8K ohms plate-to-plate is the recommended load for a pair of EL84s at a typical operating point. The problem is the schematic doesn't tell you what brand of transformer is used in this circuit. Any time you have global feedback in an amplifier, you must know the specific output transformer the circuit is designed for. Otherwise the amplifier may be unstable. This is particularly a problem in the high frequencies well above 20kHz. The amplifier might be oscillating but you would not know it, and it could wreck the amplifier and even your speakers.
For instance, capacitor C8 is a very important piece, it can prevent high-frequency oscillation if the output transformer is matched to the circuit. If the transformer is wrong, it may be the wrong value.
Seems like you have bought a PCB. Everything is there except the brand of output transformer. You can purchase an 8K p-p transformer and the amp may work, but without an oscilloscope you don't know if the amp is working properly.
Have you purchased the output transformers?
Mark 1 human ears are quite good at picking up distortion, (maybe not so good for 2nd harmonic) and along with a DC voltmeter means an oscilloscope is not obligatory!
Yes, provided there is a DC blocking capcitor of suitable voltage rating, and he uses an attenuator if connecting to the tubes, especially the output tube inputs.
(100:1)
(100:1)
Its not simply about being aware, its about avoiding accidents when fatigued, on meds, when distracted, when trying to solve some problem, etc. Proper safety practices are required if you work with this stuff or you should be fired. Common sense to follow the same safety practices if you are working at home.
Also, capacitors are discharged by shorting them out or draining their charge through a resistor. Some capacitors can hold a charge for a long time. Some capacitors can recharge themselves after being discharged. So, discharge them and then measure their voltage with a meter to make sure they are fully discharged.
No one can force you to have one and learn how to use it, if that's what you mean.
My comment had nothing to do with distortion. If you're building an amplifier with any significant amount of global feedback, and you cannot check that amp for high-frequency oscillation, you risk damaging both the amp and your speakers. You might also encounter low-frequency oscialltion, which renders the amp useless unless you know how to prevent it.
Good point although both would be audible unless minimal, but of course are not desirable because of the damage risk.
Again, just to be clear, feedback amplifiers can oscillate in the ultrasonic range, undetectable to our ears.
That's entirely possible. My point is that the OP has bought, I assume, a knockoff of an AudioNote kit board that was designed around a specific output transformer. Without that transformer and without a scope to make adjustments in the circuit for a different transformer, the ampflifier could be very unstable and he would have no way of knowing until the amp overheats or a speaker is damaged.
So many replies, so much love, man. Much appreciated and thank you! 😀 Good seeing others discussing among others, versus just me. 🙂
So the lower specification and recommendation is incorrect?
😳 Oh dear. Well not sure when @oemcar and @huggygood adjusted the design, @RE 604 has run some tests, all of them plus @quadtech have built them and rave about the sound, what OPTs they have used, not seeing anything mentioned, though could have missed it.
Okay, good to know.
I have bought nothing and planned on doing point to point, I don't have the ability or desire to print my own boards.
The schematic is also missing other information, including the IPT information.
Not the recommended 5,5kΩ of the manufacture? Just came to me, shoot them a letter with the schematic and see if can make a recommendation.
More importantly, if such equipment is required, so be it. Makes no sense to cause continual damage and loose large sums of money. There is a Heathkit oscilloscope on eBay with stereo inputs if seeing correctly. What other options are there?
Over all doesn't look like a hard piece of equipment to use.
I have not, nor any parts.
So the lower specification and recommendation is incorrect?
😳 Oh dear. Well not sure when @oemcar and @huggygood adjusted the design, @RE 604 has run some tests, all of them plus @quadtech have built them and rave about the sound, what OPTs they have used, not seeing anything mentioned, though could have missed it.
Okay, good to know.
I have bought nothing and planned on doing point to point, I don't have the ability or desire to print my own boards.
The schematic is also missing other information, including the IPT information.
Not the recommended 5,5kΩ of the manufacture? Just came to me, shoot them a letter with the schematic and see if can make a recommendation.
More importantly, if such equipment is required, so be it. Makes no sense to cause continual damage and loose large sums of money. There is a Heathkit oscilloscope on eBay with stereo inputs if seeing correctly. What other options are there?
Over all doesn't look like a hard piece of equipment to use.
I have not, nor any parts.
I am all ears (pun might have been intentional 😛 ).
By the way, seems a good number for not much money on eBay, just not sure what is useable.
I barely get any of the words, leading to a lack of understanding what all this means...
I don't take medications that do this. Plus, if I am tired, not doing anything that needs full awareness. Ditto on paying full attention, no letting the dogs distract me.
Only safety practices I know are not wearing jewelry or watches, not touching live voltage, and drain the capacitors. Thought crossed my mind, should I be wearing gloves?
