Jet City JCA22H

digitalscream

OK, so up until now I've been treating my JCA22H as the backup amp, the logic being that I've always had exactly the sound I wanted from my JCA50H.

Since I changed the pickups in my S2 for lower-output ones from Oil City, I haven't been able to get quite enough gain out of the JCA50H's clean channel - the growl was there, but not that little bit of "hair" on top which lets you pick out really singing pinched and tapped harmonics.

Last night, I couldn't be bothered lugging the 50 to rehearsal, so I took the 22H instead and spent some time getting it set up exactly right. In the words of George Takei...

OHHHH MYYYYYYYYY.

Such a fucking great sound. There was even a bit more low-end grunt as well as exactly the right amount of extra hair on top, and the lead tone was just out of this world. The guys at Jet City say that the preamps are exactly the same, so the gain levels should be identical across all four amps with that preamp, but I'm absolutely convinced that there's a bit more on the 22H than the 50H. I suppose it's conceivable that the valves might be going in my 50H, but I seem to recall having exactly the same experience with my first 22H. With that in mind, I'm inclined to think that it's something to do with the fact that they've moved the effects loop (it's after the master volume on the 22H, and before the EQ stage on all the others).

In any case, the 22H just became my main amp. Hell yes.

ICBM

There is a small gain loss associated with the JCA50H's FX loop circuit, if it's the same as the SLO. (I don't have a schematic for the JCA50.) If the FX loop is within the distortion generating section of the preamp as it is in the SLO then it will reduce the gain; moving it to after the MV will stop that, even if they used the same loop circuit; the JCA22H (which I do have a map for) has a different FX loop circuit anyway though.

EL84s do have more 'gain' than 6L6s too, so that could be making the difference even if you're not pushing it into power-stage overdrive - and you might be on transients, even if you don't think you are. It takes really quite a lot of power to avoid that entirely, hence the argument as to whether "100W is too much power" or not.

I think what you really need is an amp-switching box so you can use both at the same time .

digitalscream

Cheers - I'm amazed that my total lack of in-depth technical knowledge might've led me to the correct conclusion. Guesswork FTW

I did consider the dual-amp option, but I actually don't think I need to. The only real reason to do it would be to get a cleaner/louder clean, but the fact is that we only have one song where I'd use it anyway. In any case, I could always get an A/B loop switch (better than the one I've got, anyway...) and use the clean channel of my AMT C2 in place of the amp's preamp and get a Fender-style clean if I wanted it.

ICBM

Aha... I've now found a schematic for the 50 too.

You were indeed correct .

digitalscream

ICBM said:

Aha... I've now found a schematic for the 50 too.

You were indeed correct .

Awesome sauce.

Out of curiosity, how close are the circuits to the equivalent Soldano amps? That would probably be the Hot Rod 50 Plus (minus the depth control) and the Hot Rod 25 (accounting for the EL84s instead of 6L6s)...

Si_

Has the JCA22H got a normal level FX loop or one of the usual Soldano crappy line level ones?

ICBM

At a brief look, the JCA50 and the HR50 are very close. Not sure about the HR25 yet, I'll need to look for a schematic.

digitalscream

Si_ said:

Has the JCA22H got a normal level FX loop or one of the usual Soldano crappy line level ones?

Subjective testing suggests that it's slightly lower-level than the one in the JCA50H, but still pretty hot; certainly too hot for my Belcat delay pedal.

ICBM said:

At a brief look, the JCA50 and the HR50 are very close. Not sure about the HR25 yet, I'll need to look for a schematic.

I think it's pretty certain that the HR25's power section is going to be wildly different - it uses 6L6s with some sort of power shenanigans to get down to 25W.

ICBM

digitalscream said:

I think it's pretty certain that the HR25's power section is going to be wildly different - it uses 6L6s with some sort of power shenanigans to get down to 25W.

Could be as simple as running them at lower voltages. You don't have to get a valve type "down" to a lower power, the "normal" power they produce is simply the result of running them close to maximum voltage ratings, as most designers did in the days when they were only interested in getting the most power for a particular cost. A valve set can develop any power below that if it's just run more conservatively.

Of course, it's possible that they've done some other tricks instead, like running them as triodes or using unbypassed cathode resistors*, but it isn't necessary.

(*I did this with the R&R to keep the 15W rating operational, after the new Marshall power transformer I fitted it with didn't support the low-voltage option. Works very well and gives it the dynamic feel of a lower-powerred amp, rather than just less volume.)

Dave_Mc

ICBM said:

At a brief look, the JCA50 and the HR50 are very close.

