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Post by myles on Jun 3, 2012 17:52:34 GMT -7
Hi Myles- I have a question regarding the 12AT7 tube in my Maz18 Jr reverb circuit. Mine needs replacing , and I was considering buying a JAN Philips NOS unit. However in my tube stash I have a NOS GE 5751. I was thinking of subbing the 5751 for the 12AT7. Is this a bad idea , any nasty side effects from doing something like this? Thanks for your time! The 5751 and 12AT7 have about the same gain or Mu, 60-70 but the transconductance of a 5751 is about 1200 vs 5500 of a 12AT7 and the plate current of a 5751 is about 1.0mA, about ten times less than a 12AT7. You would not have enough plate current with a 5751 to properly drive the reverb tank. But .... it might be something you might like. No harm will come from trying this so in the end, feel free to try it .... and if you like it perhaps it was a fun idea. Feel free to report back with your personal discoveries.  |
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Post by BritInvasion on Jun 3, 2012 18:23:00 GMT -7
Thanks so much for your input Myles! I think I'll give it a try and I'll post the results.
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Post by mickey on Jun 8, 2012 14:21:49 GMT -7
Hi...is a 5AR4 exactly the same rectifier tube as a GZ34? I thought they were the same until I found some stuff on the web which suggests that a 5AR4 will give a bit more sag than a GZ34. I'm mostly talking NOS here. Thanks!
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Post by myles on Jun 8, 2012 14:46:13 GMT -7
Hi...is a 5AR4 exactly the same rectifier tube as a GZ34? I thought they were the same until I found some stuff on the web which suggests that a 5AR4 will give a bit more sag than a GZ34. I'm mostly talking NOS here. Thanks! They are the same. GZ34 is the European designation. On my GAB website there is a section on rectifiers and their performance. |
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Post by mickey on Jun 9, 2012 1:43:27 GMT -7
Great, thanks Myles!
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Post by Michael Bartee on Jun 12, 2012 10:24:47 GMT -7
Myles,
Due to the current state of tube production and what seems like declining quality control.
Most of us will have NOS 12AX7, NOS 5751 and NOS 5Y3 as well a saving NOS EL84's for high profile shows/sessions. Would you give your recommendation on what current production EL84, 12AX7,5751 and 5Y3 you would choose for the Carmen Ghia for day to day use? Rattle is an issue with EL84's especially in combo cabinets, are some less pron to rattle?
You are a wealth of information and I thank you for taking the time to share your knowledge and help those of us as we travel our quest for tone.
Thanks very much,
Michael Bartee
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Post by myles on Jun 12, 2012 12:56:06 GMT -7
Myles, Due to the current state of tube production and what seems like declining quality control. Most of us will have NOS 12AX7, NOS 5751 and NOS 5Y3 as well a saving NOS EL84's for high profile shows/sessions. Would you give your recommendation on what current production EL84, 12AX7,5751 and 5Y3 you would choose for the Carmen Ghia for day to day use? Rattle is an issue with EL84's especially in combo cabinets, are some less pron to rattle? You are a wealth of information and I thank you for taking the time to share your knowledge and help those of us as we travel our quest for tone. Thanks very much, Michael Bartee Michael, I will start with the rectifier. NOS 5Y3 rectifiers are very reliable and inexpensive. They are much less expensive than a GZ34/5AR4. Keep one in the amp and keep a spare and you will be set. V2, the phase inverter, 5751. I would not use any new production piece. They are little more than 12AX7 tubes that did not make the cut. Again, an NOS piece would be the route I would go. V1, the 12AX7/ECC83/7025. Totally user taste and preference. I prefer long plate tubes in the Carmen Ghia and in my own I have a Telefunken long smooth plate. The old Ei is a great tube BUT ... the can go microphonic easily with no warning. Some of the medium plate NOS pieces are terrific such as the RCA and Sylvania tubes that were used in the sixties Fender amps. The Raytheon from the past is spectacular. If I had an extra I would prefer it over a Telefunken in my own CG as they are less pricey but also sound nicer to my own ears. Output tubes - I still like the JJ EL84S for every day use but their quality has declined in regard to physical rattle. So ... trust your vendor to supply tubes that at least start out to be rattle free and buy matched quartets so you will have a nice backup set. Here are two links to some 5751 info that I wrote in the past: la-economy.blogspot.com/2010/10/vacuum-tube-series-5751-tung-sol.htmlla-economy.blogspot.com/2010/08/music-related-question-on-gt-5751m.htmlHope this answered some of your questions. |
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Post by electricflag on Jun 21, 2012 12:51:13 GMT -7
Myles.
Just a comment on biasing EL-34 powered amps on the cold side.
