I begin to worry already...
It always been vice-versa... If you fear the 'subtraction' - you anyway do it with a feedback loop. Why don't then 'enclose' the circuit into single process...
If you don't do this - it is not the differential amp. Period.
It doesn't at first. At second - if you don't do that - it has _zero_ CMRR and so - susceptible to new distortions.
There are no such thing as 'both' phases 'independent'. The signal is the difference (so common mode is not the signal). If you treat them 'independently' the ground is not excluded from the signal path. You have just two separate non-balanced/non-differential amps. Your amp is NOT fully-differential as you claim!
Where did you read that?! Mistaken again, ready slowly and carefully ... balanced I said not differential. Virtual GND in power amp is exactly on 1/2 of the signal, it's the reference point for the amp much better than undefined high Z floating. Anyhow it is my decision of how differential signal is transferred to the speaker, still way better than an OP amp diff input.
http://www.diyaudio.com/forums/vend...-mosfet-amplifier-module-293.html#post4712014
Here I clearly read:
No, not bridged. Fully balanced input/output, matched impedance differential amplifier, couldn't be more differential than this, you'll see.
No matter if the reference point is virtual or physical... All the decisions and conclusions are the same in the end.
It is pity you have chosen such limiting decision... Considering the OP amp diff input - it is arguable. But you don't need an op-amp to do proper differential design (in the end the amp itself is kind of a discrete opamp). Usually two symmetric feedback networks is everything you need.
Limiting decision, you don't have a clue, don't you lol. Tested, as said way better than any OP amp diff input. Chose this one on my responsibility to offer users best sound quality. As already said, open thread in solid state part of the forum and discuss there as much as you like, this is commercial part and your opinion is irrelevant to me. Don't push me to say you f word, bye
Rude...
As far as I remember we haven't seen any measurements that confirm this.
Just words...
You are not god so leave me my right not to believe you, especially if your claims are in conflict with logic and/or appealing exclusively to faith.
This is a thread about your product - true. This is a public and open forum - also true. I am discussing wishes for and shortcomings of YOUR product, so is on topic - also true. So, don't tell me go somewhere else... And don't be rude to your potential customers. It is an unworthy commercial behavior! I don't count you as worthy of attention anymore
As far as I know all my customers are pleased with sound quality and that is everything that matters. This is one of the best sounding amplifiers, lots of feedback from users, not all members here. We A/B compared First One against major High-End brands amps in a top systems and FO beats them all. Your little frustration maybe comes from plain envy knowing this.
Thanks for your interest. Actually I can't do much about it since attachments are fixed and cannot be changed or added. Technical specifications, contact mail, price, etc are valid.
Maybe I could help you on some topic, just ask please.
L.C.
FO V1.2 vs V1.4
Hello
this is to share some information with you about 1.2 vs 1.4
as I got my 1.4 couple of weeks ago, I gave a pair of 1.2 (which havent been used in fact) to a friend who did quite a nice integration with 2 SMPS from Audiopower (DPS400-ST-2x45Volts).
Then he told me the sound is ok but flat, no life...
I was surpised but I decided to give it a try and to compare with 1.4 using same SMPS.
I ve been listening the 1.2 for 2 hours at quite a level (pot calibrated for 66Watss into 6ohms for 0dbfs/2vrms) and it was ok but yes it was flat. Not sure how to explain, just check if your foot is knocking the floor and then you know.
As on one side I have the FO1.4 with a single hypex, and on the other side a FO1.2 with dual SMPS, I was wondering if the difference comes for the SMPS or the FO. Then I dismatled my 1.4eek and put the heatsinks on top of the FO1.2 and I ve just disconected the 1.2 and conencted the 1.4 on the 2 SMPS.
Whaou, back to life ! amaizing difference! the 1.4 ROCKS, really ROCKS, again, just check your foot. The bass are very tight and strong, and this gives an overall "loudness" like effect which brings life in the recording. also warmer.
my imediate recomendation to my friend(s) is to upgrade to 1.4!
as the DPS400 were only 45Volts, I wasnt able to push the system to its maximum. the good news is that at this voltage it is not hot at all, I got 42°C on 2Ux300 heatsink (after heavy listening) and the SMPS was at 45°C (surface, box open) with factory bias setting. This voltage si probably ideal for a bridge FO1.4 M solution.
I will test an higher power of this SMPS (S1/S2) in 52V later this month, as I think LC is right promoting dual smps with FO (also confirmed with a LTSpice simulation, this dramaticaly improve damping and crosstalk due to 0V signal configuration).
Cheers
Hello
this is to share some information with you about 1.2 vs 1.4
as I got my 1.4 couple of weeks ago, I gave a pair of 1.2 (which havent been used in fact) to a friend who did quite a nice integration with 2 SMPS from Audiopower (DPS400-ST-2x45Volts).
