hechtdavid

Hi Myles, I couldn't say specifically - I always have my amp tech set the bias for me when I re-tube. I totally trust him since he's been working for years on various amps for me. I know he does it "old school" using a scope, checking crossover notch dist etc... I'll see if I can find out. Any other tubes you like for this amp? Thanks, David

I've been getting good tone from the GT-EL34Ms and the SED Winged C EL34s but they seem to crap out pretty quickly. (6 months of mostly weekend gigs). I'm think of trying the GT-E34LS or the JJs (are they the same tube?) since they both claim to be a more powerful and longer lasting tube. What is your take on these tubes? Any others you would recommend for a Rivera Clubster 45?? Thanks, David

Hi Myles, I've been going through tubes pretty quickly in my Rivera Clubster 45. I've been getting good tone from the GT-EL34Ms and the SED Winged C EL34s but they seem to crap out pretty quickly. (6 months of mostly weekend gigs). I'm think of trying the GT-E34LS since they claim to be a more powerful and longer lasting tube. What is your take on these tubes? Any others you would recommend for this amp? Thanks, David

Hi Myles, I just scored a used Peavey Classic 30 in great shape but sorely lacking in the tube dept. (the originals) I've ordered a GT-EL84S quartet for the power section and I have some 12AX7's here and was wondering where I should install these in V1, V2 & V3. I have these tubes available: 1 - GT12AX7C 1 - GT-7025 1 - GTECC83S 2 - JJ-ECC83S Could you suggest the best positioning using these preamp tubes? Thanks in advance for your sage advice, David

David, This is all personal preference, and many other factors. Over at GT when folks ask me which tube to use, many times I have a canned answer: Tube choice and selection is very much personal taste and preference. You can find a document that will go into this in great detail, and give you information on tube types, characteristics, and also on the rating system used by GT, conversion from Mesa to GT and Fender to GT tables, matching information and more. http://www.guitaramplifierblueprinting.com is the website, and the document is the Tube Primer, v1.31 which has a link and button for download or viewing. V1.31 is 47 pages and not too bad to download. v3.20 is in two sections and about 200 total pages total, if you want a LOT of info. posted 01-06-2004 07:33 PM -------------------------------------------------------------------------------- quote: -------------------------------------------------------------------------------- Originally posted by myles111: quote: Hi Myles, I think asked should have asked my question a bit differently. I've read some of your Tube Primer - very helpful. You steered me to some Chinese 12AX7's (put in V1 & V2) that really warmed up the Twin nicely. Here goes; Can I assume that a warmer tube (like the 12AX7C) will "warm up" my 'verb? Likewise, will a 7025 make the verb brighter? Also, which one; the drive or the recovery tube, affects the tonal quality of the reverb more? Thanks again, David

David, This is all personal preference, and many other factors. Over at GT when folks ask me which tube to use, many times I have a canned answer: Tube choice and selection is very much personal taste and preference. You can find a document that will go into this in great detail, and give you information on tube types, characteristics, and also on the rating system used by GT, conversion from Mesa to GT and Fender to GT tables, matching information and more. http://www.guitaramplifierblueprinting.com is the website, and the document is the Tube Primer, v1.31 which has a link and button for download or viewing. V1.31 is 47 pages and not too bad to download. v3.20 is in two sections and about 200 total pages total, if you want a LOT of info. Hi Myles, I think asked should have asked my question a bit differently. I've read some of your Tube Primer - very helpful. You steered me to some Chinese 12AX7's (put in V1 & V2) that really warmed up the Twin nicely. Here goes; Can I assume that a warmer tube (like the 12AX7C) will "warm up" my 'verb? Likewise, will a 7025 make the verb brighter? Also, which one; the drive or the recovery tube, affects the tonal quality of the reverb more? Thanks again, David

Hi Myles, Could you suggest some tubes for a 1999 Fender "Evil" Twin reverb circuit? I have JJ's in there now: Drive: 12AT7 (V5) Recovery: 12AX7 (V6) They're a bit too shrill and thin sounding. What would recommend to warm up my 'verb? BTW, thanks for generous wisdom - past, present and future... David H. Madison, WI.

