To fthifi:
You can use two resistors in parallel or series to meet power rating. Parallel would be preferred for two reasons: Those resistors have a "sweet spot" (better specs) at higher values, so parallel connection calls for higher resistor value.
The other reason is lower inductance in parallel.
Also, statistically You can achieve lower tolerance (square root of two) if You use two resistors instead of one.
You can use two resistors in parallel or series to meet power rating. Parallel would be preferred for two reasons: Those resistors have a "sweet spot" (better specs) at higher values, so parallel connection calls for higher resistor value.
The other reason is lower inductance in parallel.
Also, statistically You can achieve lower tolerance (square root of two) if You use two resistors instead of one.
Peter,
Are these the shinkoh's? I bought some for the output zobel network of a phase linear. They sucked the life from the music. I just can't deal with it. I have to switch back to the original carbons, even though they are not matched and off value, they are INFINITELY better.
It turned mu stereo playing music, into music that sounds like a stereo.
Feedback resistors
There is a wealth of information in this thread. Thanks for all who did the testing. It helped me make choices that resulted in very well resolved amps without trying to comparison test 25 different resistor points.
I ended up using AB in the feedback position on and OTL tube amp. Amp is quite musical. I had been wondering if I should try some of the bulk foil options here such as the Caddock TF020. On rereading this thread, it appears like it may not be worth the trouble and expense. I would need 6 in total which adds up. Any thoughts from people who have gone down this road?
There is a wealth of information in this thread. Thanks for all who did the testing. It helped me make choices that resulted in very well resolved amps without trying to comparison test 25 different resistor points.
I ended up using AB in the feedback position on and OTL tube amp. Amp is quite musical. I had been wondering if I should try some of the bulk foil options here such as the Caddock TF020. On rereading this thread, it appears like it may not be worth the trouble and expense. I would need 6 in total which adds up. Any thoughts from people who have gone down this road?
Hi ... sounds very interesting ... Any chance you have a link to the specifications for manganin wire and also where to buy it?
I'm curious as I've experimented with gold leaf foil but it's less feasible above ~100 ohms given that sizes get bigger. It's also very frail to work with.
Greetings,
Jesper
P.S.: I've just found manganin on ebay.com and can see that it comes from ukraine & bulgaria etc. so this should be accessible to me.
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Caddock is thick film or thin film depending on type, not bulk foil. Unusual type, too; Caddock's technology has a good reputation.
Carbon composition resistors are about the least linear of resistors; I'd never use them in critical signal paths, let alone the feedback circuit. But if it works for you, carry on!
While I advocate bulk foil resistors, I generally can't afford the most recent technology Z-foil types. Vishay's previous technology bulk foil is still extremely good being basically the same technology and construction, so one is getting into hair-splitting and diminishing returns at this point. If I had extremely high-end speakers with the resolving power of ribbons or electrostatics, I just might be able to hear the difference in types. I'm not convinced I can hear differences between bulk foil and high quality low-Tc metal film resistors, either--but I like to go with the technically superior solution if I can afford it.
I've no idea what the Tc of gold foil is nor its linearity in general. Bulk foil and a great many wirewound and metal film resistors use nickel chromium alloys; other alloys are also used, especially for extremely low Tc. Winding your own is certainly one way to always have the value you need, and I'd like to hear more about such DIY resistors.
Carbon composition resistors are about the least linear of resistors; I'd never use them in critical signal paths, let alone the feedback circuit. But if it works for you, carry on!
While I advocate bulk foil resistors, I generally can't afford the most recent technology Z-foil types. Vishay's previous technology bulk foil is still extremely good being basically the same technology and construction, so one is getting into hair-splitting and diminishing returns at this point. If I had extremely high-end speakers with the resolving power of ribbons or electrostatics, I just might be able to hear the difference in types. I'm not convinced I can hear differences between bulk foil and high quality low-Tc metal film resistors, either--but I like to go with the technically superior solution if I can afford it.
I've no idea what the Tc of gold foil is nor its linearity in general. Bulk foil and a great many wirewound and metal film resistors use nickel chromium alloys; other alloys are also used, especially for extremely low Tc. Winding your own is certainly one way to always have the value you need, and I'd like to hear more about such DIY resistors.
Ebay of course. Its not to expensive.
Nichrome is better for higher resistances but nearly impossible to solder to.
Manganin can be had at about 350ohms per meter. I use a small cardboard tube with double sided tape on it to wind around. Find a winding tool with a turn counter on it. The kind the tattoo artists use to wind transformers with for their guns. Then experiment with how many turns it takes yo get 1k, 10k, etc.
There is an enamal insulation on the wire that must be super heated to be removed. Very hot soldering iron does the trick. I don't use sandpaper as the wire is to thin.
Google noninductive winding. Its not hard to do.
After getting acquainted with the process its about 15minutes of work per resistor mainly cuz the wire is soooooo fine. Around 46-54AWG. You DO need a big magnifying glass. So its a pain but its a hobby so its enjoyable too. Masochistic I guess!
Nichrome is better for higher resistances but nearly impossible to solder to.
