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Post by Scott on Feb 21, 2011 12:05:18 GMT -7
Thanks...
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Post by BritInvasion on Feb 21, 2011 12:32:43 GMT -7
Hi , Myles - I was wondering about tube sockets. With as much fun as tube rolling can be , it got me thinking that maybe tube sockets aren't really designed for a whole lot of pulling / inserting tubes. Does a lot of experimenting lead to premature socket failure ? I'm probably just being obsessive , but was curious if you had any opinion / observations.
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Post by myles on Feb 21, 2011 15:55:51 GMT -7
Hi , Myles - I was wondering about tube sockets. With as much fun as tube rolling can be , it got me thinking that maybe tube sockets aren't really designed for a whole lot of pulling / inserting tubes. Does a lot of experimenting lead to premature socket failure ? I'm probably just being obsessive , but was curious if you had any opinion / observations. Sockets are like most other items, there are good ones and bad one. Another factor is if the socket is chassis mounted or PCB mounted. Multiple removal and insertions of tubes can put a strain on the solder connections of PCB mounted sockets. Cheaper materials will allow some sockets to loose tension on the tube pins fast in the case of many sockets. High grade sockets (Belton is one maker of very nice sockets) will stand up to thousands of removal and insertions. Cheap sockets could show problems in a dozen cycles. Belton sockets were used in the tube test equipment at Groove Tubes in the six and a half years I was their tech support. Hundreds of tubes were inserted and removed in these sockets every day. Maybe every six months or year or two a few sockets would need replacement. There are some good sockets out there and some bad ones. Some vintage style are three major pieces; a metal ring holding a plastic or phenolic base and the pins in the base. These do not hold up all that well and have one more bad aspect, they rattle. The Belton sockets do not rattle. Back in my computer days at Data General the edge connectors had a MTBF (mean time between failure) rated in hours. For each removal and insertion of a circuit board the MTBF was reduced by 50 hours.
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Post by BritInvasion on Feb 21, 2011 18:49:51 GMT -7
Wow, very interesting and informative! I had no idea that even a quality socket could take that many cycles. Thanks for your reply , Myles.
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Post by myles on Feb 21, 2011 20:09:10 GMT -7
Wow, very interesting and informative! I had no idea that even a quality socket could take that many cycles. Thanks for your reply , Myles. Belton sockets are very nice industrial sockets that were designed for removal and insertion. Commercial sockets were used in high duty cycle equipment. Consumer grade sockets were used in things like TV, radio and guitar amps of the day. Unfortunately some folks feel that just because something is "vintage" style it means vintage tone. Vintage in many parts of the past really equates to least expensive in many cases. Same sort of issue with simple items such as resistors. Some folks feel that carbon comp is the only way to go. In some areas of the circuit that may be the case for some folks. Carbon comp have a vintage response and tone. But, these resistors drift with temperature changes and can become noisy. There are metal film type resistors which are quieter and more stable. The best high end amp folks use the best resistor for the job in the area of the circuit and don't just use one type of resistor. When I see an amp which uses nothing but vintage parts such as vintage style tube sockets or all carbon comp resistors my first reaction is to question the knowledge of the tech or builder. I the case of trying to do a dead copy of a vintage amp one might opt for all carbon comp resistors if in that era that is all that were available but there are some items that I would not go down that "vintage" path as the sonic quality of the amp would not change but the reliability would be compromised.
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Post by BritInvasion on Feb 21, 2011 20:30:46 GMT -7
Makes a lot of sense ,Myles. In the 50's only certain components were available , and weren't necessarily the ultimate in design or materials compared to units that actually were improvements a little later. Makes me realize how much thought goes into a well-designed (and built) amp when vintage parts are used where sonically needed , and up-grades used where reliability is the design goal. Thanks so much for this insight!
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Post by detuned on Feb 27, 2011 20:54:49 GMT -7
Myles, I've been enjoying your tweets about preamp tubes recently - thanks for those! (Z brethren, if you're on the Twitters & not following Myles, go take care of that now!)
