|
|
Post by myles on Sept 13, 2011 13:08:31 GMT -7
Once again thank you. How do you feel about the older EF86 / 6267 / 6J32P Svetlana tubes? I have one in my Ray at the moment and just got 4 more for $38 from the Ukraine. another side note; I have a London combo on the way that I traded a Matchless for, very excited to play it. you the man, rp The =C= Svetlanas can really range in quality. Their small signal tubes were always that way. Their 6L6 and EL34 tubes are some of the best around. But, when you get a good one they are fine and at $38 for 4 you may have found a nice deal. If you bought them from the Ukraine though then all bets are off as they could be tossed rejects that scammers are reselling. Hopefully they did not come from a salesman in the Ukraine. The Svetlana plant is in St. Petersburg as a side note. London combo on the way ... I think you will like it, haven't found many folks that don't love the amp. Matchless? Another amp I love. DC-30, Lightning, Clubman from the original days and just about all of their current lineup is cool stuff too that takes a beating on the road and hangs in there like a great amp should. Good luck on the EF86s. Hope they are all good ones. Try them all. Just because something is new it does not mean it does not have issues. You don't want spares that you can't count on when you need them. |
|
|
|
Post by myles on Sept 17, 2011 16:26:19 GMT -7
|
|
|
|
Post by randalp3000 on Sept 22, 2011 16:26:44 GMT -7
So I got me a MaxiPreamp tube tester a couple of days ago for my shop and to help me along my journey. A few late nights and many hours later I came up with a spreadsheet of my findings of almost 40 tubes. It starts off with an amazing Mullard I found in my box of old tubes and a NOS GE 12AX7 from CE Dist.(made in Italy) for a reference. These are the results of the current tubes I have in stock at the moment. The microphonic tests are very subjective and I commented on them in a manor I could understand.
Please look it over and share your thoughts and opinions.
thanks
rp
|
|
|
|
Post by myles on Sept 23, 2011 9:49:41 GMT -7
So I got me a MaxiPreamp tube tester a couple of days ago for my shop and to help me along my journey. A few late nights and many hours later I came up with a spreadsheet of my findings of almost 40 tubes. It starts off with an amazing Mullard I found in my box of old tubes and a NOS GE 12AX7 from CE Dist.(made in Italy) for a reference. These are the results of the current tubes I have in stock at the moment. The microphonic tests are very subjective and I commented on them in a manor I could understand. Please look it over and share your thoughts and opinions. thanks rp I would like to know how gain was derived. It looks as if plate resistance was not taken into account in as the primary factor on calculation of true gain. Looking at the right side of the page at the JJ tube, the GM is over 2100. Spec is 1600 and this indicates something is not right with the tube in a basic way. If you could measure standing plate current you would discover on this tube that it was very high, well above the spec of 1.2mA. Plate resistance should be 62.5k and in this tube I would say that you would find a much lower value. This collection of data show a lot of great things such as how different the same type of tube (12AX7) can behave. Bottom line - tubes with a transconductance of above 1900 or so at 250 plate volts and 2 volt bias have something wrong with them in their assembly. The classic Telefunken can exhibit TC numbers in the 1200 range which is fine. The plate resistance of these tubes can be close to 100k. This keeps TC down. Plate current can be down in the 0.6mA range as well. The high plate resistance is the key here to great performance as these are the most gainy 12AX7 / ECC83 tubes ever produced. The high gain is also a reason why some can tend to be physically microphonic more often than many other tube types. These are the exception to the rule so to speak. If other tubes are below 1200 TC I generally consider them to be weak tubes, but they do have their uses. TC below 1000, toss them. They are shot or were garbage from the start. |
|
|
|
Post by randalp3000 on Sept 23, 2011 11:13:44 GMT -7
