I'm gearing up to build ESP's P36 amp and I'm a little overwhemled with part selection. I searched the archives and suprisingly I wasn't able to find answers to my basic questions.
* Where do I get good resistors? I've seen recommendations like Holco, Vishay, Resista, etc but I'm having a hard time finding a source offering the values/ratings of what I need.
* Can I use a 2k74 in place of a 2k7?
* Is there any impact using a 1/2W when the schematic calls for 1/4W?
* Where do I get good resistors? I've seen recommendations like Holco, Vishay, Resista, etc but I'm having a hard time finding a source offering the values/ratings of what I need.
* Can I use a 2k74 in place of a 2k7?
* Is there any impact using a 1/2W when the schematic calls for 1/4W?
It's probably best to try it first with generic resistors - use 1% metal film for the low powered ones since they're so cheap though - once you have the amp built and running, if you decide you want to tweak it and add better components, throwing away a 3 cent resistor won't hurt too much. 🙂
2k74 can indeed be used in place of 2k7. Rod's circuits are usually pretty insensitive to resistor values - variances of +/-5% of the specified value are *usually* fine. Crossovers and active filters are some notable exceptions, of course, but for a power amp it's not a big deal.
Using a 1/2w resistor will work fine, as long as the leads and resistor body fit in the holes and space provided on the pcb, respectively. 1/2w resistors are often made to looser tolerances (5%) rather than the 1% that's the norm for 1/4w resistors, but they will indeed work great.
2k74 can indeed be used in place of 2k7. Rod's circuits are usually pretty insensitive to resistor values - variances of +/-5% of the specified value are *usually* fine. Crossovers and active filters are some notable exceptions, of course, but for a power amp it's not a big deal.
Using a 1/2w resistor will work fine, as long as the leads and resistor body fit in the holes and space provided on the pcb, respectively. 1/2w resistors are often made to looser tolerances (5%) rather than the 1% that's the norm for 1/4w resistors, but they will indeed work great.
Normal metal film resistors are usually 0.6 watts, same size as 0.25 W carbon.
Some 1% resistors comes in E192 values (2k74) but you can also get 1% in E24 values 2k7, 3k3 etc.
Some 1% resistors comes in E192 values (2k74) but you can also get 1% in E24 values 2k7, 3k3 etc.
Resistor selection
If you are able to purchase resistors locally, take a magnet with. Using non-magnetic resistors is a big plus sonically.
If surprises me to see what types are magnetc and what are not. One other tip, buy more than you need of every value and check every one with a meter before using. I have found Holco's and other high cost resistors than measure way off the spec'ed value. Looking back at gear built over the years I have found problems and resistors that were off value. The scenario imaged was a circuit problem damaging the resistor and making it read another value. Now I suspect the offending resistors were off value to begin with.
I am lucky and have a great supply store locally. They have A-B, TRW, and Amperex nonmagnetic resitors in stock. I prefer the sound of carbon comp, wirewound, and cermet to metal films. There are usually 5% so I buy 5 when needing 2 and match them up. But this is a personal choice, buying two !% metal films is easier.
George
If you are able to purchase resistors locally, take a magnet with. Using non-magnetic resistors is a big plus sonically.
If surprises me to see what types are magnetc and what are not. One other tip, buy more than you need of every value and check every one with a meter before using. I have found Holco's and other high cost resistors than measure way off the spec'ed value. Looking back at gear built over the years I have found problems and resistors that were off value. The scenario imaged was a circuit problem damaging the resistor and making it read another value. Now I suspect the offending resistors were off value to begin with.
I am lucky and have a great supply store locally. They have A-B, TRW, and Amperex nonmagnetic resitors in stock. I prefer the sound of carbon comp, wirewound, and cermet to metal films. There are usually 5% so I buy 5 when needing 2 and match them up. But this is a personal choice, buying two !% metal films is easier.
George
I gather the carbons do not have the tolerances or the long term stability of the metal flim. And it seems that tube builders perceive warmer sound with carbon.
Elliot: "1% tolerance metal film resistors are recommended for best noise performance and long term stability. If unavailable, 5% tolerance carbon resistors can be used with no ill effects."
I'm not sure if he is implying that the carbon resistors have lower noise and stability performance.
I'm not sure how this amp will turn out, whether I will like it or not and subsequently sell it. That being the case, I don't want to go hog wild with part selection nor do I want to cripple the device with substandard parts.
Unfortunately, the local parts bin, Active Electronics, recently closed here in Seattle. Vetco Surplus plans to expand to offer semis, caps, and resistors but not sure when. So apart from Radio Shack, I'll have to mail order everything. I'd love to find a one stop source.
Elliot: "1% tolerance metal film resistors are recommended for best noise performance and long term stability. If unavailable, 5% tolerance carbon resistors can be used with no ill effects."