I have a Remedy I'm trying to "soften up", just a bit - it's very percussive, stiff, & almost harsh. I'm also trying to clean it up a bit at gig volumes, as I don't use very much distortion as a rule.
I've subbed in a new EH 12ay7 in V1 to lower the gain a bit, & put in a decent-sounding russian 12ax7 in V2, but kept the stock PI & 6V6s. It's better, but not as sparkly as I might like...
So, questions:
If I were to go to something NOS in V1, what would you suggest? Any suggestions in general to keep the distortion down, retain the Rem's muscularity, yet smooth the amp out in general? Have you any opinions of the Tung-Sol 6V6s as opposed to the JJ's it came with?
Sorry for the onslaught of questions. :-)
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Post by myles on Feb 28, 2011 10:59:09 GMT -7
Myles, I've been enjoying your tweets about preamp tubes recently - thanks for those! (Z brethren, if you're on the Twitters & not following Myles, go take care of that now!) I have a Remedy I'm trying to "soften up", just a bit - it's very percussive, stiff, & almost harsh. I'm also trying to clean it up a bit at gig volumes, as I don't use very much distortion as a rule. I've subbed in a new EH 12ay7 in V1 to lower the gain a bit, & put in a decent-sounding russian 12ax7 in V2, but kept the stock PI & 6V6s. It's better, but not as sparkly as I might like... So, questions: If I were to go to something NOS in V1, what would you suggest? Any suggestions in general to keep the distortion down, retain the Rem's muscularity, yet smooth the amp out in general? Have you any opinions of the Tung-Sol 6V6s as opposed to the JJ's it came with? Sorry for the onslaught of questions. :-) OK ... let's take a look here .... To clean things up overall you might want to try a 5751 in the phase inverter. That will also smooth things out. The EH 12AY7 is not a tube I would pick for 12AY7 use. I would go the NOS route on a 12AY7. the AY7 is not going to be a bright or snappy tube. It is all compromise. If you want bright and articulate look for a longer plate 12AX7 for V1 and we can try to tame the amp via the phase inverter. What is in V2? The only Russian tube I would use there is perhaps a Tung Sol Reissue. Since it is just one amp and you don't have an issue of trying to get a lot of tubes to build a lot of amps you may want to consider an NOS USA medium plate tube from the 60s / 70s like an RCA 7025, GE or Sylvania. These are all neutral and articulate. I am not a fan of JJ 6V6s. Personal taste. They sound more like a 6L6 than a 6V6. Some folks love that. I don't. The JJ also used to be rugged. These days I see about a 50% rattle rate right out of the box. Electrically they are generally very sturdy. I like the Russian Tung Sol marked tubes a lot. Hope that helped. Happy playing. Myles
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Post by hymns on Feb 28, 2011 12:45:27 GMT -7
Myles ,I saw an amp being designed with an ef-86 in the PI.He was gradually use 5751 in different stages and finally hit the PI and use KT-88's as power tubes at 80 watts.I was wondering what you thought about that tube selection?
hymns
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Post by redwine on Feb 28, 2011 13:37:32 GMT -7
Myles ,I saw an amp being designed with an ef-86 in the PI.He was gradually use 5751 in different stages and finally hit the PI and use KT-88's as power tubes at 80 watts.I was wondering what you thought about that tube selection? hymns
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Post by detuned on Feb 28, 2011 13:56:43 GMT -7
Very helpful, as always - thanks Myles!
Karma your way, although I fear that's redundant in your case. ;-)
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Post by myles on Feb 28, 2011 14:10:02 GMT -7
Myles ,I saw an amp being designed with an ef-86 in the PI.He was gradually use 5751 in different stages and finally hit the PI and use KT-88's as power tubes at 80 watts.I was wondering what you thought about that tube selection? hymns It is going to be a somewhat unconvention design I would think as it will not use a ling tailed phase inverter circuit it seems. Perhaps it will be something like a tweed deluxe or Princeton. An EF86 is a pentode. For a split tail PI design you would need two of them. I suppose you could use a single pentode and split the output to each tube. Not seeing the design it is impossible to guess what the designer may be doing. On the subject of tube selection, the choice of a given tube means little if anything in many cases. A 6L6 is the output tube used, four of them, in a Fender Twin Reverb and a Soldano SLO100 yet the two amps have nothing in common. An EL84 was used in Dynaco, Scott and other fine audio pieces yet did not distort at normal levels. It was also used in the Vox AC-15 and Marshall 18 watter where it's distortion character is loved by many. Basically, tubes mean very little. How they are implemented means a lot.
