A little more information

The two main activities in my life: Helping the hungry in the late hours of the night and helping guitar players sound better one amp at a time.

I always try to remember that in order to do good one has to take action and actually do something.

I was born and raised in Los Angeles. I have watched the city and Southern California change for well over half a century.

I can be found on facebook at www.facebook.com/mylesr or on twitter at www.twitter.com/myles111us or on my own Guitar Amplifier Blueprinting website at www.mylesrose.com

Los Angeles Architectural History

Los Angeles Architectural History
1935 Art Deco at some of its finest: No. 168 - Griffith Observatory- (click on the photo for information)

Monday, November 1, 2010

Feel Free to Ask Myles - technical amplifier talk

My pants too short and 8 out of 10 amps I tested on this day failed :-)

Helping guitarists sound better, one amp at a time.  Some questions from two columns I write may be posted as blog entries from time to time. 

Some questions have been addressed in a few fun videos.  I will also post links from time to time with updates on additional questions or commentary.  If you have a specific question feel free to post it in this post as a comment, post it on one of the forums or send to my email listed in my profile here.

Guitar Player Magazine:  Music Player Forum; Feel free to ask Myles - http://bit.ly/iZGvIu 

Z-Talk Forum in the Ask the experts area, Ask Myles or Chad - http://bit.ly/lJakRD  I address amp issues. Chad Weaver (Terry Clark, Brad Paisley, Taylor Swift) addresses performing tech issues (guitars and other instruments, pickups, stage mics, wireless, life on the road etc.)

My GAB website covers a subject or two -
http://www.guitaramplifierblueprinting.com/ and there are many resources on the right side of this blog that may be of interest or help as well.  I am updating this blog site more often than my GAB website as a side note.

Click on "read more" to continue to read this particular post.


It has been a while since I updated this post with some of my forum discussions.  This is my first update for the new year and I will try to be more active in updating this post in the future.

I'm thinking about getting a new set of power tubes for my Monza.

1.) At what draw should I have the tubes matched?

2.) Also, what are some of your favorite NOS tubes and/or new production tubes for this amp?



The Monza is one of those amps where tubes can make a big change because they are an amp that does not have a lot of "stuff" in the signal path.  They are an articulate and touch responsive amp, a wonderful design.

I am not trying to be a wise guy when I come back to you with this question ... what should I have for lunch today?

Seriously, tubes are really personal taste and preference but there are a few basic rules I follow:

1.  Use a tube that meets design spec.  A good tube vendor can assure this.  Stay away from all that early or late distortion stuff or high or low ratings.  Tubes with these labels did not meet spec and there is something inherently wrong with the tube.  If something has a Groove Tubes rating from the past you want a number 5 or 6.  If the rating is only red, white or blue stay clear.

2.  Know and trust your tube vendor.

My own personal preference is for medium or long plate tubes for the phase inverter.  In your Monza, V2 is the phase inverter.

V1 in most amps is the first / main tone and gain stage and is generally the most close to the input jack.  This is the most important tube for tone but V2 is what drives the output tubes.  You can change your headroom in an amp by altering the characteristics of V2.

I prefer darker tone personally.  I stay away from bridge pickups and tend to prefer neck pickups so my personal taste is pretty darn narrow compared to most players at most any level.  This is why I said, personal preference.

BUT ... tubes I would recommend for my friends and clients?

Output tubes:  I still like the JJ EL84S although you want a good vendor that will assure they do not rattle.  Some folks like the EH EL84.

Cathode biased amps go through output tubes faster than grid biased amps.  6000 hours on a 6L6 in a Fender Super Reverb is common.  300 hours on a set of EL84s in a Vox AC30 and the tone and output will have degraded in a very big way.  Bottom line here, if you want NOS output tubes save them for studio use and do not use them for everyday use or gigging.

Preamp tubes:

The Tung Sol reissue 12AX7 is a nice front end tube that is articulate.  It is a short plate so it will boil down to personal taste.

NOS works great in these amps and an NOS tube will last decades.  They do not wear out as output tubes do.  If you have one amp to retube and are not a amp maker who needs a steady supply of tubes for production than NOS is a cool way to go for many reasons.

