Test fixture for diode noise.
Knowing that not everyone has a spectrum analyzer, I am working on a simple RF detector to get an idea of the amount of RF noise differences between various diode types and snubber circuits. Seeing the ringing on a scope can be difficult since you are looking at high frequency low amplitutude signal with a repitition rate of 120Hz. A fast (500MHz or faster) storge scope would be great for looking at this. I used such a scope to look at transient high frequency behavior of telecom protection circuits with single shot transients. Wish I still had a job and access to decent test equipment.
Knowing that not everyone has a spectrum analyzer, I am working on a simple RF detector to get an idea of the amount of RF noise differences between various diode types and snubber circuits. Seeing the ringing on a scope can be difficult since you are looking at high frequency low amplitutude signal with a repitition rate of 120Hz. A fast (500MHz or faster) storge scope would be great for looking at this. I used such a scope to look at transient high frequency behavior of telecom protection circuits with single shot transients. Wish I still had a job and access to decent test equipment.
I didn't see a reply to this post. Are the general rules for picking a power rectification scheme the same for all amps or will different rules apply for Class A and Class B amps? I also need advice on a good 5.5-6.5 digit bench meter. How good is the Fluke 850x series? What options will I need on those models and which is the best of them? What other meters should I be looking at?
totally mad company
You have just begun:
I have even made my own male plugs from small copper tubes soldered side by side. I use squalin oil for contact cleaner/treatment. Wait till you make line cords from copper shielding tape and polypropylene packing tape........... my wife just shakes her head when I do stuff like this.
You have just begun:
I have even made my own male plugs from small copper tubes soldered side by side. I use squalin oil for contact cleaner/treatment. Wait till you make line cords from copper shielding tape and polypropylene packing tape........... my wife just shakes her head when I do stuff like this.
Pick A Sound, Any Sound.
I have found the insulation material on power cords makes a substantial difference.
I have done power cord comparisons of salvaged power lead assy's out of the junkbox, and voila a whole range of sounds.
I found things like an old Sony power cord made anything connected to it sound like an old Sony !.
Ditto other leads I have tried.
The conductor type is reasonably important, but so is the dielectric material ime.
Phred, we understand.....
Eric.
I have found the insulation material on power cords makes a substantial difference.
I have done power cord comparisons of salvaged power lead assy's out of the junkbox, and voila a whole range of sounds.
I found things like an old Sony power cord made anything connected to it sound like an old Sony !.
Ditto other leads I have tried.
The conductor type is reasonably important, but so is the dielectric material ime.
Phred, we understand.....
Eric.
No help on picking a bench DVM? I know you guys must have an opinion on this if you can talk about the dielectric qualities of power cables. Please, let's move the elephants before the mice. Where is the discussion about what makes a good audio transformer and if those features are different when dealing with different amps??
Re: Re: I must be getting soft in my old age
This maybe a case where the frequency domain spectrum may give you a better idea of what kind of crap is getting injected in the PS rails, instead of looking at the time domain. The integral only gives you how intense it nothing more really.
Peter,
after seeing what Fred has done with Cu tape I am curious to know what have you done with the stuff I sent you, actually I want it back
, just kidding!
capslock said:
This maybe a case where the frequency domain spectrum may give you a better idea of what kind of crap is getting injected in the PS rails, instead of looking at the time domain. The integral only gives you how intense it nothing more really.
Peter,
after seeing what Fred has done with Cu tape I am curious to know what have you done with the stuff I sent you, actually I want it back
, just kidding!Please, let's move the elephants before the mice.
Why don't you start another thread on transformers as this thread is getting off topic. I feel that large VA ratings are one of the most important factors for a power transformer for even a small amp. Torroid transformers do not like DC hence my recommendation for AC coupling on the primany. Do a seach on "transformer" since I am sure the subject has been discussed on the forum.
P.S. Pushing too much for a response to a question is a sure fire way to not get one from me. I tend to post on the subjects that interest me and they aren't going to be of interest to everybody.
Start a new thread . I am sure you will get plenty of advice.
Why don't you start another thread on transformers as this thread is getting off topic. I feel that large VA ratings are one of the most important factors for a power transformer for even a small amp. Torroid transformers do not like DC hence my recommendation for AC coupling on the primany. Do a seach on "transformer" since I am sure the subject has been discussed on the forum.
P.S. Pushing too much for a response to a question is a sure fire way to not get one from me. I tend to post on the subjects that interest me and they aren't going to be of interest to everybody.
Start a new thread . I am sure you will get plenty of advice.
New thread about transformers started in the Solid State section. Love to have your input but noting that I've gotten under your skin, I won't expect it. So, if RFI is introduced (or not absolved) by the diodes, why can't the capacitance of the dielectric on the connecting wire or its weave be made to roll it off? Also, are all the RFI frequencies detrimental to sound or just the ones out of harmonic with the signal?
Single diodes or bridge?
I asked this in another thread but I don't think that anybody responded.
I have seen it claimed that a ready-built rectifier bridge is better than using individual rectifier diodes because the diodes in the bridge are more closely matched, being built on the same silicate strata.
Any comments chaps?
I asked this in another thread but I don't think that anybody responded.
I have seen it claimed that a ready-built rectifier bridge is better than using individual rectifier diodes because the diodes in the bridge are more closely matched, being built on the same silicate strata.
Any comments chaps?
Diodes,xformers Etc.
Hi,
Yup.
I'd like them overrated by about 40%.
And more to the point, I feel the same way about rectifiers too, all else being equal.
Never liked toroidal xformers, they're too much wideband and let the crud through both ways.Hence your suggestion for capacitive filtering on the input I presume.