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Post by Lonny Caughron on Mar 2, 2011 17:14:09 GMT -7
Myles, I just received a used KT-45. Can you suggest some power tubes and a phase inverter from mike at KCANOSTUBES? She is tube rectified but I already have a NOS one on hand to replace the sovtek.
Also what rating should I ask for and where do I need to bias the tubes at?
Thanks
Lonny
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Post by Deleted on Mar 2, 2011 23:14:33 GMT -7
Myles,
I just received my 65 Amps Empire. Great amp. I'd like to get some backup tubes for it. I was thinking of sticking with JJ 6V6s because that's whats in it. I see you like the Russian Tung Sols. Would they be fine in the Empire or should I stick with the JJs?
Would you be so kind as to recommend some preamp tubes as well? I'm not sure what is in V1-V5 as they all have the rubber covers. Especially interested in what you might recommend for V1. I was gonna go with a 12ax7lps for the PI.
Thanks, Doug
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Post by myles on Mar 3, 2011 11:13:55 GMT -7
Myles, I just received a used KT-45. Can you suggest some power tubes and a phase inverter from mike at KCANOSTUBES? She is tube rectified but I already have a NOS one on hand to replace the sovtek. Also what rating should I ask for and where do I need to bias the tubes at? Thanks Lonny Lonny, Tubes are really a personal taste issue but ... what I think works great would be .... A neutral EF86 in V1 (and keep a spare). I used to love a Mullard as it was a bit darker but a Tesla or Dario miniwatt are nice too and not as pricy. The GEC is terrific. In V2 I like a medium or long plate 12AX7. Any of the old NOS RCA, GE, Sylvania tubes from the 50s and 60s are great. Most of these also have proper plate current which is what you want to drive the output tubes properly. Output tubes ... if you go the new route here use a real Svetlana winged C from St. Petersburg. Mike at KCA has these at www.kcanostubes.com/content/sed-winged-c-el34-singles-pairs-quartets-sale-price He currently has these on sale and the price has been going up very fast. Go for Medium rating or numbers as that is a spec tube. Numbers higher or lower indicate a tube with problems in production. Set the bias at 36-38mA as a good starting point using a bias tool or bias probe. If you send me the B+ plate voltage I will provide you a little chart for the proper bias range of your particular amp.
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Post by myles on Mar 3, 2011 11:30:04 GMT -7
Myles, I just received my 65 Amps Empire. Great amp. I'd like to get some backup tubes for it. I was thinking of sticking with JJ 6V6s because that's whats in it. I see you like the Russian Tung Sols. Would they be fine in the Empire or should I stick with the JJs? Would you be so kind as to recommend some preamp tubes as well? I'm not sure what is in V1-V5 as they all have the rubber covers. Especially interested in what you might recommend for V1. I was gonna go with a 12ax7lps for the PI. Thanks, Doug Doug, Stick with the tubes that are in the amp. Different 12AX7s are used in various positions based on their characteristics. In some of the 65 Amps stuff you will see an amp with three 12AX7s and all three are different but very specific. There really is no right and wrong but after hundreds of hours of Dan and Mike tweeking things in development they came to choose the tubes that are in the amp. The rubber covers are not to hide the tubes but are there to help reject physical microphonics. Factory tubes: V1 (closer to the front panel not in the row with the others - JJ803S long plate V2, V3 Sovtek 12AX7LP (not LPS) V4 Three different tubes are used here. This is a "season to taste" position and depending on how Mike or Joe feel on that particular day this can differ. Tubes used in V4 can be a Sovtek 12AX7LP, JJ803S or a Tung Sol Reissue 12AX7 short plate. V5, phase inverter, is a JJ803S Output tubes are the JJ 6V6 as they are agressive and sturdy. If you want a replacement tube set just contact the folks at 65 and they can supply a set. You can get all of these tubes from a lot of great vendors as well. If you get them from 65 ask them to have me trace them which I would be happy to do at no charge if I am in the shop as you are on this forum.
