Subway Blues, adding a presence control, negative feedback l

Hi, recently picked up a Subway Blues but finding it lacks a bit of sparkle. I know it's a 1 x 10" and blues orientated but I would like some of the top end harmonics I got through my Studio 22. Is there a mod to either add a presence control or adjust the negative feedback loop to allow a more open sound?

I don't have any experience with the Subway models, but I struggled with the same issue with my Fender Super Champ. With the Fender, it ultimately came down to the cabinet being so dinky. Have you tried an extension cab?

I have a couple of cabs I can use but that defeats the purpose of the 'grab and go' amp I'm looking for. Wish I could find a bank of speakers to try, time and money are only two of the problems! Maybe I need to bite the bullet and keep looking for a Studio 22 or an F30.

Maybe try some pedals, like a treble boost or an equalizer.

SamuelJ86 said:

Maybe try some pedals, like a treble boost or an equalizer.

Click to expand...

A Flux-Five might be a great option.

Try one of these.
Not an EQ, as some believe, but it takes the blanket off your amp. Tightens up the bass and adds sparkle to the high end.

I haven't mucked about with presence control mods. I have however put a few resonance controls in Marshalls. And put a rotary on my old JVM to allow different amounts of negative feedback available in that area of the circuit.
How I understand the NFB loop and presence control to work is that when the dial is on 10 it's like the control is out of the circuit. Turning the control down reduces the amount of signal fed back into the phase inverter. So essentially adding a presence control wouldn't give you any more high end shimmer. And could just be used to clamp down the power section more.
This is one rare occasion where I'd suggest trying new valves. Loss of high end is usually the first thing to go as valves wear out.

Excellent article on Negative Feedback here

http://www.aikenamps.com/index.php/what-is-negative-feedback

This might help. I just looked it up and that stood out.

After that, a person could decide if they needed a presence circuit.

Thanks for all the replies, I have been experimenting with pre amp valves and also replaced the stock speaker with an Eminence legend 1058 which has helped. Biggest difference though came when I hooked the amp up to a 1 x 12" extension cab which had a fairly basic Celestion type (70/80) speaker from a Vox VT50 in it, the amp was much more open sounding even though it was a closed back cab. I would love to retain the 1 x 10 format so will ask a couple of techs about the mod supplied by afu, I had heard about a change near the input but could never find it online.

I had to redo the picture, because I made a mistake on the original. Taking out those parts and putting in a 10k resistor will change the divided volume from 60% loss to <1% loss; 68k would be about a 7% loss. 33k to 68k are better than 10k for blocking radio signals and other noise and the volume loss is not too bad.

As stated above I think the input sloping filter Is key to the attenuated the top end. In the schematic you can see a 250pF capacitor in parallel with a 1mOhm resistor. Removing the 250pF cap Will add lots of sparkle and some gain.

I have recently done this to my Express 5:25 which has a similar input filter and the clean and crunch tones are much more lively.

The Subway Rocket series has a dual function on the gain knob. The higher the setting, the more presence. So it is a presence control as well. This works fine with a lot of settings, but it spinned my head when I was looking for a proper clean sound. The more difficult it became, when I didn't understand the serial eq: one functioning as gate for the other, whilst the mid above 5 gives a fat boost.

When I got that right and I changed the stock speaker in a Greenback 10" my problems were practically over and I enjoy the amp a lot more, but the sensitivity is still very high. Good clean? There's a thin line between great and definitely unusable.