Feel free to ask Myles

[Terrell]

So, I've been looking around and now I even have more stupid questions! Like:

 

For what I'm looking for, should I replace 12AX7 with something like a 6201 or 6072?

 

And is the higher number that GT gives them mean more power to clip or clip to power?

 

Sincerely,

 

Clueless

[myles_rose]

HEY MYLES! Who makes the highest gain before breakup tubes? Or, which Tubes have the highest amount of headroom before distortion? Manufacturer wise? I'm looking for you guys who may have complaints like, "I put these (brand X) tubes in and it was loud as !@#$^, but I couldn't get it to break up!"

 

I'm trying to get a little more power out of my Juniors:

12AX7

EL84

 

Today's production tubes are down at least 20% or more on gain from spec on average.

 

The gain on each run of each type of each tube from each maker varies widely from tube to tube even in the same batch.

 

So ... the only way to do what you want is to hand pick and hand test and hand trace and hand spec at least 50 tubes to try to find a handful of good ones. This is what I do for all my blueprinting clients ... if you ever see a copy of the paperwork that was done on a particular amp each tube is documented for plate current, gain, transconductance, plate resistance and other factors so it is known what the tube is actually doing and we can replicate things when retubing the amp ... or go up, down, left or right or whatever. You cannot know where you can go if you don't know where you are in the first place.

 

If you want a proper gain / spec tube in V1 of your particular amp and a matched phase inverter in V2 then go to www.kcanostubes.com and say hello to Mike from me

 

 

They're Epiphone valve junior heads. So they came with the cheapest tubes possible I'm sure... One began to squeal like a pig on day 2. So, I immediately put GTs in them I picked up from GC. I was told that the higher the number on the matched sets of GTs, the higher the output before break up. So, I got the highest numbers they had laying around. 6 or 7s I think... If the description of the rating system is accurate, is there a 9 or a 10 and who would make that? Or, was that description just bunk?

 

So, I take it no particular brand has a cleaner louder brighter punchier tone?

 

Background: I use the heads like power amps for my Line 6 rig. I'm trying to get just enough clip to compress and round transients, but with clean low end power (punchiness) and little if any breakup. They are fairly accurate now (surprisingly so for what I paid). However, when I start pushing them to where I could possibly use them on stage, they begin to get flubbery in the bass (not enough power to pull the voice coils back) and break up in the midrange. I keep the gain knob at just under 12 o'clock (50%)...

 

Thanks for your previous reply and your help for this board. I've learned lots from reading your replies.

 

 

DO NOT use anything higher than a 6 in the Epi ... it will just run hot and sound harsh and have short life while sounding badly.

 

If you want more headroom ... and these amps were NOT designed for headroom ... use a 12AY7 in V1.

[myles_rose]

So, I've been looking around and now I even have more stupid questions! Like:

 

For what I'm looking for, should I replace 12AX7 with something like a 6201 or 6072?

 

And is the higher number that GT gives them mean more power to clip or clip to power?

 

Sincerely,

 

Clueless

 

 

You do not need a microphone grade tube in these amps ... it will do nothing other than cost more.

 

Try a 12AY7 or 5751 in V1

 

[Terrell]

So, I've been looking around and now I even have more stupid questions! Like:

 

For what I'm looking for, should I replace 12AX7 with something like a 6201 or 6072?

 

And is the higher number that GT gives them mean more power to clip or clip to power?

 

Sincerely,

 

Clueless

 

 

You do not need a microphone grade tube in these amps ... it will do nothing other than cost more.

 

Try a 12AY7 or 5751 in V1

 

Thanks!

[Terrell]

Those replies REALLY shed light on things for me... 12AY7/5751 IT IS... Thanks!

 

Curiosity takes over here: I don't understand the "why" on "it will run hot" with the higher rated tube. Is that because of the cheaper components around it? If I were to upgrade components to accommodate a cleaner power tube, where wold I start? There's a guy that makes full point to point drop in boards with better components for the VJr, would that get me a higher rated tube? Or, are higher rated tubes, just hotter? Or, is it the power supply transformer?