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Post by Deleted on Mar 3, 2011 12:58:48 GMT -7
Doug, Stick with the tubes that are in the amp. Different 12AX7s are used in various positions based on their characteristics. In some of the 65 Amps stuff you will see an amp with three 12AX7s and all three are different but very specific. There really is no right and wrong but after hundreds of hours of Dan and Mike tweeking things in development they came to choose the tubes that are in the amp. The rubber covers are not to hide the tubes but are there to help reject physical microphonics. Factory tubes: V1 (closer to the front panel not in the row with the others - JJ803S long plate V2, V3 Sovtek 12AX7LP (not LPS) V4 Three different tubes are used here. This is a "season to taste" position and depending on how Mike or Joe feel on that particular day this can differ. Tubes used in V4 can be a Sovtek 12AX7LP, JJ803S or a Tung Sol Reissue 12AX7 short plate. V5, phase inverter, is a JJ803S Output tubes are the JJ 6V6 as they are agressive and sturdy. If you want a replacement tube set just contact the folks at 65 and they can supply a set. You can get all of these tubes from a lot of great vendors as well. If you get them from 65 ask them to have me trace them which I would be happy to do at no charge if I am in the shop as you are on this forum. Thank you very much. As always, you are the best.
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Post by Lonny Caughron on Mar 3, 2011 18:27:00 GMT -7
Thanks Myles. I'll let you know when I get them in.
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Post by Scott on Mar 6, 2011 10:31:15 GMT -7
Myles, I was looking around your site, and was wondering if you had ever posed any words of wisdom, or your general impression, of NOS 7189 tubes. I have a set of NOS RCA 7189's and was wondering what you might think of them.
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Post by myles on Mar 6, 2011 11:38:55 GMT -7
Myles, I was looking around your site, and was wondering if you had ever posed any words of wisdom, or your general impression, of NOS 7189 tubes. I have a set of NOS RCA 7189's and was wondering what you might think of them. These are terrific. Think of an EL84 that can tolerate much higher voltages. The plate current output is the same as an EL84 @ 48mA at standard book voltages but the design voltage max on the plate is 400. On the grid 300. Plate Dissipation ............................. 12 W Grid No. 2 Dissipation ........................ 4 W (16 watts total) The EL84 / 6BQ5 Plate Voltage ....................... 300 V Grid No. 2 Voltage ................ 300 V Plate Dissipation ................... 12 W Grid No. 2 Dissipation ............. 2 W (14 watts total) Bottom line ... they will run stronger. You also have more output by at least two watts (in pentode mode the screen and plate wattage is combined) Most amps run EL84 tubes beyond spec at over 300 plate volts in most cases. The 7189 handles these voltages with ease and the tube is more reliable as it is generally running well within its intended design range. They also sound outstanding.
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Post by Scott on Mar 6, 2011 12:21:12 GMT -7
Thank you sir!!
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Post by jimmysmith on Mar 13, 2011 17:02:59 GMT -7
hi myles, i pm'd you and you asked me to post here, so i will, i have heard you talk about how poor quality the sovtek gz34 rectifiers are. i have owned several dr z amps and more than one has come with a sovtek, however, an rx jr came with a NOS 5y3, i realize the best way to produce amps in quantity when you have production quotas is" play test the amp at the shop with tubes that sound good, then have a customer service guy send you replacement tubes that go bad within the 90 day warranty period" in the last few years i have owned a new rx jr, ezg50, and a mazerati gt, all with at least a real noisy preamp tube, or bad set of el84s after about an hour of play time. why start off with sovteks? because other brands of rectifiers are too hard to get or jsut as bad as sovteks? i have been fortunate to be able to replace all of my gz34s with something other than sovtek, and would even use a weber copper cap instead. just how bad are sovtek recitifiers, the prime one used in almost all amps, other than the jj tesla..?