Here are a few links to some of my favorite picks for a Monza.

Great V1 or V2

V1 / V2 - http://www.kcanostubes.com/content/anos-lightly-used-test-new-sylvania-12ax7-long-plate

Short plate but an amazing V1 tube - http://www.kcanostubes.com/content/nos-rft-12ax7

V1/V2 - http://www.kcanostubes.com/content/nos-tungsram-12ax7ecc83

Cost effective V2 tubes if you want to spend less -




Happy Playing.


Why some tubes flash when first turned on.

The "flash" is perfectly normal and it's a trademark characteristic of Mullard / Amperex tubes.

The flash occurs on one side of the filament wires between the bottom plate and the inside bottom of the tube and this phenomenon only occurs when powering up from a cold start.   The sudden influx of current on the cold heater filament encounters very little resistance along this wire (hence the sudden burst of light).  So in effect one side of the tube always warms up 1st,  the second takes a while to catch up but before long the heat is evenly distributed (and your amp comes to life).

Turn off your amp - and restart it again. You won't see the same flash if the tubes are still hot - it only happens on cold startup.


Tung-Sol Reissue vs. Electro Harmonix


I'm pretty sure that I've read Myles state that the new production Tung-Sol 12AX7 is essentially an Electro Harmonix 12AX7 with some minor changes. I'm sure it on this forum somewhere, but I can't find it. What are the differences in the these tubes?



I have seen this same tube "change hats" at least three times.

This was originally the 12AX7EH (Electro Harmonix). Groove tubes called these the 12AX7R3 when they sold them.

They were a nice tube, one of the best of the current production 12AX7s of the time but were a bit pricey compared to some of the other "Sovtek" tubes.

After a bit of time (these are my opinions and thoughts) the sales dropped off and Sovtek (who owned EH) wished to get back more of the tooling costs or perhaps just wanted to tweak sales.

So, at a much higher cost the EH was brought out as the 12AX7EH Gold. A gold pin version.

It costs almost nothing to put gold pins on a tube as the process is very simple and the gold is ultra thin. One gold coin of one ounce would be enough to plate tens of thousands of tube pins.

Sales did not go over very well but now Sovtek had purchased the rights to some classic names from the past .... Mullard, Tung-Sol, Genelex, Gold Lion and even the name Svetlana for use in the USA as the real winged C SED tubes are still sold in the USA with the =C= logo.

The Tung-Sol name was placed on the EH tube and voila, the tube had one more life.

As far changes on operation, specs, traces in the EH versus Tung Sol, there are none. As far as quality control differences there are none. It is a decent tube, one of the best currently in production.

It has NOTHING in common with an original Tung Sol 12AX7 and if you look at the two of them side by side, other than pins and glass, there is no part or assembly that are alike.

As I have said many times before, even if a new tube is a good tube I feel it is a shame that some companies put great names from the past on what is generally an inferior product with no resemblance to the original.


Some talk on KT-66 tubes and my reply.

The KT66HP that the Doc originally used was a 30 watt  GT tube. Groove Tubes used the max design rating but the design rating was 22 watts with a 30 watt plate max.

The original GEC was a 25 watter design rating but 30 watt max rating.  3.5 and 4.5 watts off the screens.


A few of my own observations on some current offerings.

The JJ KT66 looks very much like a adaptation of their KT88 and has the same problems as many current JJ offerings.  It does not trace like a GEC KT66.

The Sino and Valve Art KT66 tubes have a short life compared to the original GEC.  They are also physically fragile.

The Sovtek does not impress me sonically and does not trace like a GEC.

The "Tung Sol" is an overblown 6L6 in a big bottle.  When used in ultra linear applications the screens can fail a bit more quickly than some of the others.  Prone to rattle if the amp travels.

The re-issue Genelex Gold Lions are pricy in the current production lineup but are the closest to the originals .... for the moment.  

All of the current production tubes are not recommended by me to any of my folks on tour as they are too fragile for travel on the road.  If you do take them on the road keep spares in the bus not in the truck.  They do better in a car than a truck.  Keep spares in your bunk if on a tour bus.

USE the standby switch and give the tubes time to cool down BEFORE you move an amp that has been on stage in use EVEN if the union demands you clear the stage immediately.

