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H.R. Shove and Stuff

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  1. Problem solved, ground connection on the preamp not soldered together! Thanks everybody
  2. Hello, I've having issues with hum in a JTM45 build from Triode Electronics (http://site.triodestore.com/JTM45LAYOUT.pdf) following their layout as closely as possible. Without a cable plugged in, I can dime the volumes and the hum is negligible. With a cable plugged in, even without a guitar on the other end, the hum occurs. When I touch the sleeve of the cable, it gets quieter, but still apparent (same with touching the guitar strings). When I touch the tip, I get the nice loud pop. Moving around the cable does no effect the hum as it would if it were acting like an antenna. Hum is present on both channels, but only when a cable is plugged in to the respective input. The hum volume is controlled by the volume of the channel. Turning it all the way down gets rid of the hum. The hum can be tailored by all the EQ knobs to get your favorite hum tone. The amp is plugged straight in to an outlet with three prongs (ordered an outlet tester to see if it's really grounded). The outlet is shared with a surge protector that powers a CPU, monitor/TV and a few other random audio equipment. With the surge protector off, the hum occurs. With surge protector on, but attached equipment still off, the hum gets a nice fat bass layer. When turning on CPU, TV/Monitor, etc, the hum gets more and more complex. I have a 'free app' on my phone that measures frequency. With only the amp on, I get straight jumps between 175 to 301.5Hz. Same frequency with surge protector on. With the other electronic equipment on, it seems to settle around 236.9/239.6Hz with the occasional flicker to 175 and 301.5Hz. I'm guessing it's not a coincidence that ~240Hz is roughly halfway between the two extreme frequency measurements and a multiple of 60Hz. That's as far as I got. The house is an older rental in a crowded residential area outside of Pasadena CA, if that matters. I didn't have much of a chance to play the amp after building it a few weeks ago, so I can't say if this has been a problem since the beginning, or something that just happened. I had rewired my guitar and thought it was that causing it, but it was not. I also recently installed a large metal rack shelf next to the amp. I read that these things could act like antenna, but I don't get any hum changes when I move the cable towards or away the shelf. I'm thinking my next step is to pull V1 to see if it's coming from there as it's the only active component that comes before the volume controls. If it's not coming from there, I'm guessing it's a grounding problem, but I'm not sure what steps to take if that is the case. Any help is much appreciated!
  3. Thanks for the reply WRGKMC. The idea was to put both the liquidator and the fuzznikator in the same circuit to save on money, using one transformer, as well as space. The transformer I was thinking of using is from Antek, specifically this one: Antek 50VA 240V Transformer It's got two 6.3V windings at 2A each, which I figured I could use one winding for each individual circuit, or perhaps parallel them and supply them all off the parallel windings. Then use the 220V tap to get roughly the rectified ~250V needed for both circuits B+1. The B+2 and 3 are already in parallel in the liquidator, so I thought I could simply tap another parallel voltage out for the starve voltage for the fuzznikator. I had been told that each circuit will probably only draw about 20mA each, possibly 50mA total, for B+ voltages, so I was thinking the 220V 0.1A winding would be able to power both circuits without a problem, as well as the heaters handling a little more current from whatever LFO I put in there, especially if I parallel them to distribute the load. Does any of that sound right to you? Hopefully I've explained the plan a little better than in my first post. I do have LTSpice, although I've tried to simulate tubes.
  4. Hola, I've been looking at the two tube circuits that G Forrest Cook has on his Solorb site and I've been trying to read up on how to determine the current needed for them. I'd like to put both circuits in an enclosure to save on space as well as money with only one transformer. I've been having a hard time figuring it out, so I thought I'd post my analysis and see what smarter brains make of it. Let's start with the liquidator http://solorb.com/elect/musiccirc/liquidator1/ I've found you can determine max current that can be passed by doing supply voltage/plate resistor. In that case, going from left to right on the schematic, we get 1.9mA + 18mA + 18mA + 18mA + 3.9mA + 2.6mA = ~63mA. I've read that these numbers are the max the tubes could draw, but it's unlikely that they will ever draw that much. How would I determine what is a likely number? Do I split it in half and hope for the best? The second schematic has me more baffled as it employs a push pull type poweramp using a 12AX7. http://www.solorb.com/elect/musiccirc/fuzznikator1/index.html I would forgo the last triode as I would just switch between clean and distorted instead of blending them, but the first two come in at 2.5mA using the method above. Cook mentions 10k resistance on the primary OT, so I assumed it would be something like 180V/5k, just guessing on the voltage for B+2, would be 36mA for both. That puts us at 140mA total, excluding heaters. Is that reasonable ? It sounds unreasonable, but I don't know anything. Thank you for any guidance!
