Hiwatt Hi Gain 50 - Footswitch Jack Socket Question

[SteveHiwatt]

 

Hi all

 

 

 

 

I've got a Hiwatt Hi Gain 50 combo that I have just started using the effects loop on.

 

 

 

 

This amp has a 4 button footswitch that connects to the amp via 2x TRS jack sockets on the rear (1x jack is connected to the 2x buttons on the footswitch that control Channel selection and Gain boost and 1x jack is connected to the 2x buttons on the footswitch that control Reverb and Effects Loop).

 

 

 

 

My question is about the jack socket that controls the Reverb / Loop.

 

 

 

 

I do not use the Hiwatts own footswitch (its too large so I just use a single 2x button switch to control channel/gain). However, I have found that without having anything connected to the Reverb / Loop jack socket it seems as though this defaults to Reverb on and Loop off.

 

 

 

 

I tried to simply plug in a short mono patch lead (not connected to anything) to the Reverb / Loop socket to see if that would activate the loop. It did but it switched off the reverb!

 

 

 

 

I then tried to plug in a Stereo (TRS) patch lead (as the socket is desinged to operate via a TRS cable). This did not activate the loop and also switched off the reverb!

 

 

 

 

I will most likely just get a small dual button selector switch to leave in my amp as this will solve the problem for me but i was just confused as to why inputting a mono patch lead would activate the loop but a stereo patch lead would not.

 

 

 

 

Surely they would be touching hte same contacts wihtin the amp?

 

 

 

Does anyone know why this would be the case?

 

 

 

 

Thanks

 

 

[Daehtihs]

Maybe there's some extra circuitry in the Hiwatt pedal that overcomes the issue with trs cable?

[WRGKMC]

There are NO (Normally Open) switches and NC (Normally Closed) switches. Which a manufacturer chooses to use is purely a design decision a manufacturer makes. Its their amp and they can decide to build it with whatever logic switching they choose. In your case the loop and reverb turn off when a TRS plug is connected which means they use NC switches to turn them on. It makes logical sense from a strictly electronics aspect.

 

I'd think the plugs for themselves would be switched, when you disconnect the external foot switch things like reverb should default to being on.

The loop can be a bit trickier. Most amps simply have switched loop jacks which put the gear in series when its plugged in. Bypassing the items in the loop is a matter of those units having their own foot switches.

 

Your amp manufacturer chose to add a foot switch to bypass the loop devices. I'd need to look at the schematic to see exactly how its being done. Given the fact its very bad idea to short the input and output together of any device, I doubt they are using simple analog bypassing. I suspect they are using solid state switching to connect and reconnect the items in the loop. typically a few transistors wired as flip flop circuits will do the job using a single switch to activate them.

 

I can say I'm Not a fan of active SS switching, especially in tube amps. What I dislike even more are the new amps that have logic or midi ports for switching. When those go out you are truly screwed and replacement pedals typically cost a mine, (if you can even find them by the time the unit gets old enough to fail and need replacement)

 

SS switching is susceptible to damage from heat or voltage spikes. Too much heat from the tubes to be running low voltage transistors which are susceptible to heat failure. External jacks are going to be plugged in with the amp on and the devices get zapped when the plug is only part way in. The extension cords for the switches tend to get walked on and pulled and eventually short out. With analog switching very little damage can be done when a cable goes bad. Active carries voltages which can damage things. Just a simple fact of life you deal with for having that convenience.

 

Best advice, "Never" connect or disconnect when the amp is powered on. Once use compatible switches. Never tinker like you did using mono jacks. You may wind up pumping voltage where it should be going when you short the sleeve and ring with a mono jack. The price you pay to have the amp repaired will cost you 10 to 30 times the cost of a proper footswitch.

 

By the way I just took a quick look at the schematic. Its mostly active SS component switching so its very unwise to be screwing around with those jacks if you don't want to wind up blowing the amp up. As an amp tech I used to hate repairing those circuits and every time I came across one you could be sure they blew because some boob was jacking around doing something they shouldn't have been doing. Manufacturers can only do so much to make them idiot proof while making them smart. Beyond that it simply comes down to leaving your curiosity at the door and using the gear as designed.

