OK, got them set-up and tested.
I set them up at 50mA per device. I don't tend to run my amps too hot and 1DIFFQC simmed out to be best around this value. Offset was 20mV on one and 42mV on the other, not too bad but a little higher than some others I've built. Clipping is slightly asymetrical but clean. The amp is faster than SYMEF by a fair margin, though I didn't get an exact measurement. The Very slight hiss and buzz with my ear right up to the speaker but nothing to be concerned about (my Brystons -3B and 4B- are both noisier and exhibit more buzz). There is a distinct turn-on transient but that is pretty normal with this type of amplifier.
So, onto some music.
I found the treble to be more crisp than Harrison's SYMEF and quite pleasant. No glassiness or excess sheen, but not rounded and soft like SYMEF. The detail in the top end is decent, better than SYMEF.
Midrange performance is less forward then SYMEF and in my opinion more natural. Guitars and piano sound quite good. The soudstage set by the midrange is reasonably deep and broad with the apparent placement of the performers believable which is in contrast to SYMEF placing the vocalist in your lap with the rest where it belongs.
Bass performance is a mixed response. It plays plenty deep, but seems to lack some detail down low. This sort of 'muddied' bottom end results in some masking of subtle sounds and make the bass region sound a little bigger than it should.
Overall, I'd pick 1DIFFQC over SYMEF, and to be honest I had real hope for SYMEF when I built it. The design performs better than I expected a quasi-complimentary integrated darlington construction would.
I set them up at 50mA per device. I don't tend to run my amps too hot and 1DIFFQC simmed out to be best around this value. Offset was 20mV on one and 42mV on the other, not too bad but a little higher than some others I've built. Clipping is slightly asymetrical but clean. The amp is faster than SYMEF by a fair margin, though I didn't get an exact measurement. The Very slight hiss and buzz with my ear right up to the speaker but nothing to be concerned about (my Brystons -3B and 4B- are both noisier and exhibit more buzz). There is a distinct turn-on transient but that is pretty normal with this type of amplifier.
So, onto some music.
I found the treble to be more crisp than Harrison's SYMEF and quite pleasant. No glassiness or excess sheen, but not rounded and soft like SYMEF. The detail in the top end is decent, better than SYMEF.
Midrange performance is less forward then SYMEF and in my opinion more natural. Guitars and piano sound quite good. The soudstage set by the midrange is reasonably deep and broad with the apparent placement of the performers believable which is in contrast to SYMEF placing the vocalist in your lap with the rest where it belongs.
Bass performance is a mixed response. It plays plenty deep, but seems to lack some detail down low. This sort of 'muddied' bottom end results in some masking of subtle sounds and make the bass region sound a little bigger than it should.
Overall, I'd pick 1DIFFQC over SYMEF, and to be honest I had real hope for SYMEF when I built it. The design performs better than I expected a quasi-complimentary integrated darlington construction would.
Jason, you do not disappoint 
. You pay great attention to detail both in your assembly and analysis
.
That this amplifier was your choice over SYMEF despite TIP142s and many other variables is proof that the formula does work. And yes Nelson Pass did make me modify something small.
Each of the amplifiers published by Harrison Audio Labs, has something very unique about it. Hope you take the time to discover all the secrets
kind regards,
Harrison.
. You pay great attention to detail both in your assembly and analysis.That this amplifier was your choice over SYMEF despite TIP142s and many other variables is proof that the formula does work. And yes Nelson Pass did make me modify something small.
Each of the amplifiers published by Harrison Audio Labs, has something very unique about it. Hope you take the time to discover all the secrets
kind regards,
Harrison.
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Never too late!
It is almost one year since I started building the 1DIFFQC power amplifier. My first plan was to give 1DIFFQC a stabilized power. Running into troubles, not with the1DIFFQC,but with the stabilised power, the hole project has been “sleeping” almost one year. While writing this post the amplifier is on its first test (not a “deep-test”). It was early clear that this amplifier is made from the same philosophy as the SYMEF, which I build with a very good result back in early 2012. I like amplifiers that are able to produce a tight, fast and deep bass. This give me a touch of warmt that I like. I listen very often to classical music, and it strikes me, when I go to a classic concert, how much there is of the lower register in classic music. Both the 1DIFFQC and the SYMEF do this very well . There is nothing wrong with the highs. Totally they are very musical amplifiers. I have taken some pictures. On the last picture you can see no less that four amplifiers, all of very high quality. From left to the right: Nelson Pass F5 CV turbo(finished one week ago), 1DIFFQC,The End from C and SYMEF.