These tubes do not like quick temperature changes.

The original ongoing post can be read at

Hope this was of some help.


Since we are on the subject, Myles, have you compared the EH EL-84s to the TAD EL-84s?  If so, what are your observations between the two?

I have put these up against each other on multiple occasions and will continue to do so.

My own observations (and my own taste)...

The TAD is more articulate.

The EH is less defined.  Maybe it is an update of the old Sovtek  EL84 but there seems to be a strong resemblance that I did not care for in the original tube.

The EH is longer lived before failure (plate current dropping 20% from it's original measured number).  The reason for the longer life of the EH is more due to construction than material.  More on this below.

But the TAD will not get flubby and dark as the EH as quickly as they each wear.  The EH is generally darker but some folks may like that.  Personal taste.

The TAD runs 35 degrees hotter in the same amp on the glass surface temperature.  Not anything to worry about although in amps with limited venting such as original Vox AC-30 this will heat up other components and they may age faster and drift more.

The TAD has better QA and a narrower range of drift from design spec than the EH.

The plate material thickness on the TAD is a bit lighter in weight than the EH but ... the plate material of the EH has a lot of "junk" in the iron.  There is measurable monel in the plates of the EH tubes.  Monel is generally used in ship construction.  Bottom line here, the iron in the plates of these tubes may come in many cases from scrapped ships.  Perhaps if I find radiation if it comes from Victor III subs I may use these tubes as it may help me sound better?

The TAD contaminates in their plate material is not nearly as high as that in the Russian tubes.

Whether any of this metal nonsense has anything at all to do with the sound is anybodies guess.  What is shows me is an increasing lack of quality control.

For folks in L.A. that are attending the 7th annual L.A. Ampshow if you come to the Tone Wizzards Panel on the first day and meet up with me before or after the panel I will mention a few methods to spot cathode contamination.



What's your opinion on current production 6V6's?  To me, the JJ's don't sound anything like a real 6v6 (or look like one for that matter).


I test the JJs a lot as the place where my own shop is located is in a complex where a lot of amps using the JJ 6V6 tube is used.  I have watched them decline in quality over the last year. 

They used to be a rugged tube but these days over 50% of them rattle.

They do handle high voltages but I agree, the do not sound like a sweet 6V6, they sound more like a 6L6.

The Electro Harmonix is a decent tube.  Better sounding to my ears than the JJ.  It is effectively the same tube at about 30% less price than the Tung Sol Reissue.  Both are from New Sensor who puts grand names from the past on tubes that look little like their namesake.  The designs are nowhere close as is the same case with the performance. 

One of my pet peeves is taking an iconic name from the past and putting it on generic garbage made today.  I would have less of an issue if a tube maker were to make a $50 12AX7 that was of any design that was done properly and had good QA even if not of the original design and put a name from the past on the tube.

Amp makers have it tough.  They have to ship amps out on a regular basis and having a reliable supply of tubes is impossible today.  New production that might be cost effective for them might perform well one month and the next run is garbage.  My best wishes go out to these poor folks who try to build a nice product with unstable vendors.

But ... if you are talking about a personal amp then the world is your oyster in a manner of speaking.  Go NOS.  More cost effective in the long run (the long run being over a year at this point as most production tubes will fail or rattle in that time and need replacement).  Spend three times more for NOS and you will be money ahead in the first year looking at the typical odds.  Maybe in the first few months.

NOS will last MUCH longer and sound better as they meet design spec.  In the case of preamp tubes they will generally last decades rather than months.

Some of the folks I like and trust are listed below.  There are other great folks out there too but these are the folks I know, people that I know how they test their stuff and folks than I send my GAB clients to.  If you have a vendor you think is great feel free to add them to this thread as well.


These folks will also pick out via proper testing current production tubes and at least assure they come somewhat close to design spec.  Won't make the tube last any longer perhaps but perhaps if it was built well enough (by accident) to meet spec perhaps it will last a bit longer.

Side note for folks in So Cal that I have mentioned before - if you wish to have be test and curve trace some of your own tubes (a dozen or less or we can talk about it) at no charge just drop me a note.  I don't ship things back and forth so you would have to come to the shop in North Hollywood.  You would be a part of the testing process.