Hi Myles, I've got a MusicMan 110-RD Fifty (1650-RD circuit) that's in need of some new output tubes. I seem to remember hearing something about the high plate voltages in these amps requiring some robust tubes. Considering: 1) Phillips 7581A 2) Svetlana 6L6GC 3) GT 6L6GE 4) JJ 6L6 Recommendations? Hardness #? What is the GT model # for the Svets? I've also experimented with changing the 12AX7 in the pre, but I've not noticed much difference in the lead channel sound. Am I correct in assuming that changing this tube will not affect the sound much because of the nature of the SS preamp? Thanks in advance for your sage advice. David H.

The ET: It exhibits the same problems after swapping tubes back to the old Svets, so I don't think its a tube problem. The amp works, but I'm reluctant to use it right now because of the hot bias I have to run just to get the balance to 0. I noticed when I first removed the Svets that the bases were discolored from the heat. I'd rather not run the GT 6L6GE's and burn them up too quickly since they're a bit on the pricey side. I'm assuming its time to take it in to the local amp tech. Any hypotheses? Thanks again David[/qb] David .... Well, if the same problem shows up with the svets, then its something in the amp. Perhaps a resistor failed that in in the bias balance circuit. It could be a number of things, but its an area easily trouble shot. Get it over to Fender shop, as these amps have a pretty long warranty. Drop me a line to keep me in the loop if you want me to talk to your tech. Myles[/QB] Hi Myles, Here's an up-date on the Evil Twin: I took it to my local Fender amp tech and he checked it out - looking for failed resistors etc.. and said that he could find nothing wrong with it. The amp checked out OK and that it was just a function of the tubes - GT 6L6GE's (GT rating #7). The balance is set properly at 0 but the lowest I can set the bias is around 72mV (with the bias pot fully counterclockwise). Everything seems to be working properly and the amp sounds great. Should I still be concerned that I can't dial in a lower bias, or is this one of those *if it ain't broke, don't fix it* situations? Thanks again David

Dave, It sounds like you are doing things properly, and the cheap Radio Shack DVM is not the problem, as those meters work just fine for ohms, volts, current, etc. If the meter makes numbers that change on its display, it is fine and dandy. Try swapping the tubes around, as to try to isolate a possible bad tube. Shipping damage or other physical damage in not all that uncommon, and one tube may be way out of wack. If you can put your old tubes back in and bias properly, that right there rules out your dvm, amp, procedure, and everything else. What area are your from? If you are close to Los Angeles, I would be more than happy to look at this for you at no charge. Myles Damn Myles, You are a generous guy! I wish I was close to LA, but Madison, WI. is a bit far to lug an Evil Twin. If you ever get out this way, I'd like to buy you a few of your favorite libations. But I digress... enough about how great you are. You are, and I'll leave it at that. The ET: It exhibits the same problems after swapping tubes back to the old Svets, so I don't think its a tube problem. The amp works, but I'm reluctant to use it right now because of the hot bias I have to run just to get the balance to 0. I noticed when I first removed the Svets that the bases were discolored from the heat. I'd rather not run the GT 6L6GE's and burn them up too quickly since they're a bit on the pricey side. I'm assuming its time to take it in to the local amp tech. Any hypotheses? Thanks again David

Hi Myles, I guess I didn't phase my question very well. Sorry about that.. I CAN set the bias on my evil twin at a lower setting, but at that lower bias setting, I can NOT set the balance properly. The only way to set the balance to 0 is to raise the bias setting to 77mV or more; the balance will be set to 0 - but only at the furthest conterclockwise postion on the pot. BTW, I am using a cheap radio shack DVM, and its worked fine in the past. I'm sure I'm checking bias and balance properly on this amp. Thanks again for all your generous wisdom. David

Hi Myles, Evil one needs help... I just got a new set of GT 6L6GE's for my 1999 Evil Twin and it now won't bias properly. (I think it may have had this problem before the new tubes.) To get the balance to read correctly, I have to set the bias up around 80mV (too hot for me) - and then the balance adjustment pot is set at the maximum (counterclockwise) range. Any ideas? Time to take it in for a checkup?

