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jefrs

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About jefrs

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  1. jefrs

    iPad

    As comfortable as lying in bed with an ipad? Seriously though the ipad is far more of a media player toy than a computer. What it does it is good at. Wireless. To Apple Airport for sounds, bluetooth cans! Camera. Portable. Garageband or Amplitube? Garageband is easy but Amplitube better bells and whistles. Neither anywhere near as good as a DAW on a laptop/pc.But Line6 Sonic Port (lightning) is better than Amplitube iRigHD interface
  2. It may take a moment to get the head around it but that 5V(?) high-current heater is also firing hot electrons onto the rectifier anode. They are supposed to do that and why a valve rectifier cannot be run off an ordinary heater circuit. SS diodes are more efficient. Increasing B+ will alter the bias requirement. Cathode bias can cope with a lot of variation but the one in there is intended for 5881, Rk (and load/OT) on EL34 is different. Keep an eye on the EL34, see how they glow. Can you safely measure B+ and bias volts? I don't think valve amps are designed as energy efficient appliances.
  3. Yes it has its own heater but it also forms part of the power supply, it is not wasted. That current drawn from the heater goes into the HT. It is supposed to do that. That heater is also acting as a cathode. It is not just heating the cathode but supplying power too. That is why it has its own high current supply from the PT.
  4. By drain on the heater, do you mean the valve rectifier heater? - that is supposed to be supplying power, and quite a lot of it, to the amp. It is a feature, not a fault. If you mean the other valves' heaters then that is taken off a separate winding on the P/T, it is unaffected by the rectifier whether valve or solid state. Now the pre-amp bottles run their heaters in series from a supply of +13.5VDC on mine (due to my high mains volts again) but the output valves have 6.3VAC supplied heaters.
  5. Yes, it has been running a long time ;) - but it ain't dead yet! One of the first things I had to do when I got mine, many moons ago now, was connect the fan because there was a wire off at the PCB. Then I observed it made the amp hum and had to re-route the fan wires as twisted-pair. The fan supply should not be taken from the middle of the PCB near a valve base. Part of the heat 'problem' is lack of sufficient vents and running the bottles 'upside-down'. The fan is a "computer" fan, my PC has additional fans (controlled by temperature) due to old house dusty environment and cats. The main CPU now has two mounted in tandem. How did you attach your aux fan? The 6550 is interesting. They can take an amp to 100W territory. Did you do any mods to increase power or just 'stick them in'? I find my BC30 already too fearsomely loud for a lot of use. I have no real idea what its output is with the =C=6L6GC but I suspect well over 30 watts. Hence no wish to increase power further. Ime not all 6L6 types sound alike, there is a lot of variation. So worth playing with different makes to find ones one likes. I reckon I've got my BC30 well into Bluesbreaker territory now.
  6. You can get a plug in solid state rectifier that directly replaces the 5AR4/etc bottle. example http://www.watfordvalves.com/product_detail.asp?id=3071 Expect to get more volts with solid state diode rectifier.
  7. My standby switch actually exploded out of its back. It is an AC mains switch being asked to perform at >400VDC, no wonder it arcs. Completely the wrong tool for the job. It is also an odd size. I used some big "repair washers" to fit my MV there. You do not need a standby switch, you /can/ bypass it, spade connectors are easy to do this to. Just use the on/off switch and silence the amp with the input socket (it shorts = silence) like you are supposed to do. The standby switch is a fashion accessory. The Chinese rectifier in mine also made pop-corn noises, that was arcing over too, rubbish bottle. Sovtek 5AR4 very good and can do EL34 The stock EH ECC83/12AX7 were ok except I strangely prefer the cheaper Sovtek flavour (from same factory in Saratov?), although the EH were best for, and are still on, the reverb. I have since completely re-valved the other ECC83 with a variety of bottles, notably Harma's "Retro" Mullard clones (also suspected from Xpo-Pul/Reflektor) I found some "wrong value" components in mine too, but not a cathode resistor. Bad luck. Possibly worth checking a few others. You may toast any 6V6 (max plate 315V) except JJ-6V6GTS = JJ-6V6S. The JJ appears to be a 5881 with a low current heater that sounds like a 6V6, it can take something like 800V on the anode plate, I'm not sure how much current (power) it can handle though but I've not managed to blow my pair up. Putting 6V6 in does not make the amp much quieter, cranking it up will likely take 6V6 over 26 watts, which won't do them any good at all. The 6V6 has a low power or "half current" heater because it was intended for use in vehicles with pathetic 6V batteries. Note - I am getting 420VDC because I've got very close to 250VAC on the PT set to its max 240VDC. That means I get a higher bias point too. The fixed bias point for 6L6 is -37V at 450VDC, so -34V is a good compromise for 6V6/6L6 at this B+. EL34 would want -36V. The cathode resistor self-adjusts somewhat, it's about getting that bias point almost-right that counts. We are running much higher B+ than most spec sheets, hence greater bias volts. See plate characteristics graphs ;) BTW - using the full winding of the OT, 16ohm into 16ohm speakers, sounds crisper and clearer than the 8ohm tap (into stock pair at 8ohm) FWI - "pin 1" should already be connected to cathode so it should take any octal incl EL34 although a change of cathode resistor might be advisable. Although imo the =C=6L6GC sound more open, clearer and "bigger" than the EL34 mod BC30 I know.
