lution Posted May 17, 2006 Share Posted May 17, 2006 Originally posted by ChewingAluminumFoil: Appears to not be on yours. http://www.valvejunior.com/img/misc/ValveJunior/vjcloseup.jpg CAF bummer Link to comment Share on other sites More sharing options...
blitztone Posted May 19, 2006 Share Posted May 19, 2006 Hey everyone, Decided to drop in and join the cult. I plan to get my JR as soon as possible. I browsed through the (many excellent) postings already on this forum, and also did a search on each page. Something important seems to be missing. In the JR schematic that Dennis shows, I don't see a choke. Is there really no choke (inductor) in the circuit? All these other methods discussed for hum reduction are valid, of course. But I think a few Henrys between the power supply and the tubes (at minimum the EL84) would go a long way. Forgive me if this has already been discussed, I didn't see it anywhere. -- Bob Link to comment Share on other sites More sharing options...
Ricochet Posted May 19, 2006 Share Posted May 19, 2006 No, as with most guitar amps, there's no choke in the power supply, only capacitors and resistors. But as I've often said, my amp has no problem with hum from AC ripple in the plate power supply. It's capacitive coupling of AC heater voltage to the V1B grid lead. I have an Electar Tube 10 with the same 22 uF filter capacitors as the Valve Junior. No choke. Quiet as any amp you'll find. The Valve Junior hum is not from ripple in the plate power supply. It's a poorly laid out printed circuit board that's at fault. Rectifying the heater power helps, but in my case doing it with a simple bridge rectifier and 1000 uF capacitor introduced a 120 Hz hum that could be due to transformer hum or to residual ripple in the rectified heater current being capacitively coupled to the V1B lead, I haven't decided which. It's quieter than it was, but the higher frequency hum with lots of harmonic content is more noticeable than the pure 60 Hz hum that I had before. (It gets into the ear's best response frequency range.) Adding a choke may or may not help with hum problems in general. The problem with them is that they radiate a good bit of EMF that may be picked up by sensitive components of the input stage. Resistors don't do this, and they're far cheaper and lighter, but for equivalent levels of ripple smoothing they drop more voltage and cause poorer voltage regulation where the current demand fluctuates, as with a Class AB amp. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
TheGuardian Posted May 20, 2006 Share Posted May 20, 2006 Hey guys, i'm thinking about ordering a VJ Head and I'm curious if I could connect it to the speaker of my H&K Tour Reverb (1x12 combo), without disconnecting the speaker from the Tour Reverb and being able to switch between both amps... Is there a simple way like adding another plug to the speaker? Will the speaker actually work with he VJ? (it's a Celestion G12 Rockdriver Pro 100, 8 ohms) Sorry, I'm really a newbie to electronics Regards, Andi Link to comment Share on other sites More sharing options...
orangesky Posted June 5, 2006 Share Posted June 5, 2006 hello all, i was wondering if anyone could offer me some advice? i do have experiance working on tube amps and solid state, l so i do understand the terminology . i would like to mod a valve jr. to have louder clean gain without breaking up into distortion. i'm looking for a loud clean sound that i can overdrive with a tube screamer. any ideas on a mod for this? i'd like to crank the knob to about 80% and still have a clean sound that can i overdrive/saturate if i pick aggressively. thanks, -steven Link to comment Share on other sites More sharing options...
Ricochet Posted June 5, 2006 Share Posted June 5, 2006 Steven I don't think you can practically make the Valve Junior have a louder clean sound. To do so, you'd have to have a more powerful output stage than the single EL84 it has, which is already pushed pretty hard with the voltages on the tube rather higher than the published maximum specifications. And it's rather loud for a nominally 5W amp. It's set up so the EL84 output stage maxes out in volume and is mildly overdriven before the second stage of the 12AX7 "preamp" tube is overdriven. So it's making its maximum clean volume already. It hits this level around 12:00 o'clock on the volume knob. Further travel of the volume knob can't make it louder or overdrive the output tube further as the second stage of the 12AX7 is hitting its voltage limits and can only "clip" further at the same limits. Full knob travel heavily overdrives the second stage of the 12AX7. Running an overdrive pedal into it will allow overdriving of the first stage of the 12AX7, and will overdrive the second stage of it quicker. It'll also let you turn the volume down to get a "preamp overdrive" sound from only the first stage of the 12AX7 while keeping the volume level modest, if that's desired. The amp's really putting out about 10-12W total when it's fully cranked, the 5W rating being conservative, but there's not anything you can reasonably do to make it put out more power than that. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
Broddi Posted June 5, 2006 Share Posted June 5, 2006 I tried a low gain 12ax7 and overall the amp stayed a lot more clean. However the total volume was also lower. All things considered I would say it had more clean headroom,less overall volume. Can't hurt to try it, a low gain 12ax7 is about $10.00 My home page http://www.klugemusic.com Link to comment Share on other sites More sharing options...
