Schottky vs. Soft Recovery
Hi Petter,
I just replaced the MUR120's by MSR860's in my Philips CD650 CD-Player. They are used in the +/-5V supply, not a high current application.
I feel the MSR's are better!
So I prefer the ultrasoft recovery diodes.
😎
Petter said:
Hi Petter,
I just replaced the MUR120's by MSR860's in my Philips CD650 CD-Player. They are used in the +/-5V supply, not a high current application.
I feel the MSR's are better!
So I prefer the ultrasoft recovery diodes.
😎
Getting soft in my old age
As I said in an earlier post in this thread:
"Many fast recovery diodes designed for soft recovery are starting include numbers for tA and tB in there data sheets. It may be that this ratio indicating softness is more important than just low tRR for the best sounding diodes."
I think the soft recovery types are just as important in low current application as power amps. Digital audio circuits also benefit. Non audio circuits in a preamp or amp should be looked at for soft recovery diodes as well, since their RFI contributions can enter audio circuits through paths such as interwinding capacitance's in power transformers. The 1N493X types work pretty well where 1N400X diodes are used and are not that expensive.
As I said in an earlier post in this thread:
"Many fast recovery diodes designed for soft recovery are starting include numbers for tA and tB in there data sheets. It may be that this ratio indicating softness is more important than just low tRR for the best sounding diodes."
I think the soft recovery types are just as important in low current application as power amps. Digital audio circuits also benefit. Non audio circuits in a preamp or amp should be looked at for soft recovery diodes as well, since their RFI contributions can enter audio circuits through paths such as interwinding capacitance's in power transformers. The 1N493X types work pretty well where 1N400X diodes are used and are not that expensive.
Re: Getting soft in my old age
Fred,
That just startled me as my last change was only to the digtal supply of the CDP. The DAC is powered separately with its own transformer and rectifier.
Eventually I will replace all powersupply diodes in my system, including the poweramplifier.😎
Fred Dieckmann said:
Fred,
That just startled me as my last change was only to the digtal supply of the CDP. The DAC is powered separately with its own transformer and rectifier.
Eventually I will replace all powersupply diodes in my system, including the poweramplifier.😎
Great!
The main jist (inferred meaning) was also that Schottky's could be inherently suboptimal for high current applications.
I guess Schottky's don't necessarily have soft recovery. They probably have almost no recovery. Whether that can be called soft or not is open to interpretation. I have not evaluated how this works in practical situations.
Petter
The main jist (inferred meaning) was also that Schottky's could be inherently suboptimal for high current applications.
I guess Schottky's don't necessarily have soft recovery. They probably have almost no recovery. Whether that can be called soft or not is open to interpretation. I have not evaluated how this works in practical situations.
Petter
In trying to find a source for the MSR1560, turned to searching for MUR1560 parts. At the Mouser web site, they listed the STTA1206D by SGS Thomson as an equivalent part. The data for this piece indicated the Softness factor (tb/ta) as 0.45.
The MSR1560 that Peter Daniel preferred is listed as 0.67 to 0.74, based on temperature. Unfortunately, the conditions cited for each device's softness factor were quite different. On the ST device, it was measured at 125-deg C, with Vf at 400V, If at 12A and dIf/dt at -500A/us. The On-semi data was cited at either 25-deg or 150-deg C with a Vr of 30V, If at 1A and dIf/dt at 100/us.
On-semi doesn't list the softness factor in their data sheet for the MUR1560.
So as Fred said, the data is very difficult to look at when attempting to correlate with listening tests.
For what it's worth, when I contacted On-semi to get a tech person's response for what might be better for an audio power supply (Schottky vs soft recovery), he recommended the soft recovery MSR1560.
Regards, Robert
The MSR1560 that Peter Daniel preferred is listed as 0.67 to 0.74, based on temperature. Unfortunately, the conditions cited for each device's softness factor were quite different. On the ST device, it was measured at 125-deg C, with Vf at 400V, If at 12A and dIf/dt at -500A/us. The On-semi data was cited at either 25-deg or 150-deg C with a Vr of 30V, If at 1A and dIf/dt at 100/us.
On-semi doesn't list the softness factor in their data sheet for the MUR1560.
So as Fred said, the data is very difficult to look at when attempting to correlate with listening tests.
For what it's worth, when I contacted On-semi to get a tech person's response for what might be better for an audio power supply (Schottky vs soft recovery), he recommended the soft recovery MSR1560.
Regards, Robert
Ultrasoft Recovery Diodes
Hi Robert,
I got my MSR860 from Onsemi.
I concur with the tech person at Onsemi.
Data from different manufacturers are always difficult to compare due to different measuring conditions.
I have given up a long time ago that you can estimate the sound quality from datasheets. At best these datasheets are a primer.