So I got me a MaxiPreamp tube tester a couple of days ago for my shop and to help me along my journey. A few late nights and many hours later I came up with a spreadsheet of my findings of almost 40 tubes. It starts off with an amazing Mullard I found in my box of old tubes and a NOS GE 12AX7 from CE Dist.(made in Italy) for a reference. These are the results of the current tubes I have in stock at the moment. The microphonic tests are very subjective and I commented on them in a manor I could understand. Please look it over and share your thoughts and opinions. thanks rp I would like to know how gain was derived. It looks as if plate resistance was not taken into account in as the primary factor on calculation of true gain. Thanks Myles Here's an e-mail response I got from them if it helps. Randal, the Maxi-Preamp measures transconductance in micro mhos, or thousandths of a mA. So 2.2 mA/V would read on the Pre as 2200 micromhos. Sorry about the confusion, I use both nomenclatures with this measurement, back and forth, and sometimes use the wrong one when referring to the Pre. The micromho nomenclature is the current accepted usage, as it is more accurate with 3 more digits of resolution. The Pre measures to single micromhos, and thus is extremely sensitive and highly accurate. We spent a lot of engineering time getting this exactly right. In fact all the measurements available on the Pre are like this - the noise test measures to -92 dB noise floor, or .000026 volts AC per dB. This is a very tiny signal! The biggest problem we have is isolating the measurement from RFI and other induced noise signals. The filaments on a standard 12AX7 turn out to be quite noisy thermally, for instance, who'd have thought. Or the windings of the power transformer for the unit throw out a small but present field that has to be accounted for. But that we did, and the unit has been very successful - most people wonder what they did before they had a Maxi-Preamp. |
|
|
|
Post by myles on Sept 23, 2011 11:26:48 GMT -7
I would like to know how gain was derived. It looks as if plate resistance was not taken into account in as the primary factor on calculation of true gain. Thanks Myles Here's an e-mail response I got from them if it helps. Randal, the Maxi-Preamp measures transconductance in micro mhos, or thousandths of a mA. So 2.2 mA/V would read on the Pre as 2200 micromhos. Sorry about the confusion, I use both nomenclatures with this measurement, back and forth, and sometimes use the wrong one when referring to the Pre. The micromho nomenclature is the current accepted usage, as it is more accurate with 3 more digits of resolution. The Pre measures to single micromhos, and thus is extremely sensitive and highly accurate. We spent a lot of engineering time getting this exactly right. In fact all the measurements available on the Pre are like this - the noise test measures to -92 dB noise floor, or .000026 volts AC per dB. This is a very tiny signal! The biggest problem we have is isolating the measurement from RFI and other induced noise signals. The filaments on a standard 12AX7 turn out to be quite noisy thermally, for instance, who'd have thought. Or the windings of the power transformer for the unit throw out a small but present field that has to be accounted for. But that we did, and the unit has been very successful - most people wonder what they did before they had a Maxi-Preamp. It is a nice piece of test gear. They make very nice stuff but to calculate actual gain I'd want to know the plate resistance they expect as this is critical to the calculation. I also would want to confirm the test voltages on the plate and the bias voltage. Your first test, the Mullard, appears to be a proper spec tube that meets design targets. |
|
|
|
Post by randalp3000 on Sept 25, 2011 16:27:06 GMT -7
Time for some fun.  |
|
|
|
Post by randalp3000 on Oct 5, 2011 21:40:04 GMT -7
Round 2 of of the preamp tube tests. This time I have some nice NOS RCA 12AY7's and some JAN Sylvania 5751's. The new tubes tested are 20 EH 12AX7's (these looked pretty good) and 10 EH 12AT7's.
Some observations so far is anything with a long plate seems to be prone to micro phonics. Most of the new 12AT7's would go into feedback extremely fast.