David, Bob at Eurotubes does a great matching job, and your phase inverter is a LOT better than anything you'' ever get off the shelf at random. The JJ tubes are pretty consistant in rise time, so I'd just keep that in there for now. If the rise time was off by a bit, if you had a very critical ear, you might notice a difference. I can tell you that at below 100 Hz, I can sure see a difference on a scope when I look at the output waveform when I use one of the SAG tubes. On the GE's .... get ready to be surprised ! The PI has a LOT to do with sonic quality. Sure, the output section tubes will last longer too, as they are being driven more evenly, but the sonic quality is the BIG factor. In certain amps they make a major noticible improvement. In your amp I set the GE's at about .05VDC from their testpoints. This makes the amp run a touch on the cool side, but the Twins don't get as grainy when cool as a Mesa amp as an example. The test points on the Fender amps are every bit as accurate as any bias measuring device with a meter. I wish they would have done that system 50 years ago On Fender amps I like the current draw method more than with a scope. It is something that is repeatable, and a scope view is not ... it is open to interpretation. On Marshall amps I like to use a scope as there is a certain amount of crossover notch that is needed to give them their Marshall sound. So ... save your money on the tech and buy a cheap $30 meter, and you are in business Regards, Great Myles! Once again, you've got me excited to plug and play. I'm very anxious for those GE's to arrive. One more question: When you say to set the GE's at about .05VDC from their testpoints, does that mean up or down? Since Fender recommends from .04 to .08 VDC, and seeing that .06 is in the middle, should I set it at .11 or .01 VDC? OK, I lied... one MORE question: I've been told that running them cold will yield a longer tube life, but what sonic differences would you expect to hear between running at the upper and lower ends of the bias scale? Thanks again, David

Hi Myles, I just ordered a matched quad of the GT 6L6GE's for my 1999 "Evil" Twin and was wondering if I should replace the phase invert tube with one of their SAG-AT7-MPI's. Right now I have a balanced JJ AT7 thats only a few months old (thanks to Bob@Eurotubes). I understand that GT may have a more rigorous testing/matching system than Bob, but would I notice any difference in sound? Am I correct in assuming that the PI tube has more to do with the lifespan of the power tubes than the sonic quality? On a related subject, this amp has the bias and balance test points on the back panel. The manual says to set the bias with a DVM at between .04VDC and .08VDC. What would be optimal for these tubes? Do these test points give as acurate a reading as as in-line bias meters? OR Should I take it to a tech and have it done with a scope and a signal? Kudos and thanks again for all your help. David

David, The 7025's may be too bright for some tastes. I'd first try one of these in V2. If that does not do the trick, then put the tube back in V2 that was there, and try the 7025 in V1. Your grainy nature may come from the output section now being driven in a different way than before if you have more or less gain going to the phase inverter. Is your bias adjusted properly? The 7025's are the "Fender sound", but newer Fender designs went to the 12AX7's rather than the 7025's. I generally like a 12AX7 in V1 and V2 of these amps, rather than a JJ version, I'd prefer a JAN version of a USA tube (mostly still under $20), either GE's, Philips, or RCA. The next choice on my list for these are the Sovtek 12AX7LPS or the 12AX7EH (Electro Harmonix) tubes, but be sure you know their output, as a tube that is too hot will add all sorts of noise and coarseness to the sound. The best and safest bet on this attack, is to save time and get what you really want. What you want are tubes for V1 and V2, both 12AX7's, from Watford Valves, with a rating of 215 or so for V1 and 240 or so for V2 using their scale. (For my clients, this would be a rating of 92 for the V1 tube and 108 for V2). Regards, Hi Myles, Is there anyplace in the US that will "rate" these tubes? For your clients, what do the numbers 92 and 108 refer to? I'm hoping to get something domestically.. Thanks again, David