I concur with the findings of Peter and Michael and I am very happy this long journey of my endeavour has found a tempory end here.
Hi Robert,
I got my MSR860 from Onsemi.
I concur with the tech person at Onsemi.
Data from different manufacturers are always difficult to compare due to different measuring conditions.
I have given up a long time ago that you can estimate the sound quality from datasheets. At best these datasheets are a primer.
I concur with the findings of Peter and Michael and I am very happy this long journey of my endeavour has found a tempory end here.
faster and soft
Another couple of possibilities for very soft recovery diodes with even faster reverse recovery time would be:
http://www.irf.com/product-info/datasheets/data/8eth06.pdf
http://www.digikey.com/scripts/us/dksus.dll?Detail?Ref=44911&Row=107839
http://www.fairchildsemi.com/ds/IS/ISL9R860P2.pdf
http://www.arrow.com/
Another couple of possibilities for very soft recovery diodes with even faster reverse recovery time would be:
http://www.irf.com/product-info/datasheets/data/8eth06.pdf
http://www.digikey.com/scripts/us/dksus.dll?Detail?Ref=44911&Row=107839
http://www.fairchildsemi.com/ds/IS/ISL9R860P2.pdf
http://www.arrow.com/
PAMPERS FOR DIODES.
Hi,
In case you're working with +/- 50V rails and want to get rid of the diodes hash altogether (well, most of it) an interesting approach can be found here:
TUBE REGULATOR.
Post # 42 and onwards.
Also check Brett's link to AA where Gary Pimm gives a perfect theoretical model in one of his post there.
It obviously has its' limits for solid state high current applications but Gary gives a very good explanation on what exactly goes on.
Enjoy, 😉
Hi,
In case you're working with +/- 50V rails and want to get rid of the diodes hash altogether (well, most of it) an interesting approach can be found here:
TUBE REGULATOR.
Post # 42 and onwards.
Also check Brett's link to AA where Gary Pimm gives a perfect theoretical model in one of his post there.
It obviously has its' limits for solid state high current applications but Gary gives a very good explanation on what exactly goes on.
Enjoy, 😉
Fred,
Thanks for posting those last two devices. I had looked at one of the two items you mentioned in your last posts prior to purchasing the MBR20200CT Schottkys (after scouring the Digikey and Mouser catalogs).
The one thing that had bothered me with the IR 8eth06 was what seemed to me like excessive voltage (Vf) drop as the current draw increases. This would not only heat up the recitifiers more than an equivalent Schottky, but would not it also result in power supply sagging at greater values, behaving like an in-series resistor? How might this affect dynamics and transients that required large currents? I should think it might compress them. (But then, maybe that is a good thing, like a tube sort of compression at clipping.)
In looking over many data sheets, I saw that IR devices did this, while most On-semi and IXYS seemed more likely to have relatively linear Vf figures.
Certainly, if the softness factor is important, the ISL9R860P2 device from Fairchild has it in spades. But it too seems to have a pronounced Vf droop.
Comments about the Vf droop?
Regards, Robert
Thanks for posting those last two devices. I had looked at one of the two items you mentioned in your last posts prior to purchasing the MBR20200CT Schottkys (after scouring the Digikey and Mouser catalogs).
The one thing that had bothered me with the IR 8eth06 was what seemed to me like excessive voltage (Vf) drop as the current draw increases. This would not only heat up the recitifiers more than an equivalent Schottky, but would not it also result in power supply sagging at greater values, behaving like an in-series resistor? How might this affect dynamics and transients that required large currents? I should think it might compress them. (But then, maybe that is a good thing, like a tube sort of compression at clipping.)
In looking over many data sheets, I saw that IR devices did this, while most On-semi and IXYS seemed more likely to have relatively linear Vf figures.
Certainly, if the softness factor is important, the ISL9R860P2 device from Fairchild has it in spades. But it too seems to have a pronounced Vf droop.
Comments about the Vf droop?
Regards, Robert
foward voltage drop
I don't what "excessive" actually is, but it is pretty easy to specify a couple volts higher transformer secondary for use of the soft recovery diodes. The forward resistance of the diode is calculated from the slope of the voltage vs. current curves and is about 0.1 ohms for the soft recovery diodes and about 0.01 ohms for the Schottky diode at several amps.
The transformer secondary winding resistance is probably going to be a number somewhere in this range. I measure about 0.13 ohms for my 225 VA Plitron. So we are looking at less than a 2 to 1 difference in the effective resistance seen charging the filter cap rather than the 10 to 1 difference one might assume looking at the diodes alone in this case. Some people also advocate the use of added resistance in series with the secondary winding to limit peak charging current to the caps. This can reduce high frequency diode noise and transformer saturation during the peak current when the diodes conduct while charging the capacitor.