Please share your thoughts.
rp
Myles what would you consider to be a reject with these measurements and also in regards to micro phonics?
thanks
rp
|
|
|
|
Post by myles on Oct 6, 2011 8:38:50 GMT -7
Round 2 of of the preamp tube tests. This time I have some nice NOS RCA 12AY7's and some JAN Sylvania 5751's. The new tubes tested are 20 EH 12AX7's (these looked pretty good) and 10 EH 12AT7's. Some observations so far is anything with a long plate seems to be prone to micro phonics. Most of the new 12AT7's would go into feedback extremely fast. Please share your thoughts. rp Myles what would you consider to be a reject with these measurements and also in regards to micro phonics? thanks rp You have a very large spreadsheet and I am not sure what I should look at. Very time consuming. If you want to discuss a consulting rate for ongoing services we can talk. If something rattles toss it. If something howls or squeels toss it. If something is more than 25% or so off design spec and is a 9 pin signal tube toss it. |
|
|
|
Post by randalp3000 on Oct 6, 2011 10:12:29 GMT -7
Round 2 of of the preamp tube tests. This time I have some nice NOS RCA 12AY7's and some JAN Sylvania 5751's. The new tubes tested are 20 EH 12AX7's (these looked pretty good) and 10 EH 12AT7's. Some observations so far is anything with a long plate seems to be prone to micro phonics. Most of the new 12AT7's would go into feedback extremely fast. Please share your thoughts. rp Myles what would you consider to be a reject with these measurements and also in regards to micro phonics? thanks rp You have a very large spreadsheet and I am not sure what I should look at. Very time consuming. If you want to discuss a consulting rate for ongoing services we can talk. If something rattles toss it. If something howls or squeels toss it. If something is more than 25% or so off design spec and is a 9 pin signal tube toss it. Myles, the last thing I want to do is waste your time. You have been extremely helpful to me and others on this forum and I really appreciate your shared knowledge. I'm just trying to collect some data on new tubes with some old ones thrown in for comparison and share my findings with you and the other fine members on this site. Hopefully I can get some feedback from this community as well. Thanks for summing up what should be tossed, I haven't seen this addressed on the forum yet. If it has I missed it but now we all know. rp |
|
|
|
Post by myles on Oct 6, 2011 14:35:34 GMT -7
You have a very large spreadsheet and I am not sure what I should look at. Very time consuming. If you want to discuss a consulting rate for ongoing services we can talk. If something rattles toss it. If something howls or squeels toss it. If something is more than 25% or so off design spec and is a 9 pin signal tube toss it. Myles, the last thing I want to do is waste your time. You have been extremely helpful to me and others on this forum and I really appreciate your shared knowledge. I'm just trying to collect some data on new tubes with some old ones thrown in for comparison and share my findings with you and the other fine members on this site. Hopefully I can get some feedback from this community as well. Thanks for summing up what should be tossed, I haven't seen this addressed on the forum yet. If it has I missed it but now we all know. rp Feel free to ask questions on specific tubes or a few at a time and I will be happy to try to help. When I see a page of stuff it takes too much time and time is the only non-renewable resource  |
|
|
|
Post by Eddie on Oct 25, 2011 2:05:15 GMT -7
Myles,
I recently bought two pairs of EH EL84 tubes for my MAZ Jr. I like the sound of them fine, but I noticed they (both tubes equally in either pair) have a slight orange glow on the sides. Not "red plating" by any means, but the plates are definitely beginning to glow. They don't smell overly hot.
All my other pairs of power tubes have been JJ and none of those seemed to have glowing plates.
Is this normal for this tube in a MAZ Jr.?
I have checked it with a 5751 PI as well as a 12AX7 PI.
Thank you!
Eddie
|
|
|
|
Post by myles on Oct 25, 2011 9:55:27 GMT -7
Myles, I recently bought two pairs of EH EL84 tubes for my MAZ Jr. I like the sound of them fine, but I noticed they (both tubes equally in either pair) have a slight orange glow on the sides. Not "red plating" by any means, but the plates are definitely beginning to glow. They don't smell overly hot. All my other pairs of power tubes have been JJ and none of those seemed to have glowing plates. Is this normal for this tube in a MAZ Jr.? I have checked it with a 5751 PI as well as a 12AX7 PI. Thank you! Eddie Eddie, What you have is a pair of tubes that are outside of design spec and there is too much plate current for the amount of bias supplied. In a word, defective tubes. In a more complex way of looking at things, back in the days of Groove Tubes and their 1-10 rating system these tubes would be on the high side of the scale, 8,9,10. If you can put these on a tester that measures plate current at spec voltages (250 plate, 250 screen -7.3 bias) you will probably see more than the spec 48mA plate current. Get rid of them. Return them to the vendor and request a replacement set of tubes that meet spec. www.guitaramplifierblueprinting.com/Tube/6BQ5-rca.pdf |
|
|
|
Post by randalp3000 on Oct 25, 2011 11:00:00 GMT -7
I have some of those as well, on the box there are some measurements. Gm which i believe to be the transconductance that speck is 11,300. The second is Lp, would that be the plate current? And if so we would want something below 48?