Last week I was reading your Guitar Amp Blueprinting site about Dr. Z amps. There was interesting note on biasing EL-34 powered amps on the cold side. Not just Z's, but also Marshalls and Hi-Watts.
So, I rebiased a 50 Watt EL-34 powered Marshall of mine to 34mA. The results was just like you said - It smoothed out the harshness. I was pleasantly surprised!
Thanks for the tip!
-Rick
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Post by myles on Jun 21, 2012 13:26:46 GMT -7
Rick, You are quite welcome. Happy playing .... and your amp will run cooler and have longer tube life. Hot=harsh Cold=grainy Thankfully there is a middle ground where there is a nice balance. Funny, it seems to generally fall where the tube makers originally said it should be |
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Post by Deleted on Jun 21, 2012 17:40:07 GMT -7
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Post by myles on Jun 21, 2012 19:46:26 GMT -7
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Post by Deleted on Jun 22, 2012 12:46:47 GMT -7
Thanks, Myles. You are always a great help. And what a great answer, too! |
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Post by myles on Jun 22, 2012 13:40:38 GMT -7
Thanks, Myles. You are always a great help. And what a great answer, too! You are quite welcome. |
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Post by bigben55 on Jun 23, 2012 10:19:22 GMT -7
Reposted for Myles from the Z28 page. Is this normal?
I just got my Z28 back from the tech after getting new tubes and bias. It had JJ 6L6S tubes in it, and they rattled, and being as they were in it when I bought it used in February and I didnt know how many hours were on them(and I've played the hell out of it since getting it!) figured it was time. I got a matched quartet of Tungsol RI 6V6's from Dougs Tubes, so I got two spares that I can plug and play. The preamp tubes were new 2 months ago(good ones-a NOS Tesla EF806S hi grade and a JAN GE 5751 from KCA).
I have read the JJ 6V6s are more like 6L6s. My tech confirmed that, stating NOT to use them anymore, since he biased the Z28 for the Tungsols, and that using the JJ's would be like biasing the amp VERY VERY hot. No biggie. I bought the Tungsols because I wanted 6V6s that actually sounded like 6V6s, and they were highly recommended.
It's like a whole new amp! Not better or worse, just different. All my knob settings for my 3 different guitars needed mass tweaking. The amp now is a little less loud(tech told me it would be), but the character of the overdrive is much different. Less punchy, more wide open and gushy. It's not AS easy to clean the amp up with the guitars volume knob. #1, the full on lead tones sound better, but the overall clean headroom is reduced. And it's brighter overall.
I ask this because this is my first Z. I've owned many amps, and have changed tubes in many amps, but NEVER has a tube change been nearly as drastically tone altering. Is this normal for Dr.Zs, specifically the Z28? I am not complaining, the amp sounds awesome, and no tube rattle. MUCH better with my 335. I feel like it sounds how it SHOULD sound now. I posted a thread months ago asking for settings, tried some that others swore by and didn't like them. NOW I know why: it was the tubes! So I'll ask again for settings, because I really need to re-tweak everything.
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Post by bigben55 on Jun 23, 2012 10:21:27 GMT -7
Typo. It had JJ6V6S's in it.
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Post by myles on Jun 23, 2012 10:35:54 GMT -7
Reposted for Myles from the Z28 page. Is this normal? I just got my Z28 back from the tech after getting new tubes and bias. It had JJ 6L6S tubes in it, and they rattled, and being as they were in it when I bought it used in February and I didnt know how many hours were on them(and I've played the hell out of it since getting it!) figured it was time. I got a matched quartet of Tungsol RI 6V6's from Dougs Tubes, so I got two spares that I can plug and play. The preamp tubes were new 2 months ago(good ones-a NOS Tesla EF806S hi grade and a JAN GE 5751 from KCA). I have read the JJ 6V6s are more like 6L6s. My tech confirmed that, stating NOT to use them anymore, since he biased the Z28 for the Tungsols, and that using the JJ's would be like biasing the amp VERY VERY hot. No biggie. I bought the Tungsols because I wanted 6V6s that actually sounded like 6V6s, and they were highly recommended. It's like a whole new amp! Not better or worse, just different. All my knob settings for my 3 different guitars needed mass tweaking. The amp now is a little less loud(tech told me it would be), but the character of the overdrive is much different. Less punchy, more wide open and gushy. It's not AS easy to clean the amp up with the guitars volume knob. #1, the full on lead tones sound better, but the overall clean headroom is reduced. And it's brighter overall. I ask this because this is my first Z. I've owned many amps, and have changed tubes in many amps, but NEVER has a tube change been nearly as drastically tone altering. Is this normal for Dr.Zs, specifically the Z28? I am not complaining, the amp sounds awesome, and no tube rattle. MUCH better with my 335. I feel like it sounds how it SHOULD sound now. I posted a thread months ago asking for settings, tried some that others swore by and didn't like them. NOW I know why: it was the tubes! So I'll ask again for settings, because I really need to re-tweak everything. I am not sure of what the question here might be but a JJ 6V6 and a Tung Sol Reissue 6V6 will sound and feel different. The Z28 is a grid biased amp and will generally have longer tube life than a cathode biased amp like a Remedy. You need to rebias grid biased amps when changing or replacing tubes. |
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Post by bigben55 on Jun 23, 2012 10:44:58 GMT -7
Sorry Myles. My amp sounds WAY different than it did. My question is, making that tube swap and bias (65%) , to be expected to make such a huge tonal difference? Never is 20 years of owning tube amps.has a tube change been so noticeable.