A lot of you have taken me up on this in the past.  There is no limit on number of visits so feel free to contact me if you want to do it again :)


Myles I was just reading that thread on tube dampers from a few months ago and you said that you wouldn't suggest adding anything to a tube with too much weight/mass, why so if I may ask? Would this include those metal sleeves that cover some preamp tubes?

The metal tube shields are there for a few reasons.  One is to hold the tube in place if the socket is not all that tight.  The other reason is shielding from stray electons to reduce noise.

Unfortunately, electrons like to move as directly as possible from the cathode to the plate.  The tube shield is attached physically to the chassis and therefore is ground.  So, the ground actually can change the flow of electrons enough to make a difference in performance in some amps.  Many times you will notice a difference in tone if you take off a tube shield and put it back on.

How many high end audiophile amps can you recall that had metal tube shields?  Not many.

There are pros and cons to the metal shields.  Same goes for tube dampers.  I would rather select a proper tube than try to fix one that is of questionable quality via a tube damper.  At one amp maker I know they take their good tubes which are in critical positions and install a light piece of conventional shrink wrap tubing on the tube to give the tube a bit longer life when it comes to physical interction inside the amp.


Myles, I was reading about the Z Wreck on your blog and you were talking about the tube that Brad Paisley was using. I was curious as to what EL 84s he was using these days. Is it true that the JJ 84s have not been as reliable recently?

Russell - Brad uses the stock tubes in his Z-Wreck and in that amp the Doc supplies NOS tubes. The output tubes are 7189 which are stronger physically than the EL84 and can operate at a higher voltage.

There is a datasheet on my GAB website where you can see how much higher the voltages run on these great tubes.   http://www.guitaramplifierblueprinting.com/files/7189_Sylvania.pdf

In regard to EL84 tubes, they are not getting any better for sure. There are many "new ones" coming out all the time. Same tubes with different labels and new claims that have bad QA, short life and rattle in many cases. It is not getting better.


Hi Myles.

My question is re an old 64 Fender Bassman head, used for bass. I have replaced the power and preamp tubes, used DeOxit on the sockets, had Orange County Speaker test the speakers, but when the amp gets turned up past 5 there is an audible "breaking up" or electric static sound that I thought was microphonic tubes in the beginning. Can resistors or capacitors give off an unpleasant sound when pushed at loud volumes? Thanks for your insight and help, Steve


Resistors and caps making noise?  You bet.

Carbon comp resistors are generally more noisy and less stable than nature when compared to modern resistors.  They also break down over time from heat.  The can become noisy and drift in value.  Very common.  Many folks love carbon comps as they are warmer and vintage in tone to the ears of many folks over metal oxide or metal film resistors which are more stable and cost less.  Some amps use both types.  In tone effecting positions the carbon comps are used.

Bypass caps - also a problem in older amps as they age and dry out.  In some areas of a circuit you want zero volts leakage through the cap to ground.  Even a few millivolts can cause problems such as stray noise. 

I have seen countless amps with many volts leaking to ground and the caps needed replacement.

Easy fix - replacement.  Not very expensive either.  Will quiet things down and bring your amp back to life.  You might also want to check for cold solder joints that became brittle over time and touch them up.  Also fast and easy.

One more question from today:

Hi Myles, before i ask my question I'd just like to say God bless you. I've read most of your guitaramplifierblueprinting website and I've learned just so much about guitars and amps and tubes etc. I am now actually a better guitar player, so thank you for doing all of this and for having this thread!

Q: I just got a little Swart Space Tone (the little one without the reverb) and it sounds good with the stock tubes (all new production JJ's) but I really don't think they are doing the amp justice, and more importantly the rectifier is a 5AR4 which is way too much for this little amp in my opinion. What NOS tubes would you suggest for this amp? I apologize if you answered this before but I couldn't find it. It's a 12AX7, 6V6 and you can go with a 5Y3, 5U4 or 5AR4 for the rectifier. I was thinking about going with a NOS 5U4, would you advise against this?

Thanks in advance!


