Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dpm309 on September 07, 2015, 01:13:56 pm
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Just completed several mods, including aux and line out, on a Blues Jr. Wanted to add a dummy load so that when using the line out, you could cut out the speaker. This would be good for recording situations or just wanting to listed through headphones. I have attached a schematic of what I am trying to do. All I need is to add the 8 Ohm/25W resistor and a SPDT toggle switch. I have a 8.2 ohm/ 25 wirewound resistor that I am planning on using. Looks like it will work but wanted to get a second pair of eyes on it and if anyone has tried this before.
Thanks,
Dan
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This is what I did for a "zero volume" stage where the guitar is run into the PA system. It's been used almost 3 yrs now with no issues and it sounds great. I bought the H&K Red Box off ebay for about $50. As an FYI, I used a 100w 8 ohm resistor and it doesn't even get warm using 6K6 or 6V6 tubes.
With respect, Tubenit
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Looks good! Since I don't have a Red Box, I will probably go with what I drew up previously. I ordered a 50W 8 ohm resistor since the 25W might get a little hot. These amps run about 15watts so the 50 watt resistor should not get too hot.
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I have another dumb question on the toggle switch I am planning on using. Since there is not enough room to install a standard SPDT toggle switch I was planning on using a mini SPDT toggle switch rated 5A at 125VAC. Any issues with using this? I also realize the amp will have to be off or in standby mode before switching the dummy load on or off.
Dan
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I have a Blues Jr, and would like to build a stand alone load box using this plan, connected to the amp speaker output jack by a speaker cable, rather than switched like this one, and (presumably) attached to the amp. I do a little home recording, and would like to use the Blues Jr connected via the line out to my Focusrite. Any thoughts or advice? Any recommendation for an added capacitor to maintain tone?
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Google: M2 attenuator. The schematic and explanation is on the Marshall forum, which I can't access (I was banned because I had "too many accounts" even though I didn't, and there is no way to correct this).
The Red Box works well, and Tubenit and others swear by them.