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#1
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mono el84 amp kit
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. |
#2
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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. |
#3
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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. |
#4
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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. |
#5
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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. |
#6
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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? |
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