Members fly135 Posted February 5, 2008 Members Share Posted February 5, 2008 Cooltron pedal uses a 12AU7 tube. But get this.... The specs for this pedal claim "Current Consumption: 95 mA" on 4 AA batteries. Near bottom of page. http://www.voxamps.co.uk/pedals/cooltron.asp However the spec for the tube says 300mA just to light the heater... http://www.nj7p.org/Tube4.php?tube=12AU7 WTF?? OK, that's why they call it cooltron. But how can the tube work if the heater isn't up to temp? Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted February 5, 2008 Share Posted February 5, 2008 Google "starved plate". Link to comment Share on other sites More sharing options...
Members olcircuits Posted February 5, 2008 Members Share Posted February 5, 2008 Google "starved plate". I understand what you're saying, but even a "starved plate" design requires the heaters to be functioning at full voltage and requires a lot more current than 95mA. The "plates" and the heater are two separate things and work off of two separate supplies.The heater requires a constant 12.6v @ 150mA or 6.3v @ 300mA (depending on how you wire it [series/parallel]. The heater creates the "glow" you see. The 12.6v or 6.3v tap on amplifier power transformers is the power is the power supply for these. The plates are run at full voltage (often between 200v-250v) or "starved" (12v+). The rectifier in an amp serves the power for the plates.I've always assumed that the voltage is being stepped up in those pedals, but that was before seeing the part about running it on 4 AA batteries.I'd like to see how Vox is doing this. Perhaps the four AA batteries are powering an opamp and an LED to simulate tube glow... see: Behringer. Link to comment Share on other sites More sharing options...
Members Kassanova Posted February 5, 2008 Members Share Posted February 5, 2008 Yep, its the old "glow for show" trick. Link to comment Share on other sites More sharing options...
Members mike.sartori Posted February 5, 2008 Members Share Posted February 5, 2008 Well, from what I hear, those tube zendrives just use the tube as a clipping diode, it's like a totally passive part - they just hook it up in the clipping section, probably from 1 point to 1 other point. Link to comment Share on other sites More sharing options...
Members Uma Floresta Posted February 5, 2008 Members Share Posted February 5, 2008 Well, from what I hear, those tube zendrives just use the tube as a clipping diode, it's like a totally passive part - they just hook it up in the clipping section, probably from 1 point to 1 other point. That's true. Seems like a waste of a good tube. Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted February 5, 2008 Share Posted February 5, 2008 I understand the two separate supply voltages Mark, and I am also perplexed by how Vox is doing things. I too, would imagine they using a step up for the heater voltage, but again, with four AA's, the current just isn't there. Heck, before reading this thread, I didn't even know that battery power was an option on those pedals - I thought they were AC only. Does Vox include a schematic with the manuals? Link to comment Share on other sites More sharing options...
Members mike.sartori Posted February 6, 2008 Members Share Posted February 6, 2008 That's true. Seems like a waste of a good tube. Not when you can charge $infinity for it! Link to comment Share on other sites More sharing options...
Members echodeluxe Posted February 6, 2008 Members Share Posted February 6, 2008 Does Vox include a schematic with the manuals? they dont even provide a schematic with their amps. i had to do some serious sluething jut to get the schematic for my ac30cc2. i'll look around. im guessing the tubes in these pedals are for show. the current is just not there. Link to comment Share on other sites More sharing options...
Members jove Posted February 6, 2008 Members Share Posted February 6, 2008 I understand the two separate supply voltages Mark, and I am also perplexed by how Vox is doing things. I too, would imagine they using a step up for the heater voltage, but again, with four AA's, the current just isn't there. Heck, before reading this thread, I didn't even know that battery power was an option on those pedals - I thought they were AC only.Does Vox include a schematic with the manuals? Phil The designer of these pedals is rather famous in audio electronics design.He's been doing it since the 60's and has created a lot of classic pedals.The tube is definitely not there just for show.If you're really interested, PM me and I can direct you a bit. Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted February 6, 2008 Share Posted February 6, 2008 Phil The designer of these pedals is rather famous in audio electronics design. He's been doing it since the 60's and has created a lot of classic pedals. The tube is definitely not there just for show. If you're really interested, PM me and I can direct you a bit. PM sent. PS As I said in the PM, please note that I didn't say the tube was "just for show" - that was someone else. I don't know enough about the circuit to say HOW it is used; that's why I was curious about the schematic. Link to comment Share on other sites More sharing options...