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Post by myles on Mar 13, 2011 17:15:50 GMT -7
hi myles, i pm'd you and you asked me to post here, so i will, i have heard you talk about how poor quality the sovtek gz34 rectifiers are. i have owned several dr z amps and more than one has come with a sovtek, however, an rx jr came with a NOS 5y3, i realize the best way to produce amps in quantity when you have production quotas is" play test the amp at the shop with tubes that sound good, then have a customer service guy send you replacement tubes that go bad within the 90 day warranty period" in the last few years i have owned a new rx jr, ezg50, and a mazerati gt, all with at least a real noisy preamp tube, or bad set of el84s after about an hour of play time. why start off with sovteks? because other brands of rectifiers are too hard to get or jsut as bad as sovteks? i have been fortunate all of my gz34s with something other than sovtek, and would even use a weber copper cap instead. just how bad are sovtek recitifiers, the prime one used in almost all amps, other than the jj tesla..? Jimmy, It is hard for amp makers to have a steady supply of good tubes and rectifiers for production numbers of amps. The Sovtek is not great but it is more reliable than the Chinese. The JJ is hit and miss but generally the most reliable .... this month. There are a lot of 5Y3 NOS rectifiers out there at reasonable cost. Not so much with a GZ34 / 5AR4, but an NOS GZ34 will last a long time and is worth the money. I generally keep a solid state plug in as a backup. The reason amp makers use what they use is cost. The stuff works most of the time. The cost of an amp would be MUCH higher if NOS tubes were used or if new production tubes were tested, traced and burned in.
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Post by jimmysmith on Mar 13, 2011 17:54:57 GMT -7
i understand, thanks myles. i think i am going to go with a couple nos 5v4,s,, funny about those jj tesla gz34s when they came out, everyone was touting them, i tried a couple in about 3 z's i had, and got immediate loud noise and problems,, stopped using them for a while, then i bought a used other brand amp with one in it and it is fine. i see what you mean, one month they are good , the next , not.
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Post by myles on Mar 22, 2011 13:46:26 GMT -7
i understand, thanks myles. i think i am going to go with a couple nos 5v4,s,, funny about those jj tesla gz34s when they came out, everyone was touting them, i tried a couple in about 3 z's i had, and got immediate loud noise and problems,, stopped using them for a while, then i bought a used other brand amp with one in it and it is fine. i see what you mean, one month they are good , the next , not. JJ goes up and down. The last few batches of their 6V6 and 7591 tubes have shown a lot of physical microphonic issues. The JJ803S long plate dropped about 20% in gain and went up about 35% in plate current output due to low plate resistance. This is not a good thing in 12AX7 type tubes as a side note.
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Post by detuned on Mar 23, 2011 11:23:26 GMT -7
Myles - tool your advice regarding my Remedy, although I didn't go all NOS (tax season).
JJ ECC803s in V1, Tung Sol 12AX7 in V2, & NOS JAN Phillips 5751 in V3 to tame the output. I haven't got 'round to replacing the 6V6s yet (again, tax season!).
MUCH improved. The 803s is full of long plate goodness, lots of sparkle & character, & the 5751 smooths out the amp nicely. Almost all the hardness & "sproinginess" is gone, & my strat sounds almost Jim-like. If only I had the chops to back it up!
Many thanks for your input. You are a scholar & a gentleman!
