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Tweed Component Selection Help & Speaker Question

Discussion in 'Shock Brother's DIY Amps' started by timewaster1700, Apr 10, 2018.

  1. SngleCoil

    SngleCoil Tele-Holic

    560
    Apr 13, 2010
    Charlotte, NC
    I know "cork sniffing" has already been well covered in this thread, but I wanted to chime in with an observation from my recent servicing of a Matchless HC-30. I opened the chassis expecting to find only the best named components...and I found plenty of good quality hardware. Carling switches, Swithcraft jacks, Belton sockets, CTS pots and HUGE transformers. What I didn't find was a collection of super premium capacitors...coupling caps were Mallory 150s, e-caps were a mostly Samwah (had never heard of them, but later found they are just ordinary consumer grade caps used in a bunch of Samsung products)

    The only thing that I would consider "mojo" components were the 1-3 watt carbon comp resistors throughout (that were all well within spec where I could test them) with a few carbon films here and there. They also use polystyrene caps vs. silver mica or ceramic in for smaller values. I know polystyrene is said to have very nice audio qualities, but my understanding is that their capacitance drifts rather easily with temperature variation. That amp runs very hot, and It didn't seem to have any noticeable change in tone so I guess it's not that big of a deal as far as this amp was concerned anyway.

    Anyway the bottom line is that the Matchless was very impressive from a build quality standpoint. And the lack of super premium capacitors didn't hurt the tone one bit. I would expect to see more and more carbon or metal film resistors in even "boutique" builds as existing supplies of CC resistors are depleted. I know from trying to source components for my own upcoming build, finding tightly spec'ed carbon comp resistors in 1+ watt values is becoming very expensive. If you want to put a little extra into the hardware side, good switches, jacks, etc. that's not a bad place to spend a few extra dollars since they have some physical wear and tear.
     
    Sam VanLaningham likes this.
  2. Urshurak776

    Urshurak776 Tele-Meister

    406
    Jul 2, 2004
    Charlotte
    I am in Charlotte also, so will definitely check out Hoffman. Thanks SngleCoil.
     
  3. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    Thanks for the tips! Its well worth it to me to spend extra on the mechanical components so they last. Good to know the type of resistors and capacitors doesn't matter too much. I'll just shoot for accurate ones.
     
  4. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    Nevermind. I found an answer to my question on one of uncle Doug's videos.
     
    Last edited: Apr 14, 2018
  5. JuneauMike

    JuneauMike Friend of Leo's

    May 5, 2015
    Alaska
    Uncle Doug saves the day again.
     
  6. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    By the way I’ve been meaning to tell you your profile picture is awesome!!
     
  7. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    Do you guys think the 10" Cannabis Rex speaker will sound similar to the 12"? I'm starting to lean in that direction. Listening to the clips of the Cannabis Rex it seems like a solid versatile speaker that would probably work really well for my style of music and if I didn't like it I could always sell it and get a Weber or something else.
     
  8. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    I have a couple questions regarding resistor size/wattage. I spent a ton of time understanding the schematic and writing out how it all works and I'm feeling pretty good about that so now I've moved on to creating my parts list. I want to make sure I get the right wattage resistors.

    1. Am I being too particular on these that I've selected so far:
    The Aiken website says he uses 1W, 500V and 2W, 750 V so I've been making sure my metal film resistors have high enough voltage rating. Reading his excerpt on noise it sounds like resistors with a larger physical size (higher wattage rating) tend to be less noisy and the most noise prone section of the circuit is between the input jacks and the first pre-amp stage. So I think I'm going to use some 2W, 500V metal film resistors I found for the 68k grid stoppers. I figured to play it safe I'd make the 100k and 56k plate load resistors able to handle 750V so the size I was able to find on mouser for metal film was 3W. I realize these are WAY over spec'd for the pre-amp section. I just picked them for low noise properties and they're each less than $0.50 a piece so the price is not bad.

    2. What should the 470 ohm and 22k B+ circuit resistors be?
    These are the two resistors I'm most concerned with getting the correct wattage as they handle the high voltage power side of things. I noticed the plates of the 6V6GT's are tapped prior to these resistors so I can see these resistors don't need to handle the main current draw of the power tubes. However they do need to be able to handle the combined current draw of all 4 pre-amp plate currents and the power tube screen grid. Seems what I can find online is that for these resistors in the 5E3 people use a 5W resistor but I don't see how that is ok. 5W/(340 V) = 14.7 mA which is tiny! Do the 4 pre-amp plates and the two screen grids really draw less than a maximum of 14.7 mA ? That's less than a little LED draws. I want to calculate out the numbers but I can't seem to find what the screen grid current is on the 6V6GT's. For the 12AX7 I'm getting:
    For V1A:
    1W max dissipation / 155 V = 6.5 mA max
    For V1B:
    1W max dissipation / 160 V = 6.25 mA max
    For V2A:
    Same as V1B = 6.25 mA max
    For V2B:
    1W max dissipation / 205V = 4.88 mA max

    Just adding these 4 maximum values together without even factoring in the 6V6 screen grid current gets me: 23.88 mA which is already greater than the 14.7 mA max that 5W can provide coupled with 340 V. I realize the amp isn't running at max, but I guess I figured the resistor wattages would be designed around worst case scenario. Also how do I figure out what a more reasonable current draw would be in the tubes?

