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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


4 posters

    Of Caps and Resistors

    quadaptor
    quadaptor


    Posts : 60
    Join date : 2009-05-04

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    Post by quadaptor Sat Sep 07, 2013 11:12 pm

    Which work best. Metal film or carbon resistors, and does the difference really matter? Also, are there any makes of resistors that work best? And speaking of caps, what gives you the best bang for the buck when used in amp PC boards? Many thanks for your help.
    Analog Man
    Analog Man


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    Age : 61
    Location : St. Louis, MO - On The Hill

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    Post by Analog Man Sun Sep 08, 2013 8:52 am

    quadaptor wrote:Which work best. Metal film or carbon resistors, and does the difference really matter? Also, are there any makes of resistors that work best? And speaking of caps, what gives you the best bang for the buck when used in amp PC boards? Many thanks for your help.
    As far as caps for best bang for the buck, I use Jantzen superior Z caps. They are rather large though and you will form the leads accordingly. They do not color the sound, pretty clean.
    As far as resistors go, it is a matter of personal preference. I have used both but prefer carbon resistors.Cool
    Bob Latino
    Bob Latino
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    Post by Bob Latino Sun Sep 08, 2013 9:19 am

    There are two types of "carbon" resistors > carbon composition and carbon film. Carbon composition were found in most vintage tube gear. They are cheap to make, have a wide tolerance level and tend to drift their value (usually high) as they age ... carbon film resistors are higher quality and don't tend to drift their value.

    Most audio gear today uses metal film and metal oxide resistors. Metal film can hold high tolerances of 1% (and lower) and don't drift in value over the years. You can read more about resistor differences at the link below ..

    Resistor differences ..

    Bob
    quadaptor
    quadaptor


    Posts : 60
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    Post by quadaptor Sun Sep 08, 2013 11:04 am

    Many thanks for your replies. I've been looking at the boards offered by Dynakits and wondering what was the difference between the carbon and metal resistors. I'm also puzzled by caps. I've talked with some folks who don't have a high opinion about the Russian PIO caps and have heard their "warm sound" may be attributed to this type of cap having a tendency to roll off the highs. Though they do give good bang for the buck.
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    Post by Guest Sun Sep 08, 2013 11:32 am

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    Last edited by PeterCapo on Wed Dec 02, 2020 4:12 pm; edited 3 times in total
    Bob Latino
    Bob Latino
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    Post by Bob Latino Sun Sep 08, 2013 11:47 am

    Re: Quadaptor > "some folks who don't have a high opinion about the Russian PIO caps and have heard their "warm sound" may be attributed to this type of cap having a tendency to roll off the highs."

    I have had all the VTA amps (VTA ST-70, ST-120 and M-125) tested with the Russian PIO caps. Frequency response testing shows that the top end is NOT rolled off when using the Russian PIO caps as main coupling capacitors.  The top end response goes up to 30 KHz to 40 KHz before even starting to drop slowly ... The Russian PIO caps have a sense of smoothness on the top end causing them not to sound as "hot" or "sharp" above 10 KHz as some film coupling caps. This may cause you to THINK that the top end is "missing" somehow, but it IS there.

    Many have seen these graphs at the link below before of a VTA ST-70 (with Russian PIO coupling caps) tested by a customer. The TOP TWO graphs are frequency response for the left and right channels. Response was down about 6 dB @ 100 KHz, about 1/2 dB @ 40 KHz and essentially flat at 20 KHz. The VTA ST-120 and VTA M-125 have virtually identical frequency response.

    Testing the VTA ST-70

    Bob
    arledgsc
    arledgsc


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    Post by arledgsc Sun Sep 08, 2013 12:32 pm

    Old school carbon composition resistors have a nasty issue of changing value over time especially when used as plate resistors.  Plus they are noisy (electron hiss) versus more modern resistors.  Yes, metal films are accurate and stable but with that can sound clinical but you may want that.  Generally, carbon films are the way to go for stable resistors with a nice sound.  Personally, I would only use carbon comps to restore a vintage piece of equipment. Metal oxides are great for power resistors like used in the high voltage supply.

    I used Russian PIOs for a while and found them to be warm, detailed, and well extended on the upper side.  Swapped them out chasing a sibilance problem that was more tube related than anything I could find.  But frequency response wasn't lacking with the PIOs.  You certainly can't argue the price you pay for them!
    quadaptor
    quadaptor


    Posts : 60
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    Post by quadaptor Sun Sep 08, 2013 12:47 pm

    Many thanks to all again. This is the type of information that makes forums such as this one worth "tuning in to"!

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