I'm not sure if he is implying that the carbon resistors have lower noise and stability performance.
I'm not sure how this amp will turn out, whether I will like it or not and subsequently sell it. That being the case, I don't want to go hog wild with part selection nor do I want to cripple the device with substandard parts.
Unfortunately, the local parts bin, Active Electronics, recently closed here in Seattle. Vetco Surplus plans to expand to offer semis, caps, and resistors but not sure when. So apart from Radio Shack, I'll have to mail order everything. I'd love to find a one stop source.
Rod's not mentioning that the carbon film resistors have any better noise, stability, or any other specs - simply that if you already have them, you can use them, as they are sometimes easier to find and/or cheaper.
Even the most mediocre metal film resistor is far superior to even the best carbon composition resistors of the 60's in every measurable spec.
Some of the most wideband high precision amplifiers in the world are inside analog oscilloscopes in the amplifier section - if you ever open one up that was made recently, I guarantee you that you won't see a single carbon film or carbon composition resistor anywhere. They have terrible noise, temperature drift, voltage coefficient, and hygroscopic properties that are in some, an order of magnitude (or even more) worse than even a generic $0.01 metal film resistor.
I wouldn't waste your time trying to find exotic resistors, but that's just me. 🙂
Even the most mediocre metal film resistor is far superior to even the best carbon composition resistors of the 60's in every measurable spec.
Some of the most wideband high precision amplifiers in the world are inside analog oscilloscopes in the amplifier section - if you ever open one up that was made recently, I guarantee you that you won't see a single carbon film or carbon composition resistor anywhere. They have terrible noise, temperature drift, voltage coefficient, and hygroscopic properties that are in some, an order of magnitude (or even more) worse than even a generic $0.01 metal film resistor.
I wouldn't waste your time trying to find exotic resistors, but that's just me. 🙂
Digikey (.com) has uniformly good prices and just about everything you need in terms of the basic components. Give them a call or email them to get the print catalog. You'll think you hit a goldmine. Get them to ship USPS priority and things will only take about 2 days and very cheap shipping. Mouser is an alternative.
Nelson Pass builds multi-thousand $ amps with non-exotic resistors, so I wouldn't sweat it.
That's my
!!
I live just outside the 5th largest city in the country and there's basically noplace to buy electronic components here. I guess we're not considered a center of the electronics industry.
Nelson Pass builds multi-thousand $ amps with non-exotic resistors, so I wouldn't sweat it.
That's my
!!I live just outside the 5th largest city in the country and there's basically noplace to buy electronic components here. I guess we're not considered a center of the electronics industry.
Hi!
And those exotic parts you can order at Partsconnexion
http://www.partsconnexion.com/
They have everything a DIY hifi builder needs, at least regarding passive parts...
Hope this helps,
bye,
Arndt
And those exotic parts you can order at Partsconnexion
http://www.partsconnexion.com/
They have everything a DIY hifi builder needs, at least regarding passive parts...
Hope this helps,
bye,
Arndt
For a pretty good survey of moderate to high-end parts, you can also print out Michael Percy's catalog. It's a good price reference, too. His prices are pretty fair on just about everything, and the best on some items.
www.percyaudio.com.
www.percyaudio.com.
Resistors
Gain and Biasing resistor should be metal film, Carbon comps can generate noise. I like to use Dale, IRC
Corning
For metal film, I prefer to use RN60 resistor they sound better that lower wattage RN55 type.
Feedback, signal coupling and filter resistors should be the highest quality. Vishay, Caddock, Dale, IRC are just a few.
Power emitter resistor can should non inductive wire wound or thick or thin film types, Check with Caddock, IRC, and Dale.
Carbon Films are much better that Carbon Comps and are good for high speed applications. Sometime
The spiral cut in a metal film resistor can generate noise in high speed circuits.
Check that the resistors your purchasing do not ferrous metals leads. You can check this with a Magnet.
Also check the Vishay web site they have purchased many of the good reisstor companies.
😉 😉
Gain and Biasing resistor should be metal film, Carbon comps can generate noise. I like to use Dale, IRC
Corning
For metal film, I prefer to use RN60 resistor they sound better that lower wattage RN55 type.
Feedback, signal coupling and filter resistors should be the highest quality. Vishay, Caddock, Dale, IRC are just a few.
Power emitter resistor can should non inductive wire wound or thick or thin film types, Check with Caddock, IRC, and Dale.
Carbon Films are much better that Carbon Comps and are good for high speed applications. Sometime
The spiral cut in a metal film resistor can generate noise in high speed circuits.
Check that the resistors your purchasing do not ferrous metals leads. You can check this with a Magnet.
Also check the Vishay web site they have purchased many of the good reisstor companies.
😉 😉
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