Updated 05/12/05
Guitar amplifier blueprinting?    What the heck is that all about?

"Blueprinting" sets up and tunes an amplifier much in the same way as blueprinting the
engine and suspension for a car.  Using proprietary methods, we match the amplifier to
the guitarist or bass player, for his particular playing style.

A guitar amplifier can be compared in some ways, to  a production automobile.  When it
comes off the assembly line, it must meet basic requirements which are within a broad
range of specifications.  An amplifier can be "tuned", much in the same way that a race
car is set up for a certain driver on a certain track ... suspension, engine tuning, etc.  

We do not "hot rod" an amplifier, that is not the purpose here.   The amplifier is
specifically set up for a particular guitar player's style and musical tastes.

The best amplifier manufacturers in the world, even if they had the time, cannot set up
an amplifier in this manner. There is no direct contact between the player and the  
manufacturer in most cases.  Sometimes you will hear of amp builders that do this, such
as Dumble, but in most cases, this is not the norm.

Amplifiers are also shipped with various styles and brands of tubes.  An amplifier using
6L6 style tubes, may be shipped with Sovtek, Svetlana, Tesla, or others.  Each are very
different in sound.  A "6L6" amp may use 5881, 6L6B, 6L6C, KT-66, tubes also... all
different.   During the process, we may swap tubes many times, working with the client
to capture his "sound".  Preamp tubes are especially critical in this area.

After the tube types are chosen,  we move on to the second objective in this area;
matching the output section of the amplifier.

Mis-matched tubes work against each other.  Your notes will not "sing".  Some notes
will die a quick death of decay.  Sustain is reduced dramatically and even absent at
some frequencies.  It is very important in a class A/B design, to have a close match in
the output section.  Any difference in waveform will be cancelled out in the NFB loop as
used in Marshall and Fender style amplifiers.

Many times a player will have some notes "sing" and others sound lifeless.  They
usually explain to me, that it is "a dead spot in the neck" of their particular guitar.  At this
point, I have them try another guitar,  if available, of the same type.  About 90% of the
time, they are surprised.  The other guitar shows the same "dead spots" on the same
notes.  It is not the guitar ... it is the amp.    I also show them why this is happening on a
 scope with a signal generator.  This is one of the reasons that the player must be
present when we go through this process for the first time.  This is not a procedure
where you can drop off your amp and pick it up a few weeks later.

Another common source of these "dead spots", is an imbalanced 12AT7 or 12AX7
phase inverter or driver.  Very few people match the two sides of a preamp triode.  
Some of the vendors selected to be shown in our tube vendor section can do this.

When it comes to preamp tubes, most vendors check that the tube "works".  They will
also sometimes check that it is not microphonic.  That's usually the end of the story.  It
is not practical to expect that any tube seller would match the two sides of a dual triode
as a general practice.  This is time consuming, and requires specialized equipment.  It
involves going through a LOT of tubes and FINDING the pick of the batches.  You
cannot make matched triodes, you have to find them.  This would easily double the cost
of existing preamp tubes from suppliers.  Some folks that sell tubes for high end audio
and hi-fi applications will perform this matching at additional cost.  The cost is money
well spent.  Less the 5% of preamp tubes are matched within the range we use for our
phase inverters.  Typically on a good day you will find 1 in 20 ... on an average day it
can be 1 in 50.

A mismatched output section - If one puts the amp on the scope with a lower frequency
input waveform, it is easy to see the non-linear waveform between the upper and lower
sides of the sine wave.  Even the most non-technically involved person can "SEE" the
problem as well as hear the problem.   This test is done during the blueprinting process.
 THIS IS EXTREMELY CRITICAL FOR GUITARS USING DROPPED TUNINGS OR 7
STRING GUITARS WHICH TAX THE LOWER FREQUENCIES.

The first stage of gain, or the first preamp tube (usually called V1), is a very important
and tube in your amplifier.  It sets the initial gain, tonal qualties, and noise floor for the
amplifier.  If you follow the link in the tube reviews to the 12AX7 section, there is a
technical paper on this subject, along with some tips and hints.

