Mesa Boogie Bass 400+
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iampoor1
Well-known member
Are all the screen resistors intact?
Doesn't that amp have 8 or 12 power tubes in a 19in rack? Insanity....
Doesn't that amp have 8 or 12 power tubes in a 19in rack? Insanity....
I have had the pleasure of undressing one of those sexy beasts before ,found a dry joint (not the kind you smoke) between the transformer heater wiring and the board . 5881 aka 6PS3 ,one of the hardiest tubes known to man ,ledgend has it all soviet era propaganda speakers ran off them.Boogie bass 400 easily competes with the big daddy Ampeg SVT's .I have added a mains driven big bore fans to Svt's on a couple of ocassions just to keep temps down a bit under arduous conditions ,on /off switch can be easily included for studio usage too .Mesa's a pleasure to work on too compared to late 80's and beyond Svt's, Laser pointed thermal probe works a treat for checking for weak output tubes in these big beasties too .
ask for a matched duodecuple when ordering new tubes. 
did you know that 12 is the largest number with one syllable?
Twelve is a composite number, the smallest number with exactly six divisors, its divisors being 1, 2, 3, 4, 6 and 12. Twelve is also a highly composite number, the next one being twenty-four.
Twelve is a sublime number, a number that has a perfect number of divisors, and the sum of its divisors is also a perfect number. Since there is a subset of 12's proper divisors that add up to 12 (all of them but with 4 excluded), 12 is a semiperfect number.
Twelve is the smallest weight for which a cusp form exists. This cusp form is the discriminant Δ(q) whose Fourier coefficients are given by the Ramanujan τ-function and which is (up to a constant multiplier) the 24th power of the Dedekind eta function. This fact is related to a constellation of interesting appearances of the number twelve in mathematics ranging from the value of the Riemann zeta function at −1 i.e. ζ(−1) = −1/12
the fact that the abelianization of SL(2,Z) has twelve elements, and even the properties of lattice polygons.
There are twelve Jacobian elliptic functions and twelve cubic distance-transitive graphs.
The human body has twelve cranial nerves.
Force 12 on the Beaufort wind force scale corresponds to the maximum wind speed of a hurricane.
The 12th moon of Jupiter is Lysithea.
The Book of Revelation contains much numerical symbolism, and a lot of the numbers mentioned have 12 as a divisor. 12:1 mentions a woman—interpreted as the people of Israel, the Church or the Virgin Mary—wearing a crown of twelve stars (representing each of the twelve tribes of Israel). Furthermore, there are 12,000 people sealed from each of the twelve tribes of Israel, making a total of 144,000 (which is the square of 12 multiplied by a thousand).
There are 12 days of Christmas. The song Twelve Days of Christmas came from the traditional practice of extending Yuletide celebrations over the twelve days from Christmas day to the eve of Epiphany; the period of thirteen days including Epiphany is sometimes known as Christmastide. Thus Twelfth Night is another name for the twelfth day of Christmas or January 5 (the eve of Epiphany). Similarly, Eastern Orthodoxy observes 12 Great Feasts.
In Twelver Shi'a Islam, there are twelve Imams, legitimate successors of the Islamic prophet, Muhammad. These twelve early leaders of Islam are—Ali, Hasan, Husayn, and nine of Husayn's descendants.
Imāmah (Arabic: إمامة) is the Shī‘ah doctrine of religious, spiritual and political leadership of the Ummah. The Shī‘ah believe that the A'immah ("Imams") are the true Caliphs or rightful successors of Muḥammad, and Twelver and Ismā‘īlī Shī‘ah further that Imams are possessed of supernatural knowledge, authority, and infallibility (‘Iṣmah) as well as being part of the Ahl al-Bayt, the family of Muhammad. Both beliefs distinguish the Shī‘ah from Sunnis.
In Quran, the Sura number 12 is Sura Yusuf (Joseph), and it is located in Juz'a (Arabic : الجزء) number 12. This Sura narrates the story of Prophet Yusuf and his 11 brothers, making 12.
In Hinduism, the sun god Surya has 12 names. Also, there are 12 Petals in Anahata (Heart Chakra.)
Most calendar systems have twelve months in a year.
The Chinese use a 12-year cycle for time-reckoning called Earthly Branches.