Ricochet Posted June 6, 2006 Share Posted June 6, 2006 The only way it can give "more clean headroom" is in letting you turn the volume knob farther before it breaks up. What you get within that range, scaled to what you had before, will sound very much the same. I suggest readjusting your thinking. The first half or so of the knob travel is the maximum volume. The rest is overdrive. They balanced it that way because modern players want more crunch available than the users of the original 1950s practice amps the Valve Junior is patterned after; they were balanced to stay clean very nearly to the maximum volume setting. If you really want more volume knob travel while it's clean, that's easy to accomplish of course. The simplest means is adding resistance between the coupling cap from the first half of the 12AX7 and the volume pot. But, I hardly think it's worth modding the amp just to be able to turn the knob farther and get the same result along the way (with less overdrive available at full twist.) "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
Broddi Posted June 7, 2006 Share Posted June 7, 2006 I guess it's hard to explain but my results were as I stated. More clean headroom. That is to say I could play as clean as before and slightly louder before tube saturation. In fact with the amp dimed I was just able to push the el84 into slight saturation. ------------------------ "The only way it can give "more clean headroom" is in letting you turn the volume knob farther before it breaks up." ------------------------ That was the result. But the clean tone was also louder than the clean tone I had before. The amp does not get as loud when cranked, but it stays somewhat clean. ------------------------ "What you get within that range, scaled to what you had before, will sound very much the same." ------------------------ Not the result I got. It's hard for me explain the louder and cleaner before breakup, but overall when cranked the amp is not as loud. The only way to hear what I'm hearing is to drop in a low gain preaamp tube. My home page http://www.klugemusic.com Link to comment Share on other sites More sharing options...
Ricochet Posted June 7, 2006 Share Posted June 7, 2006 OK. I don't think it should work that way, but if it did for you, that's terrific! Hearing's a pretty subjective thing. If you like what you hear, that's the main thing. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted June 7, 2006 Author Share Posted June 7, 2006 I had two side by side when I did all my experiments. Unless you can A/B, I dunno. CAF Link to comment Share on other sites More sharing options...
Junior 1 Posted June 8, 2006 Share Posted June 8, 2006 If I would like to use my 8" Valve Junior speaker, in it's cabinet, with my Valve Junior head, do I have to wire in a new jack? The 1/4 " jack plugging into the Valve Junior doesn't come directly from the speaker! Link to comment Share on other sites More sharing options...
Ol Boy Rivers Posted June 9, 2006 Share Posted June 9, 2006 Howdy from the south yall. Ol' Boy rivers here, New to the forum. This is the only thing ive been into so far, As my valve junior hasnt been bought yet but sure as a horse shoe its gunn' be. Im getting the head version, Though. So we'll see how well it works out, Thanks yall! Never trouble trouble till' trouble troubles you. Link to comment Share on other sites More sharing options...
Fumblyfingers Posted June 9, 2006 Share Posted June 9, 2006 How do Ol' Boy. Welcome to the forum....lotta good folks here. Interesting about these Valve Jnr amps. I have been just observing and finally made the decision to just go buy one, but GC are out and Sam Ash say they don't carry them. Bummer. I may even have bought two! Question to the VJ knowledgeable folks here. Is the head version quieter then? I want to use this amp specifically for recording. Any ideas how that might work for me. Also, I have a Marshall 4X12 cab and also considering making a couple enclosed or partially enclosed single speaker cabs, either 8" or 12" possibly with Celestions. Any thoughts there. You guys really know your crap on these amps man! Link to comment Share on other sites More sharing options...
Junior 1 Posted June 9, 2006 Share Posted June 9, 2006 The head is quiet. The combo hums. I think they will eventually do the same fix to the combo as the head, if they didn't already. I have both and run the head into a 1x12 cabinet with a Celestion Rocket 50. They both sound great and to be honest with you, even though it hums, I still love the combo. The Weber speaker they put in it seems to match so well. Welcome Ol'Boy. Link to comment Share on other sites More sharing options...
