Thanks Joe. I decided to spice them up a bit with the type S series. A lot of work was done by earlier engineers in the golden era of class AB amplifiers. Surprisingly they all were able to achieve perfection in their own way from Japan, to UK to USA , the cold North and others. Were now in the golden age of class D amplifiers. I wonder what chatGPT will design for us.
As technology is advancing were now faced with the limitation of resolution of the human ear, eye and brain. What sets audiophiles apart is that their brain processes what is coming from the ear in a particular manner, even two audiophiles can differ in what they consider hifi. As Tv screens are getting better, how much can the eye resolve? The brain has a filter of what it considers acceptable for ear and eye. Once anything is within the boundaries of the filter, the brain applies all manner of normalization. At this point what shows the differences are the measurements.
Audiophiles are always curious people and are unlikely to swear by just one amplifier.
They could even have different amplifiers for different seasons, time of the day or even mood or music type.
Let me know how many are interested in PCBs for this https://www.diyaudio.com/community/threads/not-blameless-amplifier-red.392236/#post-7174557
They could even have different amplifiers for different seasons, time of the day or even mood or music type.
Let me know how many are interested in PCBs for this https://www.diyaudio.com/community/threads/not-blameless-amplifier-red.392236/#post-7174557
I am thinking of what product content to put on this new channel. If you have video submissions you'd like to share including system sound demos let me know https://www.youtube.com/@modulardesignsystems
The PASS X250 is much like the SYMEF, except that it excludes the output stage from the negative feedback loop. SYMEF uses BJTs, X250 uses FETs. SYMEF is a class AB amplifier and is not fully symmetrical, but they should have pretty similar sound signatures other than the fact that symef will damp the bass modes in the room making for a more realistic bass reproduction. But as always take everything with a pinch of salt and taste the pie for yourself as we all have different tastes, preferences and needs. It also has an added edge over the SYMEF in some scenarios as well as the other way round. In one of the opamp threads here I asked the scenarios under which two inverting opamps sound better that two non inverting amplifiers in series, I guess only Pass got the joke and chuckled to himself. Some of the the major catalysts in my early audio engineering days were Self and Pass. Each with their own styles and approach to things. Pass is more laid back probably due to the good weather, beaches and sun. Self is a British gentleman.
Drilling template courtesy Audio Nautica
https://www.pcbway.com/project/shareproject/W568925AS1F1_SYMEF_Drill_Template_Rev0_3a0e915c.html
https://www.pcbway.com/project/shareproject/W568925AS1F1_SYMEF_Drill_Template_Rev0_3a0e915c.html
This amplifier exists in so many versions out there, but I still think we have the best 'one'. It might also be infatuation. You see most people grew up thinking their mama cooks the best cause thats the food your taste buds got conditioned on. Its like telling some people who grew up listening to class D and small digital amps that there exists class A, AB amplifiers. The issue is that its our brain that hears and once conditioned it will hear what it wants. The age group at audio shows is also telling. Theres a lot more grey hair than other hair colors. Nico is this yours
The original 1DIFFQC is a crazy amplifier. It does everything right and only uses 50% feedback. On the other hand the SYMEF does something the 1DIFFQC cant and that is it makes even unlistenable music listenable, it cleans up the music probably even better than a tube amplifier. It makes people that suffer from listening fatigue or who have bright speakers want to listen to music again. Lets see how the new tough cookie on the block the 1DIFFET will be received https://www.diyaudio.com/community/...ier-for-whatever-speaker.401371/#post-7405506.
Every amplifier has its sound, character or voicing THD says not much. Every stage introduces some loss as such we want to derive some voltage gain or current gain. The LTP can have 6dB TO 20dB of gain, no more no less. By default the LTP already has 13dB of current gain as such we maybe satisfied by deriving no further voltage gain for the purposes of fidelity. Why? because the LTP cannot fix its own errors. With the LTP having improved the resolution of the input signal by a whooping 13dB what next? The LTP performance can be further improved by a class A buffer for that accuracy. The resistance seen at the base is usually (RE+re+(1/ gm))*hfe. The resistance seen at the collector is usually RE+e. Thus for the LTP the voltage gain is defined by the collector resistor divided by the degeneration resistors. For SYMEF we have remained true to this ideology. Not only that we successfully swamp out re. Two birds, one stone. Now that means that our VAS has to do all the lifting, if we immediately go for voltage gain, we still have some of the defects from the LTP but then again it also means we introduce fewer errors we cant fix. Our VAS is our voltage amplifier. We are going to be doing all the heavy voltage lifting here so current gain must be kept between 6dB to 9dB with LTP current as reference remember LTP current for line level should be between 500u to 2mA. For SYMEF we take a completely different approach before going for voltage gain; we simply take a detour further distancing ourselves from the defects of the LTP and sample disturbances from both rails in the process as well as going through N and P devices. By the time we go for voltage gain, weve been around town and for good cause. From here each output stage you choose has its own signature. From here on its pure current gain only. The three stage Emitter follower leads the pack. The quasi, mosfets and CFP each have their own characteristics and place. These are just but some of the secrets that make the SYMEF a competitive amplifier in whatever weight category. Well Nico here's the secret formula after 12 years LOL
But is this the only school of thought? Definitely not.
But is this the only school of thought? Definitely not.
Other considerations are VAS cascodes in asymmetrical designs should have their reverse collector current limited by a base resistor to match the opposite side to ease recovery. AB output switching stages should be biased atleast into class A for the 1st watt. Subsequent driver stage should be biased at 100mA, while the pre-driver should be at 6dB to 10dB of the VAS current. In these designs the VBE multiplier should have a relaxed 6dB to 10dB sensitivity in reference to 1mA. A switch off capacitor may improve mosfet performance but not so much BJTs. In terms of output stages, three stage EFs and Quasis work well, mosfets with drivers are good output choices depending on application and sound character. This takes out much of the guess work in coming up with a design that sounds good off the bench.