The power supply source impedance seen by the amp is determined by the filter capacitor except during the period when the cap is being charged by the diodes. This is a almost lways a shorter time period than the interval when the filter caps are being discharged by the load current. Look at your ripple voltage for the ratio of these charge and discharge times for the filter caps.
The bottom line is that it can be misleading to compare data sheets outside the context of the circuit in which the part is to be used. There seems to be a growing consensus that the soft recovery diodes sound better than shottkys and that is what I have experienced in my test as well. I would definitely investigate the use of snubbers when using shottkys and perhaps even some small value series resistors with either diode type.
I don't what "excessive" actually is, but it is pretty easy to specify a couple volts higher transformer secondary for use of the soft recovery diodes. The forward resistance of the diode is calculated from the slope of the voltage vs. current curves and is about 0.1 ohms for the soft recovery diodes and about 0.01 ohms for the Schottky diode at several amps.
The transformer secondary winding resistance is probably going to be a number somewhere in this range. I measure about 0.13 ohms for my 225 VA Plitron. So we are looking at less than a 2 to 1 difference in the effective resistance seen charging the filter cap rather than the 10 to 1 difference one might assume looking at the diodes alone in this case. Some people also advocate the use of added resistance in series with the secondary winding to limit peak charging current to the caps. This can reduce high frequency diode noise and transformer saturation during the peak current when the diodes conduct while charging the capacitor.
The power supply source impedance seen by the amp is determined by the filter capacitor except during the period when the cap is being charged by the diodes. This is a almost lways a shorter time period than the interval when the filter caps are being discharged by the load current. Look at your ripple voltage for the ratio of these charge and discharge times for the filter caps.
The bottom line is that it can be misleading to compare data sheets outside the context of the circuit in which the part is to be used. There seems to be a growing consensus that the soft recovery diodes sound better than shottkys and that is what I have experienced in my test as well. I would definitely investigate the use of snubbers when using shottkys and perhaps even some small value series resistors with either diode type.
Re: Re: Schottky vs. Soft Recovery
I asked Mr. Hagerman if I could post his comments. He said yes.
Refer to schematic here (towards bottom of page).
Jim's comments preceeded by ">>" I deleted stuff that wasn't relevant this discussion.
Enjoy 😉 .
mlloyd1
+++++++++++++++++++++++++++++++++++++++
----- Original Message -----
From: "Jim Hagerman" <jim@hagtech.com
To: "Michael Lloyd" <mlloyd1.enteract@rcn.com
Sent: Friday, March 21, 2003 12:18 AM
Subject: Re: bugle
Thanks. I saw it and looked over the schematic when I ordered the board. Do you mind if I ask a few questions? I understand if you don't wish to give out IP 🙂
>>I don't mind. I post schematics and manuals for free. Don't make any money on these kits - they're just advertisements to draw attention to the expensive products.
1. Why the high speed diodes around the regulators (D1, D8) and across the output (D4, D6)? High speed or soft recovery is not necessary here.
They protect the regulators and normally do nothing, I thought. Leakage
Current issues maybe?
>>Only because I use them in the rectifier circuit. Better to order all the same type so nobody mixes 'em up.
2. I understand the series resistors (R1, R11, R2, R12). But why the "paralleled" resistors (R4, R7, R6, R9)? Maybe R4, R7 do some damping
of the transformer inductance? I expected to see a series R-C across the transformer secondaries and/or across the diodes (although these particular diodes may not really need it).
>>R4 and R7 are snubbers for the transformer secondary coils. The
leakage inductance rings with stray winding capacitance and through the rectifiers every time they turn off. Normally you see a series C, but all that does is cut power dissipation, not really an issue at low voltage.
>>R6 and R9 (also R3 and R10) provide a standing current to bias the regulators up into more of a class-A working region. What this does is make the regulators less sensitive the changes in external load current. Shunt regulation works even better, but is way too inefficient and costs more.
I actually intended to bias them even harder, but this came out ok.
>>You see, regulators do well providing current transients to the output, but are terrible at sucking it up. A fast drop of load current will often cause the regulator to go open loop.
3. I'm thinking the LM317 and LM337 are less noisy devices. 🙂
>>Most of the noise is at low frequencies. If you really want something better, look to some of the more modern Linear Technology or Micrel parts.
>>I really wanted to do a custom super-regulator type design, but didn't have the time.
…
Good luck!
…
Jim Hagerman
Hagerman Technology LLC
…
+++++++++++++++++++++++++++++++++++++++
I asked Mr. Hagerman if I could post his comments. He said yes.
Refer to schematic here (towards bottom of page).