Members tetaJ Posted February 6, 2008 Members Share Posted February 6, 2008 send me the schematics too so i can draw a Christmas tree on it, i wouldn't differentiate a toaster from a rocket Link to comment Share on other sites More sharing options...
Members Kassanova Posted February 6, 2008 Members Share Posted February 6, 2008 If this pedal is special, why not give us all a brief explanation of how? Link to comment Share on other sites More sharing options...
Members jamesclark Posted February 6, 2008 Members Share Posted February 6, 2008 What's the big secret? Link to comment Share on other sites More sharing options...
Members mlabbee Posted February 6, 2008 Members Share Posted February 6, 2008 I read something somewhere about how they've come up with a circuit that gets the tube to funciton normally at very low voltages and current draw - can't find where I saw it, though . . . Link to comment Share on other sites More sharing options...
Members mlabbee Posted February 6, 2008 Members Share Posted February 6, 2008 Gee - maybe the Vox website? D'oh!http://www.voxamps.co.uk/pedals/cooltron.asp Scroll down . . . Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted February 6, 2008 Share Posted February 6, 2008 Gee - maybe the Vox website? D'oh!http://www.voxamps.co.uk/pedals/cooltron.aspScroll down . . . From the Vox website: "Want to know how it all works? Normally, tubes are used at high voltages and this restricts their use in battery-powered devices such as guitar effects pedals. Historically, attempts have been made to use tubes at low voltages in what has been dubbed Link to comment Share on other sites More sharing options...
Members jamesclark Posted February 6, 2008 Members Share Posted February 6, 2008 So did HD design the Vox pedals? Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted February 6, 2008 Share Posted February 6, 2008 That was one of the names that popped into my head too. But I honestly do not know guys - jove has not replied to my PM yet. Link to comment Share on other sites More sharing options...
Members jamesclark Posted February 6, 2008 Members Share Posted February 6, 2008 Thanks Phil- Link to comment Share on other sites More sharing options...
Members Kassanova Posted February 6, 2008 Members Share Posted February 6, 2008 Yeah, thanks. I wonder if they use a similarly designed circuit for the Vox AD series amps? Link to comment Share on other sites More sharing options...
Members dirk-hendrik Posted February 6, 2008 Members Share Posted February 6, 2008 Now, if there weren't all these considerations about pirates, stealing, theft and lawsuits, loss of profit etc etc because a few motivated DIY-ers set up a forum starting with free, continued with stompboxes and being a .org domain... .......Everyone here could have looked for themselves how the tube is incorporated in that circuit. Which is indeed alternative. Cold-kathode circuit, but not in a configuration where the tube is used as 2 antiparallel diodes. This could not be the case since that trick is patented by Fender. Link to comment Share on other sites More sharing options...
Members andreas Posted February 6, 2008 Members Share Posted February 6, 2008 I took one of those apart once, but didn't look at how the tube operates... Vox advertises them as true bypass, but they (at least the Bulldog Overdrive I peeked into) are actually regular output switching only ("hardwire bypass", if Dunlop would have named it). /Andreas Link to comment Share on other sites More sharing options...
Members 3 Chord Rock Posted February 6, 2008 Members Share Posted February 6, 2008 Yep, its the old "glow for show" trick.I know some pedals do that, but I doubt that was in mind for my Bulldog....they use a blue LED. "Man thats a cool running tube, it even glows blue!" I don't know any of the technical side, so sorry there, but I do know the pedal sounds organic, very dynamic, compared to other dirt pedals ,like I've only heard in the Damage Control offerings (I haven't tried any other tube pedals). Even if it's all in my head, sound good to me. Link to comment Share on other sites More sharing options...
Members Uma Floresta Posted February 6, 2008 Members Share Posted February 6, 2008 Now, if there weren't all these considerations about pirates, stealing, theft and lawsuits, loss of profit etc etc because a few motivated DIY-ers set up a forum starting with free, continued with stompboxes and being a .org domain..........Everyone here could have looked for themselves how the tube is incorporated in that circuit.Which is indeed alternative. Cold-kathode circuit, but not in a configuration where the tube is used as 2 antiparallel diodes. This could not be the case since that trick is patented by Fender. I doubt Vox has even heard of Freestompboxes.org. Link to comment Share on other sites More sharing options...
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