Bias has a great impact on the way an amplifier sounds, distorts, and compresses.  
Most amps are set to a specific value as the norm.  If one sets bias in a conventional
manner, the amp will generally have good tube life overall, and work fairly well.

Bias can be set to other values, which can change sound and feel.  It will also change
power, tube life, and where the amps output section starts to distort.  Amps that have a
grainy character as a design (such as Mesa Rectifiers), can also have their output
section adjusted, even if you wish to maintain the fixed bias feature of these amps.  
Marshall amps with a crunch character can have this "moved" to lower or higher volume
ranges in the amp.  In a class A amplifier, there are other methods of producing the
same results and even fixed bias amps such as these have tricks that can be done.

Once we know what you want, what you like, and we have made it happen ...all of this
is recorded and documented.  This makes it possible in the future to have your amp
serviced if you cannot be available.

Once your amp has been blueprinted, you are one of our clients.  If you are in the local
area, you will be given a phone number to call for help, or be met at the studio or
performing venue to fine tune or change things before a session or performance.

The service of blueprinting an amplifier generally takes about three hours, although in
some cases, can take longer.   Email me if you would like additional information.
As of May 2005 I am now taking blueprinting appointments for evenings and weekends.
Amplifier blueprinting consists of the following operations and quite a bit more:

1.  Scope the amplifier for clean output before work is started.  Record output in watts.

2.  Scope the amplifier for maximum output in watts before work is started.  Record output.

3.  Measure and record B+ Voltage, idle current, bias voltage.

4.  Check Bias / current draw on existing output section.  Record results.

5.  Record percentage of current draw of output section.  Record results.

6.  Check match of side A and B, and microphonics of all tubes in preamp section of amplifier.  
Discuss various qualities of different preamp tubes and reach a target objective.  All preamp tube
characteristics will be documented.

7.  Check the dynamic match of the phase inverter.  If not matched, this will be replaced, whether
the amp is blueprinted or not, with a matched phase inverter.

8.  Have Musician play amplifier and discuss qualities they would prefer if any.

9.  Install new output tubes if desired and re-bias amplifier, or if non-adjustable  bias or class A,
replace the current  tubes with tubes of the best optimum range for the player's style, taste, and
primarty guitar(s).

10.  Work with musician changing idle dissapation as to focus in on their particular needs, style,
primary guitar, etc.  Adjust as required.

11.  Check phase inverter and match of output section using LF waveform to check for optimum
phase balance.  If necessary, replace phase inverter again.  The phase inverter at this point is
optimized to compliment the rise time of the output tubes.

12.  Measure and record the final current draw.

13.  Measure and record the final percent plate dissapation.

14.  Scope the amplifier for clean output.  Record output in watts.

15.  Scope the amplifier for maximum output in watts.  Record output.

If the musician wishes, he may supply his own tubes of his preference.  I will test and classify these
tubes as part of the process.  I am not in the "tube selling" business, and there are perhaps better
avenues for tube purchasing than using me as a tube salesman.  I will be happy to advise in any
case.
Here is a forum question I answered that goes into some of the aspects of blueprinting actually:

Originally posted by GITTarzann

I just retubed my XTC with some tubes that I bought from Doug and I must say DAMN !!

What a difference it made. I don't know if GT SAG tubes would have made more of a difference or
not.  I thought about getting my tubes from GT, but 30 bucks looked a little more friendly compared
to 80.00 plus shipping taxes etc.

I still might try it to see if it makes a difference. My tubes were labeled 110/110, 110/110, and
110/110 B. I am thinking that this means gain and the B means balanced, but gives no indication of
output.

Myles do you mean by you heading the SAG portion of GT, that the tubes marked SAG are the tubes
that you would sell to your clients ?
If I was going to try the GT tubes would you suggest maybe trying the V1, or would you just do the
HiGain collection ?

BTW I also really enjoy all of your help and comments you post on the board. You are
knowledgeble and very generous to give this info so freely.  Thanks:)


GITTarzann ...............