There are twenty-four hours in a day in all, with twelve hours for a half a day. The hours are numbered from one to twelve for both the ante meridiem (a.m.) half of the day and the post meridiem (p.m.) half of the day. 12:00 after a.m. and before p.m. (in the middle of the day) is midday or noon, and 12:00 after p.m. and before a.m. (in the middle of the night) is midnight. A new day is considered to start with the stroke of midnight. The basic units of time (60 seconds, 60 minutes, 24 hours) can all perfectly divide by twelve.
In one solar year there are roughly 12 lunar months: ( one solar year / one average lunar month ≈ 365.2422 solar days / 29.5305 solar days ≈ 12.3683 ≈ 12 )
In Canadian football, 12 is the maximum number of players that can be on the field of play for each team at any time.
In cricket, another sport with eleven players per team, teams may select a "12th man", who may replace an injured player for the purpose of fielding (but not batting, bowling or keeping wicket).
In rugby league, one of the starting second-row forwards wears the number 12 jersey in most competitions. An exception is in the European Super League, which uses static squad numbering.
In rugby union, one of the starting centres, most often but not always the inside centre, wears the 12 shirt.
ASCII and Unicode code point for form feed.
The number of function keys on most PC keyboards (F1 through F12)
The number of keys in any standard digital telephone (1 through 9, 0, * and #)
Microsoft's Rich Text Format specification assigns numbers congruent to 12 mod 256 to variants of the French language.
Twelve Girls Band
Twelve is the number of pitch classes in an octave, not counting the duplicated (octave) pitch. Also, the total number of major keys, (not counting enharmonic equivalents) and the total number of minor keys (also not counting equivalents). This applies only to twelve tone equal temperament, the most common tuning used today in western influenced music.
The twelfth is the interval of an octave and a fifth. Instruments such as the clarinet which behave as a stopped cylindrical pipe overblow at the twelfth.
The twelve-tone technique (also dodecaphony) is a method of musical composition devised by Arnold Schoenberg. Music using the technique is called twelve-tone music.
The 12-inch single is a vinyl record format.
Twelfth Night is a progressive rock band
12 Play is an R. Kelly album.
The Number 12 Looks Like You is a mathcore band.
"12", a Song from Brave Murder Day by Katatonia.
12 is a studio album by German singer Herbert Grönemeyer.
Twelve is an album by Patti Smith.
Twelve Deadly Cyns...and Then Some is an album by Cyndi Lauper.
D12 a rap group also known as the Dirty Dozen.
Musical group named 12 Stones
12 Hundred is a song by band Mushroomhead of their Savior Sorrow album.
12 is the 12th studio album by Keller Williams.
"12" ("Dodeka" in Greek) is one of the most well-known hits by Anna Vissi
12 is the number of studio albums the band The Beatles released.
now about 11: ;D
did you know that 12 is the largest number with one syllable?
Twelve is a composite number, the smallest number with exactly six divisors, its divisors being 1, 2, 3, 4, 6 and 12. Twelve is also a highly composite number, the next one being twenty-four.
Twelve is a sublime number, a number that has a perfect number of divisors, and the sum of its divisors is also a perfect number. Since there is a subset of 12's proper divisors that add up to 12 (all of them but with 4 excluded), 12 is a semiperfect number.
Twelve is the smallest weight for which a cusp form exists. This cusp form is the discriminant Δ(q) whose Fourier coefficients are given by the Ramanujan τ-function and which is (up to a constant multiplier) the 24th power of the Dedekind eta function. This fact is related to a constellation of interesting appearances of the number twelve in mathematics ranging from the value of the Riemann zeta function at −1 i.e. ζ(−1) = −1/12
the fact that the abelianization of SL(2,Z) has twelve elements, and even the properties of lattice polygons.
There are twelve Jacobian elliptic functions and twelve cubic distance-transitive graphs.
The human body has twelve cranial nerves.
Force 12 on the Beaufort wind force scale corresponds to the maximum wind speed of a hurricane.
The 12th moon of Jupiter is Lysithea.
The Book of Revelation contains much numerical symbolism, and a lot of the numbers mentioned have 12 as a divisor. 12:1 mentions a woman—interpreted as the people of Israel, the Church or the Virgin Mary—wearing a crown of twelve stars (representing each of the twelve tribes of Israel). Furthermore, there are 12,000 people sealed from each of the twelve tribes of Israel, making a total of 144,000 (which is the square of 12 multiplied by a thousand).