Even more so when working at home, those around you don't have the knowledge or training on how to help or if do, remember (ex. use a non conductive pole to remove a body from a live circuit).
And keep checking? Keep them grounded with the leads?
Okay, so this is a design you decided to build. I would find something that offers more known quantities, especially the ouput transformer. For instance, a Dynaco ST35. Push-pull EL84, a tried-and-true design, and the replica output transformers are easy to purchase. You can build it and be assured that it will work without a problem. There are also a lot of designs by forum members that specifify a particular Hammond or Edcor transformer for which they have optimized the circuit.
I'm entirely sympathetic that you want to build you own amplifier. We all started somewhere! It's enormous fun, and a good challenge to learn what's involved. I only learned three years ago to use an oscilloscope but it has opened a new world of DIY for me.
I might suggest a simple single-ended, no feedback design. That is a great way to learn about schematics and circuits with very little risk involved. Either that or a push-pull design that has been proven to work.
How much power are you looking for? What kind of speakers are you trying to drive?
I'm entirely sympathetic that you want to build you own amplifier. We all started somewhere! It's enormous fun, and a good challenge to learn what's involved. I only learned three years ago to use an oscilloscope but it has opened a new world of DIY for me.
I might suggest a simple single-ended, no feedback design. That is a great way to learn about schematics and circuits with very little risk involved. Either that or a push-pull design that has been proven to work.
How much power are you looking for? What kind of speakers are you trying to drive?
'Stand on a thick rubber mat' is serious. 'Keep your left hand in your back pocket' is serious. What often results in death is current flowing through the left arm, down through the heart area and through a leg or legs to ground. Cement floors contain water and are considered conductive for this risk factor. Arcing through the soles of shoes has resulted in deaths and or severe injuries.
Other than that, plan out your test electrical measurement physical movements, and practice those moves you will be making while the power is off and the circuit is discharged. A loose scope or DVM ground lead falling off and hitting a high voltage node can be extremely dangerous.
DVM probes and meters are good up to about 600v. Peak voltages in tube circuits such as pulsating voltages before rectifiers can often go above that value. A high voltage DVM probe is a wise investment for working on HV circuitry. https://www.amazon.com/high-voltage-probe/s?k=high+voltage+probe Make sure to keep track of where the ground lead is and that it is secure at all times.
Capacitors can be discharged by shorting across their terminals. A screwdriver is sometimes used for that purpose (sometime referred to as a 'crowbar'). It may be wise to wrap some bare wire around the metal screwdriver shaft and secure the wire to a solid, reliable ground. Be very careful to note where the bare wire is at all times and that it doesn't touch anything it isn't supposed to.
Don't just listen to me either. Read up on the subject. Here is one page you might take a look at: https://robrobinette.com/Tube_Amp_Safety.htm
Regarding medications, sleep medications have been known to affect daytime behavior. Any med you take may have some risk factor. Read drug information for patients carefully to see if there are possible risk factors for driving or using heavy machinery. High voltage work may also be affected if driving and or use of machinery are known risk factors.
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Highly recommended to me based on my objectives.
As I said, my hangup is all the hours put into it. However, if not buildable, then not buildable. I will see if an answer comes from somewhere and if not soon, go with the Dynaco. Maybe even look for a BOM while waiting.
Okay.
Challenge is right, ha.
Also a big cost savings, a pair of Audio More L1s (this is the clone) cost about $6.000USD. A kit starts out about $2.000USD.
Interesting.
Preference be a PP.
About 10 watts.
Still waiting for a response. https://www.diyaudio.com/community/threads/stereolithos-build-bib-for-full-bass.395109/
I did also ask for modeling, however, seems I have upset so many folks that not only getting refused help with the amplifier build, also anyone willing to help with the modeling; hopefully my perception is incorrect. So, bought an inexpensive wired keyboard and mouse so can use the old Windows desktop to run the programs and teach myself. I have ended up teaching myself a lot, sometimes just figuring it out on my own, like removing an ingrown toenail (had to do it twice as missed a piece, not easy with all the blood). And of course I didn't have anything for the pain either, though not a lot, helps being a redhead.
If any use, this is a previous response in a previous thread.
"In regards to components:
A phono pre for moving coil cartridge (already have for a MM).
A pre amp that has additional inputs, be nice if can use my existing system's components, of really high quality and love the sound and ability. Not sure if even need a pre amp. With this requirement not expecting a simple design.
An amp of simple design that will be of at least medium quality so not itching right away to go mucking with it (in other words, comparable or better than the SU-Z600 integrated).
Active crossovers.
Preference be bi-amping, with SS for the woofer and tube for the upper and high ranges.
BIB speaker cabinets with mid grade speakers."