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My amp's power supply has 2 tube rectifiers. I was wondering if it were possible to use a hybrid SS + tube to get a higher output but a slow voltage ramp up? Maybe if i hook up the sockets in series and put the tube first? Or maybe in parallel with the tube first. cheers, Dak
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Adding 30 volts B+ will get you barely noticeable increase in volume, but it will throw off your bias and potentially over-volt your caps. Your OPT is a limiting factor too.
my amp has EICO HF87 output trannys which are good for 35watts. My bias is adjustable from 0 to -60 volts so i dont have concerns about that. My caps are good for 550vdc but i don't know the surge voltage rating.
So, i don't think i have any concerns accommodating a modest increase in B+ voltage.
DAK & Co.
I think you may be missing the point of having two tube rectifiers to begin with. It's done that way because more current is needed than the 225ma one 5AR4 can provide. The two rectifier tubes are arranged in parallel. Plates to plates, cathode to cathode.
If you substitute one tube with a SS rectifier, naturally it will turn on immediately and produce an abnormally high voltage until a) the circuit tubes start conducting, b) the 5AR4 starts conducting and the transformer current splits between the two. At that point, the drop across the tube rectifier comes into play and should drop the voltage to a more nominal level.
As for adding SS rectifiers in SERIES with the tube plates, that is done to simply prevent damage to the power transformer should the rectifier catastrophically short out. The SS rectifiers will take over the rectification job and all is well except, the B+ voltage will rise by about 40 Vdc. If your filter caps. aren't rated for the increase in voltage, they could be destroyed.
Finally, if you want more B+, why not just use heavy duty (3A) ss rectifiers to begin with? The cathode stripping theory has been debunked by engineer David Gillispie. Besides, if cathode stripping exists, why don't rectifiers suffer from this? Their plates are brought up to maximum secondary voltage as soon as the power switch is turned on while the tube is still dead cold.
with the full voltage of SS rectifiers. I would not think of doing this on a whim and not have sufficient voltage capability with my capacitors. Having a slow voltage ramp up is not only a cathode stripping issue or non issue in audio amps, but a parts and tubes issue as well. Off to full on voltage cycles will wear out your parts and tubes much faster than a controlled voltage ramp up via an indirectly heated rectifier.
With my dual tube rectifier power supply it is an opportunity to easily explore the possibility of having a higher B+ voltage for using other tubes and getting more flexibility out of the power supply. I don't see any other way of doing this on the secondary side of the PT.
FL, pointed to a method involving a switch on the SS rectifiers which is certainly doable, but i am hoping for a plug in solution. cheers, Dak
SS rectifiers in front of 5AR4's. They do the heavy work, the 5AR4 further reduces the ripple and as mentioned elsewhere, you have the slow turn on. I also used a thermistor to ease the stress on the tube rectifiers.
iBasso DX100,DX50 DX90. Chord Hugo. HiFiman 901s balanced. RSA Intruder, The Lightning. Fostex TH900 balanced, HE1000, HE-6, 560, 500, JH13 Pro balanced. Lyr2, Audeze. Balanced mostly with Whiplash cables. Photo gallery: www.pbase.com/jamato8
with the high voltage supply. Or are they in parallel like the rectifiers shown in the Mission Amp as posted by FenderLover, but without the switch?
I put the SS in front of the tubes to do the initial rectifying, which also take stress of of the tubes and they last a lot longer. The voltage is dropped by the tubes and you should come out about the same.
iBasso DX100,DX50 DX90. Chord Hugo. HiFiman 901s balanced. RSA Intruder, The Lightning. Fostex TH900 balanced, HE1000, HE-6, 560, 500, JH13 Pro balanced. Lyr2, Audeze. Balanced mostly with Whiplash cables. Photo gallery: www.pbase.com/jamato8
I tried both ways and it made no difference. The B+ came up immediately so no slow voltage ramp up. Is you ss rectifiers grounded?
When i tried putting a ss octal socketed rectifier in my amp the voltage came up immediately.
Edits: 08/05/16
Why not just use SS rectifiers plus a time delay/soft start circuit? K&K Audio makes a convenient kit for that purpose.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Hi JKT, i have already made the PS. I am very pleased with it and mostly wanted to play with some options for increasing power and also reducing the current load of the power trans. I was hoping that a combination of SS and tubed rectifiers would allow me to have my cake and eat it too! cheers, Dak
PS, i guess i could eat half a cake by using a plug in on one socket and at the least reduce the current load by 2A.
The Ongaku amp had SS rectifiers with a 5AR4 following them. It's only purpose was for the slow warmup characteristic.
Though, it'd be nice to eliminate the manual switching.
So this scheme will allow a slow warmup with the 5ar4 then when the B+ is up you can switch in the SS rectifiers. I wonder if there is any noise when the switch is thrown? thanx for the post, Dak
I'm not familiar with this feature on these Mission Amps. But, I'd imagine you get a noise similar to switching on a standby.
I found an article on the Ongaku by Kondo, from the Sound Practices magazine circa 1992. Interesting article, btw, in it the schematic is given and that shows a 5ar4 x 4 rectifier scheme for the B+. Maybe the Ongaku you are referring to is an updated version?
Hi Al, do you know how AN had the rectifiers arranged? It would be great if you could direct me to a schematic. tyvm, Dak
mt
You will not get higher voltage unless the rectifier tube is out of the circuit. Possibly a switch to cut out the tube rectifier after warmed up. What is the load your amp needs from the twin rectifiers? What type rectifiers are they?
I replaced 1 5v4 with a SS rectifier in an octal socket of my own making. i used some high volt Schottky rectifiers in the octal socket.
What happened was HIGH VOLTAGE immediately appeared at the output. This was 630v which dropped down to 350v after 20 seconds which is 10v more than all tube rectifiers. Just thought i would let you all know .
Would wiring the rectifiers sockets differently from parallelled to series be different? thank you for the input,
MY experience with a switch in an energized circuit is that there is going to be a noise when it is turned off or on. Sometimes the noise is loud and disturbing. If making the power supply half ss results in only a slow warm up then that would be a positive result as it would save 2
amps of current in the power trans. cheers, Dak
Hi chip, i am using 5ar4 rectifiers.
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