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Post by myles on Mar 23, 2011 14:38:08 GMT -7
Myles - tool your advice regarding my Remedy, although I didn't go all NOS (tax season). JJ ECC803s in V1, Tung Sol 12AX7 in V2, & NOS JAN Phillips 5751 in V3 to tame the output. I haven't got 'round to replacing the 6V6s yet (again, tax season!). MUCH improved. The 803s is full of long plate goodness, lots of sparkle & character, & the 5751 smooths out the amp nicely. Almost all the hardness & "sproinginess" is gone, & my strat sounds almost Jim-like. If only I had the chops to back it up! Many thanks for your input. You are a scholar & a gentleman! You are really welcome. The Remedy really loves a 5751 in the P.I. position for a few reasons. 1. Smoother than most 12AX7s and yields more clean headroom if desired. 2. A bit higher plate current when running at the same sort of voltage and bias parameters of a 12AX7 even though the gain is a bit less. The plate current controls / drives the output section a bit more accurately than a 12AX7 (most current production ones anyway). 3. The Remedy is solid state rectified and a phase inverter with a bit slower rise time is preferred by many rock and blues players. Then again, if you were a heavy metal maniac the Remedy might not be a first choice for an amp. Bottom line, the Remedy is a very cool amp as it comes from the factory but from my point of view you took it up another notch in coolness. Not the greatest shot in the world, taken via cell, but this is Brad Paisley's Remedy and the settings that Jody Harris uses: and a bit more .... In the shot below, the blurr is Jody Harris. He plays the Remedy seen in the other shots in the Brad Paisley group.
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Post by Ben on Mar 23, 2011 14:49:11 GMT -7
Myles - Hope this finds you well. I've been on a search for a NOS PI for my Maz NR as I find it gets way overlooked in all of preamp tube discussions. Tried a balanced (1600 both sides) NOS 5751 RCA Blackplate and although it smoothed the power section quite a bit, it obviously doesn't have the drive of a regular (well, as consistent as they can be that is) 12AX7 such as the Sovtek LPS. Would you have any recommendation for brands and models for both a 12AX7 and 12AT7? I know TC plays into play, but I am not quite sure how it will affect the amp. I sure would not want to loose any touch sensitivity, clarity or well, the magic mojo the Maz NR has I can only assume that the 12AT7 will show more drive/gain than the 5751, but how much more is key. I don't mind sticking with a 12AX7, but it's gonna have to be one that is alot better sonically than the current production. I don't mind spending a tad more, but won't be putting a Telefunken in there either if I'll be swapping it out every other power tube swap! Looking forward to your input on this! Tks again Ben
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Post by myles on Mar 23, 2011 15:19:41 GMT -7
Myles - Hope this finds you well. I've been on a search for a NOS PI for my Maz NR as I find it gets way overlooked in all of preamp tube discussions. Tried a balanced (1600 both sides) NOS 5751 RCA Blackplate and although it smoothed the power section quite a bit, it obviously doesn't have the drive of a regular (well, as consistent as they can be that is) 12AX7 such as the Sovtek LPS. Would you have any recommendation for brands and models for both a 12AX7 and 12AT7? I know TC plays into play, but I am not quite sure how it will affect the amp. I sure would not want to loose any touch sensitivity, clarity or well, the magic mojo the Maz NR has I can only assume that the 12AT7 will show more drive/gain than the 5751, but how much more is key. I don't mind sticking with a 12AX7, but it's gonna have to be one that is alot better sonically than the current production. I don't mind spending a tad more, but won't be putting a Telefunken in there either if I'll be swapping it out every other power tube swap! Looking forward to your input on this! Tks again Ben Ben,
I will copy and paste your commentary so I can address each point hopefully....I've been on a search for a NOS PI for my Maz NR as I find it gets way overlooked in all of preamp tube discussions. ....... Not too hard to find. Some vendors I use and prefer are below. There are other great vendors out there but these folks are who I use personally and who I recommend to my clients. They can all match tubes very nicely:www.kcanostubes.comwww.dougstubes.comwww.tubedepot.comTried a balanced (1600 both sides) NOS 5751 RCA Blackplate and although it smoothed the power section quite a bit, it obviously doesn't have the drive of a regular (well, as consistent as they can be that is) 12AX7 such as the Sovtek LPS. ..... The gain on the 5751 will be lower. The amp will be less agressive. Yes, it will smooth things out. A proper spec 12AX7LPS will have proper drive current. In the end there is no right or wrong. It is a matter of personal taste and preference.Would you have any recommendation for brands and models for both a 12AX7 and 12AT7? I know TC plays into play, but I am not quite sure how it will affect the amp. I sure would not want to loose any touch sensitivity, clarity or well, the magic mojo the Maz NR has ...... Transconductance is something of a false indicator. For a phase inverter I don't look at TC or gain. I look at plate current and plate resistance. If the plate resistance is within spec (62.5K at 250 plate and 2 volt bias) then then tube has a good chance of being excellent. Since the phase inverter drives the output tubes I look for current rather than TC or gain.
