bordonbert wrote:Bulgaria? WOW! I had no idea you were that far away in that direction Silkman. Please let me compliment you on your English. I really had thought you may be American but I considered your English spelling and grammar to be too good for that. As an Englishman with a real love for my language, it's a pleasure to swap ideas with you. Ok, to the job at hand.
You raise some very good points and I was going to advise on them once I knew whether you were interested in this idea. Let's deal with 4) first. Yes, I also find that adding any resistive load will impact on the sound through the speaker just as we both feel the GM36 internal resistive Power Soak does. I don't think it is unusable but I do think it is definitely slightly different. I run other amps, in particular Marshalls which are notorious for having to be loud to sound at their best. I have made a number of simple fixed resistive filters, just simple L-pads, which drop the power to the speaker down by set fractions while keeping the load the amp sees constant. These do work but there is always a slight change in sound. While I really do mean slight and it can be trimmed out a fair bit with control settings, I find it can never be fully removed. I UNDERSTAND THERE HAS TO BE SOME GIVE AND TAKE DOING THIS.
One piece of advice I can definitely recommend you try out is to change your speaker setup when you drop the power in this way or with the internal power soak. One of the most significant changes when you reduce power is that the speaker cone excursion decreases of course. Guitar speakers are not at all like hifi speakers and are designed to work out of their "linear excursion region" which is the exact opposite of what a hifi speaker does. We actually want them to compress and distort the sound in their own unique way. In reality, they drop out of that "overdriven" region fairly quickly in sound level terms. The answer is to run a much smaller speaker which will by driven harder by the lower signal level. For example, if you are using the GM36 with a 4x12" cabinet or even a 2x12" cabinet and you want to drop the power level to say 5W, swap the speaker for a 1x12". The speaker will not be damaged by the lower 5W output but it will be driven harder than the multiple speakers would, enough to still add its own overdrive tone. I genuinely find this is one of the most important differences in sound on full power and reduced. If you are already running a 1x12" then I can only suggest you use a less powerful 12" speaker, perhaps even a 10" instead. I USE A STRAIGHT 2X12" HALF STACK FOR WHICH I HAVE INTENTIONALLY CHOSEN A 65W CREAMBACK AND A 50W CELESTION A-TYPE SPEAKERS SO I CAN DRIVE THEM HARDER WHEN NEEDED. I CAN USE ONE OR THE OTHER SEPARATELY (THEY ARE 16 OHMS EACH) OR TOGETHER IN PARALLEL AT 8 OHMS. EVEN 5W WITH ONE SPEAKER MAKES THE HOUSE RATTLE
Like you, I consider the dynamics do change a touch when the reactive elements in a real speaker load are buffered from the amp's output. As you already know, it is possible to build more accurate complex loads which include reactive elements to mimic a true speaker. These require quite large coils for the inductive side and most people think it too much fuss. As you have also spotted, they are expensive to build and to buy! To the point where I really don't consider them worth the money. Just as you say, it would be cheaper to buy a new less powerful amp. An alternative approach to this may be to simply fully load the GM36 with a resistor so there is no sound output from it. Tap off the signal to the Cab M from that. It is very possible that you will find you can put that dynamic aspect back in with the Cab M. YES, I HAVE OBSERVED THAT IN SEVERAL YOUTUBE VIDEOS! Then monitor the Cab M signal through a bland flat hifi type amp/speaker combination, similar to those used in a front of house PA setup, so what you hear is purely the lively Cab M signal without any further contribution from the monitor amp/speaker setup Cheap disco/PA type amp/speaker combos are easily available nowadays and are all that would be needed once the GM36 and Cab M have done the work. You could try this with your current PA setup if you have one available. THOUGHT ABOUT THAT TOO, I HAVE AN ALESIS RA150 RACKMOUT AMP
The take off for the Cab M is a very simple two resistor chain across the speaker/resistive load. These are at a much higher impedance than the speaker line, so high that they would not even be noticed by either amp or speakers. The spice simulation I set up yesterday shows that the Redbox drops the signal level by about 40-50x according to the options. Two resistors of 39k and 1k would do the trick and be a starting point. They just connect in series with the 39k connected to the speaker output line and the 1k to the speaker ground line. The Cab M signal is then taken from across the 1k resistor. Accidentally shorting out either one of those resistors will cause the amp no stress but, be careful, shorting out the 39k when in use would increase the signal to the full speaker level so the Cab M input would be severely overloaded. With a soldered hard wired setup which is protected with insulation this should not be a likely problem. As I said before, I would personally build this into a short through cable and also make a "resistor on a plug" type of load plugin. That way you can use the resistor for silent playing or a speaker for playing as normal while monitoring via the Cab M. VERY USEFUL ADVICE, THANK YOU!
I've attached a mockup of the setup which would do this. All of the parts should be available to you, there is nothing odd or rare. You can use the short extender type cable with a speaker too of course with a normal speaker cable in place of the resistor plugged into it. The resistors show the correct colour codes for 39k and 1k. These will give you the safety you need in protecting the Cab M from very high signals and they could easily be changed afterwards if they are not quite correct. GOT YOU.