 

The final most important question: I read from this one mod guy, (the one that makes the p2p wiring drop ins), that upgrading the Output Transformer, really clears up the low end. Does this jive with your experience?

[myles_rose]

So, I've been looking around and now I even have more stupid questions! Like:

 

For what I'm looking for, should I replace 12AX7 with something like a 6201 or 6072?

 

And is the higher number that GT gives them mean more power to clip or clip to power?

 

Sincerely,

 

Clueless

 

 

You do not need a microphone grade tube in these amps ... it will do nothing other than cost more.

 

Try a 12AY7 or 5751 in V1

 

Thanks!

 

If you want to do something that is about as cool as it gets call Patrick at Mercury Magnetics ( www.mercurymagnetics.com ) and grab their transformer kit.

 

[J. Dan]

I'm working on a Fender 75 combo amp for a friend and ran into an issue.

 

I've got everything checked out and seems to be working properly except the Lead pot. I already figured out the switching method on this amp and that it's working properly: Lead Master Pot switches in/out properly (Red Ring from Footswitch Grounded/ungrounded) and Lead pot switches in/out properly (Plain Tip from footswitch grounded/ungrounded).

 

However, in the lead position, there is not much gain, and the lead pot, when turned up reaches max volume at about 50% then goes back down. You cannot overdrive it with the lead channel.

 

The next two tube stages must be fine because the clean channel also runs through these and seems to work fine. Before I dig much further into it, I was reviewing the schematic to see if I could determine what it might be.

 

Half of the 12AT7 tube labelled V3B looks like a buffer stage feeding the lead channel from the clean channel - is this correct? Any reason why the lead pot would affect it's operation or should I move beyond that since I AM getting signal? I noticed that the clean signal is present at the stage with V2B when the lead channel is activated - any chance some weird phasing thing could be going on, or a voltage bleed-through that could be screwing with the V3B stage (bad capacitor)? I'm assuming the Lead Pot itself is fine because there is no scratchiness or dropout, just a smooth transition from 0 up and back down (but not all the way). I'm also assuming the tube is fine because the other half feeds the reverb send, and reverb tank works fine.

 

FYI - schematic I refer to is at:

 

http://www.geocities.com/twoseriesfenders/fender_75_schem.pdf

 

FYI - Background: I am an electrical engineer and have done much of my own service, but do not have a great deal of experience with tube amps, though I understand how they work and am capable of basic troubleshooting.

[bennyguitfiddle]

Hey Myles

I have a mesa/boogie studio cal.

recently the low end has become loose or like

a low end flutter

is this my power tubes?

I haven't replaced them for at least a year.

[myles_rose]

I'm working on a Fender 75 combo amp for a friend and ran into an issue.

 

I've got everything checked out and seems to be working properly except the Lead pot. I already figured out the switching method on this amp and that it's working properly: Lead Master Pot switches in/out properly (Red Ring from Footswitch Grounded/ungrounded) and Lead pot switches in/out properly (Plain Tip from footswitch grounded/ungrounded).

 

However, in the lead position, there is not much gain, and the lead pot, when turned up reaches max volume at about 50% then goes back down. You cannot overdrive it with the lead channel.

 

The next two tube stages must be fine because the clean channel also runs through these and seems to work fine. Before I dig much further into it, I was reviewing the schematic to see if I could determine what it might be.

 

Half of the 12AT7 tube labelled V3B looks like a buffer stage feeding the lead channel from the clean channel - is this correct? Any reason why the lead pot would affect it's operation or should I move beyond that since I AM getting signal? I noticed that the clean signal is present at the stage with V2B when the lead channel is activated - any chance some weird phasing thing could be going on, or a voltage bleed-through that could be screwing with the V3B stage (bad capacitor)? I'm assuming the Lead Pot itself is fine because there is no scratchiness or dropout, just a smooth transition from 0 up and back down (but not all the way). I'm also assuming the tube is fine because the other half feeds the reverb send, and reverb tank works fine.

