I've finally finished my first valve amp build, it's taken about two years. I built the amp once in one chassis, wasn't happy so started again.
Each mono block has it's own PSU with a 625VA handwound/overwound toroid mains tfmr with 9 second soft start for the HT/B+. There is also two protection circuits so that that if Ik of each EL34 exceeds 100mA a thyristor engages a relay that cuts the neutral to the main tfmr as well as no speaker/load protection.
Specs - 0.01% @ 1w, 0.07% @ 10w, 0.21% @ 50w and 0.28% THD @ 112.5w this at 1khz. N/ripple = 20mV. F response 3dB @ 1dB @ 5hz, flat to 28khz, 3dB @ 33khz.
Valve line up 6AU6 triode strapped for the front end with CCS load, two ECC99/6H6N's as the LTP phase splitter with CCS in the tail.
OPT's are Hammond 1650TA, caps 105 deg mostly of reputable makes, Bourn pots, Vishay resistors so most components of good quality but not boutique.
Woodwork is sycamore, hand planed from a tree, took ages as my tools are very basic. Chassis handmade from 2mm ali sheet.
Lastly though the design of most of the amps is my own work I lifted quite a few ideas of Patrick Turner and also picked his brains via email, thanks Patrick. Anyone wishing to build high powered amps or any valve/tube amp should have a butchers at his site, an invaluable resource for tinkerers and artificers.
Andy.
Each mono block has it's own PSU with a 625VA handwound/overwound toroid mains tfmr with 9 second soft start for the HT/B+. There is also two protection circuits so that that if Ik of each EL34 exceeds 100mA a thyristor engages a relay that cuts the neutral to the main tfmr as well as no speaker/load protection.
Specs - 0.01% @ 1w, 0.07% @ 10w, 0.21% @ 50w and 0.28% THD @ 112.5w this at 1khz. N/ripple = 20mV. F response 3dB @ 1dB @ 5hz, flat to 28khz, 3dB @ 33khz.
Valve line up 6AU6 triode strapped for the front end with CCS load, two ECC99/6H6N's as the LTP phase splitter with CCS in the tail.
OPT's are Hammond 1650TA, caps 105 deg mostly of reputable makes, Bourn pots, Vishay resistors so most components of good quality but not boutique.
Woodwork is sycamore, hand planed from a tree, took ages as my tools are very basic. Chassis handmade from 2mm ali sheet.
Lastly though the design of most of the amps is my own work I lifted quite a few ideas of Patrick Turner and also picked his brains via email, thanks Patrick. Anyone wishing to build high powered amps or any valve/tube amp should have a butchers at his site, an invaluable resource for tinkerers and artificers.
Andy.
Attachments
Long ago I was an artificer ..used KT55 in submarines. Very hard to find these valves now.
Approp heater current for that 12 off EL34....I'm currently doing a parallel 3 using 6550 stereo 12 valves in all. I gave up the idea of DC heater for the output stages long ago.
Well done, now one can turn the room radiator down !
rich
Never was an RN artificer Rich, the name just popped into the old noggin one day. I wired the EL34's in two 18.9v windings, 3 EL34's in series, though it's hard to get bang on with a toroidal tfmr so actual voltage is 18.7v or similar.
AC htrs for the OP stage is fine especially if your OP stage is PP although I had to re-route my htr wiring, it did cause issue's how I had it before. Look forward to seeing your build.
Thankyou El Sid, more oomph than needed but I started with one OPT I got cheap off ebay, the rest followed.
Andy.
AC htrs for the OP stage is fine especially if your OP stage is PP although I had to re-route my htr wiring, it did cause issue's how I had it before. Look forward to seeing your build.
Thankyou El Sid, more oomph than needed but I started with one OPT I got cheap off ebay, the rest followed.
Andy.
"120w PP UL monoblocks."
120W ! Is it necessary to reach the back row of a large concert hall ? 😕
120W ! Is it necessary to reach the back row of a large concert hall ? 😕
On more oomph "With amps there's no such thing!" I agree in a way, apart from satisfying our inner kid with a box of matches and a stick of dynamite a bit more head room never hurt. These take 1.5v RMS to get the full whack out of them, my PC which is my main lazy music player only does about 1v RMS. With my Mission 720's which are about 85dB the volume controls are at about 12 o'clock for a bit more than average listening volume.
