Amp building can't find parts

Discussion in 'Shock Brother's DIY Amps' started by Triple Threat, Aug 5, 2011.

  1. Triple Threat

    Triple Threat TDPRI Member

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    So after 7 years of reading, researching, and telling people I am going to build my own amp....I start making a laundry list of parts to order.

    My problem is I am having a hard time finding a few of the items. I was orginally going to use Atom caps and couldn't find the values anywhere from anyone so I subbed some different brands.

    I am currently making a lightning clone using this layout http://trinityamps.com/Trinity15layoutrev9.gif

    couple questions for you amp people out there.....

    I was not able to find the 1.2k carbon comp and 10k carbon comp in 1/2 watt so I subbed 1 watt. I assume this is ok??
    Also on the 120 15W power in the layout as close as I could find was a 120 10W.

    Also last question if anyone can help. I am unable to find the 22k 3W Metal power, .0015uf Mallory 150, and the 250uf 63V Electrolytic. Any help would be appreciated.
     
  2. printer2

    printer2 Poster Extraordinaire

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    Using 1W resistors instead of 1/2 watt resistors is preferable. 10W for the 120 ohm should be fine. The 22k does not need to be a metalized resistor, use what you can get. The 250uF, you can vary up and down from that value a bit (people have used from 1000uF to 50uF), I would have no problem with a 50V there.
     
  3. Triple Threat

    Triple Threat TDPRI Member

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    Will I run into any issues having the rest of the resistors 1/2 watt? I already placed the order for that stuff and hope to be able to use it all.
     
  4. vinman

    vinman Tele-Meister

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    I didn't look up your specific parts, but I have used these two places for 90 percent of parts building my amps.

    http://www.hoffmanamps.com/
    http://tubedepot.com/index.html
    both have really quick shipping .

    IMHO you don't have to use carbon comp resistors or Atom caps. There are other caps on these sites that are just as good. the metal film resistors will fine although if I remember right, they use a different code system. I'm not being one of those guys that are trying to tell you what to do, but a lot of the hype is just that on parts.
    Good luck on your build and DON"T FORGET ....you will be working with HIGH VOLTAGES. So make sure you look before you leap. A lot of info can be found on the Hoffman site. A whold library full.
     
  5. jhegel

    jhegel Tele-Meister

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    A few more suppliers:

    Mouser.com

    tubesandmore.com

    Angela.com

    radiodaze.com
     
  6. Triple Threat

    Triple Threat TDPRI Member

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    Thanks for the info guys. I was really trying to find a place that I could order all my parts at once. I couldn't do it. I had searched Mouser, Allied, Digi Key, etc

    Ended up getting most from Antique Electronic Supply and from West Florida Components. I should have probably looked at ebay as well, but I was just trying to use one source. And of course trying to do this on a budget as well :lol:

    I have been reading for a few years and after a custom built amp deal that went bad, it pushed me over the edge to make my own amp. I also have the Inside Tube Amp book by Dan Torres on the way as well. I am sure I will be bugging guys in this section a lot in the near future. Thanks again.
     
  7. David Barnett

    David Barnett Doctor of Teleocity

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    For the 250uF cap, you're more likely to find 220uF.

    Many people substitute 150 ohms for the 120-ohm cathode resistor, there's more availability in different watt ratings, and it runs the output tubes slightly easier.
     
  8. printer2

    printer2 Poster Extraordinaire

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    Yeah, I think you are fine with them.
     
  9. Keyser Soze

    Keyser Soze Tele-Holic

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  10. guiltless

    guiltless Tele-Meister

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    www.turretboards.com has a ton of stuff as well... even some parts that are hard to find. And if you are going to spring for expensive caps, check out Jupiter. I know there are some boutique guys out there are ditching Sozo and vintage mustards altogether for these.
     
  11. celeste

    celeste Friend of Leo's

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    Handmade Electronics carries IRC GS3 3 watt resistors, in fact the only place I know that does. They are the quietest and most neutral MF I have run into and if I need better, the only place to go is bulk metal foil resistors at $5-10 each. They also have the best price I have found on mil spec 2w pots
     
  12. telex76

    telex76 Doctor of Teleocity Ad Free Member

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    Thats the problem I had when building my Vibro Champ clone. By the time you have to pay shipping from 3 or 4 suppliers, it adds quite abit to the cost of the build.
     
  13. celeste

    celeste Friend of Leo's

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    That is one of the reasons you can not justify building an amp for economics. If you build a lot of amps then you stock up and cut the shipping costs, but for a single amp, if you are picky about the parts, shipping is going to be a sizable part of the total cost.

    I have been holding off ordering more GS3's till I can justify buying more pots, just to keep the shipping in line
     
  14. Triple Threat

    Triple Threat TDPRI Member

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    Made some progress tonight. Still missing a few caps/resistors but got all the turrets staked in the board and the components on it for the most part. Still need to solder and run wire. If anyone sees any problems let me know.

    [​IMG]
     
  15. JohnnyCrash

    JohnnyCrash Doctor of Teleocity Gold Supporter

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    It might be a minor thing, but you might consider replacing that 51pF cap from a ceramic to something else (silver mica, prop, etc).

    If you can't find 51pF in anything other than ceramic, maybe try a 47pF instead.

    It'll still work and sound fine, but a lot of people recommend against using ceramics in most places (except bright caps on volume pots, etc) for tonal reasons. I've used ceramics in a pinch and they sound fine, for the most part.

    Otherwise, everything looks great.