 

FYI - schematic I refer to is at:

 

http://www.geocities.com/twoseriesfenders/fender_75_schem.pdf

 

FYI - Background: I am an electrical engineer and have done much of my own service, but do not have a great deal of experience with tube amps, though I understand how they work and am capable of basic troubleshooting.

 

 

There can be many different things causing problems and trouble shooting in email is not the way to address things, especially in an amp as complex as these. I would need to see the amp on a bench.

 

 

[myles_rose]

Hey Myles

I have a mesa/boogie studio cal.

recently the low end has become loose or like

a low end flutter

is this my power tubes?

I haven't replaced them for at least a year.

 

This can be many things but change out the power tubes first and if that does not fix things check all the voltages and assure they are stable such as B+, grid, bias and the high voltage to all the preamp tubes is in spec.

 

 

 

 

[J. Dan]

UPDATE: I opened it up and it ended up being really simple. The lead pot was twisted and the hot end of the pot was touching the case of the reverb pot. I bent the pin back so it wasn't touching and it works fine now. Whew!

 

[court]

Hey Myles,

I have a Vox ac30cc2 and i hear static/ crackling when i play into it. I knew it wasnt the guitar and i bypassed it thru the loop station and external speaker to see if it was the speakers. Its not the speakers because it came out of an external speaker also. I opened the back of the amp up and started tapping the metal that the external outs and loop bypass are connected to and that makes the crackle. Its vibrations that im causing that makes that crackle in the amp. The sound from my notes are still good but its that crackle when i vibrate some part of the amp that is making that happen. Any thoughts at all as to whats wrong with my vox? thanks alot. P.s. i never changed the tubes in it either.

 

Court

[myles_rose]

Hey Myles,

I have a Vox ac30cc2 and i hear static/ crackling when i play into it. I knew it wasnt the guitar and i bypassed it thru the loop station and external speaker to see if it was the speakers. Its not the speakers because it came out of an external speaker also. I opened the back of the amp up and started tapping the metal that the external outs and loop bypass are connected to and that makes the crackle. Its vibrations that im causing that makes that crackle in the amp. The sound from my notes are still good but its that crackle when i vibrate some part of the amp that is making that happen. Any thoughts at all as to whats wrong with my vox? thanks alot. P.s. i never changed the tubes in it either.

 

Court

 

Court,

 

This can be many things from a bad input jack to a bad preamp tube, bad socket for the tube and 100 other things. These are complex amps and you should get it to a qualified tech.

 

 

[miroslav]

Hi Myles

 

Im trying to get some clarity on the multi-tap/multi-impedance amps and the best load to use.

 

This discussion came up on another forumand someone said that even though an amp is meant for 8 ohmsusing a 16 ohm load will give better tone/performance...he said someone told him it was cuz the windings of the output tranny get cooking more...???

 

My understanding has always been that amps are designed for a specific best fit/best choice loadand while other loads may work fine with the ampit is the best fit/best choice load that will give you the best performance from said amp.

And even with multi-tap ampsonly one of the taps would be a best fit/best choice when taking account of the overall design of the ampbut the other taps are still quite useable.

 

Any substance to that Myles?

That an amp meant for an 8 ohm load will sound/perform better with a 16 ohm load?

 

Thanks!

[myles_rose]

Hi Myles

 

Im trying to get some clarity on the multi-tap/multi-impedance amps and the best load to use.

 

This discussion came up on another forumand someone said that even though an amp is meant for 8 ohmsusing a 16 ohm load will give better tone/performance...he said someone told him it was cuz the windings of the output tranny get cooking more...???

 

My understanding has always been that amps are designed for a specific best fit/best choice loadand while other loads may work fine with the ampit is the best fit/best choice load that will give you the best performance from said amp.

And even with multi-tap ampsonly one of the taps would be a best fit/best choice when taking account of the overall design of the ampbut the other taps are still quite useable.

 

Any substance to that Myles?

That an amp meant for an 8 ohm load will sound/perform better with a 16 ohm load?

 

Thanks!