Tube selection is all about personal taste and preference when it comes to tone. In regard to reliability, very few of the production tubes made today will come anywhere close to the reliability, life or consistency of tubes from the past.

Amp makers do not have the luxury of using NOS tubes. They are not as available, are pricey and there is no ongoing reliable supply. But you have that option with a single amp.

You can plug a 6L6 into the amp but I do not recommend it. Stick with the 6V6. Right off the bat contact somebody like www.kcanostubes.com or www.dougstubes.com or a vendor you trust and get a better 6V6 than the stock JJ. The JJ is harsh and edgy. It sounds more like a 6L6 than a 6V6. There is nothing sweet about the tube. If you want a hard edge then it is a fine tube (when you find one that does not rattle ... maybe they fixed that in their last batch). If you want vintage tones go NOS with a GE, RCA, Sylvania, Marconi, or just about anything made in the 50s or 60s.

JJ 12AX7 - again, toss it. Go with an NOS offering. RCA, Sylvania, GE etc. for the USA vibe. RFT, Brimar etc., for the Brit or Europe vibe. Or, one of each and swap depending on mood.

Lose the 5AR4. Overkill, too high of voltages in the amp, stiff and constipated. Even Swart offers an NOS 5Y3 as an upgrade. NOS 5Y3 is the way to go.

At this point you will have made a big improvement in tone and reliability.

If you want to take the next step, a huge one from a tone point of view, and increase the string to string balance, articulation, sustain and definition of the amp, consider replacing the output transformer. The stock Heyboer OT is nice but to my ears they were more Brit / Marshall in character. When you want distortion and do not care about notes smearing or lack of stacked defined harmonics they are a fine piece of metal. If you want to take the amp to the next level talk to the folks over at www.mercurymagnetics.com Ask for Patrick, he is great. At low and medium levels the amp will sing and open up rather than work in a more narrow range.

Mercury stuff is more expensive and that is one reason why not all great amp builders pick them as their choice. Just like tubes and capacitors, quality is generally more expensive.

Think of it this way, when it comes to transformers they are the most expensive part in your amp (if a good set was used). Transformers are the heart and soul of an amp. If you want to compare amps to cars and you drove a classic Ferrari BB-512, do you think it would handle better with some $1000 P7 Pirelli tires or some Pep Boys hard rubber compound economy tire? Same black color, both round (sort of, one is actually more round than the other) and both fit on your car.

Sorry for the long winded answer. Hopefully I have made my point.

Red Iron Amps and octal base preamp tubes in the most recent post.
Red Iron Amps: http://soc.li/SPhEzqb

Last post: Preamp vs poweramp distortion. Groove Tubes content. 5751 content.
Ask Myles or Chad - amp or live playing questions: http://soc.li/IYmZ4hX

RCA NOS in a Dr. Z MAZ 18 NR?
Ask Myles or Chad - amp or live playing questions: http://soc.li/IYmZ4hX

More tubesync and biasing dialogue. TubeSync: http://soc.li/oqxZlDL

My commentary at the end of the current thread. Can you play unbiased amp? http://soc.li/eF957Gi   
Sometimes I just scratch my head. TubeSync: http://soc.li/oqxZlDL

Hi Myles, I received 2 Mullard tubes from a friend of mine and would like to know your thoughts and if I could use them in my Maz Jr.  Markings on the tubes are identical and are as follows: 000-4024 - CV4024 - KQDD/K - 85-09 Discussion starts here:   http://bit.ly/kiGVvm

Below - Z-28 rectifier question

Below, Marshall JMP 100 tube seclection question:

Below, Feel free to ask Myles question on an NOS EL84

When I am not "helping guitar players sound better one amp at a time" I work with the homeless in Los Angeles with my great folks at Union Rescue Mission ( http://www.urm.org/)  Los Angeles has the largest homeless population in the United States.  If you would like to help there are many ways to do that from the URM link via their website.  They even have paypal capability (I made the first paypal contribution when this was implemented).  Any donation is tax deductible. 

If you are in a hurry and don't want to deal with the web you can feed five people for $10 in less than 30 seconds.  To donate $10 to Union Rescue Mission, text the letters URM to 85944. You will receive a confirmation text message. Reply with the word YES to complete the transaction.

Thank you.

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