    --

    As far as finding the exact values, first builds can be intimidating in this regard.

    You have a lot more variety/elbow room available to you, you don't have to follow a parts list super-strictly.

    Capacitors have two values. The first is the actual capacitance, the second is the amount of voltage the part is built to handle. The first value is most important for tone/sound. The second is only important for functionality. For instance if your first filter cap is rated for 200vDC and your power transformer/rectifier is feeding that cap 350vDC, it will likely fail. So for this value, all you have to do is make sure the voltage rating is safely above the voltages that part of the circuit will be seeing, you can even go higher to be safe (sometimes much higher).

    For instance, you don't have to find exactly 33uF 450v for cap1. Looking at a GZ34/5AR4 data sheet, you can see that it's max input cap can be as high as 60uF, so you could even use a 16, 20, 22, 25, or 30, 40, 50, 60uF. Larger values will improve bass response, but even a 20uF is fine to reduce ripple and keep AC hum out of your power section.

    As far as voltages, your transformer is spitting out 285v, but rectified it might be a little more coming off of the GZ34/5AR4 (maybe around 350-375 volts), so your first cap can be rated for 450, 500, or even higher voltages. I wouldn't use anything smaller though, in case of voltage spikes or you decide later to use SS rectifiers.

    For cathode bypass capacitors, preamp tubes usually only see a few volts there, so you have many more options for finding capacitors to order - from 9v, 16v, up to much higher ratings. The value is very important here though, for tone. Marshall used very small values on the Bright channel's preamp tube (0.68uF), which will completely change the gain and character. The 25uF in your layout allows full frequency response, but you can fudge it a little from 10, 16, 20, 22, or 25uF and it'll generally sound the same.

    Cathode biased power tubes on the other hand see higher voltages, generally from 10 to 15 volts. So for this capacitor, you'll want a little safe room, 25v might be fine, but I'd use at least 50v, just to be safe. As celeste informed me a long time ago, using very large capacitance values (2,200uF+) here will make the amp sort of behave more like a fixed bias amp, so this value is for tonal preference. Like printer2 said, some people use 47 or 50uF up to larger values.

    Resistors come in standard values, so finding the right value shouldn't be too hard. As far as wattage, 1/2 or 1 watt are fine in most places - except for the power tubes' cathode resistor (the big 120 or 150 ohm), and the power filtering section (all of those 22k resistors between the 22/33uF filter caps). The power tubes' cathode ressitor should be rated for at least 5 watts, but I would use 10w to be safe (you can use even higher wattage if you'd like, but the ceramic power resistors get pretty large in size). The filter section resistors should be at least 1w, but many people go with higher wattage there to be safe, like 2 or 3 watt metal oxide.


    When I first started building - finding the exact values freaked me out a bit, so I hope this helped.

    Your board looks great, please keep the photos coming - it makes me feel like I'm building an amp, which will keep me from indulging my addiction for building even more amps HAHA!
     
  16. Triple Threat

    Triple Threat TDPRI Member

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    Thanks for the info. Johnny Crash. I was actually thinking about that 51pF ceramic disc this morning and pulled it out.....well actually truth be told my 5 year old saw the board on the table and "helped me fix it" LOL Anyway, I left it out and will get something else in there as I have a few other odds and ends to order.

    I was thinking I needed exact values on the layout so I was starting to stress out a little bit trying to source everything. I am having fun so far and learning a lot as I go.

    One other thing I had a question on was the outer foil.... which way to orient these and should I be testing it? I don't have a scope, but could always make this gadget http://www.youtube.com/user/SoundGarageTales#p/u/36/VP6ZIHXq6Yg

    Thanks again to all of you for the info. and comments.
     
  17. sjhusting

    sjhusting Tele-Afflicted

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    A few additions to Johnny's advice -

    Parts have tolerances. Especially electrolytics have wide tolerances, up to 20%. What this means is that, for example, there is no practical difference between a 20uF and 22uF filter cap. The 20uf might be anywhere from 16uF to 24uF.

    In general, for caps (including coupler caps) a difference of a few uF, nF, or pF (say, between 51pF and 47pF) is not audible and using one instead of the other will not do bad things to the amp.

    I've never worried about the outer foil. If it's marked (like on SoZos) I use it; if it's not, oh well. It seems to me on a first build you have other things to worry about than the outer foil.

    One personal preference: on the first filter cap (the 'reservoir' cap) I try to go to double the voltage coming out of the rectifier or more; often this means using two caps in series. This is because that cap bears the brunt of the spikes when you turn on and I like to have a big safety margin. But there are gadzillions of amps out there working fine for decades that don't do this.

    have fun

    steven
     
  18. tubeswell

    tubeswell Friend of Leo's

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    Hi Triple Threat, FWIW while you are contemplating the layout, it'd pay to think about how you are going to wire the ground return part of the circuit, as this is where beginner's strike the most problems with unwanted hum. Useful article here: http://valvewizard2.webs.com/Grounding.pdf
     
  19. JohnnyCrash

    JohnnyCrash Doctor of Teleocity Gold Supporter

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    Very cool article. Thanks for posting that.
     
  20. Triple Threat

    Triple Threat TDPRI Member

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    Thanks for the info. I appreciate all the help I can get. I have the rest of my parts for the board on order and they should arrive in the next couple weeks.

    Tubeswell - I plan on star grounding like in the layout on the trinity website like this http://trinityamps.com/Trinity15layoutrev9.gif
    I figured it would be a bit easier. Are the big caps usually grounded in most amp designs for quiet factor?
     
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