 

 

Your friend is incorrect. Running an 8 ohm cab into the 16 ohm tap will be a mismatch. It will not perform properly. Running an 8 ohm cab into a 4 ohm tap can blow the output transformer.

 

If you want to use the entire winding of an output transformer that is 4-8-16 ohm selectable then get a 16 ohm cab for the 16 ohm setting.

[miroslav]

Follow up questions...

 

Given a 4-8-16 ohm selectable output amp...will there be any tone and/or performance quality differences between those outputs when using a 4 ohm, 8 ohm, or 16 ohm speaker with its respective output of the amp.

4-to-4

8-to-8

16-to-16

In other words...does the amp sound/perform exactly the same with each of those matched combinations?

 

 

 

And...with a multiple output amp (4-8-16 ohm)...is there one output choice that would be considered "best" when taking into account the overall design of that amp?

 

Thanks!

[myles_rose]

Follow up questions...

 

Given a 4-8-16 ohm selectable output amp...will there be any tone and/or performance quality differences between those outputs when using a 4 ohm, 8 ohm, or 16 ohm speaker with its respective output of the amp.

4-to-4

8-to-8

16-to-16

In other words...does the amp sound/perform exactly the same with each of those matched combinations?

 

 

 

And...with a multiple output amp (4-8-16 ohm)...is there one output choice that would be considered "best" when taking into account the overall design of that amp?

 

Thanks!

 

Some people do not think it will sound exactly the same in each matched position. Some feel that a 16 ohm speaker using the 16 ohm tap will sound best.

 

[BadLife]

I just blew a tube in my Fender Vibrolux Reverb it is in the 4th position looking at it from the back and counting from the right. It looks like alka seltzer in the pointy end of the tube. It had 7025 RCA tubes in it and had recently been retubed with Tung-Sol 12AX7 tubes. Does this sound like a bad tube or an amp problem? Also what tubes interchange with the 7025? I was under the impression that the old 7025 tubes were able to take a lot more abuse that the 12AX7? Is it safe to stick in one of the old 7025 tubes? They were supposed to be microphonic but I never noticed if they were. This is the same amp I inquired about earlier that had the feed back problem and this is one of the tubes you suggested that I move although the tube I traded with was also a 12AX7. Also the pointy end of the tube is black. Maybe it lost its vacum?

[myles_rose]

I just blew a tube in my Fender Vibrolux Reverb it is in the 4th position looking at it from the back and counting from the right. It looks like alka seltzer in the pointy end of the tube. It had 7025 RCA tubes in it and had recently been retubed with Tung-Sol 12AX7 tubes. Does this sound like a bad tube or an amp problem? Also what tubes interchange with the 7025? I was under the impression that the old 7025 tubes were able to take a lot more abuse that the 12AX7? Is it safe to stick in one of the old 7025 tubes? They were supposed to be microphonic but I never noticed if they were. This is the same amp I inquired about earlier that had the feed back problem and this is one of the tubes you suggested that I move although the tube I traded with was also a 12AX7. Also the pointy end of the tube is black. Maybe it lost its vacum?

 

From the input jack:

 

v1 - closest to the input jack ... 12ax7

v2- 12ax7

v3 12at7

v4 12ax7

v5 12ax7

v6 12at7

 

Any 12ax7, 7025 or ecc83 can be used in v1, v2, v4, v5 They are all the same spec tube.

 

It sounds as if the tube did loose it's vacuum and was broken if it is white. Black or silver is fine.

 

 

 

 

[BadLife]

Thanks for the information. I was leaning to the loss of vacuum as the cause. Never had that happen before. I tried one of the old 7025s in it and its seems to work fine.

[Sauce]

Hey Myles I guess no one has thrown this up here but I'm curious so I'll pitch it to you. There's a thread down below about production starting up at the old Mullard plant for new tubes. The tubes look different and they're claiming some interesting things too (link),

 

"The E813CC has the same performance as the world renowned ECC83. Unlike the ECC83 however the variability in performance between two valves is reduced from an industry standard ±20% down to ±10%. Obvious benefits in application set-up are obtained by this new performance.

