6H8C driver tubes, all of which appear new. The chassis is stainless, which surprised me. I expected plain steel with light rust. It's going to get painted anyway. It does, in fact come with a pair of 150uF power supply capacitors, which I now know is wrong thanks to those of you who are here. Those two were going in the trash anyway. There are so few components in the amplifier that for a few dollars I can upgrade all of them. I have some decent quality Chinese parts on hand from other kits that may end up inside this one. Not everything made in China is bad.
I watched with interest the recent video from @stephe where she indicated that 5k output transformers were doing better than 3.5k as far as distortion in her EL34 SE amp, albeit with a little less power. Since I'm contemplating getting some bigger OPTs from China, I'm wondering if I should use 3.5k or 5k?
I haven't tested the power transformer and likely won't until after the 1st of the year. Step 1 will be to get some inexpensive but larger OPTs on order from China. Step 2 will be to put together a power supply, probably using the rectifier tube and diode hybrid approach above. I tested my wall outlet last night and it's now up to 123 volts. How high the power companies intend to push it, I have no idea.
I watched with interest the recent video from @stephe where she indicated that 5k output transformers were doing better than 3.5k as far as distortion in her EL34 SE amp, albeit with a little less power. Since I'm contemplating getting some bigger OPTs from China, I'm wondering if I should use 3.5k or 5k?
I haven't tested the power transformer and likely won't until after the 1st of the year. Step 1 will be to get some inexpensive but larger OPTs on order from China. Step 2 will be to put together a power supply, probably using the rectifier tube and diode hybrid approach above. I tested my wall outlet last night and it's now up to 123 volts. How high the power companies intend to push it, I have no idea.
Come On guys. this should be a 'no brainer'. Less talk & more thought,
the time of the Greek Philosophers is a long way back in the rear view mirror.
Two of One KV SS diodes, each in series with its own 100R resister, all built inside an Amphenol plug.
I built mine that way at least 30 yrs ago. And before that bought the same kind of thing all sealed in
an Amphenol Octal plug marketed by New Sensor Corp.👍
Time to move on.🙂
Not quite yet. If I start a new thread people will get mad. If you look through the thread, it turned into more than the title suggests, and I'm going to keep the tube rectifier after all. In other words, I was wrong about it and also changed my mind. As for making a SS replacement, no. I'm going to try the diode-tube hybrid approach mentioned above and see if it works. People above also seemed interested in what came in the kit, so I gave an inventory,
The kit just got here Friday afternoon, and I want to get some larger OPTs on order from China. Not sure about 3.5k vs. 5k yet. It's off topic, but if anyone knows, say so please. See Stephe's video in post #94.
Also in the kit, a choke labeled 4H 200mA that's about the same size as the OPTs. DC resistance measures 53.7 ohms. Looks nice.
Now I will fiddle in PSUdesigner, and then put the kit away until after the first of the year. I have two kits spread out all over the place. I'll start a build thread next year because I will then know what B+ voltage I have, and I'll need help with the audio circuit when the time comes next year.
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I like this simple mod. One half the peak plate current, increased tube life and will reduce voltage drop/sage across the tube for a bit more B+.
Bonus, it can be easily undone to restore vintage units to original. Simply great.
What am I doing wrong in PSUdesigner? Learning all of this is very confusing (for me).
power transformer 320-0-320 VAC with no load
power transformer primary 21 Ohms
power transformer secondary 48 Ohms per half
4H choke 54 Ohms
5Ц4С is equivalent to 5Z4 so I used 5Z4 in PSUdesigner
Even if I put two 150uF in PSUdesigner, I'm still not getting what I would expect, even though it's a 110V transformer being fed 122V. Schematic shows 310 volts and I only get 303 volts in PSUdesigner. If I put in a 6.8uF for the first capacitor to get closer to where we are supposed to be for the rectifier tube, I only get 294 volts. A "reasonable" target is 350-400V, correct?
power transformer 320-0-320 VAC with no load
power transformer primary 21 Ohms
power transformer secondary 48 Ohms per half
4H choke 54 Ohms
5Ц4С is equivalent to 5Z4 so I used 5Z4 in PSUdesigner
Even if I put two 150uF in PSUdesigner, I'm still not getting what I would expect, even though it's a 110V transformer being fed 122V. Schematic shows 310 volts and I only get 303 volts in PSUdesigner. If I put in a 6.8uF for the first capacitor to get closer to where we are supposed to be for the rectifier tube, I only get 294 volts. A "reasonable" target is 350-400V, correct?
The transformer has a calculator for effective secondary resistance - fill that out to get the appropriate effective resistance.
If you aren't using the identified rectifier tube for its model then expect some 'tolerance'.
If you aren't using the identified rectifier tube for its model then expect some 'tolerance'.
The 5Z4 rectifier tube in PSUdesigner is the Chinese copy of the 5Ц4С. I did try the included transformer calculator as shown below, and unless I am using it incorrectly, I get 255 volts with a 6.8 uF capacitor. I must be doing something wrong.