Are there numbers we should be looking for or should be asking for when we purchase tubes for our Z's (EL84's)?
thanks
rp
|
|
|
|
Post by myles on Oct 25, 2011 13:13:00 GMT -7
I have some of those as well, on the box there are some measurements. Gm which i believe to be the transconductance that speck is 11,300. The second is Lp, would that be the plate current? And if so we would want something below 48? Are there numbers we should be looking for or should be asking for when we purchase tubes for our Z's (EL84's)? thanks rp Lp is generally plate current, at times it is also seen as Ip. 48mA is design spec at design test voltages. You can be above or below this, say 10% on either side and have a nice tube. Above 55mA the tubes would be hot running, the control grid is probably not done correctly, bad QA and bad assembly. Above 60mA you could expect short life and trouble. Even in an amp that was class A/B grid biased and even when the tube can be adjusted within proper range you still have a defective tube prone to early failure. This is true of all of the common guitar amp output tubes. |
|
|
|
Post by randalp3000 on Oct 25, 2011 14:06:19 GMT -7
Man I'm gettin' tired of these crappie new tubes. I have 2 quads and 2 pairs of new Eh's and they are Gm 7600, Lp 22, 8100/25, 6500/18, 8100/30. I would assume the same be said for really low numbers as well?
we all appreciate your help Myles
thanks
rp
|
|
|
|
Post by Eddie on Oct 25, 2011 16:39:06 GMT -7
Myles, I recently bought two pairs of EH EL84 tubes for my MAZ Jr. I like the sound of them fine, but I noticed they (both tubes equally in either pair) have a slight orange glow on the sides. Not "red plating" by any means, but the plates are definitely beginning to glow. They don't smell overly hot. All my other pairs of power tubes have been JJ and none of those seemed to have glowing plates. Is this normal for this tube in a MAZ Jr.? I have checked it with a 5751 PI as well as a 12AX7 PI. Thank you! Eddie Eddie, What you have is a pair of tubes that are outside of design spec and there is too much plate current for the amount of bias supplied. In a word, defective tubes. In a more complex way of looking at things, back in the days of Groove Tubes and their 1-10 rating system these tubes would be on the high side of the scale, 8,9,10. If you can put these on a tester that measures plate current at spec voltages (250 plate, 250 screen -7.3 bias) you will probably see more than the spec 48mA plate current. Get rid of them. Return them to the vendor and request a replacement set of tubes that meet spec. www.guitaramplifierblueprinting.com/Tube/6BQ5-rca.pdfMyles, Swapped them out for two pairs of JJ's. The vendor was nice to deal with on the phone, and I feel they took good care of me once I called them about the EH being out of spec. Chalk up a good customer service point for Musician's Friend. And chalk up another KARMA point for Myles! Thanks, Eddie |
|
|
|
Post by myles on Oct 25, 2011 17:22:35 GMT -7
Eddie, What you have is a pair of tubes that are outside of design spec and there is too much plate current for the amount of bias supplied. In a word, defective tubes. In a more complex way of looking at things, back in the days of Groove Tubes and their 1-10 rating system these tubes would be on the high side of the scale, 8,9,10. If you can put these on a tester that measures plate current at spec voltages (250 plate, 250 screen -7.3 bias) you will probably see more than the spec 48mA plate current. Get rid of them. Return them to the vendor and request a replacement set of tubes that meet spec. www.guitaramplifierblueprinting.com/Tube/6BQ5-rca.pdfMyles, Swapped them out for two pairs of JJ's. The vendor was nice to deal with on the phone, and I feel they took good care of me once I called them about the EH being out of spec. Chalk up a good customer service point for Musician's Friend. And chalk up another KARMA point for Myles! Thanks, Eddie Outstanding. Happy playing. |
|
|
|
Post by Eddie on Oct 30, 2011 23:18:52 GMT -7
Myles,
What are your thoughts on the so-called "cryo" treated tubes?
