Questions about tube amps.

1) How are T. Miranda tube amps built?

We use 2 building methods: fiber glass printed board, and point-to-point (P2P) circuit.

The P2P amplifier will cost abou 70% more than the printed board one. This is due to
the P2P be a much more elaborate and time consuming technique than the printed circuit.

2) What are the advantages and disadvantages of the two types construction?

Printed Circuit (P.C.I)- Picture A (Blues Jr Fender)

Printed circuit amp building was adopted by guitar amp manufacturers in the mid 1970's, due to the
large demand for their products. It became impossible to have a one man per amp in the manufacturing
line. Companies then decided to invest more in publicity and compromise the product's quality, using
automated manufacturing processes, less expensive parts, and printed circuit boards. These
amplifiers usually suffer from the so called parasite capacitance, which is a "ghost" component not
present in the design, which is due to the very close distance between components and also due to
the printed circuit. This effect can generate a electro magnetic field and currents in undesired
frequencies. Because this effects is usualy not in the design, its effect is often unpredicted,
causing the amp to sound inconsistent and unstable.

PS: From the point os view of mantainence, printed circuit amps are very limited,
and dificult to be modified.


Point to Point Circuit: picture 1 (Marshall Plexi custom shop) , picture 2 Fender super reverb(1968),Foto 3 Vox ac-30.

This is what was used in all amps up to the mid 1970's (60s,50s,30s). In this technique, component leads are soldered
directly between each other with no printed board tracer whatsoever. In this case parasite capacitance is nearly
eliminated, plus, resistor overheating will not damage the circuit board, which is something that reduces the amps
life span.  Escept for the price, ususly higher, there are only advantages in owning a point-to-point amp. Usually,
components in these amps are all had selected and high quality, transformer in these amps are (and were in the past)
grain oriented, and the harmonic richness of these amps is legendary. All great tones in the history of electric
guitar were created with the help of these amplifiers. Today, many lcustom builders have a line
of these point-to-point amps. It is very common to find amps from de 40's, 50's and 60's being used today by
professional musicians. Amps like Supro,Fender Blackface, Marshall Plexi, ac-30 Vox, Orange etc..(watch out
for these companies still make amps but often not with the same quality or care), still going strong and working.
Nothing like most nowadays big companies' modern amps, that need go to a repair shop after a couple of years in use
(I own a repair shop too and I know what I am talking about).

Another important factor is the components' quality in large factories. For example, in the past, resistors
were rated at 3-20 watt power. Nowadays, they went down to 1/4 watt. Capacitors were high quality paper/oil
or sprague, now they are generic. Potentiometers were also great quality and were replaced by chinese cheap ones.
Grain oriented transformers and their great harmonic richness  were replaced by dull iron silicon transformers.

Everyone should beware of instrument magazines and their rave reviews of products. Remember they are paid big
bucks by the big companies to advertise their products... so they can't be that impartial. Learn how to find
out what your favorite players ACTUALLY use in stage and recording... you'll be surprised.

PS: From the point os view of mantainence, point-to-point are great amps, as they are easy to repair and modify.

That's it!!! Cheers -

T. Miranda