There are 12 days of Christmas. The song Twelve Days of Christmas came from the traditional practice of extending Yuletide celebrations over the twelve days from Christmas day to the eve of Epiphany; the period of thirteen days including Epiphany is sometimes known as Christmastide. Thus Twelfth Night is another name for the twelfth day of Christmas or January 5 (the eve of Epiphany). Similarly, Eastern Orthodoxy observes 12 Great Feasts.
In Twelver Shi'a Islam, there are twelve Imams, legitimate successors of the Islamic prophet, Muhammad. These twelve early leaders of Islam are—Ali, Hasan, Husayn, and nine of Husayn's descendants.
Imāmah (Arabic: إمامة) is the Shī‘ah doctrine of religious, spiritual and political leadership of the Ummah. The Shī‘ah believe that the A'immah ("Imams") are the true Caliphs or rightful successors of Muḥammad, and Twelver and Ismā‘īlī Shī‘ah further that Imams are possessed of supernatural knowledge, authority, and infallibility (‘Iṣmah) as well as being part of the Ahl al-Bayt, the family of Muhammad. Both beliefs distinguish the Shī‘ah from Sunnis.
In Quran, the Sura number 12 is Sura Yusuf (Joseph), and it is located in Juz'a (Arabic : الجزء) number 12. This Sura narrates the story of Prophet Yusuf and his 11 brothers, making 12.
In Hinduism, the sun god Surya has 12 names. Also, there are 12 Petals in Anahata (Heart Chakra.)
Most calendar systems have twelve months in a year.
The Chinese use a 12-year cycle for time-reckoning called Earthly Branches.
There are twenty-four hours in a day in all, with twelve hours for a half a day. The hours are numbered from one to twelve for both the ante meridiem (a.m.) half of the day and the post meridiem (p.m.) half of the day. 12:00 after a.m. and before p.m. (in the middle of the day) is midday or noon, and 12:00 after p.m. and before a.m. (in the middle of the night) is midnight. A new day is considered to start with the stroke of midnight. The basic units of time (60 seconds, 60 minutes, 24 hours) can all perfectly divide by twelve.
In one solar year there are roughly 12 lunar months: ( one solar year / one average lunar month ≈ 365.2422 solar days / 29.5305 solar days ≈ 12.3683 ≈ 12 )
In Canadian football, 12 is the maximum number of players that can be on the field of play for each team at any time.
In cricket, another sport with eleven players per team, teams may select a "12th man", who may replace an injured player for the purpose of fielding (but not batting, bowling or keeping wicket).
In rugby league, one of the starting second-row forwards wears the number 12 jersey in most competitions. An exception is in the European Super League, which uses static squad numbering.
In rugby union, one of the starting centres, most often but not always the inside centre, wears the 12 shirt.
ASCII and Unicode code point for form feed.
The number of function keys on most PC keyboards (F1 through F12)
The number of keys in any standard digital telephone (1 through 9, 0, * and #)
Microsoft's Rich Text Format specification assigns numbers congruent to 12 mod 256 to variants of the French language.
Twelve Girls Band
Twelve is the number of pitch classes in an octave, not counting the duplicated (octave) pitch. Also, the total number of major keys, (not counting enharmonic equivalents) and the total number of minor keys (also not counting equivalents). This applies only to twelve tone equal temperament, the most common tuning used today in western influenced music.
The twelfth is the interval of an octave and a fifth. Instruments such as the clarinet which behave as a stopped cylindrical pipe overblow at the twelfth.
The twelve-tone technique (also dodecaphony) is a method of musical composition devised by Arnold Schoenberg. Music using the technique is called twelve-tone music.
The 12-inch single is a vinyl record format.
Twelfth Night is a progressive rock band
12 Play is an R. Kelly album.
The Number 12 Looks Like You is a mathcore band.
"12", a Song from Brave Murder Day by Katatonia.
12 is a studio album by German singer Herbert Grönemeyer.
Twelve is an album by Patti Smith.
Twelve Deadly Cyns...and Then Some is an album by Cyndi Lauper.
D12 a rap group also known as the Dirty Dozen.
Musical group named 12 Stones
12 Hundred is a song by band Mushroomhead of their Savior Sorrow album.
12 is the 12th studio album by Keller Williams.
"12" ("Dodeka" in Greek) is one of the most well-known hits by Anna Vissi
12 is the number of studio albums the band The Beatles released.
now about 11: ;D
MagnetoSound
Well-known member
I serviced one or two of these before. I didn't have the luxury of a matched duodecuple. I balanced them in pairs, and then group-balanced the pairs, IIRC.