Fumblyfingers Posted June 9, 2006 Share Posted June 9, 2006 Interesting. Could you sum up why the combo sounds better. Is it just the speaker in it? Are these available for purchase anywhere. Once the mods are done that you guys talk about, is it as quiet as the head only version? I have never modded an amp but I am handy with a soldering iron. I was a motorcycle mechanic for 23 years and did a lot of electrical repair and I also work as a film lighting tech now where we are using 1500A generators and lotsa three phase stuff. So I think I can do that work if I follow the instructions well. Does shorting the prongs on the power cord, say with a screwdriver shaft, get rid of any stored charge in the caps inside or is that an old wives tale? A naughty we used to do in the motorcycle biz is take a condensor, hold it onto the cylinder head of a bike to ground it and then kick the bike over ( sparkplug out ) and allow the H/T plugwire to arc onto the positive terminal of the condensor. Kick it over a few times and get a nice charge built up in there, Then we would just take the condensor and set it on the parts counter and wait until some nosey customer picked it up to look at it. Always good for a laugh! Link to comment Share on other sites More sharing options...
Ricochet Posted June 9, 2006 Share Posted June 9, 2006 I've been told, but can't confirm, that newly produced VJ combos incorporate the same hum fix as the head. Epiphone's been silent about the hum from the beginning. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
Fumblyfingers Posted June 9, 2006 Share Posted June 9, 2006 That is good news. I will test one at a store as soon as I can find one. Thanks. Link to comment Share on other sites More sharing options...
Ricochet Posted June 9, 2006 Share Posted June 9, 2006 FF, the speaker in the combo IMO is a very nice sounding one. It's been said that the same speaker is sold by Weber Vintage Sound Technology as a "Ceramic 8." Again I can't confirm this, but it's been reported on several fora. One guy said he spoke to Ted Weber and was told that it was true, but it wasn't his best model, or something like that. The Weber Ceramic 8 has long been recommended as a replacement in the Electar Tube 10 (which isn't directly comparable as it's a ported closed cab.) I've used Jensen MOD speakers in several amp projects and like their sound. They're also very affordable. The filter capacitors will NOT be drained by shorting the power cord! The rectifier diodes would prevent any "backflow" of current, but in any case the power transformer isolates the amp circuit from the power supply. Many amps contain bleeder resistors that slowly let down the charge on the filter caps, but I don't recall any in my VJ combo, and the schematic at http://valvejunior.com/ doesn't show any path for charge to leak to ground when the tubes aren't conducting. Much of the charge will leak away quickly when the power's shut off, before the cathodes cool, but they could retain some charge for weeks if they don't completely drain then. The safe way to discharge filter capacitors is with a probe containing a resistor of, say, 1K ohms (to prevent arcing, the value's not critical) anchored to the chassis on one end and held or clamped to the lead on the high voltage side of the first filter capacitor and held there for several minutes. You need to be insulated from the high voltage while doing this; you can do it with an insulated voltmeter probe as the contact, or by simply using a power resistor whose insulated body is big enough to let you hold it without getting your fingertips near the "hot" wire. Or tape a resistor to a nonconducting chopstick. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
strangedogs Posted June 9, 2006 Share Posted June 9, 2006 My Local GC is supposed to call me as soon as more come in but just checked with musiciansfriend and they have the combo's in stock - dude told me it's the 2nd generation ones too Might go ahead and order one tonight... "well fellas... there's 1 other thing yer gonna need to make it in Rock & Roll besides all them guitars and amps and drums and things. They call it A SONG..." Link to comment Share on other sites More sharing options...
LPCustom Posted June 9, 2006 Share Posted June 9, 2006 I made a 2x10 cabinet for my Valve Junior. I think it sounds far better than the original 8 inch Weber speaker. I used two Celestion Tube 10 speakers, 8 ohms each for a 4 ohm load. I wish you guys could hear it. I think it sounds great and it will get loud. I designed the new cabinet in the style of the original. It has two slots in the back like the newer VJ combos. I cut in two opposing corners on the front. http://www.crystalblack.com/valvejuniorcombo2x10.jpg This is what it looked like while I was working on it and remembered to take a picture. I've since radiused all the corners, and put hardware on the corners, installed feet and a carrying strap and modified the original connecting cable for the speakers so it plugs into both speakers in parallel. I haven't decided what to cover it with (after three months). I have cane grill cloth on there right now. I haven't had much time to work on it. You know what they say about the cobbler's children's shoes... I'm thinking of covering it in cocoa brown tolex and using oxblood grill cloth on it. Born on the Bayou Link to comment Share on other sites More sharing options...