    Thanks for the help!
     
  9. jimgchord

    jimgchord Tele-Holic

    Age:
    45
    571
    Apr 3, 2018
    victor,ny
    Orange drops are junk. Mallory 150 is all you need, the rest are essentially hype.hoffman is great to deal with. If you want lower voltage get a mojo 759(heyboer)
     
  10. jimgchord

    jimgchord Tele-Holic

    Age:
    45
    571
    Apr 3, 2018
    victor,ny
    You will like it if you like that blanket over the amp kinda sound
     
  11. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    Thanks for the help.

    Yikes are you being facetious? blanket over an amp sound is no Bueno.
     
  12. jimgchord

    jimgchord Tele-Holic

    Age:
    45
    571
    Apr 3, 2018
    victor,ny
    That was my experience with the 12" model. I really like warm but this was too warm...almost muffled. If you play jazz it would be a great speaker with the right amp, other than that its definitely not for me
     
  13. JuneauMike

    JuneauMike Friend of Leo's

    May 5, 2015
    Alaska
    The Cannabis Rex and the Weber xxA125-H series are hemp cone speakers and the hemp material is thicker than papers thus the warm thundering sound. @jsnwhite619 has some sound samples of a 12 inch CR. I wrote you earlier on my experience with this speaker and others. Tweed amps aren't known for their bass response, so a hemp coned speaker is a decent antiicdote to that. But honestly, i could have lived with the Fender Special Design speaker from my Blues Jr if I had to. No matter what speaker you use, you've always got EQ options right there on your guitar, and on the amp.

    Speaker selection sucks, because there's no right answer and you will probably second guess your selection forever. But its important to get off dead center and pick something just so the project isn't held up. Alnico speakers were in these amps originally.
     
  14. JuneauMike

    JuneauMike Friend of Leo's

    May 5, 2015
    Alaska
    1. Am I being too particular on these that I've selected so far:
    The Aiken website says he uses 1W, 500V and 2W, 750 V so I've been making sure my metal film resistors have high enough voltage rating. Reading his excerpt on noise it sounds like resistors with a larger physical size (higher wattage rating) tend to be less noisy and the most noise prone section of the circuit is between the input jacks and the first pre-amp stage. So I think I'm going to use some 2W, 500V metal film resistors I found for the 68k grid stoppers.

    Nah, 1watt metal film will give all the noise reduction you need there, better yet super accurate 1% Rubys would be nice. Otherwise, buy several and take the three closest to 68k. Everything in the signal chain adds noise, and everything in the input stage gets magnified later in the output.

    I figured to play it safe I'd make the 100k and 56k plate load resistors able to handle 750V so the size I was able to find on mouser for metal film was 3W. I realize these are WAY over spec'd for the pre-amp section. I just picked them for low noise properties and they're each less than $0.50 a piece so the price is not bad.

    Again, 1 watt is fine. If you just want to do it to do it, that's fine too, but most all of the resistors in this amp could be 1/2 watt, and you d be fine.

    2. What should the 470 ohm and 22k B+ circuit resistors be?
    These are the two resistors I'm most concerned with getting the correct wattage as they handle the high voltage power side of things. I noticed the plates of the 6V6GT's are tapped prior to these resistors so I can see these resistors don't need to handle the main current draw of the power tubes.

    I don't have my notes handy, but the dropping string doesn't handle much current. I thought they were 1 watt, but I recall using 2 watt metal comp here. I also used 1 watt metal comp on 1.5k output grid stoppers. I may be wrong, but I thought Leo had under-spec'd those droppjng resistors anyway as sort of a caveman-style circuit breaker (this is how rumours get started, ha).
     
    Last edited: Apr 15, 2018
  15. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    Yeah sorry I forgot you already mentioned the 10" Cannabis Rex. I really like what I hear here:
    so I'm leaning towards just giving it a try. But idk my curiousity is there for the Weber alnico. I agree with you picking a speaker is the worst part haha. Too many options. All the recordings sound different and are on different amps so its impossible to get a good feel.

    Ok Thanks for all the info on that. In some cases I'll probably go a bit larger because the price is almost negligible but good to know the ratings fot the different sections.
     
