Members Verne Andru Posted November 22, 2009 Author Members Share Posted November 22, 2009 Originally Posted by gnolivos Verne:I snipped C9 and C12 today. I did one leg of each only, in case I wanted to solder back in.In any case, what is the expected behavior of the Tone knob after the mod? Reason I ask is that I was *hoping* this would make the tone knob act as any other amp such that: Left is darker, right is brighter.However, both before and after the mod, I experience the same overall behavior on the V8 tone knob: Left is dark, right is dark, and middle (12 o'clock) is bright. Not good. This is consistent with what I wrote. Taking C12 out of the circuit doesn't affect how the tone knob works, it removes the mid-range "honk" that gives the amp some of it's boxy tone.To make the tone knob work for the full range of it's sweep, you have to lift one leg. ATM all 3 legs are connected to the circuit - for full sweep you should only have a center wiper and 1 side providing the input. I'm going from memory here, but my guess is to lift the leg that connected to C12. I never bothered, as I gutted the stock tone circuit and built my own with separate bass/mid/treble, so you're on your own with this one. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 22, 2009 Author Members Share Posted November 22, 2009 Originally Posted by gnolivos By the way, finished the cabinet off today with the logos. It's no Marshall, but who cares. I love the way these old style JTM45 cabinets look Click here for PhotoBucket pics:Album Well done! Certainly 1 of a kind and doing all the mods gets your tone well within Marshall territory so it can sound as good as it looks. Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 22, 2009 Members Share Posted November 22, 2009 Verne,I looked at the V508 mod schematics (http://www.guitarnuts.com/amps/vc508..._schematic.pdf) and found very interesting mention in there of a Tone mod, that "makes tone knob act as a real tone control".I'm no electronic engineer, so just looking at the schematic I couldn't quite make sense of it. Looks like they are bypassing the wiper altogether? Nah, can't be. EDIT: Looks like the jumper one side of the pot, rather than lifting it. Correct?Incidentally, I don't think they ever discussed lifting C12 on the V508 mod. I do notice improvement in overall sound after the C9/C12 lift, so that was a great little tip, thanks!Can you take a quick look at the V508 schematic near the tone pot... and let me know your thoughts? If I can get this tone knob to act like a normal one, I will be immensely happy with this amp. Right now it acts almost symmetrical... dark all the way left, bright at 12'oclock, and again dark all the way to the right Thanks for compliments on the amp. It was not cheap though Originally Posted by Verne Andru This is consistent with what I wrote. Taking C12 out of the circuit doesn't affect how the tone knob works, it removes the mid-range "honk" that gives the amp some of it's boxy tone.To make the tone knob work for the full range of it's sweep, you have to lift one leg. ATM all 3 legs are connected to the circuit - for full sweep you should only have a center wiper and 1 side providing the input. I'm going from memory here, but my guess is to lift the leg that connected to C12. I never bothered, as I gutted the stock tone circuit and built my own with separate bass/mid/treble, so you're on your own with this one. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 22, 2009 Author Members Share Posted November 22, 2009 I know that schematic and mods well. I tried his tone control mod and it either didn't work, or I wasn't happy with how it worked. It was after being frustrated with his approach that I decided to go with separate bass/mid/treble controls doing it from scratch. His mods are "typical" mods one does to a valve amp without giving the actual circuit much thought. I've spent quite a bit of time with the V8 and I think my mods reflect a more thorough approach to the tone issue. I'm working on a mod schematic and should have it posted later today. Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 22, 2009 Members Share Posted November 22, 2009 Cool, thanks. I'm going to add the jumper for the Tone pot for now, and see how I like it. Looking forward to your mod schematics!!! Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 23, 2009 Author Members Share Posted November 23, 2009 Consolidated V8 Mods Schematic:http://www.verneandru.com/WebApp/Dow...-schematic.pdf I think I got everything. I'll go over it once I get a chance to print a hardcopy. There are a few more mods than what I've posted in this thread. Most of it is removing components that suck tone. Adding the new tone stack is the biggest job, but is well worth the effort for the added tone and flexibility. Let me know of any errors/omissions you spot. Good luck and happy modding! Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 23, 2009 Members Share Posted November 23, 2009 I've read on other V58/508/8 mod threads that the optimal opamp replacement chip is the NE5532. Was going to start with the opamp mod, but now debating which one to use. (this one or the TLE2072?) Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 23, 2009 Author Members Share Posted November 23, 2009 Originally Posted by gnolivos I've read on other V58/508/8 mod threads that the optimal opamp replacement chip is the NE5532. Was going to start with the opamp mod, but now debating which one to use. (this one or the TLE2072?) It depends on what you're going for. In my experience, the TL072 and NE5532 are pretty much the same - hi-volume, mediocre opamps used in just about everything. They work, but tend to be noisy and don't do your tone any favours. That's why you find them in just about everything.OTOH, the TLE2072 is part of TI's Excalibur series. These are the best-of-the-best opamps available, period. If you want pristine clean tones and righteous gain, this is the one to go with. They do tend to oscillate when driven really, really hard, but IME I've usually found the tone I want long before this is a problem.The other alternative I've considered is JRC 4558 chip or JRC 2043 chips that were used in classic Tube Screamers. These are pretty nasty sounding chips, but they should add that classic tone to the amp. Not sure if they'll do the clean headroom any favours though.The opamp section of the V8 acts as a boost before the first 1/2 of the 12AX7 preamp tube. So it follows that, just as the type of boost pedal you use before the amp will colour the tone, the type of opamp used in the V8 will act in a similar manner.For my purposes I was looking for an amp that could go from chimey clean to righteous roar using only the controls on my guitar. The TLE2072 is the best choice for what I'm wanting in a Class A amp. I will probably try the JRC in my second V8 just for {censored}s and giggles. Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 24, 2009 Members Share Posted November 24, 2009 Verne,Question for you... I changed my 12AX7 to a 12AT7 (JJ tube), and I don't quite experience the same thing you describe below. I think things may have improved very slightly, but still, if I get the gain knob past 9 o'clock, it starts breaking up (more noticeable with my Gibson SG humbucker setup, but also with the Telecaster to some extent). Net, not too different from the behavior I experience before the tube swap.I did also change the EL84 to a JJ, and I think it was rated 'high gain 95' or something like that. Do you think this could be interfering?I'd love to be able to to 12 o'clock and keep it clean. Right now, my amp is awesome for crunch and gain (usually have it at 12 o'clock setting for this). but when I go for clean tones, I have to back the gain to 3 o'clock, and there is just not enough volume even with the vol knob set all the way up. Originally Posted by Verne Andru I just finished changing pre-amp tubes - I put in a NOS GE 12AT7. I was looking for JJ's, but when the guy mentioned he had some NOS I couldn't resist.As suspected I gained between 25 and 30% clean headroom. Added bonus is the amp has got a really nice, smoky tone to it now and all the boxiness is gone. I was using a bit of delay and reverb to round out the tone and take the bite out of the 12ax7, but it sounds great by itself now. The pedals are a bonus!With humbuckers [Ric 650] I can push the gain to noon and it stays clean. Gets some nice hair on it around 12:30 and after that it's crunch city. With my strat [fat strat with Dano lipsticks in the neck and mid] it stays clean to around 2:30 then we're into serious SRV territory. I can crank the gain wide open with the strat and it still sounds great. The hotter buckers in the 650 start getting a bit nasty close to wide-open, but still nothing like before. The 12at7 lets a bit more of the darker el84 tone to get through, which I think is a good thing. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 24, 2009 Author Members Share Posted November 24, 2009 Originally Posted by gnolivos Verne,Question for you... I changed my 12AX7 to a 12AT7 (JJ tube), and I don't quite experience the same thing you describe below. I think things may have improved very slightly, but still, if I get the gain knob past 9 o'clock, it starts breaking up (more noticeable with my Gibson SG humbucker setup, but also with the Telecaster to some extent). Net, not too different from the behavior I experience before the tube swap.I did also change the EL84 to a JJ, and I think it was rated 'high gain 95' or something like that. Do you think this could be interfering?I'd love to be able to to 12 o'clock and keep it clean. Right now, my amp is awesome for crunch and gain (usually have it at 12 o'clock setting for this). but when I go for clean tones, I have to back the gain to 3 o'clock, and there is just not enough volume even with the vol knob set all the way up. There are a lot of issues at play and it's really a sum of the part thang.IIRC I had already done the opamp change, which gave me more and cleaner headroom before I mucked with the tubes. Old school tubes and amps were designed to reduce distortion to a minimum [generally speaking] whereas newer amps are designed to enhance distortion - so I wouldn't be surprised newer tube designs depart from the NOS I used as far as the amount of gain they put out. The higher gain EL84 is certainly a factor. As is the guitar. My Ric has very low output mini-humbuckers so it's not going to be driving the front end of the amp as hard as, say, your SG.With my rig running my strat, the gain knob is around 11:00 before I start getting hair on the tone. The Ric pushes it to around 12:00 yet my Les Paul with SD Jazz in the neck and JB in the bridge I can't get past around 9:30 before it starts breaking up.Hope this helps. Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 24, 2009 Members Share Posted November 24, 2009 Excellent info Verne, this definitely helps. I think my next mod will be the opamp change. May even put a socket first. Looks like it may be kinda tricky to work in there, but I'll give it a shot. Have some experience with soldering irons, and actually have a newer higher end unit now with adjustable temp. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 24, 2009 Author Members Share Posted November 24, 2009 If you're doing the socket route, be sure to get the good kind. There are 2 types. I used the cheapo first time and the chip would shake loose from time to time causing the amp to hum horribly. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 26, 2009 Author Members Share Posted November 26, 2009 Originally Posted by allstarmobi I Link to comment Share on other sites More sharing options...