 

* 10 year life

* Planar valve design

* CRT cathode proven technology

* Supersedes ECC83

* 6.3V driving voltage

* B9A pin base"

 

Just wondering if you had any input, thoughts or anything else to share on this. Thanks a lot, much appreciated.

[myles_rose]

Hey Myles I guess no one has thrown this up here but I'm curious so I'll pitch it to you. There's a thread down below about production starting up at the old Mullard plant for new tubes. The tubes look different and they're claiming some interesting things too (link),

 

"The E813CC has the same performance as the world renowned ECC83. Unlike the ECC83 however the variability in performance between two valves is reduced from an industry standard ±20% down to ±10%. Obvious benefits in application set-up are obtained by this new performance.

 

* 10 year life

* Planar valve design

* CRT cathode proven technology

* Supersedes ECC83

* 6.3V driving voltage

* B9A pin base"

 

Just wondering if you had any input, thoughts or anything else to share on this. Thanks a lot, much appreciated.

 

The bottom line on this sort of thing is if it is a good price and you like how it sounds then it's a cool deal.

 

 

[BadLife]

This is a dumb question. I have a tube and I can't figure out what the heck it is. I am pretty sure I got it to use in a Valve Junior. It has a diamond with an O in it on the top left is OTK on the top right is 2 on the bottom left is V on the bottom left is 82. On the other side it has 6111411-EB with 0582 under it and 17 under that. It looks like an EL84 to me. Any idea? It has 9 pins if that helps.

[Sauce]

Hmm alright. Thanks Myles!

[myles_rose]

This is a dumb question. I have a tube and I can't figure out what the heck it is. I am pretty sure I got it to use in a Valve Junior. It has a diamond with an O in it on the top left is OTK on the top right is 2 on the bottom left is V on the bottom left is 82. On the other side it has 6111411-EB with 0582 under it and 17 under that. It looks like an EL84 to me. Any idea? It has 9 pins if that helps.

 

 

If it was in a valve jr. and the amp worked and it is not a 12ax7 then it is an EL84.

 

 

[myles_rose]

Hmm alright. Thanks Myles!

 

You are welcome.

 

 

[Sauce]

Hey Myles, another quick question if you don't mind. What's your speaker preference in your Deluxe Reverb? I have a '74 silverface and I'm toying with the idea of putting something else in it.

[myles_rose]

Hey Myles, another quick question if you don't mind. What's your speaker preference in your Deluxe Reverb? I have a '74 silverface and I'm toying with the idea of putting something else in it.

 

This is really a personal issue. I have used a Celestion Vintage 30, H30, and a Vox Blue or silver bulldog is pretty amazing too. Ted Weber has some great offerings. The AlNiCO speakers are just incredible in these amps and many are very efficient ... 1 watt in = 100db out so you can have lots of clean headroom when you need it.

 

 

[Sauce]

Interesting thanks. So you think AlNiCO is the way to go? How does that work exactly in a 22 watt amp like the Deluxe Reverb with most of the classic-style bluedogs being 15 rated at watts?

[myles_rose]

Interesting thanks. So you think AlNiCO is the way to go? How does that work exactly in a 22 watt amp like the Deluxe Reverb with most of the classic-style bluedogs being 15 rated at watts?

 

A Vox blue is a 15 watt continuous rating speaker but handles 30 watts peak. The Deluxe Reverb typically is closer to 28 watts actually, some at even 30 as a side note. Most folks don't run them flat out and have great luck with them. Another bit of info ... the first Marshall 4x12 cabs were loaded with silver bulldogs ... 60 watts of speaker capacity behind a 100 watt amp that could put out 140 watts plus as typical or higher. There were some speaker failures but most folks did not have problems and they were the best cabs Marshall ever built. Vox also had 4x12 cabs with these speakers that were run off the AC-50 and Super Beatle amps and some of the AC-100 amps which sounded great.

 

A Celestion H30 is also a great speaker in the amp and some folks like Greenbacks as well. Ted Weber has some great 50 watt AlNiCO speakers that are smooth and great sounding that work very well and then in that case you can crank things to "10" all day long.