Am interested in building a mono EL84 power amp. Have been searching
the web for kits, schematics, etc. Was hoping someone might have a
recommendation or helpful advice. I have previously built three tube
amps from kits The Sound Valves VTA-70 and they came out working fine.
I can read schematics and gather the parts and machine a chassis but
from what I've been reading laying out the parts is an art in and or
itself so I'm not to sure if it would be a good idea for me to stray
from a kit. The amp is for a guitar preamp I have. I have half a dozen
EL84 and I am thinking if I can use just one single ended that I'll be
able to get nice compression at modest volume levels enough for
practicing or recording. Thanks.

Hi NGS,

I'm not to sure if it would be a good idea for me to stray
from a kit.

since you have build kits already and can read schematics,
I would like to encourage you to pick a simple one of
the literally dozends or hundreds of EL84 amp schematics
out on the 'net and breadboard it. Then measure through
it, note the values and apply small changes, for example
to cathode or plate resistors, and remeasure and think
a bit about the changes that happened.

I've been reading laying out the parts is an art in and
or itself

Don't get distracted by mumbo jumbo - there is no black
art but some simple dependencies defined by some simple
formulae like Ohms law, and so on. And there is a small
batch of also simple rules of thumb one should keep in
mind until one gets deeper understanding of what is going
on.

If you fear hum being introduced by wrong wiring layout,
just consequently stick to the star ground technique,
except for the part from the input jack over the volume
pot to the driver grid: Just use the "patch cable approach"
there, with jack insulated from chassis.

With this in mind you can't do much wrong with a simple
EL84 SE and you should have no fear to start experimenting,
but always keep in mind the potentially letal dangers of
high voltages.

Since you are opting for an EL84 based SE guitar amp
output stage, there is no point in using expensive
iron. Just go for a reflected primary impedance of
between 7k to 10k and watch out that the OPT could
handle the few tens of mA an EL84 will pass through
it.

Tom

--
The first rule of magick is simple: Don't waste your time
waving your hands and hoping, when a rock or club will do.

My reprint of the _Mullard Tube Circuits for Audio Amplifiers_ includes
a SE EL84 amp with schematic and construction plans. The reprint is
published by the Audio Amateur Press and is availble from Old Colony
Sound and likely other sources as well, such as Antique Electronic
Supply.

NGS wrote:
Am interested in building a mono EL84 power amp. Have been searching
the web for kits, schematics, etc. Was hoping someone might have a
recommendation or helpful advice. I have previously built three tube
amps from kits The Sound Valves VTA-70 and they came out working fine.
I can read schematics and gather the parts and machine a chassis but
from what I've been reading laying out the parts is an art in and or
itself so I'm not to sure if it would be a good idea for me to stray
from a kit. The amp is for a guitar preamp I have. I have half a dozen
EL84 and I am thinking if I can use just one single ended that I'll be
able to get nice compression at modest volume levels enough for
practicing or recording. Thanks.

A dirty little secret is to pull the two SE mono amps from an Akai M-8 reel
to reel player. Do a cap job on it and watch out! It will flat out sing
like a champ.

Kelly




"NGS" wrote in message ...
Am interested in building a mono EL84 power amp. Have been searching
the web for kits, schematics, etc. Was hoping someone might have a
recommendation or helpful advice. I have previously built three tube
amps from kits The Sound Valves VTA-70 and they came out working fine.
I can read schematics and gather the parts and machine a chassis but
from what I've been reading laying out the parts is an art in and or
itself so I'm not to sure if it would be a good idea for me to stray
from a kit. The amp is for a guitar preamp I have. I have half a dozen
EL84 and I am thinking if I can use just one single ended that I'll be
able to get nice compression at modest volume levels enough for
practicing or recording. Thanks.

I don't know anything about guitars but when I started out in tube amps
I built a Fender Princeton schemo as a hi-fi amp, the one with the
6SL7, which gave the whole thing a super warm tone. The tone of any SE
amp depends on the driver to a much larger extent than on the output
tube. If you want the simplest SE amp adaptable to EL84, try the Fender
Champ model 5C1, which is very similar but simpler. I got these schemos
out of Aspen Pitman'sThe Tube Amp Book. That book is probably a bit
downscale for you now that you have experience of those kits but when I
had nothing else in the beginning I found it very interesting. You can
also get the various Champ and Princeton circuits a lot of places on
the Internet. BTW, the difference in quality you hear at a gig between
the Champ and the Princeton has little to do with the circuits and
plenty with the fact that the Princeton has a rather beefy output
transformer and the Champ makes do with limp output iron. Mo' iron
means more volume before the amp overloads and betta' bass too. If you
want to look at a very successful hi-fi SE implementation of the EL84
try the DECware kit whose schemo is published on the net. HTH. --
Andre Jute

NGS wrote:
Am interested in building a mono EL84 power amp. Have been searching

the web for kits, schematics, etc. Was hoping someone might have a
recommendation or helpful advice. I have previously built three tube

amps from kits The Sound Valves VTA-70 and they came out working
fine.
I can read schematics and gather the parts and machine a chassis but
from what I've been reading laying out the parts is an art in and or
itself so I'm not to sure if it would be a good idea for me to stray
from a kit. The amp is for a guitar preamp I have. I have half a
dozen
EL84 and I am thinking if I can use just one single ended that I'll
be
able to get nice compression at modest volume levels enough for
practicing or recording. Thanks.

Kelly Molles wrote:
A dirty little secret is to pull the two SE mono amps from an Akai M-8 reel
to reel player. Do a cap job on it and watch out! It will flat out sing
like a champ.

Is this an EL84 based? what is (are) the output tubes?