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Post by myles on Jun 23, 2012 14:39:31 GMT -7
Sorry Myles. My amp sounds WAY different than it did. My question is, making that tube swap and bias (65%) , to be expected to make such a huge tonal difference? Never is 20 years of owning tube amps.has a tube change been so noticeable. I think that output tubes on a Z-28, which is a very articulate amp, does make a very big difference. Happy playing! |
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Post by randalp3000 on Jul 3, 2012 9:10:25 GMT -7
Myles, I have a story and a question.
I picked up an Amplitrex awhile ago and I've been using my #3 backup original Rx, other 2 need cap jobs. I've also started bringing my Wreck for a backup to the Rx. The Wreck has been acting a bit weird and I wasn't too sure of the Rx so I went and checked all the tubes. The ones in the Wreck tested all very good, 20% or better to spec. The Rx, V1 and V2 were a bit on the weak side so I put a NOS Ay7 in V1 and a very good Eh in V2 and the phase inverter tested VG so I left it, Sovtec lps.
Well I get to my gig Sat night and the Rx is completely dead, I found out last night the PI was completely dead, no current or tc, nothing on both sides. It went from working and testing great to dead in 3 days with no use.
The Wreck has had an intermittent problem that I was wondering if you've ever run into with a tube. The amp would go from sounding great like it should to dropping about 30% in volume with all the top end gone. This would continue to happen all night at a four hour gig. It would sound great for a few songs then it would fade for awhile and come back again later.
Have you ever experienced anything similar that was tube related?
thanks for your time and I apologize for rambling.
randy
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Post by myles on Jul 3, 2012 9:44:21 GMT -7
I will try to reply in the body of your message .... Myles, I have a story and a question. I picked up an Amplitrex awhile ago and I've been using my #3 backup original Rx, other 2 need cap jobs. I've also started bringing my Wreck for a backup to the Rx. .... so far I am slightly lost but if you are saying you bought an AT-1000 that is ultra cool. The Wreck has been acting a bit weird and I wasn't too sure of the Rx so I went and checked all the tubes. The ones in the Wreck tested all very good, 20% or better to spec. The Rx, V1 and V2 were a bit on the weak side so I put a NOS Ay7 in V1 and a very good Eh in V2 and the phase inverter tested VG so I left it, Sovtec lps. ...... One issue with tube testers is that most do not check noise, microphonics or sonic issues. The AT-1000 takes something of a snapshot when it runs it's test. If there is something odd going on with the tube it may not catch that problem. Well I get to my gig Sat night and the Rx is completely dead, I found out last night the PI was completely dead, no current or tc, nothing on both sides. It went from working and testing great to dead in 3 days with no use. ..... You could have just had a tube die a sudden death especially if it was a current production tube. You could have a component that shorted or something that caused the tube to die so you may want to check voltages and have a quick look around. The Wreck has had an intermittent problem that I was wondering if you've ever run into with a tube. The amp would go from sounding great like it should to dropping about 30% in volume with all the top end gone. This would continue to happen all night at a four hour gig. It would sound great for a few songs then it would fade for awhile and come back again later. ........ I would check all the tubes and the power supply in the amp. Have you ever experienced anything similar that was tube related? .... Yes, but it can be other things as well. thanks for your time and I apologize for rambling. randy .... No problem ... My replies are within your writing prefaced with ....... |
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Post by randalp3000 on Jul 3, 2012 10:01:03 GMT -7
thanks for your time Myles.
yes it's an at-1000 and it is a glorious beast, I can be a bit obsessive compulsive
I also use a Maxipre for measuring the noise level and listen for microphonics and other noises.
The snapshot thing makes a lot sense
I'll try some new tubes first and let it run for awhile, It would be much easier if it wasn't intermittent and time is something I don't have much of.
thanks for your time, have a great 4th....