Manganin can be had at about 350ohms per meter. I use a small cardboard tube with double sided tape on it to wind around. Find a winding tool with a turn counter on it. The kind the tattoo artists use to wind transformers with for their guns. Then experiment with how many turns it takes yo get 1k, 10k, etc.
There is an enamal insulation on the wire that must be super heated to be removed. Very hot soldering iron does the trick. I don't use sandpaper as the wire is to thin.
Google noninductive winding. Its not hard to do.
After getting acquainted with the process its about 15minutes of work per resistor mainly cuz the wire is soooooo fine. Around 46-54AWG. You DO need a big magnifying glass. So its a pain but its a hobby so its enjoyable too. Masochistic I guess!
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Check out this item I found on eBay: http://pages.ebay.com/link/?nav=item.view&id=310648084530
Plus a winder like this but needs a counter on it
http://pages.ebay.com/link/?nav=item.view&id=360676131936
I use 900F temp to solder off insulation. Maybe could be lower but that works for me.
Here is example of tubes
http://pages.ebay.com/link/?nav=item.view&id=290395880682
Plus a winder like this but needs a counter on it
http://pages.ebay.com/link/?nav=item.view&id=360676131936
I use 900F temp to solder off insulation. Maybe could be lower but that works for me.
Here is example of tubes
http://pages.ebay.com/link/?nav=item.view&id=290395880682
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Ok, taking the bait..
After reading up on it, I ordered a spool of manganin wire. (ebay item 310710055588)
Will wind my own resistors for both the amp feedback circuit and the DAC I/V. Thanks udailey.
Earlier I had planned to take an old toaster to harvest Nichrome wire. The manganin looks like a far superior route even tho I had to spend a few $
To complete the picture, I ordered Amtrans and Caddock TF0202 to compare with the manganin based Ayrton-Perry winding on a flat former. I'm currently using Takman. Should give a nice set of comparisons. Be a while as I am early in the DAC build.
On the amps I also ordered Caddock TF020 to compare to the current Allen Bradley currently in the feedback.
If the the non inductive manganin resistors are half as good as I think they will be they'll be another DIY deal. I figure with $15 worth of wire I can easily construct several I/V 50r resistors using Ayrton-Perry winding on a flat former. With short wire they should be virtually non inductive. The amp takes 3k. I'll wind these bifilar (low inductance) as it uses 1/4 the wire. Still 27 feet per resistor.
After reading up on it, I ordered a spool of manganin wire. (ebay item 310710055588)
Will wind my own resistors for both the amp feedback circuit and the DAC I/V. Thanks udailey.
Earlier I had planned to take an old toaster to harvest Nichrome wire. The manganin looks like a far superior route even tho I had to spend a few $
To complete the picture, I ordered Amtrans and Caddock TF0202 to compare with the manganin based Ayrton-Perry winding on a flat former. I'm currently using Takman. Should give a nice set of comparisons. Be a while as I am early in the DAC build.
On the amps I also ordered Caddock TF020 to compare to the current Allen Bradley currently in the feedback.
If the the non inductive manganin resistors are half as good as I think they will be they'll be another DIY deal. I figure with $15 worth of wire I can easily construct several I/V 50r resistors using Ayrton-Perry winding on a flat former. With short wire they should be virtually non inductive. The amp takes 3k. I'll wind these bifilar (low inductance) as it uses 1/4 the wire. Still 27 feet per resistor.
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First impressions of Caddock USF 300 series
First test results in amp feed back position. I replaced an Allen Bradley 3.0k feedback resistor with a Caddock TF020 film resistor. Almost immediately you know there is a difference and for the better. I am now only 60 mins into listening and the improvement is obvious and well worth the effort and the $14 investment.
I understand these take a while to settle in so I'll hold off critical listening. Some people talk about a vail being lifted. The detail was there before. The definition now is just so much tighter. Every sound is in a tighter pin point vs being blurred.
I chose these over bulk foil as some inmates had described them as accurate but still musical.
The amps were already pretty good. OTL 6c33c with premium parts. improvement in resolution is substantial, but still musical and not sterile. I will let these settle in for 50 hours and see if they continue to refine.
Next experiments will be in DAC I/V. I have the Amtrans and Caddock TF020 ready to pop in. But I will savour the feedback upgrade first.
First test results in amp feed back position. I replaced an Allen Bradley 3.0k feedback resistor with a Caddock TF020 film resistor. Almost immediately you know there is a difference and for the better. I am now only 60 mins into listening and the improvement is obvious and well worth the effort and the $14 investment.
I understand these take a while to settle in so I'll hold off critical listening. Some people talk about a vail being lifted. The detail was there before. The definition now is just so much tighter. Every sound is in a tighter pin point vs being blurred.
I chose these over bulk foil as some inmates had described them as accurate but still musical.
The amps were already pretty good. OTL 6c33c with premium parts. improvement in resolution is substantial, but still musical and not sterile. I will let these settle in for 50 hours and see if they continue to refine.
Next experiments will be in DAC I/V. I have the Amtrans and Caddock TF020 ready to pop in. But I will savour the feedback upgrade first.
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