Jim's comments preceeded by ">>" I deleted stuff that wasn't relevant this discussion.
Enjoy 😉 .
mlloyd1
+++++++++++++++++++++++++++++++++++++++
----- Original Message -----
From: "Jim Hagerman" <jim@hagtech.com
To: "Michael Lloyd" <mlloyd1.enteract@rcn.com
Sent: Friday, March 21, 2003 12:18 AM
Subject: Re: bugle
Thanks. I saw it and looked over the schematic when I ordered the board. Do you mind if I ask a few questions? I understand if you don't wish to give out IP 🙂
>>I don't mind. I post schematics and manuals for free. Don't make any money on these kits - they're just advertisements to draw attention to the expensive products.
1. Why the high speed diodes around the regulators (D1, D8) and across the output (D4, D6)? High speed or soft recovery is not necessary here.
They protect the regulators and normally do nothing, I thought. Leakage
Current issues maybe?
>>Only because I use them in the rectifier circuit. Better to order all the same type so nobody mixes 'em up.
2. I understand the series resistors (R1, R11, R2, R12). But why the "paralleled" resistors (R4, R7, R6, R9)? Maybe R4, R7 do some damping
of the transformer inductance? I expected to see a series R-C across the transformer secondaries and/or across the diodes (although these particular diodes may not really need it).
>>R4 and R7 are snubbers for the transformer secondary coils. The
leakage inductance rings with stray winding capacitance and through the rectifiers every time they turn off. Normally you see a series C, but all that does is cut power dissipation, not really an issue at low voltage.
>>R6 and R9 (also R3 and R10) provide a standing current to bias the regulators up into more of a class-A working region. What this does is make the regulators less sensitive the changes in external load current. Shunt regulation works even better, but is way too inefficient and costs more.
I actually intended to bias them even harder, but this came out ok.
>>You see, regulators do well providing current transients to the output, but are terrible at sucking it up. A fast drop of load current will often cause the regulator to go open loop.
3. I'm thinking the LM317 and LM337 are less noisy devices. 🙂
>>Most of the noise is at low frequencies. If you really want something better, look to some of the more modern Linear Technology or Micrel parts.
>>I really wanted to do a custom super-regulator type design, but didn't have the time.
…
Good luck!
…
Jim Hagerman
Hagerman Technology LLC
…
+++++++++++++++++++++++++++++++++++++++
mlloyd1 said:
"excessive droop"
If you look at most soft recovery diodes (non-Schottky), you will see that they all (or is that too much of a generalization?) have very high Vf at high current. This actually lengthens the conduction period and is not necessarily a bad thing at all.
Petter
If you look at most soft recovery diodes (non-Schottky), you will see that they all (or is that too much of a generalization?) have very high Vf at high current. This actually lengthens the conduction period and is not necessarily a bad thing at all.
Petter
Fred
Is there any sonic advantage to using common cathode diode (dual diode) parts in building the bridges. Is the answer different when using Schottkys instead of fast ultrasoft diodes? Do all Schottkys need a snubber?
Is there any sonic advantage to using common cathode diode (dual diode) parts in building the bridges. Is the answer different when using Schottkys instead of fast ultrasoft diodes? Do all Schottkys need a snubber?
Semlab
Semlab Soft recovery diodes in the UK. These look like some very good devices.
http://www.semelab.co.uk/power/data_c3diodes.shtml
Semlab Soft recovery diodes in the UK. These look like some very good devices.
http://www.semelab.co.uk/power/data_c3diodes.shtml
Damper Resistors
Hi,
I just inserted 0.75 Ohm damper resistors between the transformer and the bridge rectifier (digital +/-5V supply) of my Philips CD-650 in analogy with the bugle supply.
The bridge rectifier is comprised of three MSRD620CT.
Much to my amazement sound is again less "screamy".
I am almost inclined to define a "screaming factor".....😉
I intend to do a all battery supply for this player but unfortunately it does not work without the analog supply. I don't see any connection between the analog and digital supply but apparently the analog voltage must be present. Anyone has any idea???😕 😕 😕
Hi,
I just inserted 0.75 Ohm damper resistors between the transformer and the bridge rectifier (digital +/-5V supply) of my Philips CD-650 in analogy with the bugle supply.
The bridge rectifier is comprised of three MSRD620CT.
Much to my amazement sound is again less "screamy".
I am almost inclined to define a "screaming factor".....😉
I intend to do a all battery supply for this player but unfortunately it does not work without the analog supply. I don't see any connection between the analog and digital supply but apparently the analog voltage must be present. Anyone has any idea???😕 😕 😕
...and try a similar value >after< the rectifiers but before the
supply capacitors.
I think you'll get similar results.
supply capacitors.
I think you'll get similar results.