  16. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    I'm considering replacing the fuse socket on the 5F11 with a master volume and just having the fuse dangle inside the cabinet. Anyone see a problem with this? I've just been trying to figure out where to fit that master volume and I reckon nowadays that fuse probably almost never blows so I doubt I need the fast access to it. Thoughts?
     
  17. dan40

    dan40 Tele-Holic Silver Supporter

    958
    Aug 19, 2015
    Richmond Va
    My usual resistor list consist of 1/2 watt metal film for the 68k's and 1m on the input, 1 watt metal or carbon film for the preamp tube plates and 1 watt carbon film for everything else. The two dropping resistors were originally 1 watt carbon comp but I prefer to use 2 watt metal oxide for these. If you decide on screen grid resistors for the power tubes, 470 ohm to 1k, 2-5 watt metal oxide or wire wound are a good choice. For the 1.5k grid stoppers on the power tubes, anything 1/2 watt or higher is fine as there is very little current going through them.
     
    Nickfl likes this.
  18. Smokingheadstocks

    Smokingheadstocks Tele-Meister

    102
    Mar 18, 2018
    Blue Planet
    A lot of bad advice around here... Everything matters, metal film resistors are not the same thing than carbon comp resistors, not all caps sound the same, for different reasons (i.e some are more susceptible to temp variations and their value will easily drift, same thing happens with CC resistors). Transformer are EXTREMELY complicated animals (yeah they look simple but they´re not!), specially the output transformers when it comes to sound amplifiers. You definitely need to get some books, a lot of coffee and study until your crack disappears, and that´s just to get a taste of it.

    This stuff is not easy to grasp.

    Now, if you want to build an amplifier that will sound ok-ish, then yeah, use whatever you want as long as the components are not the cheapest crap from ebay.
     
  19. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    @Smokingheadstocks I admit I'm a little frustrated by your reply. You appear to assume that I am not putting effort into this and just want others to hand me information, so let me give you a little more information on what's really going on in my life.

    I agree getting a book would be a good idea, I will give you that. However, I'm reading and STUDYING a ton from the information I am finding online. I spent about 13-14 hours in the last two days alone creating a word document that explains how the entire 5F11 circuit works and what every single component does. This is after a ton of other hours I haven't even tracked reading Rob Robinette's website, watching videos from Uncle Doug, reading Aiken Amplifier's webpage all while studying the 5F1, 5E3, and 5F11 schematics. And when I say study, I mean STUDY not just glance at. This isn't a casual project to me and I want to do it right. But some things you can only learn from experience and that's why I ask questions from others with more experience. My background is mechanical engineering and I have found that so many things learned in books at school were far too idealized to describe how something works in the real world. Most of the time, its people's experience and intuition that help them find a solution to a real world problem.

    I'm doing all high wattage, low noise, metal film resistors. I want a quiet, excellent sounding amp. I don't need the mojo. I continually read good things about Mallory 150 and F&T caps so I will probably go with those. However I have also been reading Aiken's suggestions for pots that don't change their value as much when heated so I am still researching and deciding. The pots will be CTS and Alpha. The switches, Carling. The transformer I'm still deciding but probably a Hammond or Classic Tone.

    Overall I feel I now have a pretty dang good grasp on the general function of all the components, what they do, and what they are there for. However the values and some of the calculations I'm still in the process of learning. I'm infinitely far from being an expert on amplifiers, but I no longer feel clueless or confused looking at these schematics and I've found the whole process of understanding it to be fascinating.

    I don't think its an unreasonable question to ask about the resistor size on the voltage dropping resistors and want an explanation for why those sizes were chosen. If you're an expert please enlighten me on where I went wrong on the calculations above. I calculated a max current draw possible from the pre-amp section of 24 mA which is well over 14.7 mA that a 5W resistor can handle on a 340 V circuit. What is wrong with my analysis?
     
  20. JuneauMike

    JuneauMike Friend of Leo's

    May 5, 2015
    Alaska
    @timewaster1700, if you read it more closely you'll see he's talking about us. There is a small and crusty sect among this group who believe that tweed amps were handed down by mystical shamen and only those Special Forces amp gurus with "the right stuff" can attempt to build them. In other words, you roadied for Warrant in the 80s, or were in a cover band with a guy who sold pot to Pete Townshend's amp tech.

    Just press on, make a mess and sort it out. If you find a chassis on eBay at a good price, don't worry that it will kill your tone. It won't. Have fun, just like all of us. Learn, grow, play.

    P.S.: is anyone else kinda grossed out by the mixed metaphors of "studying until your crack disappears" "just to get a taste of it?" Ew, dude. Just ew.
     
    dan40 likes this.
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