5C1 Resistors

[dtjacob]

Hello:

I'm in the process of getting the parts together to build a 5C1 & I'm having trouble finding the exact value resistors listed in the schematic........I know that there is some kind of tolerance here, but I don't want to end up with something that isn't going to work. Can anyone help???????

Thanks.

[Rhodesplyr]

Hello:

I'm in the process of getting the parts together to build a 5C1 & I'm having trouble finding the exact value resistors listed in the schematic........I know that there is some kind of tolerance here, but I don't want to end up with something that isn't going to work. Can anyone help???????

Thanks.

OF753JE Ohmite Carbon Composition Resistors

25k seems to be a more obsolete value, but you can either parallel two 51k resistors or use 24k. Remember, in the old days when the 5C1 came out, resistor tolerances were pretty loose. No resistor values in the 5C1 look terribly critical to me except the output tube cathode resistor since that will set output tube bias. I assume you'll use some sort of wirewound for that.

I might be tempted to toss in a filter choke for all or part of the 500 Ohm power dropping resistor, but I suppose that might make the amp behave slightly differently.

[tubeswell]

The resistors mainly used in 50s Fender amps were carbon comp because they were the cheapest alternative at the time, and they are characteristically imperfect as far as tolerance is concerned. If you build your 5C1 with these, then at least the resistor components will be fairly authentic. (But you may want a 5W cement resistor for the output tube bias). So if you can't find 500R, 470R will do, 270k will work in place of 250k, 68k will do for the input grid resistors, 2M2 will do in place of 2M, 4M7 in place of 5M.

But the sound is not just a product of the resistors, its a result of the sum total of all the components and they way they are put together, so even if you did get the 'perfect' resistor values, you'd still struggle to replicate all of the other components (although you might get an authentic sounding OT with a paper bobbin). But I'd say its nigh on impossible to get Astron caps anymore, so you'll have to use some other make of caps anyhow. Then there's a nice old NOS pot with a good taper, and the vintage Jensen, Oxford, Utah speakers etc (although Weber does a good assortment of modern equivalents), not to mention the NOS tubes. So you'll probably have to make-do with modern equivalents

[Bruce / Mission Amps]

Most of those early tweed amps used parts with anywhere from + or - 10% to + or - 20% !!!
Get close with 5% resistors, and you'll be closer then Fender was.

[dtjacob]

Thanks to everyone for the help............I kind of figured that the tolerances wern't real tight, but I wanted to be sure.

[Rhodesplyr]

But I'd say its nigh on impossible to get Astron caps anymore, so you'll have to use some other make of caps anyhow.

I haven't tried these, so I can't vouch for the claims they make, but Jupiter Condenser is making a Vintage Tone Capacitor that is *supposed* to sound like the Astrons. Again, I've only read their marketing, so don't shoot the messenger ;-)

Amplifier Parts - Specialty Guitars

[Rhodesplyr]

Then again....

Considering that Fender's 5C1 circuit was built in the early to mid 1950s, I'd be surprised if their coupling capacitors weren't some flavor of impregnated paper capacitor, otherwise known as wax-dipped.

That's what Leslies of that era had in them. "Impregnated paper" was the term used at the time; I had to do some research on these at one point and looked at R&D papers on them from the 1930s-1950s. You start seeing Mylar capacitors around 1960.

If you want to try paper caps, look on eBay for Russian military surplus caps starting with the code K40. They are very similar to the Sprague Vitamin Q's.