Your other points:
1) Yes you could run the amp at 36W though I would recommend mounting the power resistor used for the load on a piece of aluminium sheet to act as a heatsink if you are using very high powers. It will get hot as it is designed to do. There is a pic of the simple look of this in the attached diagram. UNDERSTOOD!
2) With the power resistor in place the whole things will be silent. (Remember my point about the possibility of then monitoring after the Cab M for this setup.) There should be no adverse effects to the amp. A resistive setup is the easiest load for an amp to drive. They are built with the ability to cope with loads like speakers which are reactive and more awkward. That said, I do not recommend becoming one of the "DIME IT FOR GOD'S SAKE OR IT WILL SOUND CRAP!" crowd. This is a very silly approach to take with any amp. It actually achieves nothing real and puts the amp onto maximum stress all the time. This is the reason people report their amps being damaged by resistive power soaks. It wasn't their stupidity of course, it must have been the one thing engineers will tell you is not going to cause a problem. Even my 100W Marshalls all wake up and sound great from about Master Volume 4 setting. The main point to consider in my experience is the change of speaker size to match the sound level you want to get out. Using my 100W JVM800 with a single 12" 30W G12M Greenback speaker and keeping the volume to about 3-4 gives me a decent sound for home playing, (maybe not late at night but it is not ridiculous during the day), and the tone is fine at least for me. I AGREE. I DON'T GO FOR MAXED OUT MASTER LEVEL. WITH MY GM36 PRESETS WELL BALANCED, IN A LIVE SITUATION AND ON A BIG STAGE, I NEVER GO BEYOND 10-12:00 WITH THE AMP AT 36W AND BOTH SPEAKERS RUNNING IN PARALLEL AT 8 OHMS.
3) I've added the pic of the wiring for the tap. As long as you take care to get the resistors connected to the correct socket terminals with the 1k to ground and the 39k to the signal line and you make sure the Cab M line is taken from ground and the junction it will be protected with those values. You could even replace the 1k resistor with a pot of the same value to make the level variable but that is taken care of in the Cab M anyway. They do match what the simulation showed to be the Redbox levels in the amp. THANK YOU!
Interesting you should say about the GM40D. I have never really been convinced that the GM40D is significantly different to the GM36 enough for me to be interested. It is different, just not quite enough to justify the expense for me. I ONLY MENTIONED IT BECAUSE ITS REDBOX CAN BE DISABLED MANUALLY AND THAT COULD FEED THE CAB M (OR ANY SIMPLE CAB MODELLER) WITH A FULL RANGE NON-FILTERED SIGNAL. However, depending on what range of music you play, I would definitely recommend you have a listen to the new H&K Nano amps. They are designed to fill in the gap and offer more vintage/classic tones which I don't think our H&K "budget" amps like the TM and GM series do particularly well. These amps do seem to offer much better Vintage & Classic tones. I don't play real metal myself, (I'm 60s/70s heavier rock mainly), so I can't really say how good the Metal variant sounds to a metal player but it is worth looking into. These amps have new technology in them, the Class D outputs have actually been used in bass amps for some time now but the modelling side is done using the "Black Spirit" approach. This makes them super small without any penalty and with really good sounds available. They are well priced too, so not out of our market. I'm seriously considering one of them as a small backup to my other amps for gigging. I can't easily transport a number of guitars and two great lumps of amp setup in a small car like mine. My GM36 which does not get used too much nowadays could be sold to fund a Nano Classic with enough left over for a new speaker to match. I recommend you have a listen on YouTube if you haven't already. I WAS THINKING ABOUT THEM AS I LIKED WHAT I SAW IN THE YT REVIEWS. PROBLEM IS I COULD ONLY USE ONE OF THESE SET FOR A CLEAN "EDGE-OF-BREAKDOWN" TONE AND THEN I WOULD NEED TO GET ALL MY HIGH GAIN SOUNDS FROM PEDALS WHICH I DO NOT LIKE QUITE MUCH. I PREFER THE FLEXIBILITY OF A MULTICHANNEL AMP WHERE I TEND TO HAVE THE HEAVIER CHANNELS ADDITIONALLY SCULPTED/COLOURED WITH DIRT PEDALS SET AT VERY LOW GAIN. I NEED TO BE ABLE TO COVER LOTS OF DISPARATE STYLES (AS I DID IN THE BULGARIAN "THE VOICE" FRANCHISE) USING STYLE-SPECIFIC PRE-PROGRAMMED BANKS. THUS I HAVE MOST OF MY PEDALS AND THE GM36 CHANNELS ORGANISED IN DIFFERENT BANKS RECALLED BY MIDI SWITCHER. IF I MAINLY DID CLASSIC ROCK OR BLUES, A SIMPLER SETUP WITH A NANO AMP AND PLAYING WITH THE GUITAR VOLUME KNOB WOULD CUT IT, BUT UNFORTUNATELY NOT IN MY CASE
I HAVE ATTACHED MY CURRENT PEDALBOARD PHOTO HEREWITH.
If there is anything I have missed here or if anything else occurs to you just post it on and I'll let you know.
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