Princeton (Panasonic?) C1815 Based Amp Questions

[yamtempura]

Hi Everybody,

First time poster, long time lurker. I have a lot of experience working on and designing tube amps, but have only dabbled a bit in solid state amps. I've been commissioned to design an amp for a friend ("commissioned" is a fancy way of saying build for free/fun) based on a beloved weirdo Japanese solid state amp he has. The amp is a Princeton "Prince" T-70 model. From the very little I've found about them, they seem to have been built by Panasonic. I'm not expecting anyone to be familiar with this particular amp, but I was hoping that maybe somebody was familiar with any other amp designs that used the C1815 transistor. I'm curious to see if there's a more common model (one with readily available schematic for example) that also used this NPN transistor as the basis of its pre-amp.

Any help or pointing in a direction would be infinitely appreciated! Thanks!

[Enzo]

2SC1815 is a very common transistor, or at least used to be.   I have a drawer of them.   60v 150ma, complement to the 2SA1015.  Low noise type.

Just about any small NPN transistor would work in its place.  This isn't like choosing 12AX7 versus 12AU7.   If I wanted to make a circuit based on the C1815, I could just as easily used 2N5210 instead.  Being aware the 2SCxxx types have the legs in different order from 2Nxxx.   SO you need not find a schematic using the C1815 specifically.

There are some short cuts.  Instead of builoding a whole power amp stage, you could just use a TDA2040 or similar TDA chip.  A bazillion small guitar amps based on that power amp exist.   I don;t know how big the target amp is or how many features.   Your basic practice amps are all similar.  A chip PA and a dual op amp or two for preamp.

You want all discrete transistors?  Then typially you are looking for old schematics, like original Peavey Classic or an old Kustom or whatever.  Peavey now makes what they call "transtube" amps.  They don't sound bad at all.  It stands for tube sound from transistors.  But what it more or less is, is darlington pairs wired in a circuit that is configured like a triode circuit.

Look at the Blazer 158 transtube I attach, a basic amp that sounds good.  ELiminate the reverb and you have the Rage 158 TT.

[yamtempura]

Hi Enzo,

Thanks so much for the help, you're always an amazing resource! I'm actually thinking of taking the preamp from his solid state amp and using a tube output section, so I think the Peavey Classic is a great place to start looking. I do also prefer to use all discrete transistors if possible, just because I'm more comfortable with that configuration.

Although I can't find a schematic for the amp I'm trying to capture the vibe of, at least I have the amp itself, so I think I'll draw out the traces of the PCB and do some signal tracing, and hopefully it'll be fairly easy to recreate its essence.

[Enzo]

Hybrid amps require not only the regular low voltage supplies for the solid state parts, but also the high voltage and the filament supplied for the tube parts.  So usually that means either using two power transformers or finding a special transformer with all the voltages - like one from a Pevaey hybrid.

So really, for practical reasons, I'd just build a transistor amp and be done with it.   Just personal opinion.  Or make it a preamp and plug into the FX return of some tube amp.

Op amps are not hard to learn about, and you never will if you don't try, so think about that. Especially if you wind up just copying some circuit.   Really old PV amps had transistor preamps, and the most recent are the transtube series which are back to transistors. For a while there, the 80s and 90s, they used mostly op amps.

That Blazer uses 2SC1740 or something like that, but I see no reason you could not build the exact same thing with 2SC1815.

Look up PV Century, a good basic transistor preanp, though we'd want a different power amp.  Or the PV Standard, just build one channel of the preamp, and it has a basic power amp that would be OK.  But i am still in favor of a TDA2040 power amp or maybe an LM3886 type.