The Dynaco Tube Audio Forum

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


    Of Caps and Resistors

    Share

    quadaptor

    Posts : 59
    Join date : 2009-05-04

    Of Caps and Resistors

    Post by quadaptor on 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

    Posts : 56
    Join date : 2013-09-01
    Age : 54
    Location : St. Louis, MO - On The Hill

    Re: Of Caps and Resistors

    Post by Analog Man on 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
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Of Caps and Resistors

    Post by Bob Latino on 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

    Posts : 59
    Join date : 2009-05-04

    Re: Of Caps and Resistors

    Post by quadaptor on 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.

    PeterCapo

    Posts : 380
    Join date : 2008-12-05

    Re: Of Caps and Resistors

    Post by PeterCapo on Sun Sep 08, 2013 11:32 am

    Anecdotally, plus from my own experience, carbon comp resistors could be described as sounding “warm and somewhat fuzzy,” which is not to say they sound bad, and they have their own following.  I think they add to the traditional tube amp lushness.  Carbon comp might be the best choice as grid stopper resistors to avoid effects of parasitic oscillation, that is, resistors in series with the tube’s grid, like in the Stereo 70.  But, not everyone uses them there, just the same.  Here’s some info from Aiken Amps: http://www.aikenamps.com/TI_Aiken_Q&A.html

    Carbon films retain a warmer sound and are probably more disciplined-sounding than carbon comp, but here is an interesting commentary from Alta Vista audio that says too many can make the sound "overdamped:" http://www.altavistaaudio.com/resistors.html

    Metal film resistors sound detailed and clear, I think, as do metal oxide, but some say metal film resistors impart a sterile or clinical quality to the sound and that metal oxide can sound kind of dry.

    Regardless of which kind you use, as long as they are of an appropriate value, tolerance and power rating, any of these should work fine.  The only other performance parameter to consider is the voltage rating.  Some resistors, usually metal films, and notably the Holco resistors from a while back, might have insufficient voltage ratings, but it’s probably not an issue for most metal films that are available.

    I think the difference in sound between different kinds of resistors is more subtle than the difference in sound between different capacitors.  The Russian PIO K40Y-9 might not be so much rolled-off as they are smooth and tone rich.  I found they had plenty of detail and top end in my PAS rebuild, maybe just a bit on the dark side but very enjoyable.


    Last edited by PeterCapo on Sun Sep 08, 2013 11:58 am; edited 2 times in total

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Of Caps and Resistors

    Post by Bob Latino on 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

    Posts : 330
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Of Caps and Resistors

    Post by arledgsc on 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

    Posts : 59
    Join date : 2009-05-04

    Re: Of Caps and Resistors

    Post by quadaptor on 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"!

    Sponsored content

    Re: Of Caps and Resistors

    Post by Sponsored content Today at 2:40 pm


      Current date/time is Thu Sep 29, 2016 2:40 pm