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Post by myles on Jul 3, 2012 15:44:02 GMT -7
thanks for your time Myles. yes it's an at-1000 and it is a glorious beast, I can be a bit obsessive compulsive I also use a Maxipre for measuring the noise level and listen for microphonics and other noises. The snapshot thing makes a lot sense I'll try some new tubes first and let it run for awhile, It would be much easier if it wasn't intermittent and time is something I don't have much of. thanks for your time, have a great 4th.... Great test gear. You are set for life. With the AT-1000 you could provide a service where people bring tubes to you and for $5.00 a tube you test them and give them the printout sheet. That is much more than most other folks do even if they wanted. |
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Post by muzacman02 "Jamie" on Jul 6, 2012 19:46:12 GMT -7
HEY MYLES I bought some NOS like unused in box GE EL84's off Ebay cheap, anything good with these? I also had a good deal on some Sylvania labeled EL84's are these very delightful for my Stangray, Thanks for the suggestions. Jamie
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Post by myles on Jul 6, 2012 20:11:32 GMT -7
HEY MYLES I bought some NOS like unused in box GE EL84's off Ebay cheap, anything good with these? I also had a good deal on some Sylvania labeled EL84's are these very delightful for my Stangray, Thanks for the suggestions. Jamie Both of these are terrific and will last much longer and IMHO sound much nicer than any current EL84 offerings. Hopefully they are in nice matched sets but generally, good NOS tubes were pretty darn closely matched as they met specs much more closely than tubes made today. Happy playing. |
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Post by skeets1640 on Aug 20, 2012 11:44:35 GMT -7
Myles from reading the forums I know you are the tube expert around here. I just picked up the now discontinued Orange Rocker 30 for a good price and am quite pleased with the amp. It is a very good aggressive hard rock amp in the vein of a JCM 800 but with a little less treble and more of a lower midrange punch rather than the upper mid range punch of the JCM 800. It came stocked with JJ's (power and pre) which sound ok but are a little harsh to my ear. What would you say would be the best choice for EL34's in an amp like this? I would like to look at mostly newer made tubes but would be willing to check out NOS that are under $100 a pair. What do you think of the SED Winged =C= EL34? Thats what I was leaning towards. Also what would you go with for reasonably priced 12ax7's? It has three 12ax7's for a 3 stage gain. How do the winged C 12ax7's from st. petersburg sound? Dougs tubes has them for 20.00 per tube.
Again i'm looking for a slightly warmer slightly darker tone than the JJ's are giving me. Sorry for the long message. I really appreciate any advice you could give. Thank you for your time. Cheers!
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Post by myles on Aug 20, 2012 14:39:07 GMT -7
Winged C for the output tubes.
Not =C= for the preamp.
For the preamp I would go with something else. Then again, it is a personal taste matter but I would go medium plate NOS such as RCA, Sylvania, or GE. But again, that is my personal preference. NOS will not only sound better, be more articulate but also last MUCH longer.
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Post by skeets1640 on Aug 21, 2012 5:30:05 GMT -7
I have an RCA 12ax7 and RCA 6v6 in my Supro 1606 and they sound fantastic. Thanks for the suggestion Myles. Cheers!
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Post by skeets1640 on Aug 21, 2012 6:23:32 GMT -7
Myles MIke a Kcanos recommended NOS Tesla's at $50 a pop. Would you think these would be a good choice for the 12ax7's? Thanks
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Post by myles on Aug 21, 2012 9:50:27 GMT -7
Myles MIke a Kcanos recommended NOS Tesla's at $50 a pop. Would you think these would be a good choice for the 12ax7's? Thanks It is really a matter of personal taste. I am not a big fan of the Tesla 12AX7 or the later tubes by JJ when the factory was shut down and resurrected. Most of the tubes are a bit mid rangy for my taste but let me repeat ... MY taste. I prefer something more vintage and smooth with less of an edge. Rockers like that edge, modern rockers (80s and later). Then again, for your amp which is a rocker's amp and not a blues players amp Mike may be right on the money with the Tesla. The Teslas are very well made and will last many years so the cost is actually pretty low if you compare them to a $14.95 tube that will last a fraction of the time. |
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Post by Matt on Aug 28, 2012 8:06:45 GMT -7
Hi Myles,
I'm currently playing a Maz 38 NR with NOS Jan GE 7025 tubes in V1 and V2 along with a NOS Jan GE 5751 in the PI.
As much as I like the tone, I'm looking for as much additional clean headroom as possible and I'm considering putting 5751 tubes in V1 and V2.
However, I have no idea which ones are best and also no idea what the differences are between the gray plates and black plates as well as the various makers (GE, Sylvania, etc.)
Also, what power tubes would you recommend to get the least amount of distortion from the power section?
Any advice on this is greatly appreciated.
Thanks!!
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