3 tube 8 watter Valco style amp with swamp sound

I've had real good luck building this Valco 510-11 circuit. For those who would enjoy retrofitting old and good looking vintage cabinets, this design fits the bill. The sound is fat and stuffed to the brim with harmonics. What one could call a "bedroom" amp.

I would be willing to assist in sourcing the 3 common tubes, transformers, and related components. Total cost will be somewhere around $200+ however this circuit is fairly forgiving and used power transformers, sockets, knobs, & chassis not only make the amp look better, it's cheaper as well.

Uses a 5Y3GT, a 6SL7, & a single 6V6. The last one I built went into a suitcase. The preamp section was biased well below maximum, but acted so hot that with the modd'ed preamp volume when turned up added a vibrato. This design is extremely sensitive, simply hammering the neck plays loud. 

In this small venue (Cigar Box Nation) I will be glad to share my schematics & links to the most reputable parts suppliers. This amp will not only fit a small foot print, but will preform well with a standard guitar & will allow you, the tube novice (and experienced builder alike) to enjoy the amp that Jimmy Page used to record Stairway To Heaven with. 

Search the web for Valco 510-11 images. The drawing is tilted slightly, that's the one.

If there is some interest, I'll post a couple of pics of what I have, maybe a youtube clip as well.

Rest regards, Doug


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  • Sold the one built here for 500 smakers. Working on 2 more currently. For some reason the ser#1013 has an incredible Billy Gibbons- Magnatone sound. Here is a link to listen .....https://www.youtube.com/watch?v=Rs35RvBGxIs&list=UU9W4Vl201YkwF... 

    I could put together a kit for those who want to give this amp a try. Punched out sheet metal chassis included. Just leave me a note here & I'll get back to you. So far I've had good luck with the Magnetic Components power transformers. This company is making their stuff in the USA and was the OEM supplier for the Valco way back in the mid 1940s. 

    Happy Thanksgiving everyone, -Doug

    • Sounds AWESOME Doug!!!

      And a Happy Thanksgiving to you & yours!

    • Has anybody tried to build this 3 tube 8 watter yet? I have serial numbers 19 & 20 all caged up & waiting for a new home. 

      Best, Doug

  • Here is a video of my latest 3 tube mod'ed Valco 510-11 creations


  • Here it is finished. Just a quick cellfoan pic, better documentation coming. The paint was still tacky..


  • It's completed! 

    May do another video tomorrow. This amp is very, very quite when plugged in with no strumming. Super gluing the twisted 6.3Vac filament wires into the corners really did the trick in that regard. Initially off the amp was low in it's output. I went into the cathode resistors, R3&4 (pre-amp tube), tried a couple different cap-resistor combos, with about a 50% improvement, them today went over R1&2 and clipped one end of R1 & mini-clipped my way into the circuit with my trusty resistor decade box, it only took going to 220k from 270k, with a BIG improvement, then onto R2 which went way down. These are NOS tubes, ended up at 47K which actually set the overall tone & not much volume improvement, but thats OK because it's loud, really loud. My bias is still to high on the 6V6 at 20 watts (max is 12 watts for this class "A"). Guitar amps can enjoy a limited tube life mainly because the owners are used to replacing their tube every hundred hours or so, unlike the HIFi builders who like you may imagine love to keep their stuff running & running all the time. In that case I would bias the 6V6 tube more around 8 watts.

    There 2 reasons why I have been tweeking this, actually 3. The last one bascilly is it just was low on volume, the 1st is always that I always seem to have slightly different outcomes, and it's oK because I experiment with different types of components. Example (updated schematic & BOM coming) I used the ever popular .001uf/1500 volt ceramic disk cap across the 1st set of 10uf/450 volt filter caps,  ($0.60ea)(connected in series for a 900Vdc rating). This is more like a Silicone diode setup, with no tube rectifier. It's a very small cap designed to catch very fast pulsations (AC) & still turn them into D.C. More of a protection item, but you can't hurt this (any) straight tube amp with almost any power blip. The 2nd & 3rd set of (series-ed) filter caps, C-6&7 were again connected in series & were the larger 47uf/450V ($1.60ea), That is 2ea for C6 & 2ea for C7. The 3 position "MODE" switch, or Mojo switch, is always populated with the pre-amp's cathode to ground resistor & capacitor combos. Trying these lets you find all sorts of tones tested normally with only one of these "MASTER" or "PRE" volume maxed and the other set safely halfway down. For instance, I was looking for the cleanest setting for the full CCW rotary switch position "1" and found another more dirty combo on the 2nd cathode (6SL7 tube). The other 2 positions are for the most part fairly clean except when you have the "PRE" volume turned up, then you can tell the difference. So in your process of tweeking realize that establishing your tone from this amp (or any other) or whats more commonly called "voicing", it seems like a never ending process. Once you learn the different sounds and attempt to find them in your circuit with component swapping, you will realize that at different times, different guitars, venues that your tastes will drift away from what you originally liked. That's OK, and back to voicing you will go. I sometimes simply start another build, but this time perhaps with different manufactures of coupling caps, other values, even using some WWII era caps that seen to test OK, and there always that different Power Transformer.....which changes up more than I want to realize with the high voltage winding being 50 AC volts or so off in one direction or another.

