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IXYS HiPerFreds, Fairchild Stealths, Cree SIC Shottkies.I know the technical differences, but.....
What are the "sonic" differences when used in a Greatz Hybrid bridge?
Since the tube is the "slowest" recovery element of the equation, and the one that gives the bridge it's basic sonic signiture, does the type of diodes mentioned above really make a substantial audible difference?
Say the tube will be a 5U4G and the B+ around 490 VDC after the filter.
JD
Edits: 03/12/12 03/12/12Follow Ups:
Hi Jeff,More likely the diodes are failing from overvoltage than current in my own experience. Higher current rated diodes may be noisier on switching due to more capacitance. Peak curernt in a FWB with cap input is no more than 7X the continuous current. $0.02
Edits: 03/15/12
snubbers should help with the noise?
JD
snubbers should help with the noise?always
This 1200V doubler uses UF4007 in series with the HV ceramic cap across each diode to help with switch-off and equalize the reverse voltage.
Edits: 03/15/12 03/15/12 03/15/12
Thanks Michael!
Jeff
is not the only factor. In my experimentation with Bybee purifiers, I am of the belief that solid state diodes actually induce a phase shift between current and voltage, which is non existence with tubes, since the cathode is what generates the B+. You are, of course, entitled to your own opinion.
I generally run diodes paralleled with a tube rectifier. The circuit must be modeled on the solid state devices, voltage wise, but one can remove the tube rectifier while the unit is running with no harm (except for the heart attack from experienced tube veterans!). Inevitably, the circuit sounds better ( better highs, more detailed midrange) with the tube inserted, although the great advantage is that I can run any rectifier I want, as the solid state diodes handle the bulk of the load. The solid state devices certainly add bass as I can now increase the first capacitor to very large values.
Ar any rate YMMV
Stu
yes, all that..
but what of the sonics?
JD
question, as I clearly state the sonic differences.
Stu
The hybrid bridge will be second best in sonics on high efficiency speakers where you can easily HEAR such things.It will not be as clear sounding as if you used four tube rectifiers or four solid state devices. It will be a SONIC degrade.
Why?? I'm no engineer, I'll leave that for others to theorize over, but there are different conduction angles, rise times, and so, on EFFICIENT speakers, the hybrid bridge DESTROYS some of the music, and what we are trying to achieve as honest, neutral reproduction.
The diodes in a full wave bridge need to be EXACTLY the same, all four, not two solid state and two tubes. The diodes in a full wave bridge need to be EXACTLY the same, all four, not two solid state and two tubes. The diodes in a full wave bridge need to be EXACTLY the same, all four, not two solid state and two tubes. The diodes in a full wave bridge need to be EXACTLY the same, all four, not two solid state and two tubes.
Maybe we need to use eight devices in a bridge, four tube AND four solid state, just as Uncle Stu suggests....( I need to TRY that !!) at least they would all be the configured the SAME !!
Jeff Medwin
Edits: 03/14/12
Thanks Jeff...
I'm just considering the diodes on an alreay built circuit. I happend to kill one diode with an inadverdent spike when I powered down and powered up the amp. Since I have to replace the baddy, I thought I'd pose the question because there are a few different types available now that were'nt when I built the circuit.
It presently has Cree SIC's but came across the HiPerFreds and Stealths when I looked for diodes in the ratings required.
I'm not looking to change the topology, just the diodes.
JD
Hi Jeff,
In that case, maybe you should ask "what will be the most reliable part I can use" and seek a 1600 VDC PIV part that can do Amperes. Beats an amp failing, and with solid state you want to over-rate it to get it reliable.
The VAC in my new 6AQ5 SE stereo amp is 318 VAC, and I am starting out with a 1600 VDC at 35 A. bridge.
Jeff Medwin
ok... gots me some 1800V 60A jobies coming in. IXYS DH60-18A in a TO 247 form factor. Spendy, but I'll be done with it.
JD
Sure those parts will work. And if you got a great deal on them, why not. But if purchasing retail parts, going to this level of safety factor (i.e. overkill) is just wasting money.
Please report back to us all if they sound the same, or better, or worse to you than what you had in there Jeffrey. They should not fail !!!
Jeff Medwin
4007's and Fairchild Stealth both snubbed .01 ceramic, with a Schtotkky or tube following in the hybrid...
tube was tube rectifier sound except slightly deeper...Schtoktky sorry can't type tonight...was really excellent...this is in a 4 6v6 guitar amp...ok
next...
guts removed .... head installed...tomorrow Frankenstein returns
Bedtime..
-3db
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