  8. Do please note that my main "tone opening up" mod was to put 820k shunts around both R5 and R6 (both 1Meg), reducing it to 450k. The logical reason for using a 1W resistor here is that they are longer and can thus "stand off" a higher voltage, not that they pass much current, even if they had the entire HT across them, they would only see 0.18W P=E^2/R. My C4 "bright cap" is now on a bright switch. However the CH2 "bright cap" C6 is disconnected. Do check component values here, I found some on the PCB that did not match the circuit diagram. Also, for interest, my B+ appears to be 420VDC with the cathodes at 34.3V wrt ground. I also separated the HT from the heater wires, and twisted them. And another note that I separated the speaker socket ground so it does not return through the main PCB. Why would you pass that current through the main PCB? It's supposed to go to the O/T. These things do make the BC30 hum less. I did post up a circuit diagram here, with my mods on it but it was only as large are permitted and so may not be entirely legible. I can read it, it pops up very large and you can determine the original circuit. That's at post#145 - http://forum.gibson.com/index.php?/topic/43505-blues-custom-mods/page__view__findpost__p__758439 I have A/B'd mine with an EL34 mod BC30 and imo not much to choose between them, very adjacent. Actually they only modified for EL34, not the R5/R6 shunt so it still sounded congested. In theory, the EL34 is supposed to make it a trifle louder. In practice the little mods I made to mine made it too loud, too easy to drown out the rest of the band, hence the MV. =C=6L6GC
  9. I have used JJ-6V6GTS aka JJ-6V6S in there with no problem at all but have not / would not crank it right up. No red plate there. Note our mains is almost 250VAC so the 240Veuro PT will be running HT B+ a wee bit higher than spec hence 34.3V seen. Usual and current op valves are =C=6L6GC it's not just loud, it's bloody loud! I have taken chassis pics but cannot remember if I ever posted them on here. It will be the same as yours with a bit of tidy-up plus some damage from dropping. Let me know if you really, really need them?
  10. This is a pretty old thread now but I have just been notified of a reply. Any questions re BC30 mods? 1) I changed my ISP and hence email addresses, thus notifications got lost in the aether. 2) What was the Epiphone forum is now a Gibson forum. I lost the linky. Re - Greenbacks. They do not break in but just keep sounding better and better as they age. Re - speaker cable. I tend to use mains twin-flex. Mains twin-flex is often better than fancy hi-fi speaker cable, both electrically and more robust. Do solder the connections on because they need to be low resistance, crimp connections do have a significant contact resistance. They work fine in the car where they belong, and there the contact resistance is insignificant or does not matter - or you have a Mercedes and they solder them to the wire anyway (lederhosen have belts and braces ;) Re - the reverb tank. It is a Belton unit. They bought out Accutronics, They don't come much better than the one that's in it. The Belton site is a mare's nest to figure out the correct part number. There should be a part number stamped into the OEM tank. Get the specification from that. I think it is an 8ohm feed. You need to know orientation, insulation, impedance and output. You can ring changes on length, number of springs and decay time etc. The reverb is also dependent on the send level i.e. you get more reverb as you crank it up (becomes more obvious with an MV added). Also note that if you play live and loud - turn the reverb off and let the room do it or it all turns to mush.
  11. I was suggesting the schematic does not always show the correct component values fitted to the PCB. Can you read my diagram? PM me if you need a more legible one.
  12. The reverb is quite wet. You can get an acoustic feedback howl through the tank so make sure it is bagged and secured down. The amp runs in triode or tetrode* mode, both are Class AB. Only a single-ended amp can be guaranteed to be Class A, you can build a Class A push-pull but they are low-output, little more than the SE job, and they require a /very/ large OP transformer. Depending on choice of output valve the tetrode may give 26-30+ watts at full chat. In triode mode it is likely to be over 15 watts. For some reason this is a very loud amp. This could be down to a good efficient output transformer, it is not always about watts. The OP valve bases are pre-wired for pin 1 to take an EL34 which is a pentode. Being cathode biased, you can swap different type octal bottles around with some impunity. The amp hums. The layout design is poor. The various HT, heater and signal wires are bundled together, and it has earth grounding points all over the place. The fan is supposed to be on all the time. It runs off the heater circuit and adds hum to the circuit. Anything noisy on the heater is added to the cathode. Mine was not connected from new and required poking with the soldering iron. Connecting the fan added noise. The amp gets /very/ hot without the fan. If you want feedback then turn the volume up, crank up the gain of the drive channel and bring the Les Paul up real close to the speakers.
  13. You are probably running a line level signal (2V) into a low level input (millivolts). This can work but you should not run the piggy-back amp to max volume: even so you may overload the circuit between its input and its first volume control. Better, place an attenuator between first and second amp: do you have something like a Graphic EQ pedal that can reduce the signal?
  14. Problem with any cathode/self biased amp is that you are limited to the nearest "preferred" value resistor. But near-enough is good-enough, it's called self-bias because it is self limiting. You may find it is hot now but the next value may be too cold: Murphy's Law. Another thought, if the cathode voltage is too high, do check the solder connections and redo with pukka tin/lead fluxed. These lead-free PCB are terrible for cold joints (high resistance).
  15. Tone suckers! Add your pedal FX one-at-a-time until you find the thieves, then bin them. Keep your pedal board down to the essential minimum. Ditch the ones you don't use every day.
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