Best,
Eddie
|
|
|
|
Post by myles on Oct 31, 2011 8:52:56 GMT -7
Myles, What are your thoughts on the so-called "cryo" treated tubes? Best, Eddie Eddie, I have written a lot on this subject. I studied steels, alloys and various metals for years and am a trained aviation metalsmith. I also worked with metals in the marine industry. My experience is (and others may or may not have found the same thing): Cryo treated tubes: Cost more Have a shorter life, possibly because the metal is now brittle Internal parts such as metal and micas do not expand and contract at the same rate as was the intended orginal design Cost more for less Are more prone to physical microphonics You get less performance, reliability and life for more $$$ and ... they cost more. Again, these are just my own observations. |
|
|
|
Post by Eddie on Oct 31, 2011 11:31:00 GMT -7
Myles,
Thanks for the info. Sounds like it may be another snake oil product to cryo treat tubes.
Eddie
|
|
|
|
Post by myles on Oct 31, 2011 12:18:28 GMT -7
Myles, Thanks for the info. Sounds like it may be another snake oil product to cryo treat tubes. Eddie Some folks might love them and some may swear by them. Some of my tube vendor friends that I use and trust even sell them. But my own experience differs based on testing and a bit of education on treating metal and composits with extreme heat and cold. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 31, 2011 14:31:27 GMT -7
Myles, Thanks for the info. Sounds like it may be another snake oil product to cryo treat tubes. Eddie Some folks might love them and some may swear by them. Some of my tube vendor friends that I use and trust even sell them. But my own experience differs based on testing and a bit of education on treating metal and composits with extreme heat and cold. Here in upstate New Yawk we can cryo treat anything we want come February. Just leave it in the trunk of your car over night. No extra fees incurred. |
|
|
|
Post by joek86 on Oct 31, 2011 14:53:13 GMT -7
Some folks might love them and some may swear by them. Some of my tube vendor friends that I use and trust even sell them. But my own experience differs based on testing and a bit of education on treating metal and composits with extreme heat and cold. Here in upstate New Yawk we can cryo treat anything we want come February. Just leave it in the trunk of your car over night. No extra fees incurred. PLEASE don't remind me...! LOL |
|
|
|
Post by electricflag on Nov 8, 2011 12:47:36 GMT -7
Good Afternoon Myles,
What are your thoughts on this:
In the latest Vintage Guitar Magazine, Paul Reed Smith says Derek Trucks lent him the Marshall amp Duane used in the Fillmore East performances. He claims the wiring and components are a little different than others from that time period. However, PRS claims he produced an amp that "nails" Duanes tone, but I can't find a clip anywhere to back that up.
Also, in the lastest Guitar Player Magazine another interview with Derek Trucks" "...The Duane Allman Fillmore East amp 'surfaced'...They took pictures and sent them to PRS...it was wired like a bass amp with Ampeg SVT-style tubes...with other idiosyncrasies..." The article was not specific on which tubes.
It is easy to get caught up in the excitement of moment...But it's been forty years since Skydog's passing. What if you and Doc Z were presented with the amp?