Also 120w isn't that mush more in terms of SPL than a 50w amp. They can do about 145w with a sinewave IP, but that's daft, you can hear the tone coming out of the OPT with a dummy load, snigger, where's the matches...
Talking of loud amps I have a box of 813's under the bed, a PP 400w is on the cards though this presents some serious engineering problem's, not least winding the OPT's and mains tfmr.
TFL, Andy.
Also 120w isn't that mush more in terms of SPL than a 50w amp. They can do about 145w with a sinewave IP, but that's daft, you can hear the tone coming out of the OPT with a dummy load, snigger, where's the matches...
Talking of loud amps I have a box of 813's under the bed, a PP 400w is on the cards though this presents some serious engineering problem's, not least winding the OPT's and mains tfmr.
TFL, Andy.
There lies the nub,..for real headroom, the pressure mounts. I used a 800-1kW mains transformer with my 250+250W using parallel p-p KT90's.
Identical stereo amps on the same chassis lends well with BTLoading, my case hey up to 500W. This is the sort of power a 4" voice coil starts working and what the frame of the house is made of..
rich
120 watts is 20.8 dBW.
105 dB/W + 20.8 dBW = 125.8 dB!
I was considering building a new living room, large enough to run my GE turbojet from a fighter jet.
The idea is to do a comparison of dB sound levels of live and recorded sound sources.
Just joking.
105 dB/W + 20.8 dBW = 125.8 dB!
I was considering building a new living room, large enough to run my GE turbojet from a fighter jet.
The idea is to do a comparison of dB sound levels of live and recorded sound sources.
Just joking.
wowww impressive build, I did same journey power vs low power, I love low power with no feedback, music comes alive with 2nd harmonic distortion, love it, of course this is personal, but still consider that our ears have a dB limit...joking...enjoy the music
"120 watts with 100 to 105 db speakers is really loud." They actually do 145w, albeit tested only briefly. I would think most high powered amps never get used at near max volume apart from at end of party's when some drunk cranks it up then toasts your speakers : )
Thanks kissabout2002, this build has been more about the building than the end product, I've learned a lot. Next one will be a lot simpler and of sensible power OP.
Andy.
Thanks kissabout2002, this build has been more about the building than the end product, I've learned a lot. Next one will be a lot simpler and of sensible power OP.
Andy.
power with music playing is substantially lower than 120 watts, this is because music has far lower energy content than a sine wave of the same amplitude used to arrive at that power rating....in reality a 120 watt amp amp derived using sine waves can be 40 watts using music....always remember this...
yes, most listening will happen in the 2 watt levels most of the time, getting to 40 watt on peaks of transients....
i have this belief however that i would rather have it and not need it, than need it and not have it.....this is me...
i have this belief however that i would rather have it and not need it, than need it and not have it.....this is me...
"power with music playing is substantially lower than 120 watts.... etc" exactly Tony, I remember popping a meter on the OP of an amp when I first started learning about audio electronics and being gobsmacked that average voltage was about 1.5v RMS, this with music being over comfortable listening levels. Even taking into account the difficulty of accurately measuring a complex waveform, it was a valuable lesson.
"i have this belief however that i would rather have it and not need it, than need it and not have it.....this is me..." fair point.
"i just like to see the odd bonkers build." Thanks aardvarkash10 and thanks all for your kind words and interest.
Andy.
"i have this belief however that i would rather have it and not need it, than need it and not have it.....this is me..." fair point.
"i just like to see the odd bonkers build." Thanks aardvarkash10 and thanks all for your kind words and interest.
Andy.
Hi richwalters,
you said "Talking of loud amps I have a box of 813's under the bed, a PP 400w is on the cards though this presents some serious engineering problem's, not least winding the OPT's and mains tfmr".
Have you resolved your engineering problem's and find the OTP ?
I want to build a PP 813 (~250w, since Altec 260a), but I can't find a good OTP and don't want input and intermediate transformer, just 6sn7 or other tube for drivers ...
you said "Talking of loud amps I have a box of 813's under the bed, a PP 400w is on the cards though this presents some serious engineering problem's, not least winding the OPT's and mains tfmr".
Have you resolved your engineering problem's and find the OTP ?
I want to build a PP 813 (~250w, since Altec 260a), but I can't find a good OTP and don't want input and intermediate transformer, just 6sn7 or other tube for drivers ...
Sowter custom size R wound to be a 9K:8 with the feedback winding. That would be 250W at 30Hz.
The grid choke may be a little harder to find.
The grid choke may be a little harder to find.