    For the most part, using the original Valco 510-11 schematic for your first build can't be bad. My modded "hot rod" more like "Rat Rod" is a fun way to exceed the norms and have your way with the thing. The Master Volume control is simply a way to enjoy splitting up the overdriven sounds of each of the two tubes. You can actually hear the FAT 6SL7 coming in with the "PRE" maxed out and the master volume turned down to halfway, and vise versa. With the Master Volume maxed, and the PRE turned halfway down, there is that smooth 6V6 overdriven sound that many, many guitar amp aficionado will tell you their like nothing else, no 6L6, or anything else can touch. Placing a microphone in front of one of these little gems is a very popular way of studio recording and even live performances. Don't let size fool you. A 1.5 amp fuse is perfect. And by the way, when I called this a "bedroom" amp, well, you could gig with this amp in a small bar, it's loud. Which brings me to another subject, the Speaker~

    Speakers for guitars are a different breed. Some say that it's efficiency that makes a good guitar speaker. Well for this amp that's a good point. Warehouse Speakers    link    http://wgs4.com/  is the most respected outfit with all guitars players & amp techs alike. This model   link   http://wgs4.com/12-g12q-20-watts      ...the infamous 12G is a good deal at fifty bucks, Amazon has this Eminence Cannabis Rex 12 inch   link   http://www.amazon.com/EMINENCE-CANNABISREX16-12-Inch-Rhythm-Speaker...     which last November I found for only $65, not that I'm promoting a weed based amp speaker, but darn, the thing sounds really mellow. Actually any "Eminence" speaker is top shelf stuff. The only thing better is any "ALNICO" type that uses a super magnet- Aluminum & Nickel, that really kicks out the notes, kicks out the notes right out of your wallet too! I have been blessed however with old speakers recovered from junk HiFi sets, old defunct music equipment. Like the old saying goes, someone's junk is someone's treasure, and so it goes. Remember that '46 NOS Fender 10" Alnico in that old radio cab? It sounds like no other I might add. So to close know this, this amp relies on a large emitter, speaker. Even dual 12s or even 10s, or 8s. Single or dual, this is going to have perhaps the largest impact on your tone. Take your chassis (when it's all buttoned up) down to your local Guitar Center & try one of their speaker cabs out. Hey that's what their there for.

    Seth; tell us more about that little combo cab you found. What size speaker does it have? I refurbed many of those things. Great for projects like this. Check out your local fabric shop & look for some vinyl table covering material, table cloth. It's a rel nice Tolex (amp covering) type material. plenty cheap & available. Tons of choices. Also the fun thing is to buy your own wood, Lowes & Home Depot will cut your project out for free, and build the period correct looking box that at that time were made (get this) to look exactly like a TV!  Has this little rounded corner square hole dead center. Others had a delicate scroll sawed logo across the speaker hole. Speaker covering is also a have to have. I found some real nice stuff at these fabric shops, also the best at Hobby Lobby craft store in the window treatment aisle.  link   http://shop.hobbylobby.com/products/brown-woven-decorative-panel-wi...     this is see through salt & pepper looking with browns, tans & reflective to boot. Would make real nice retro speaker grille covering. Actually the current trend is retro, so ride that tide!  Always search on your smart phone for their instore coupon. I found one for 70% off. Presented it on my smart phone to the cashier & whola!

    Can't wait for 'yall to start in on yer own 3 Tube 8 Watter. -Doug



    • Well, my "donor amp" is a busted Epiphone Valve Jr. It powers up, tubes started glowing, but does not pass audio. The guy I got it from said he was playing a bass though it and it just went silent on him. I have not opened it up yet to see what I can find. At the very least I will flip the amp over and change the decal on it. It looks better with the speaker on top.
      I already have two of the head versions of this amp, each modded differently, and they sound good through a 1x12 I built myself. I also have some donor parts from an old hi-fi I could mix in.
      I think the cobo has an 8 inch speaker, but the coffee has not kicked in yet so I'm not sure.
      Now to see if I can upload pictures.


    • Very nice Seth. Hey, you know with a bass, most amps hate those, except a bassman! You think it could be the speaker?  Simple test is use a AA battery and see if the diaphragm moves, even an ohm meter (on the ohms scale) will make a small scratching sound, or at least a reading on the meter. Also the Output XMF could of died. If the B+ supply is solid state, could be the rectifier, but normally it will not entirely fail, just sound weird.

      Seth, have you seen this?   link     http://forum.gibson.com/index.php?/topic/48731-new-epiphone-valve-j...   Good luck man, let us know how you are coming along -Doug

    • Had not read that one. I think in total for 3 modified versions of this amp, all of which sound good to me, I haw paid less than $200. So not too bad. I even ended up with spare tubes out of the deal.
      The speaker does work, the rest remains to be tested. I should actually modify my story of what is wrong. A hiss/humm can be heard, but no sound from anything put into the amp is heard. The guy who sold it said that "you can see a resister or something burned up." I took that to mean there may be a blown cap. We will see. If it becomes a donor I can use the parts from this one to fix my two that I use, though it could also be cool to have a combo for gigging.
      So many options.
    • With the link I read- a puddy knife is needed to open it up. Maybe not so hard if it's already been opened. A resistor? Maybe in the bias supply, or the cathode resistor, both on the larger side. Looks real sweet from the outside.

      A friend who does mainly Fender repair says that almost every amp built from the 80s on has failed in one way or the other within 5 years, especially the newest ones from China. Says that they last a year or 2 at best.  

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