A decent PSU is half the amplifier IMHO, so we better pay attention to what we put our money on.
Cheers,
Hi,
Yup.
I'd like them overrated by about 40%.
And more to the point, I feel the same way about rectifiers too, all else being equal.
Never liked toroidal xformers, they're too much wideband and let the crud through both ways.Hence your suggestion for capacitive filtering on the input I presume.
A decent PSU is half the amplifier IMHO, so we better pay attention to what we put our money on.
Cheers,
Hi Peter,Peter Daniel said:I didn't know you were such a tweaker Fred
You must have forgotten this thread from your H. Potter days.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=2197&highlight=Aleph+fast+bridge
If you read this link, you'll notice that Fred (HH) used the IXYS Fast diodes in his tweaking of his Aleph3, having tried many others diodes (Way to be consistant Fred
).Fred, your contributions to the forum have alway been appreciated.
Question: Peter, what diodes have you tried on your Aleph 5? You have touched on it before in one of the past threads, but I couldn't find it. Do you think your MUR860's are too small for an Aleph 5 if used per rail in a monoblock?
Thanks,
Rodd Yamashita
PS: Peter, has the H. Potter legacy officially become the stuff of legend?
HH's Tweaked Aleph3
Attachments
HarryHaller said:
Of course I remember.
The above was a first post from HH that I saw and we started on this forum in about the same time.I used regular bridges in my Aleph5, because at the time I wasn't aware of a difference thay make. MUR860 might be a bit small for that application, but you can either parallel them (but again I don't know how it changes sonics), otherwise you could use MUR1560 as I remember they sounded pretty good too. If you need more softness and presence in vocals, MUR1520 is a good candidate. Don't use diodes from Fairchild as they are very edgy and have glare. I found Motorola and On Semi parts better sounding.
In my AlephX I used IR 30ETH06 diodes, but again comparing 15ETH06 in my GC I found MUR better.
"Don't use diodes from Fairchild as they are very edgy and have glare."
Perhaps you should rephrase that as "I didn't like the some of the Fairchild diode's of a particular part number." I think that the whole subject of high speed diode selection and the use snubber circuits is just starting to be addressed. That was the whole point of this thread. As I have mentioned before, the regulatory requirements for lower levels of EMI (RFI) have developed a new design criteria for high speed diodes. The original design emphasis for high speed diode were for fast recovery times.
This parameter is given as tRR (t subscript rr). Design for low tRR was to reduce switch losses in high speed circuits such as switching power supplies. Low tRR numbers give less electrical losses in these circuits. This minimizes heat production and increases efficiency for switching supplies and is a highly desirable goal.
The desire to reduce EMI contributions, as well as overshoot voltage spikes that can damage circuits, has lead to emphasis on the soft recovery characteristics. The tRR measurement is divided into a tA and tB portion. The ratio of tB/tA as well as the rate of change of the tB interval defines the softness of the diode and the amount of EMI generated by the diodes reverse recovery characteristics. Lowering of this EMI is what we are trying to do with the use of this diode types for audio supplies. Snubbers are another tool in reducing this EMI and the development of soft recovery diodes was to free the designer from having to use these snubber circuit which and cost and complexity to a switching power supply design. Selection of diodes based on these tA and tB numbers on the datasheets is complicated by the fact that the numbers are not always measured under the same test conditions. Reading data sheets is tricky even for engineers. Data sheets are written as advertising for parts, and are written in a way to emphasize the parts virtues and downplay it's shortcomings.
I have been doing the dreaded market survey of some of the 8A to 30A parts that might be suitable for audio supplies. For data on a couple of interesting soft recovery diodes:
http://www.fairchildsemi.com/pfPrint/IS/ISL9R1560G2.html
http://www.irf.com/product-info/datasheets/data/hfa08tb60.pdf
Perhaps you should rephrase that as "I didn't like the some of the Fairchild diode's of a particular part number." I think that the whole subject of high speed diode selection and the use snubber circuits is just starting to be addressed. That was the whole point of this thread. As I have mentioned before, the regulatory requirements for lower levels of EMI (RFI) have developed a new design criteria for high speed diodes. The original design emphasis for high speed diode were for fast recovery times.
This parameter is given as tRR (t subscript rr). Design for low tRR was to reduce switch losses in high speed circuits such as switching power supplies. Low tRR numbers give less electrical losses in these circuits. This minimizes heat production and increases efficiency for switching supplies and is a highly desirable goal.
The desire to reduce EMI contributions, as well as overshoot voltage spikes that can damage circuits, has lead to emphasis on the soft recovery characteristics. The tRR measurement is divided into a tA and tB portion. The ratio of tB/tA as well as the rate of change of the tB interval defines the softness of the diode and the amount of EMI generated by the diodes reverse recovery characteristics. Lowering of this EMI is what we are trying to do with the use of this diode types for audio supplies. Snubbers are another tool in reducing this EMI and the development of soft recovery diodes was to free the designer from having to use these snubber circuit which and cost and complexity to a switching power supply design. Selection of diodes based on these tA and tB numbers on the datasheets is complicated by the fact that the numbers are not always measured under the same test conditions. Reading data sheets is tricky even for engineers. Data sheets are written as advertising for parts, and are written in a way to emphasize the parts virtues and downplay it's shortcomings.
I have been doing the dreaded market survey of some of the 8A to 30A parts that might be suitable for audio supplies. For data on a couple of interesting soft recovery diodes:
http://www.fairchildsemi.com/pfPrint/IS/ISL9R1560G2.html
http://www.irf.com/product-info/datasheets/data/hfa08tb60.pdf
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