 

If your gear requires a dual TRS switch to operate properly then use one. Second guessing how it was designed will only increase the possibility of doing something stupid that could damage the gear. Generic switches are $10 or less on eBay. I bought my Marshall and Fender switches on eBay for less then $10 each and they are actual branded switches, not generic. I could have made my own but by the time I paid for the jack switch, cable and box I'd be paying over $25 just in part. If the pedals are simple you just need to know if the switches are latching or momentary and whether there is phantom power to operate an LED.

[SteveHiwatt]

There are NO (Normally Open) switches and NC (Normally Closed) switches. Which a manufacturer chooses to use is purely a design decision a manufacturer makes. Its their amp and they can decide to build it with whatever logic switching they choose. In your case the loop and reverb turn off when a TRS plug is connected which means they use NC switches to turn them on. It makes logical sense from a strictly electronics aspect.

 

I'd think the plugs for themselves would be switched, when you disconnect the external foot switch things like reverb should default to being on.

The loop can be a bit trickier. Most amps simply have switched loop jacks which put the gear in series when its plugged in. Bypassing the items in the loop is a matter of those units having their own foot switches.

 

Your amp manufacturer chose to add a foot switch to bypass the loop devices. I'd need to look at the schematic to see exactly how its being done. Given the fact its very bad idea to short the input and output together of any device, I doubt they are using simple analog bypassing. I suspect they are using solid state switching to connect and reconnect the items in the loop. typically a few transistors wired as flip flop circuits will do the job using a single switch to activate them.

 

I can say I'm Not a fan of active SS switching, especially in tube amps. What I dislike even more are the new amps that have logic or midi ports for switching. When those go out you are truly screwed and replacement pedals typically cost a mine, (if you can even find them by the time the unit gets old enough to fail and need replacement)

 

SS switching is susceptible to damage from heat or voltage spikes. Too much heat from the tubes to be running low voltage transistors which are susceptible to heat failure. External jacks are going to be plugged in with the amp on and the devices get zapped when the plug is only part way in. The extension cords for the switches tend to get walked on and pulled and eventually short out. With analog switching very little damage can be done when a cable goes bad. Active carries voltages which can damage things. Just a simple fact of life you deal with for having that convenience.

 

Best advice, "Never" connect or disconnect when the amp is powered on. Once use compatible switches. Never tinker like you did using mono jacks. You may wind up pumping voltage where it should be going when you short the sleeve and ring with a mono jack. The price you pay to have the amp repaired will cost you 10 to 30 times the cost of a proper footswitch.

 

By the way I just took a quick look at the schematic. Its mostly active SS component switching so its very unwise to be screwing around with those jacks if you don't want to wind up blowing the amp up. As an amp tech I used to hate repairing those circuits and every time I came across one you could be sure they blew because some boob was jacking around doing something they shouldn't have been doing. Manufacturers can only do so much to make them idiot proof while making them smart. Beyond that it simply comes down to leaving your curiosity at the door and using the gear as designed.

 

If your gear requires a dual TRS switch to operate properly then use one. Second guessing how it was designed will only increase the possibility of doing something stupid that could damage the gear. Generic switches are $10 or less on eBay. I bought my Marshall and Fender switches on eBay for less then $10 each and they are actual branded switches, not generic. I could have made my own but by the time I paid for the jack switch, cable and box I'd be paying over $25 just in part. If the pedals are simple you just need to know if the switches are latching or momentary and whether there is phantom power to operate an LED.

 

Thanks a lot for the detailed reply and info!

 

Didnt need the lecture though, as mentioned I am going to be putting a footswitch in the socket as a solution.

I was jsut curious about the technical reasons for why a mon plug would have one affect and why a stereo plug would have a nother.

 

Thanks again