D12 a rap group also known as the Dirty Dozen.
It's also the perfect bass drum mic.
Enough with the twelves already!
D12 a rap group also known as the Dirty Dozen.
It's also the perfect bass drum mic.
Enough with the twelves already!
Hi Cj ,
A few questions come to mind ,
What would be the typical winding scheme for big tube transformers like that ,
what positions would the windings be on the bobbin ,
would the primary be layered and interleaved with insulating tape ,
If both half primaries are wound consecutively ,does there end up much difference in the resistance of the two halves ,
What does 'lap 3' refer too .
Thanks again.
A few questions come to mind ,
What would be the typical winding scheme for big tube transformers like that ,
what positions would the windings be on the bobbin ,
would the primary be layered and interleaved with insulating tape ,
If both half primaries are wound consecutively ,does there end up much difference in the resistance of the two halves ,
What does 'lap 3' refer too .
Thanks again.
it is hard to guess at the coil structure, probably not more than five sections like S-P-S-P-S like a lot of amp OPT's use, but bending #11 around the core will be tuff, so they might have gone bi-fi for that wind,
EIA code is 606 which is Schumacher,
the pri DCR is balanced well so they might have used two different gauges to compensate for turn length,
freq response does not have to be that good for a bass amp but this thing tested flat up to 50 K,
not hard to do with a low ratio job, night too many OPT's use 10:1 for the 8 ohm wind,
capacitance is not a worry with this much power as there is plenty of current to charge the small caps created by the winds, so leakage is the dominant factor as to frequency response.
if this amp blows another fuse then we will rewind the OPT and thus obtain winding data.
Lap 3 means lace the core 3 x 3.
EIA code is 606 which is Schumacher,
the pri DCR is balanced well so they might have used two different gauges to compensate for turn length,
freq response does not have to be that good for a bass amp but this thing tested flat up to 50 K,
not hard to do with a low ratio job, night too many OPT's use 10:1 for the 8 ohm wind,
capacitance is not a worry with this much power as there is plenty of current to charge the small caps created by the winds, so leakage is the dominant factor as to frequency response.
if this amp blows another fuse then we will rewind the OPT and thus obtain winding data.
Lap 3 means lace the core 3 x 3.
Dunno how you missed that the first time! You went deeper into number theory than I ever learned (do you actually know all those things or just looked them up?) as well as a lot of numerology and then religion..CJ said:yeah, no, i don't know what got into me, might need a 12 step program,
You discussed Islam, but you totally skipped over Christianity - Jesus of course had 12 followers called Disciples. There's the Trinity, the three aspects of the Christian Deity, and of course three is a prime factor of 12.
There was a Christian organization named the Oxford Group before and during WWII. They had an "alcoholic contingent" that has six (a perfect number!) steps in their "way of life" - among its members were bankrupt stock trader Bill Wilson and proctologist Bob Smith. After Buchman made some public comments in favor of Hitler well after the Nazi atrocities had come to light, Wilson and Smith separated from the Oxford Group movement (which shortly after renamed itself Moral Re-Armament and is most recently named Initiatives of Change), and formed a separate organization after the name of the book Wilson was writing: "Alcoholics Anonymous." This was of course the original 12-step group, the steps being expanded by Wilson from Oxford's six steps, and with the strong Christian connection it's likely the number of steps being 12 has to do with the 12 Disciples of Jesus. And there's a good bit of numerology in the AA organization (there are also 12 traditions, many of the sayings have three parts, and there are Four Absolutes held over from the Oxford Group).
But a power amp with 12 output tubes must be awesome. I can only imagine how much it weighs.
MagnetoSound
Well-known member
But a power amp with 12 output tubes must be awesome. I can only imagine how much it weighs.
12 tons!
12 tons!
I used a couple of tricks from that Mesa preamp in my own tube preamp (the shift switches).
They also had a version with 6550's, right? Or was a totally different model altogether?
I used to own (and lug around) a Trace Elliott VR350, never again, that thing was 50kg in it's rack sleeve. The Mesa is probably more still?
They also had a version with 6550's, right? Or was a totally different model altogether?
I used to own (and lug around) a Trace Elliott VR350, never again, that thing was 50kg in it's rack sleeve. The Mesa is probably more still?