Members Preacher Posted November 29, 2009 Members Share Posted November 29, 2009 Originally Posted by Verne Andru Consolidated V8 Mods Schematic:http://www.verneandru.com/WebApp/Dow...-schematic.pdfI think I got everything. I'll go over it once I get a chance to print a hardcopy.There are a few more mods than what I've posted in this thread. Most of it is removing components that suck tone. Adding the new tone stack is the biggest job, but is well worth the effort for the added tone and flexibility.Let me know of any errors/omissions you spot.Good luck and happy modding! This is awesome, Verne! Thanks for all the work done to document the mods and answer questions! Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 29, 2009 Members Share Posted November 29, 2009 Well I have bad news. I did the opamp swap today, and essentially had to resort to clipping the legs of the old chip, and soldering the new one (TLE2072CP) in place. I made sure to orient it the proper way, paying attention to the round (pin 1?) marker. At any rate, put everything back together, and while the amp powers on, I get no sound. On the other hand, if I plug my guitar through the FX/LOOP (halfway in, as per known trick) I manage to get sound out of the amp. First of all, TLE2072CP is the correct replacement chip, right? Secondly, anyone here with enough experience to theorize what could be wrong here? I checked 3 times already for continuity and possible shorts, and everything looks fine. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 29, 2009 Author Members Share Posted November 29, 2009 TLE2072ACP Unless you damaged the pcb [which takes work to do] these are the things I'd check: - chip is the right way around - there is a small circular indent on the TLE that's pretty hard to see that helps you orient the chip - there is a bad solder joint on one or more of the legs of the chip - you overheated the board which caused one or more of the surrounding components to become desoldered - the chip is bad [highly unlikely] Since the output section is working, it's really a matter of trouble-shooting the problem. Truth be told, this is part of the job, so don't sweat it. There are many times I've done something and have had to spend 3 to 4 times more time trying to track down what I did wrong than it took to do the mod in the first place. Be cool and methodical. A multimeter is really handy for stuff like this. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 29, 2009 Author Members Share Posted November 29, 2009 Anybody thinking of a replacement speaker, THD is blowing out their alnico voiced 10" on eBay for $15.http://cgi.ebay.com/THD-Vintage-10-G...mZ320443580685 I have not tried them, but for the price I'm ordering 2 and will take my chances. Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 29, 2009 Members Share Posted November 29, 2009 Thanks Verne for the info...! My chip says TLE2072CP, much like the mouser link you provided in earlier post. So, looks like I have the wrong chip altogether? Sure it is TLE2072ACP then? Will try to find one online, see if I have better luck than the "CP" version which is sold out everywhere. Also will check orientation. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 29, 2009 Author Members Share Posted November 29, 2009 The ACP is the Excalibur, the CP is not. Both should work just the Excalibur is a better chip. Check, double-check and triple check the solder joints. 11 times out of 10 it's a bad solder joint. Link to comment Share on other sites More sharing options...
Members dcindc Posted November 29, 2009 Members Share Posted November 29, 2009 If had to unplug anything during disassembly, check those. Check everything you touched. But it's likely a bad joint. Are these thru plated or double sided boards? Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 29, 2009 Author Members Share Posted November 29, 2009 Thru plated. Where ya been dc? Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 29, 2009 Members Share Posted November 29, 2009 Thanks Verne, I re-soldered every pin, and now it works. What a RELIEF!!!! Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 29, 2009 Author Members Share Posted November 29, 2009 Originally Posted by gnolivos Thanks Verne, I re-soldered every pin, and now it works. What a RELIEF!!!! So, once your heart stops pounding like a 50 lbs hammer, can you tell any difference in tone or gain? Sound any different? Link to comment Share on other sites More sharing options...
Members gnolivos Posted November 29, 2009 Members Share Posted November 29, 2009 Sadly, I broke my JJ tube when putting everything back together, and had to revert to stock EL84 Sovtek tube. The JJ had a long curved tip, and the bracket fastened on it the wrong way, too much pressure, and snap! (damn it).Right now, the gain is pretty nasty, but I think it is the Sovtek. I have another JJ on order.I *think* I notice a humm that was not there before. Will have to look into that. Originally Posted by Verne Andru So, once your heart stops pounding like a 50 lbs hammer, can you tell any difference in tone or gain? Sound any different? Link to comment Share on other sites More sharing options...
Members Verne Andru Posted November 29, 2009 Author Members Share Posted November 29, 2009 If you're getting hum that probably means the chip still isn't soldered properly. Link to comment Share on other sites More sharing options...
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