after recently seeing a video on an old Magnatone Melodier Deluxe Model 109, i instantly fell in love. simple design, it'd be perfect for apartment use, and i like the fact that it featured dual 8" speakers for something a little different. somehow it quickly went from "i want one" to "screw it, i'm going to BUILD one!" i'm in need of a new amp and i've thought about building one for a while now, and considering how simple the circuit is, i figured this would be a good place to start. i'm working on a pretty loose timeline, in the sense that i'd like to get it finished around New Year's, which should be easily doable. this way i'll be able to spread out the cost of parts and feel like i'm getting closer to my goal, instead of just stashing away cash every week and trying my best not to spend it on something else (which i kind of have a problem with) plus, this gives me the opportunity to learn more about the inner workings of tube amps, since i don't want to jump in blind. i've already spent the past few nights reading all sorts of stuff (RCA Receiving Tube manuals, tons of amp building websites, etc.) the higher-level electronics theory pretty much goes right over my head, but i'm not interested in designing my own circuits either, so for now i'm sticking with info that i think will be most important. i'm enjoying the learning process so far! the Melodier 109 is a pretty simple amp: one 12AX7 pre, 2x6V6 cathode-biased power tubes in P-P, 5Y3 rectifier, volume, tone. two instrument inputs and a mic input with its own volume control. here's the schematic for the Melodier 109 for those unfamiliar with it: fwiw, this is the ONLY schematic of the 109 online: every website has the exact same one (probably "borrowed" from the person who originally scanned it)! info about this amp is sparse, especially when it comes to the electronics. luckily i'm already to the point where i understand a lot of it, and no doubt it'll be even easier as i do more homework on tube circuits. i have found it pretty neat that i keep having these "AHA!" moments, where i learn something and then a bunch more of the circuit instantly makes more sense. i'm sure i'll be asking more questions as i go, but for now i've got a couple that maybe some of the amp gurus here could answer. first off i should mention what i plan on doing with the circuit, and then i'll get to the questions. i actually don't plan on making any major changes to the circuit, aside from a 3-prong power cord (natch), and getting ride of one of the instrument inputs (and perhaps the mic input. i'm still not sure if that might be a useful alternative guitar input or not.) i'll be using an undrilled chassis and i'll buy a raw cab since i already know how to cover cabinets. i'm not really interested in staying true to vintage with the components, so i'll most likely use Tefzel or Teflon wire, electrolytics instead of cans and all of the transformers i've got in mind are "stand up" type so i don't have to punch or nibble big holes in the chassis. ...which brings me to my first question, regarding the OT: Q1: all of the tube data sheets for two 6V6's in p-p suggest an 8K Ohm primary. what little info i've found regarding the Melodier 109 suggests that it most likely used an OT with a primary in the 6k6-6k8 Ohm range (as did a lot of similar amps of that era.) i'll most likely be running into an 8Ohm speaker load like the original amp, so will it make much difference as to which primary value i use? from what i gather, the 6k6 Ohm will give me a bit more lows and highs, whereas the 8K would cut those a little in favor of midrange. keep in mind that i'll most likely be using a 2x8" config (which, given their small size, makes me wonder if that's why they originally went with around 6k6 rather than 8k?) Q2, regarding cap voltage values: this one is probably a bit more important than the above OT question. obviously the cap farad values are on the schematic, so that's not a problem. but i'm wondering if there's an easy way to determine the VOLTAGE value to use? of course i can go higher, but that gets more expensive and space-consuming (especially with things like the filter caps.) should i go by the plate voltage, or is there a relatively simple math equation i can use? anyway, i think that's all i've got for now. i'm really looking forward to collecting parts, the learning process and building the thing. i'm sure i'll have other questions as i progress, but i'm also doing a ton of reading for my own benefit. after playing for 25 years, i'm glad i finally know HOW tubes do what they do, and the whole thing is continuing to fascinate me!