Good small valve amp for keyboards?

[Hugh Robjohns]

Excuse the crude drawing, but it should be something like this:

Insert and solder one end of both the 1k2 and 10k resistors into the centre pin of the destination jack plug.

Then take the other end of the 1k2 and solder to the screen barrel of the destination jack plug.

Wire the unbalanced cable in the usual way to the source jack plug.

Place some sleeving over the centre wire at destination end and solder to the free end of the 10k resistor. Use sleeving to protect the junction and prevent shorting against the barrel.

Solder the cable screen to the destination barrel.

Swear loudly because you forgot to put the jack plug body and cap over the cable first....



Remake destination end and then label the cable in some reliable way to indicate that (a) it introduces 20dB attenuation and (b) which end is the destination end (the one with the resistors in it).

As Dave says, the resistor values aren't too critical. Anything above 10k is fine for the series resistor (the red one above), but the shunt (green) resistor should be about 1/10 of it's value for 20dB attenuation.

A higher value for the shunt will give less attenuation, and a smaller value will give more. If the shunt and series resistors are equal, you'll get just 6dB of attenuation.

[Luke W]

Swear loudly because you forgot to put the jack plug body and cap over the cable first....

One of the worst feelings in the world.

[Drew Stephenson]

And yet one so commonly experienced!

[ef37a]

Thanks Hugh.

Re "forgetting" Lost count how many times I have put a 15A rubber plug on a T lamp and forgotten that the outer must go on first! Quick snip with the side cutters fixed that one.

Been a loooong time since I was on a lighting deck, do they still use 15A plugs?

Dave.

[Luke W]

Been a loooong time since I was on a lighting deck, do they still use 15A plugs?

Dave.

It's still pretty standard for dimmers to terminate to 15A sockets.

[Arpangel]

Excuse the crude drawing, but it should be something like this:

20dB instrument attenuator.png

Insert and solder one end of both the 1k2 and 10k resistors into the centre pin of the destination jack plug.

Then take the other end of the 1k2 and solder to the screen barrel of the destination jack plug.

Wire the unbalanced cable in the usual way to the source jack plug.

Place some sleeving over the centre wire at destination end and solder to the free end of the 10k resistor. Use sleeving to protect the junction and prevent shorting against the barrel.

Solder the cable screen to the destination barrel.

Swear loudly because you forgot to put the jack plug body and cap over the cable first....



Remake destination end and then label the cable in some reliable way to indicate that (a) it introduces 20dB attenuation and (b) which end is the destination end (the one with the resistors in it).

As Dave says, the resistor values aren't too critical. Anything above 10k is fine for the series resistor (the red one above), but the shunt (green) resistor should be about 1/10 of it's value for 20dB attenuation.

A higher value for the shunt will give less attenuation, and a smaller value will give more. If the shunt and series resistors are equal, you'll get just 6dB of attenuation.

Many thanks, that's very clear.
Leaving the cover off of a DIN plug is the worst feeling, but DIN plugs are the work of the devil anyway...

[ef37a]

The trick with DIN plugs is to use a socket in a vice to plug the pin assembly into, heat shunts it a bit and gives all round access.
Then, put wee bits of silicone sleeving over each wire as you go and run it down to each pin. Then if you make a "whisker" it does not short.

I used to LOVE making up cables of all sorts, 15 pin VGA high density are lots of fun. I found it very "zen" !

Dave.

[Arpangel]

The trick with DIN plugs is to use a socket in a vice to plug the pin assembly into, heat shunts it a bit and gives all round access.
Then, put wee bits of silicone sleeving over each wire as you go and run it down to each pin. Then if you make a "whisker" it does not short.

I used to LOVE making up cables of all sorts, 15 pin VGA high density are lots of fun. I found it very "zen" !

Dave.

I used to like making leads too, but not as I've got older, I tend to avoid it now, buying them instead. It's like I don't want to waste time making leads when I can be making music, when I think about the time I must have spent making leads, days, months, it's scary, and it's this feeling that time is ebbing away and I must make valuable use of every minute.

[Arpangel]

OK, all is amazing with this little Roland Cube.........however (there's alaway a "however")
I'm getting some truly mind blowing sounds out of this thing with my synth, especially using the distortion setting on the amp, but "I think" the COSM technology used to create the overdrive is also giving me gating effects, brief pumping in between notes. It's not the end of the world, but I'd prefer it if it wasn't there. I'm guessing, that if this was a proper valve amp then that gating effect wouldn't be there? If this is the case I may need a valve amp.

[ef37a]

OK, all is amazing with this little Roland Cube.........however (there's alaway a "however")
I'm getting some truly mind blowing sounds out of this thing with my synth, especially using the distortion setting on the amp, but "I think" the COSM technology used to create the overdrive is also giving me gating effects, brief pumping in between notes. It's not the end of the world, but I'd prefer it if it wasn't there. I'm guessing, that if this was a proper valve amp then that gating effect wouldn't be there? If this is the case I may need a valve amp.

Well now! Valve amplifiers can suffer something called "Blocking Distortion" which might sound similar? Won't happen in any competent design mind.

The Cube might object to the continuous nature of a synth's signal? Guitar signals are spikey and short lived. Pretty sure the Roland will be a class D amplifier and such amps can be modified to be very loud for (say) guitar signals but shut down for relatively small amplitude sines. The very potent Blackstar ID range can kick some serious A with a guitar but you struggle to get more than a few watts out of them on the bench with a sig genny!

Two consequences to that.
The amps have a reputation for delivering "valve like" stage volumes and they don't go wrong!

You could ask Roland if there is a firmware update?

Dave.

[The Elf]

...and all of these points are the reason why I strategically run my keys through a Line 6 Helix!

[Arpangel]

OK, lots going on here, my synth is noisy, also not at home yet, so haven't been able to attenuate the input to the amp. It's being hit with a full on synth output, and is responding accordingly. I think when I put my little mixer in the chain things may improve regarding the gating effect.
Sounds blooming damn amazing though, noise and all! The first time I've really explored amps and synths, it's going to be the way forward, micing up the amp.