Interesting.

That's interesting about the el84 and 6L6 too. Obviously this isn't scientific, but on my hayden where you can switch between an el84 and 6v6 on the fly, the el84 seems to have a little more distortion, even at silly low volume levels. I just assumed it's because it broke up earlier.

That's probably something which is completely unrelated, though, and now I'll look silly )

digitalscream

Dave_Mc said:

ICBM said:

At a brief look, the JCA50 and the HR50 are very close.

Interesting.

Not only that, but if you're happy to order from the US, then you can order a custom Jet City amp modded (by Soldano) with Mercury Magnetics transformers, the depth control and a choke...which would basically turn a JCA50H into a Hot Rod 50+.

Dave_Mc

probably not, i mean i already have the 50 watt head )

I just meant it was nice to know it was fairly close to a soldano. I figured it was, and the word on the street was that it was, but it's nice to have it confirmed.

Do you have a link to the schematic ICBM?

Also it's interesting that you're saying the 22 sounds better- I know I normally advise going for the 50 for all the extra it costs, for the extra headroom and bigger power tubes which normally (to my ears, anyway) translate to a high gain amp sounding more the way you'd expect.

ICBM

Dave_Mc said:

Do you have a link to the schematic ICBM?

This is the JCA50:

http://i.imgur.com/K2fq0.jpg

And this is the original HR50 (not the +, so single channel only)

http://nicosonic.com/sites/default/files/pics/Soldano HR50 SL60 + XL mod.jpg

You should be able to work out how close they are! There's a cap value between the first two gain stages that's different (470pF vs 270pF) and an extra cap after the FX loop in the JCA... there may be more but I'll leave you the fun of Spot The Difference .

Dave_Mc

Awesome, thanks

Yeah they do seem pretty close. Which is excellent

Am I right in thinking that the JCA has basically taken the low and high inputs and made them switchable (alongside separate gains and masters)? If so, that's a pretty handy way to give the illusion of two channels... sort of makes you wonder why he didn't do it on the hot rod. Works better than a footswitchable boost, too, with the separate gain and master controls.

ICBM

I don't have a schematic for the Hot Rod 50+, but from what I've read that's basically what it is, and the JCA50 is a fairly straight copy of it.

AlexHunter

digitalscream said:

Dave_Mc said:

ICBM said:

At a brief look, the JCA50 and the HR50 are very close.

Interesting.

Not only that, but if you're happy to order from the US, then you can order a custom Jet City amp modded (by Soldano) with Mercury Magnetics transformers, the depth control and a choke...which would basically turn a JCA50H into a Hot Rod 50+.

How much would that set me back in dollars then? The import rate and shipping I could work out.

AlexHunter

digitalscream said:

Dave_Mc said:

ICBM said:

At a brief look, the JCA50 and the HR50 are very close.

Interesting.

Not only that, but if you're happy to order from the US, then you can order a custom Jet City amp modded (by Soldano) with Mercury Magnetics transformers, the depth control and a choke...which would basically turn a JCA50H into a Hot Rod 50+.

How much would that set me back in dollars then? The import rate and shipping I could work out.

Dave_Mc

ICBM said:

I don't have a schematic for the Hot Rod 50+, but from what I've read that's basically what it is, and the JCA50 is a fairly straight copy of it.

Ah I see, thanks. I forgot about the + version ) It's almost like mike soldano knows what he's doing

jimmyd

I'm thinking about getting a new amp and posts like these (and finding subsequent youtube videos like these) is not helping...



Really like the tone this dude gets.  I know a lot of it is coming from the Splawn cabinet and the sheptone pups but it's ace !

digitalscream

@AlexHunter - dunno, spec it yourself  http://www.ampfactory.com/50h-custom/

EDIT: To save you time...base model is $500. Mercury Magnetics transformers will be $250 each extra (PT and OT). EL34 or KT88 mod is $25.

@jimmyd - my amps sound a tiny bit brighter/spikier than that (and I think he does some compression tricks on his vids), but it's reasonably likely that's down to the speaker combination (V30 and G12T-75). You certainly won't get that tone from the stock Jet City speakers. However, his videos are pretty close to the real thing.

AlexHunter

@digitalscream ; I had a feeling you'd say something like that. So with all mods done the amp would come out at $1300, shipping/duty/VAT would max at around $500 - probably less. But that's still going to work out at over £1000. So if you were buying both new I can see the benefit, save yourself a grand on a Soldano and get the Jet City but..... there have been three Soldano Hot Rod's on ebay in the past month that went for under £1000. New Jet City or Secondhand Soldano?