  5. Thanks again for all the info! I pulled back the casing around the three wires to see if I could figure out what was going on, and it turns out that one of the two wires that were connected to the PCB was ground/shield/whatever. One of the two wires has a red casing that I'm assuming is part of the signal. The other is bare wire, the same wire that was connected to ground of the LM381N. The short wire that was not connected is in a black casing. Why would they only use one half of the mic? Here are some pictures. Probably used at a school or bowling alley or something. Mic Base. Besides what's written on there, there aren't any more identifiers for what it is. There was a sticker/metal plate on the bottom but all the writing has rubbed off. Top PCB mounted to base. Has the chips for the buttons. Main PCB. Didn't take too great of a picture as there's a lot going on and it would be hard to figure anything about with tracing it. Some notable chips are the LM381N, LM384N, DM74123N (multivibrator) and DM7410N (CMOS stuff). There are a handful of 2N3567 transistors and a power supply section. Here are the wires coming out of the microphone neck after they were stripped back a bit. The two long ones were connected to the PCB while the shorter black one was tucking inside unconnected. There is some black insulation on the longer wire, but that is actually a smaller piece of wire connected to the longer non-insulated section. They must have cut it too short and needed to make it a bit longer to reach the PCB. I guess I could just wire up the three wires to an XLR and plug it into a mic preamp and see what happens?
  6. Hey WRGKMC, thanks for the reply. The reason I think that the short wire is one of the sides of the mic and not ground is because on the PCB, the one black wire that was connected to the PCB was connected to pin 4 of an LM381N, which is ground, according to the data sheet. I can't tell where the other red wire goes on the PCB at the moment, but it's near the Lm381N, so perhaps that is acting as a preamp? There are a handful of chips and transistors, regulators, etc on the PCB, not too intuitive, but I can tell a decent amount are for the electronic switching. There is also a preamp and amp for the little speaker in the unit. I measured the resistance across the two wires that were connected to the PCB and got 658 ohms. When I touched the leads with the probes, a scratching noise came out of the mic as I moved a probe up and down. I guess that means a transformers up there somewhere? I can get some pictures tomorrow, but thanks for the info! I think we're on the right track now
  7. There's a thrift shop next to my gym that I occasionally stop by - today I saw the long brachiosaurus neck of one of those old intercom mics that could have been used at bowling alleys or drive through's at a fast food joint. Took it apart - some useful stuff for other projects, but I really like the buttons So I thought I'd re-purpose the mic and enclosure for a lo-fi recording mic and maybe put a few effects or filters in the base to make use of the buttons. Anyway, the point of this thread was when I finally turned all the innards into outards, I couldn't figure out how to remove the neck of the mic to get to the mic itself so I couldn't get to it. There were two wires coming from the mic that were connected to the PCB, but there was also a very short wire that was stuffed up inside the housing that was not connected to anything. From the PCB connections, it looks like one wire was ground, the red wire was connected to the PCB and a short stub of a black wire was unconnected. Is it safe to assume that the red is the +/pin 2 and the short black is -/pin 3? Is there a way to check using a multimeter? Does it matter as long as it's consistent? Is there a reason they only used one of the two outputs for the system? As a side questions: any fun ideas for effects/filters/etc that are useful in real time that aren't too easy to implement on the DAW? There are 4 buttons and a 7 segment single digit display. I'll house a simple preamp inside, but besides that, the skies the limit. Thanks for your advice. Matt
  8. Phil, you are the man. An analog filter in a giant box is hilarious. Unless it was tube based, but if the 'analog delay' inside is a BBD, I'd imagine they could have had opamps, if not transistors back then. God help us if there is a tube based BBD phaser/flanger circuit out there that Pure Tube didn't make. I just listened to Cry Baby Cry. The phase we are talking about is on the acoustic guitar in the right channel? Not very pronounced at all. It's hard to even hear if it's sweeping or stepped. Very interesting, thank you Phil.
  9. A tuner is way harder to make than a distortion or a wah. Not even the same category of electrons.
  10. WRGKMC also recommended the MOTU stuff. Looks awesome, but while less than $2k could technically be in my budget of less than $500, I'm going to guess that it isn't
  11. This photo came up recently and the strange sloped front enclosure caught my eye. A few controls and a meter in such a large box? Anyone know what that could be? So simple and sexy. Almost doomsday-ish.
  12. The 18i8 looks alright with the four line ins, thanks for the recommendation. The M-Audio interface is good timing as well, I'll check it out!
  13. Thanks for the replies. The MOTU stuff is way out of my price range, but looks to be functionally what I'm looking for . I guess I was delusional that there would be similarly priced internal or external sound cards that were just a bunch of inputs and outputs. I suppose somewhere south of $500 would be budget. The M-Audio 1010LT seems to have been discontinued for a while now. My motherboard has a few PCI and PCIe inputs, so that's fine. I'm considering just forgetting about it and getting the Scarlett 6i6 and recording drums Glyn Johns method. It does make sense that most entry level type products would assume that the user doesn't have the rest of the equipment and puts it all in there.
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