Thinking of using direct rectified AC mains (120VAC) and +15V or 7.5V adapter regulated down for heater. Output transformer gives the isolation. 15-watt design or less.
Any thoughts or advice?
Any thoughts or advice?
If you really are what you say, you wouldn't posit this idea on a forum of hobbyists.
Google 'responsibility'.
Jan
Google 'responsibility'.
Jan
OK -- good point -- mains transformer is understood as safety barrier and output transformer would need to be specially built for safety.
Like the antique radio swap fest I was at when someone set a live chassis radio on a metal radiator.
Switching supply for both high and low voltage -- discontinuous mode flayback transformer provides barrier
That is safe
That is safe
Both the input and output need to be floating (that requires the best engineering, parts, and implementation),
OR,
They need to be ground referenced.
Floating circuits - many will not pass UL, CSA, or other regulatory agencies.
There is a reason for those regulations:
Even a diy'er who is not producing a commercial amplifier . . .
We are all subject to Safe Design to prevent electrocution.
Prevent "The Surviving Spouse Syndrome"
Safety First!
Do not promote circuits, ideas, or schematics on diyAudio that are unsafe.
Yes, many schematics have unsafe voltages (inside the chassis).
The real problem comes when an un-knowledgable user gets shocked by an amplifier that has all the covers on, but is a "floating chassis", which was not designed properly.
OR,
They need to be ground referenced.
Floating circuits - many will not pass UL, CSA, or other regulatory agencies.
There is a reason for those regulations:
Even a diy'er who is not producing a commercial amplifier . . .
We are all subject to Safe Design to prevent electrocution.
Prevent "The Surviving Spouse Syndrome"
Safety First!
Do not promote circuits, ideas, or schematics on diyAudio that are unsafe.
Yes, many schematics have unsafe voltages (inside the chassis).
The real problem comes when an un-knowledgable user gets shocked by an amplifier that has all the covers on, but is a "floating chassis", which was not designed properly.
Ok -- I will limit my discussion to circuits where such issues are not a factor
Thank you for your advice
Thank you for your advice
Bluejay,
I am sorry.
I overlooked your post that mentioned use of switching supplies.
UL and CSA approved (genuine approved, not just a vendor lie), should make for safe operation, as long as care is taken for the rest of the circuit and chassis.
My CD players use switchers, and 2 wire plugs. CSA and UL approved products.
All the amplifiers I designed and built use 3 wire power mains, 3 wire plug, and 3 wire IEC socket.
And, for fire safety, I use 2 fuses in series, a fast blow, and a slow blow, to prevent problems for most kinds of parts failures, as well as protection from those nasty Hot Starts caused by power mains drop outs and back on transients.
The chassis is directly connected to the ground of the 3 wire system.
I am sorry.
I overlooked your post that mentioned use of switching supplies.
UL and CSA approved (genuine approved, not just a vendor lie), should make for safe operation, as long as care is taken for the rest of the circuit and chassis.
My CD players use switchers, and 2 wire plugs. CSA and UL approved products.
All the amplifiers I designed and built use 3 wire power mains, 3 wire plug, and 3 wire IEC socket.
And, for fire safety, I use 2 fuses in series, a fast blow, and a slow blow, to prevent problems for most kinds of parts failures, as well as protection from those nasty Hot Starts caused by power mains drop outs and back on transients.
The chassis is directly connected to the ground of the 3 wire system.
I was just thinking of using a safety approved 48V adapters -- two in series for 100V. Is that too low a voltage for power stage tubes?
I would also consider a boost after 48V but that might also be a safety issue to present in this forum as that would be a discrete design and if not done right it could create very high voltage output
I would also consider a boost after 48V but that might also be a safety issue to present in this forum as that would be a discrete design and if not done right it could create very high voltage output
Just use a 120:120 transformer and use it for isolation. Easy-peasy safe.
The moderation team take a dim view of mains connected audio devices. Generally we do not allow the posting of such projects here.
However, since this thread has now taken this into consideration and changed direction, we will let the thread stand.
From the forum rules.
3. Working on live and non isolated power supplies as well as high voltage equipment carries risk. Much of today's equipment uses power supplies derived from circuitry that is both live at all times and that also has no isolation from the incoming mains supply. This can be lethal to those unfamiliar with this mode of operation. Even probing the circuitry with mains powered test equipment carries an immediate and lethal risk. It is therefore the responsibility of the person working on such equipment to ensure that they are fully conversant with safe working practices which include (but are not limited to) powering both the item being worked on and the test equipment from an isolated supply. Tube/valve circuitry also poses a lethal shock hazard due to the high voltages typically encountered. Again, the person working on such projects should be conversant with safe and good working practices.
Fair enough
I have been designing solid state effects and full amps using 24V adapters -- tube design is new to me so will be mindful of the safety concerns.
As guitar player I want to study the harmonic performance of tube amps. There is the second and third harmonic generation that both solid state and tube designs can easily do -- I think the big difference is how these harmonics come up dynamically with volume. Experimenting with well known designs and hearing it is the best way. However -- simulation is also wonderful tool and very grateful for this forum as a source for tube spice models
I have been designing solid state effects and full amps using 24V adapters -- tube design is new to me so will be mindful of the safety concerns.
As guitar player I want to study the harmonic performance of tube amps. There is the second and third harmonic generation that both solid state and tube designs can easily do -- I think the big difference is how these harmonics come up dynamically with volume. Experimenting with well known designs and hearing it is the best way. However -- simulation is also wonderful tool and very grateful for this forum as a source for tube spice models
Understand that you must make sure that there is no continuity between either terminal (hot and neutral) of the AC line input and anything that can be touched by anyone using the device. This is especially important in a guitar amp as the fretting hand will clamp down on the strings of the guitar in an electric shock event. There has been at least one public event in the last 50 years or so where a guitar player was killed with a guitar in hand and grabbed the mic with the other.
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