I also look for rise time with a curve tracer. Depending on the application and style of the player I may desire a faster (tighter) or slower (looser) response. Chad Weaver (Brad Paisley) has a drawer of tubes with different characteristics that he swaps in and out of amps depending on how Brad feels in a given venue.
Look at the old Groove Tubes 12AX7M reissue, the later production runs had the highest TC of any 12AX7 ever made. It also had the highest plate current. But .... the plate resistance was half of design spec, or less, in most tubes. This gives very high TC, high plate current (tube runs very hot) but VERY low true gain in circuit and there is more crosstalk between the A and B sides of the tube. A classy and articulate description of this would be: Crappy tube.I can only assume that the 12AT7 will show more drive/gain than the 5751, but how much more is key. I don't mind sticking with a 12AX7, but it's gonna have to be one that is alot better sonically than the current production. .....A 12AT7 has about the same actual gain as a 5751 but has about ten times the plate current at 10mA vs 1.2mA of the 5751. It also has a very fast rise time. In Fender tolex era amps it was picked for clean headroom and good drive current to push a quad of 6L6 tubes. A simple blackface or silverface trick to make a Fender more agressive is to swap the stock 12AT7 with a 12AX7. Plug and play ... no adjustment needed..... Side note ... a 5751 is a wonderful tone generator (front end tube) but a 12AT7 is not. The gain is about the same but a 12AT7 is harsh.I don't mind spending a tad more, but won't be putting a Telefunken in there either if I'll be swapping it out every other power tube swap! ..... Telefunken 12AX7s are not a good choice at any cost for a phase inverter from my point of view. Most have very low plate current, very low transconductance. But, with plate resistance of 80-100k which was common, their true gain in circuit was over 100 in many cases. They are the highest gain 12AX7 / ECC83 tubes made. Because of the high gain they were very responsive but the high gain made them more prone to physical microphonics. .... One more side note on PI replacement.... 6L6s are hard to drive. So are 6550s and KT88s. EL34s are not too bad but amps with master volume controls can tax the phase inverter on EL34 amps depending on setting and depending on the master volume being pre or post an area of the cicruit. EL84 tubes are very easy to drive. I the case of your MAZ the PI will last many output tube changes. I have seen no change in specs on PIs in MAZ, Mazerati, or other Dr. Z EL84 based amps over a dozen output tube changes unless the PI had some sort of quality defect issue built into the tube originally.Looking forward to your input on this! ........ Well, there is some of my thinking. If you have other questitons or want to talk more feel free to post.Myles
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Post by Ben on Mar 23, 2011 16:45:39 GMT -7
Myles, sir, once again you've manage to make me quite a bit smarter. And I thank you for the time taken to share it all once again with all of us. I've been getting my NOS tubes from Brent Jessee @ www.audiotubes.com. I have heard very good things from all of the vendors you have also listed. I have been going back and forth in V1 in the Maz, between some of the 5751 RCA Blackplate that I have and the one Mazda 12AX7 that I also have. Great, great tube - very rare also I am told. Got it for something like $30 if I recall correctly. On topic though - I prefered the caracteristics of the 5751 in V1 and in the PI. I've tried one in both at the same time and the amp came a too tammed for what I had in mind. Knowing a proper speced 12AT7 would have the same gain as a 5751, it would not be the tube I'm looking for - you've just saved me the purchase of a NOS tube that I wouldn't have used elsewhere. Will be providing some feedback when I do get my hands on a new PI Tks again! Ben
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