Then he told me the sound is ok but flat, no life...
I was surpised but I decided to give it a try and to compare with 1.4 using same SMPS.
I ve been listening the 1.2 for 2 hours at quite a level (pot calibrated for 66Watss into 6ohms for 0dbfs/2vrms) and it was ok but yes it was flat. Not sure how to explain, just check if your foot is knocking the floor and then you know.
As on one side I have the FO1.4 with a single hypex, and on the other side a FO1.2 with dual SMPS, I was wondering if the difference comes for the SMPS or the FO. Then I dismatled my 1.4
eek and put the heatsinks on top of the FO1.2 and I ve just disconected the 1.2 and conencted the 1.4 on the 2 SMPS.Whaou, back to life ! amaizing difference! the 1.4 ROCKS, really ROCKS, again, just check your foot. The bass are very tight and strong, and this gives an overall "loudness" like effect which brings life in the recording. also warmer.
my imediate recomendation to my friend(s) is to upgrade to 1.4!
as the DPS400 were only 45Volts, I wasnt able to push the system to its maximum. the good news is that at this voltage it is not hot at all, I got 42°C on 2Ux300 heatsink (after heavy listening) and the SMPS was at 45°C (surface, box open) with factory bias setting. This voltage si probably ideal for a bridge FO1.4 M solution.
I will test an higher power of this SMPS (S1/S2) in 52V later this month, as I think LC is right promoting dual smps with FO (also confirmed with a LTSpice simulation, this dramaticaly improve damping and crosstalk due to 0V signal configuration).
Cheers
Attachments
Last edited:
one or two SMPS that is the question
By the way, I ve done some simulations in order to better evaluate the theoretical impact of using a single PSU instead of two, as this topic has been raised many time.
in fact all the concern is about the current return in the ground wire (going back from FO to PSU) which is generating a shift in the 0V signal as the "in-" of each FO chanel is located on the FO PCB.
Hopefully these wires will be in the range of 1 to 5 mili ohm according to equations.
I enclose below the result of 3 simulations which are interresting not in term of absolute value, but in term of delta by comparaison to a dual supply simulation.
Also all my simulation are made with a model for the FO and the Hypex which is far from the reality (but not stupid).
http://www.gopix.fr/image-4523_573DE253.jpg
Okay, so first with a single supply, the 0Volt signal (RCA socket) should be connected to a center of a star or a T, starting from the PSU and then spliting to both FO. Both "in-" should be left unconnected. That seems to give the most efficient result. The crosstalk is evaluated at 112db @1khz instead of 200db ish for a dual supply, this is certainly acceptable... The damping factor of the amp woud be divided by 17 (say an order of magnitude) and this is probably where we have the most concern.
One solution is to use a differential receiver upfront between the Source and each FO, or eventually none for the first chanel and one for the second channel. The second simulation demonstrates that the crosstalk is increased by 40db ish and the damping factor is back to normal !
http://www.gopix.fr/image-943E_573DE253.jpg
and then, considering the above posts about bridging the FO and using a differential source, I have evaluated the CMMR of such configuration. obviously the CMRR is directly linked to the potential error in the gain of the FO, which are dependent on some resistors in the feedback loop.
with 1% resistor the CMRR is 40db and rise to 60db with 0.1% resistor. LC can enlighten us on this. (Damping is almost same).
http://www.gopix.fr/image-F341_573DE253.jpg
if we put a differential receiver upfront, such as That1200 or INA134, this will be up to 85db CMRR, with the concern of an additional component in the signal path.
I have just launched in production a smal PCB (51x21mm) containinng 2 regs and 1 or 2 that 1200. It can be used as a differential receiver for FO, or as a way to solve the damping issue and to use FO with a single SMPS thus reducing overall cost, or as a way to bridge to FO with the second That being inverted.
I enclose the picture of the PCB, and I plan to open a topic later this month showing more details and results with it, not to polute LC thread. As I will receive 20 PCBs next week, if you guys are interrested by 1 or 2pcb just drop a message and I can send you a basic mail free of charge under the condition that you contribute by sharing your practical experience.
hope this is of interrest, and appropriate here and then
By the way, I ve done some simulations in order to better evaluate the theoretical impact of using a single PSU instead of two, as this topic has been raised many time.
in fact all the concern is about the current return in the ground wire (going back from FO to PSU) which is generating a shift in the 0V signal as the "in-" of each FO chanel is located on the FO PCB.
Hopefully these wires will be in the range of 1 to 5 mili ohm according to equations.
I enclose below the result of 3 simulations which are interresting not in term of absolute value, but in term of delta by comparaison to a dual supply simulation.