Fumblyfingers Posted June 9, 2006 Share Posted June 9, 2006 Ricochet thanks very much for all the info. Much appreciated. That's cool about the new gen amps, Strange. Looks like I won't need to do the mod after all which is good....I will leave such work to the experts like Ricochet and others here who know their stuff. LP that looks good bro'. Post pics of the finished product. Any chance you can whip up a little audio sample of this puppy as it is now? Link to comment Share on other sites More sharing options...
Xplorer Posted June 10, 2006 Share Posted June 10, 2006 LPCustom: Nice job dude! That looks sweet! Any other plans to cover the wood, piping etc...? What a horrible night to have a curse. Link to comment Share on other sites More sharing options...
LPCustom Posted June 10, 2006 Share Posted June 10, 2006 Originally posted by Xplorer: LPCustom: Nice job dude! That looks sweet! Any other plans to cover the wood, piping etc...? Thanks! I wish I had more time to work on it. I think I'm going to cover the "wood" (it's actually MDF) with a cocoa brown tolex. You can see a swatch of that here: http://www.mojomusicalsupply.com/cgi-bin/mojotone/7310000.html The swatch here is too dark and too red for what it actually looks like. I put Marshall cane on it as the grill cloth but I don't care for the looks of it now that it's on. I think I'm going to change it to this: http://www.mojomusicalsupply.com/cgi-bin/mojotone/6301004.html I also have some of this. I can't make up my mind about this. This isn't exactly what it looks like but it's what they say it looks like. This is far too light in color. What I have is darker and more of a wine color. http://www.tubesandmore.com/images/inv/S-G302.JPG I also have some white piping. I'll probably try that out to see if I like the look with it. The original cab has piping. So I probably will put piping on it. I just took a couple of pictures of it. Sorry about the poor picture quality. Here's what the front looks like, now: http://www.crystalblack.com/valvejuniorcombo2x10_front.jpg And here's a shot of the back. http://www.crystalblack.com/valvejuniorcombo2x10_rear.jpg I'm actually considering rebuilding it in pine for two reasons. The first is that I made a mistake on the back when I cut the speaker cable channel (got it on the wrong side). The other is that The MDF is too fragile for my taste and too heavy. The amp weighs in at 43 pounds, now. MDF is heavy stuff. I have inserts to cover the amp section screws on the top. But I'm not going to install them until I get tolex on it. I don't have the proper wiring installed for the speakers right now. I'm testing a stereo/mono and multi-impedance jack arrangement for my other speaker cabinets in it. That's what all the red and black wires are. The plate is not in view, I think it's in the corner of the back. Born on the Bayou Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted June 10, 2006 Share Posted June 10, 2006 Hay VERY NICE MR.!!! gotta hear sound samples when you get a chance..that looks so sweet! Just walked in from the gig and kickin back a little.. see ya tomorrow bud! http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
Ricochet Posted June 10, 2006 Share Posted June 10, 2006 LPCustom, that really looks great! Nice work! "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
myles_rose Posted June 11, 2006 Share Posted June 11, 2006 Just one point here .... a lot of folks are jumping on the DC heater bandwagon and this sometimes can reduce hum in some area but sometimes does nothing (generally the case). But ... a side downfall of DC heaters is tube wear about five times faster in preamp tubes if that is any kind of consideration. Myles S. Rose www.guitaramplifierblueprinting.com www.la-economy.blogspot.com www.facebook.com/mylesr www.twitter.com/myles111us Link to comment Share on other sites More sharing options...
Ricochet Posted June 11, 2006 Share Posted June 11, 2006 And why would that be, Myles? Got a reference? "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted June 12, 2006 Author Share Posted June 12, 2006 Well it seemed like there'd been enough interest in the Valve Junior here that I thought it might be fun to have a decidated forum where we can continue talking about this fun little amp and some of its other low wattage brethren. So you'll now find at the bottom of my ValveJunior.com page a new discussion forum. Maybe drop by and check it out. www.valvejunior.com CAF P.S. Actually the discussion forum software is something I wrote myself. I expect there will still be bugs, but maybe you guys can help me shake it out a bit. Link to comment Share on other sites More sharing options...
Ricochet Posted June 12, 2006 Share Posted June 12, 2006 That's a nice idea. I've pointed a bunch of folks over to your site. You have some good info over there. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
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