-Rick
|
|
|
|
Post by myles on Nov 8, 2011 19:07:34 GMT -7
Good Afternoon Myles, What are your thoughts on this: In the latest Vintage Guitar Magazine, Paul Reed Smith says Derek Trucks lent him the Marshall amp Duane used in the Fillmore East performances. He claims the wiring and components are a little different than others from that time period. However, PRS claims he produced an amp that "nails" Duanes tone, but I can't find a clip anywhere to back that up. Also, in the lastest Guitar Player Magazine another interview with Derek Trucks" "...The Duane Allman Fillmore East amp 'surfaced'...They took pictures and sent them to PRS...it was wired like a bass amp with Ampeg SVT-style tubes...with other idiosyncrasies..." The article was not specific on which tubes. It is easy to get caught up in the excitement of moment...But it's been forty years since Skydog's passing. What if you and Doc Z were presented with the amp? -Rick Rick, Same story that I have heard countless times. Bottom line - the topology used by PRS is not at all alike to that of any PRS amp from any of their designers. That is the minor factor but bottom line, an attempt at a reproduction will yield different results in tone, feel, response and more. The major factor - if you are not Mr. Trucks you will never sound like him. You may be able to copy his licks note for note but will not sound the same. I have had access to some pretty terrific players and their rigs, along with their tips and hints. When I play use their equipment (or others do) it does not sound the same as when they play their own equipment. Look inside a PRS amp (any model) and look at an original Marshall from the Duane era. You could not be more different. Even if copied directly the components are no longer available to make a production amp. If you look inside a PRS amp you will see their mentality is also not of the past era of amp building. This is not a bad thing or a good thing. It is just fact. On a side note, your handle "electricflag" is ultra cool, one of the groups I grew up with. Everybody in the band was stellar. Heck, don't go for the Duane tone, go for the Bloomfield tone! Just my personal point of view ;D |
|
|
|
Post by electricflag on Nov 9, 2011 8:15:16 GMT -7
Myles,
You've confirmed my suspicions on the PRS units. You and I have been playing about the same length of time. Back in the 60's we've listened to the gear of like Allman, Betts, Clapton, Hendrix, etc. within a few yards in concerts. It was magical and it's a sensation to perpetuate. Modern gear you listen to now, well it is a new era...LOL!
The Electric Flag - Thank for the compliment! Funny thing...You mentioned going for the Bloomfield tone. I started off with a preCBS Super Reverb with early 60's humbuckers. So, his tone came to be naturally. Would you believe I wanted to trade in my "old junk" for those new silver faced Fenders and impossible to find Marshall at the time?
|
|
|
|
Post by myles on Nov 9, 2011 10:01:05 GMT -7
Myles, You've confirmed my suspicions on the PRS units. You and I have been playing about the same length of time. Back in the 60's we've listened to the gear of like Allman, Betts, Clapton, Hendrix, etc. within a few yards in concerts. It was magical and it's a sensation to perpetuate. Modern gear you listen to now, well it is a new era...LOL! The Electric Flag - Thank for the compliment! Funny thing...You mentioned going for the Bloomfield tone. I started off with a preCBS Super Reverb with early 60's humbuckers. So, his tone came to be naturally. Would you believe I wanted to trade in my "old junk" for those new silver faced Fenders and impossible to find Marshall at the time? Many of us followed the same path wanting those cool new silver faced amps  |
|
|
|
Post by electricflag on Nov 10, 2011 13:16:09 GMT -7
Myles,
Let me ask you about an urban legend in your neck of the woods: Steve Lukather's modified Princeton.
The story here in Louisiana goes Luke got that huge tone in his session work by playing through a Princeton Reverb - modified by Paul Rivera. Is it true? My bet is his mods were simular to the Super Champ he produced at Fender.
-Rick
|
|
|
|
Post by myles on Nov 10, 2011 16:56:44 GMT -7
Myles, Let me ask you about an urban legend in your neck of the woods: Steve Lukather's modified Princeton. The story here in Louisiana goes Luke got that huge tone in his session work by playing through a Princeton Reverb - modified by Paul Rivera. Is it true? My bet is his mods were simular to the Super Champ he produced at Fender. -Rick Paul Rivera and Steve Lukather worked together for a number of years. The last product that Paul developed for Steve was the Bonehead series which included very high power in the head and a sub woofer speaker cab. This was a pure Rivera design. Paul is a master at Fender designs (was head of Fender R&D for many years). Rick Neilsen (Cheap Trick) was another player that used Rivera modded amps. |
|