Also all my simulation are made with a model for the FO and the Hypex which is far from the reality (but not stupid).
http://www.gopix.fr/image-4523_573DE253.jpg
Okay, so first with a single supply, the 0Volt signal (RCA socket) should be connected to a center of a star or a T, starting from the PSU and then spliting to both FO. Both "in-" should be left unconnected. That seems to give the most efficient result. The crosstalk is evaluated at 112db @1khz instead of 200db ish for a dual supply, this is certainly acceptable... The damping factor of the amp woud be divided by 17 (say an order of magnitude) and this is probably where we have the most concern.
One solution is to use a differential receiver upfront between the Source and each FO, or eventually none for the first chanel and one for the second channel. The second simulation demonstrates that the crosstalk is increased by 40db ish and the damping factor is back to normal !
http://www.gopix.fr/image-943E_573DE253.jpg
and then, considering the above posts about bridging the FO and using a differential source, I have evaluated the CMMR of such configuration. obviously the CMRR is directly linked to the potential error in the gain of the FO, which are dependent on some resistors in the feedback loop.
with 1% resistor the CMRR is 40db and rise to 60db with 0.1% resistor. LC can enlighten us on this. (Damping is almost same).
http://www.gopix.fr/image-F341_573DE253.jpg
if we put a differential receiver upfront, such as That1200 or INA134, this will be up to 85db CMRR, with the concern of an additional component in the signal path.
I have just launched in production a smal PCB (51x21mm) containinng 2 regs and 1 or 2 that 1200. It can be used as a differential receiver for FO, or as a way to solve the damping issue and to use FO with a single SMPS thus reducing overall cost, or as a way to bridge to FO with the second That being inverted.
I enclose the picture of the PCB, and I plan to open a topic later this month showing more details and results with it, not to polute LC thread. As I will receive 20 PCBs next week, if you guys are interrested by 1 or 2pcb just drop a message and I can send you a basic mail free of charge under the condition that you contribute by sharing your practical experience.
hope this is of interrest, and appropriate here and then
Attachments
Sure Do
I m realizing that due to the cables from amp to Loudspeaker, the difference in Damping between 1 or 2 PSU might be only 3 time and not 17time as metioned in previous post (which considers 0ohm for cables)!
the more I m digging on this the more I feel that one good PSU might be good enough to feed 2 big boys. Stay tuned.
I m realizing that due to the cables from amp to Loudspeaker, the difference in Damping between 1 or 2 PSU might be only 3 time and not 17time as metioned in previous post (which considers 0ohm for cables)!
the more I m digging on this the more I feel that one good PSU might be good enough to feed 2 big boys. Stay tuned.
I was wondering if the difference comes for the SMPS or the FO. Then I dismatled my 1.4
Whaou, back to life ! amaizing difference! the 1.4 ROCKS, really ROCKS, again, just check your foot. The bass are very tight and strong, and this gives an overall "loudness" like effect which brings life in the recording. also warmer.
my imediate recomendation to my friend(s) is to upgrade to 1.4!
Correct observing.
In 2015 we spent enormous amount of time voicing First One v1.4 M modules in all kind of a systems. Each time only one change to sch was done and then again listening comparison against revision before. It's the only way to evaluate and determine next revision in a proper direction, so R&D went on for a few months. Not really surprising that First One came to a certain SQ level, all that time and energy spent simply had to represent itself in a positive way.
All along R&D path we normally tested one or two PSU variants, also linear and SMPS, to say in short, at the end best SQ we got in dual mono set-up, complete GND isolation and with SMPS1200A400 power supply. That remains the same what is installed in my current First One ready made amplifiers. What you get for 800 EUR of material involved to produce First One amplifier is simply cheap in comparison to an amplifiers First One has beaten.
No doubts, simply two.
Hello,
I am planning to build a FO 1.4M to pair with 8Ohm speakers. I was considering the Hypex 1200A400 as recommended but I recently discover Cresnet SMPS. I see that the majority goes with the 500-600W model.
But since the Hypex 1200A400 is recommended over the 400A400 I believe that the Cresnet 1200 is more suited for the job with 8Ohm (and 600W only advised for lower impedance). Am I right or totally mistaken ?
Thank you.
I am planning to build a FO 1.4M to pair with 8Ohm speakers. I was considering the Hypex 1200A400 as recommended but I recently discover Cresnet SMPS. I see that the majority goes with the 500-600W model.
But since the Hypex 1200A400 is recommended over the 400A400 I believe that the Cresnet 1200 is more suited for the job with 8Ohm (and 600W only advised for lower impedance). Am I right or totally mistaken ?
Thank you.
Crossing certain system's quality margin one could hear difference among input wires, meaning SMPS's differences are even more noticeable, so quite crucial decision choosing just the right PSU. Unfortunately I was not able to test Cresnet's SMPS, as heard, his latest iteration is well accepted, but as you might well know my recommendation goes to dual mono - two SMPS1200A400.