Doug Preston does great work.

His stuff is much less expensive than the SAG stuff, as it tests one aspect of the tube.  For me to
spec a 12AX7 it takes at least 15 minutes per tube.

I have been trying to come up with a conversion scale from the VTV tester that Doug, Mike at KCA,
and Bob at Eurotubes use.  I also have one.  There are a few issues.  The VTV has something of a
gain scale.  Even when a tube measures the same on both sides, such as 110/110, the tube may
still be very unbalanced, as balance is comprised of many factors.  The VTV unit cannot not
measure the time component as an example.

The VTV tester is very cost effective though, in producing a good quality tube.  It is still a bit of
labor though, only one tube at a time, and you also have noise tests that can be done, so the tubes
you get from these folks are really great.  

As far as the price difference .... if you are happy with the end result, then it was a cool deal.  But,
you may have a tube that reads 100/100 with a slow rise time, and one that reads 100/100 with a fast
rise time.  These would play and respond differently, and to some players, that aspect of
compression is very important.  It depends on how picky one wants to be in the end.

The B would probably indicate "balanced" on the VTV balance scale.  This again, would be a
relationship of balance of the two sides in one data area.  This would not be the same as seeing
the two sides on a vacuum tube curve tracer and matching for every aspect in data in the tube.  
The matching aspect of the VTV tester yields results WAY in excess of off the shelf tubes, and
even the VTV unit may only find a match in 1 in 10 tubes, or less.

A 570 curve tracer

[img]http://www.groovetubes.com/groovetubes/images/tek570SAG.jpg[/img]

may only find 1-5 in a factory box of 100.

On your SAG question - I had known the folks at GT for a few decades.  I would come in and sift
through their stock, and chicken pick certain tubes that I needed for clients.  At one point in May
of 2002 I think, Aspen said I spent so much time here I might as well have a desk.  I was asked to
come up with a group, sort of a custom shop, for unique requirements.  From my days at Infonet
where at one point I formed at ran the ATG (advanced technologies group), I was big on those
three letter sort of deals .... (before I came to GT when I was tested the new but unreleased GE, I
coined the phrase NVM (new vintage manufacture).

So ... I started the SAG to support some of GTs folks on their F&R list (
http://www.groovetubes.com/f-n-r.cfm  .... which my the way, is a lot longer than the list here, this
list is over two years old).

The rest is sort of modern history at this point I guess.   A lot of the SAG thinking was also
published in the latest Tube Amp Book, where I contributed a number of articles, and was also the
technical consultant on the book. ... or I think that is what they called me in the front pages.

Certain SAG kits were made up, like the Marshall Hi Gain kit ... which is really a normal gain or a bit
higher, but I should have called it a High Output Kit, as it is much higher in current output than
stock tubes.

The Fender soft touch kit has a longer rise time, etc.  

We were getting a lot of requests for some specific kits over and over from the F&R folks that
tried them and would not go back to a preamp tube crapshoot.  So, in my spare time while testing,
when I see something that stands out, I keep it aside.

You can get a tube in a kit, but if you just need a V1, then it is best to talk to me a bit so I can ask
what you play music wise, your guitar, pedals or none, and more questions, so the tube could be
dialed in closer to your needs.

For my personal clients, and some folks in this forum have seen this first hand, such as those from
my last clinic, we will pop in the "same" tubes in v1, but with differeing specs, while the player
plays ... and they will tell me, I want more or less of this or that ... brighter, darker, what ever.  Once
we get to a happy place :) the data is recorded on the particular tube left in the amp.  This way we
can replicate it in the future if we need to, or build a set of 3-5 "V1 tubes" for different venues (big,
small, bright, dark), and different styles, (blues, jazz, 60s, 70s rock, metal, speed stuff, etc).

Then its on to V2 or V3 in some amps, the phase inverter, and actually matching the phase
inverter's rise time to compliment the output tube's rise time in the case of blueprinting.

Thank you for your compliments.
Click Here to return to the main page