It is almost one year since I started building the 1DIFFQC power amplifier. My first plan was to give 1DIFFQC a stabilized power. Running into troubles, not with the1DIFFQC,but with the stabilised power, the hole project has been “sleeping” almost one year. While writing this post the amplifier is on its first test (not a “deep-test”). It was early clear that this amplifier is made from the same philosophy as the SYMEF, which I build with a very good result back in early 2012. I like amplifiers that are able to produce a tight, fast and deep bass. This give me a touch of warmt that I like. I listen very often to classical music, and it strikes me, when I go to a classic concert, how much there is of the lower register in classic music. Both the 1DIFFQC and the SYMEF do this very well . There is nothing wrong with the highs. Totally they are very musical amplifiers. I have taken some pictures. On the last picture you can see no less that four amplifiers, all of very high quality. From left to the right: Nelson Pass F5 CV turbo(finished one week ago), 1DIFFQC,The End from C and SYMEF.
Attachments
Thanks for your update. Your proposed layout looks ok...providing some form of isolation for the input stages from the SMPS using the heatsinks. Power supply rating is just right. That should be one stiff bass hoping the SMPS can keep up . For this type of layout ensure the top cover is well ventilated, or are you planning on using some mechanical air flow mechanism (may not be necessary)
Looking forward to your input about sound performance. 1DIFFQC is an embodiment of a theorem in audio design that challenges some norms and other theorems
kind regards
Harrison.
. For this type of layout ensure the top cover is well ventilated, or are you planning on using some mechanical air flow mechanism (may not be necessary)Looking forward to your input about sound performance. 1DIFFQC is an embodiment of a theorem in audio design that challenges some norms and other theorems
kind regards
Harrison.
You may choose to use a regulated powersupply in case your power company has poor regulation, kindly add a DC protect circuit to safeguard expensive speakers, however if the risk is worth it and you do not abuse the amplifier and have done the necessary tests to ascertain your circuits stability, you could operate without protection. Kindly operate the amplifier within acceptable SPL levels to safeguard your hearing and the hearing of those around you. If hearing discomfort is encountered, kindly discontinue use and seek alternatives. Feel free to post your experinces with the circuit
Hi Harrison,
I have just looked over your quasi design (duh, took me five years!) and I believe it would sound wonderful.
Reasons: low loop gain with high LTP degen, heavy loading of the VAS with 68k, clever use of limiting the lowest output to 'save' the quasi inverter, phase lead rather than lag comp, judicious degen on the VAS, and of course, the quasi itself.
Lots of your amps have been very successful on the forum, and I take my hat off to.
Another beauty, huh?
HD
I have just looked over your quasi design (duh, took me five years!) and I believe it would sound wonderful.
Reasons: low loop gain with high LTP degen, heavy loading of the VAS with 68k, clever use of limiting the lowest output to 'save' the quasi inverter, phase lead rather than lag comp, judicious degen on the VAS, and of course, the quasi itself.
Lots of your amps have been very successful on the forum, and I take my hat off to.
Another beauty, huh?
HD
You know what they say about art, it gets better with age, this design was inspired by the best designs of these topologies, the degeneration mostly due to the works of Prof M Leach , Douglas Self and Rod Elliot and others. Other parts are due to the early works of Nelson Pass , not forgetting the Naim clone crew that were caught up in nostalgia of yester years, a French amplifier maker, plus many more, thats how this amp was born, the queen of them all, and not forgetting you.
The other amplifier SYMEF is another story
Two members of this forum were also the first to venture into the wilderness that being, Drowranger and PauloPT, They were quickly followed by many more including Joe.
Have been messing around with speakers of late and buck boost converters.