Thank you. Exactly what I wanted! Obviously, I cannot have a listen to the FOs. Any idea what do they sound compared to Arcam P1 monoblocks (my current amps) or Linn LK140 / Klout which are the alternatives I am considering? I listen to mostly Jazz and classical (piano / violin). Ribbon tweeters on my speakers (Robson Acoustics Voltaire's) have made a huge difference for the latter.
Series production modules will have 10 kOhm input impedance which is almost a norm for power amps, changing R2=10 kOhm to higher value could be in some cases beneficial but as always there's trade off between lower signal to noise ratio and higher input offset voltage compared to original value version, so my recommendation would be to stay well below 30 kOhm.
Could not tell the difference, since your amps are a bit of mystery to me but one of my friends evaluated First One v1.4 prototype version against Naim NAP250, maybe we'll have to ask him kindly to tell more.
I can only say how the latest version compares to First One v1.3 since I have both here mainly for comparisons reasons. Last week I gave another try to v1.3, leaving it on for a whole day playing music before critical listening took place and to be honest it plays nice for someone who didn't get hands on v1.4 yet, so it left me only to reconnect v1.4 back in the system.
I use Naim Superuniti as a source. At the moment as all in one streamer/preamp/amp. I drive with it my Thiel CS2.4 and Thiel 3.7. The amp is strong enough for normal listening. But not for loud listening.
I have used VSSA for one year and later used FirstOne1.2. FO1.2 brought refinement which VSSA was not capable off, but at the same time showed the limitations of the big capacitor in the feedback. There is not enough resolution in percussion instruments and amp has soft more pronounced bass in the instruments. Both VSSA and FO were very capable of driving demanding Thiel speakers. For me VSSA is more alround than FirstOne1.2. All 1.3 versions are more or less similar to 1.2. Even though LC probably disagrees.
Few months ago I had Nap250.2 on loan from a dealer. I was surprised how different it sounded to my Naim Superuniti alone, which has power amp similar to Naim Nap 200. Compared to Naim SU the 250.2 has more bass but it was less easy to follow the beat. Female and male voices were fantastic, really easy to enjoy and listen. Higher frequencies sounded less real almost sinthetic. Bottom line, the amp is far from perfect, somewhat coloured, but it can be very enjoyable.
Then Lazy Cat brings FO1.4 beta. This amp is so far the least coloured amp i have heard. And it is that way throughout the whole frequency range. It is powerful yet delicate. We played all kinds of music on it and performed very good giving us more insight of the recordings. We were really surprised, how much more details were there in the background of what we played. This little sounds are just in correct place. Bottom line, it sounds almost perfect, clean and clear! It has the refinement of FirstOne1.2 and 1.3 but none of the drawbacks.
Now I am waiting for a preproduction sample from lazy cat.
I haven't had time to read this entire thread yet, but what was the consensus on the SMPS 'shootout' last year and around post #340 or so? What's everyone using with their First One amps? Seems like a battle between Cristi and AP2. I can only vouch for Cristi as I have 4 of his SMPS's and they exude quality and attention to craftsmanship - something you don't too often now a days. And, they work as advertised.
Rick
Rick
Available already.
Terry aka. still4given forum member compared VSSA to GB150D and found VSSA more detailed and transparent, he's a nice guy and will explain gladly if asked. Let me remind you that First One v1.4 is quite another beast addressing sound exploration.
You can place orders already.Are you accepting orders for v1.4 already or do we have to practice patience some more
SMPS1200A400 is a perfect match to First One amplifier, also supports DC sense and remote standby/on operation. It has soft start, overcurrent protection, power/current capability, all in one PCB, plug & play no brainer. Soundwise I would recommend something else of PSU if that proved better, for sure.
It's on the test bench preparing for you. Thanks for interesting reading, it's always pleasure to follow your impressions and reviews.
Noise in tweeter channel
I have finally been able to get my entire active system setup with First One Amps and I have a slight issue which I can't quite solve. There is some noise that can only be heard through the tweeter channel. It seems different than the usual white noise hiss.
This noise is present and doesn't change whether the source is connected or not and is not volume dependant.
I have done my best to route the cables properly to avoid noise but it has made no difference.
The noise was not able to be heard through a pair of passive bookshelf speakers when the amps were tested so this seems to be an issue with the active setup.
I have made a recording of the noise with my phone which I have attached (AAC audio in a zip file). I would be grateful if anyone could listen to the file and offer an opinion if they think the noise is ground/buzz related or RFI and EMI related noise so I can decide how best to try and get rid of it.
I can just about hear the noise at the listening position which is about 2.5 metres away which makes it annoying enough to try and eliminate.
Thanks
I have finally been able to get my entire active system setup with First One Amps and I have a slight issue which I can't quite solve. There is some noise that can only be heard through the tweeter channel. It seems different than the usual white noise hiss.
This noise is present and doesn't change whether the source is connected or not and is not volume dependant.
I have done my best to route the cables properly to avoid noise but it has made no difference.
The noise was not able to be heard through a pair of passive bookshelf speakers when the amps were tested so this seems to be an issue with the active setup.
I have made a recording of the noise with my phone which I have attached (AAC audio in a zip file). I would be grateful if anyone could listen to the file and offer an opinion if they think the noise is ground/buzz related or RFI and EMI related noise so I can decide how best to try and get rid of it.
I can just about hear the noise at the listening position which is about 2.5 metres away which makes it annoying enough to try and eliminate.
Thanks
Its clear to me from the recording its buzz, and it could be related to anything, are you using any digital crossovers before the amplifiers?
A picture of the whole setup would help a lot.
I understand SMPS1200A400 has the preference, even 2 of them probably to cope with higher output needs.
Readng its specs sheet, it appears to me (wrong?) that this PSU is made to power 3 amps, whereasthe very similar SMPS1200A700 seems made for 2 amps. Why not opting for this one, once available again, for stereo applications (and then presumably 1 only would be enough, halving the PSU costs)?
Or am I just mislead by the layout of the specs sheet and the way ther power output is declared?
Thanks!
Readng its specs sheet, it appears to me (wrong?) that this PSU is made to power 3 amps, whereasthe very similar SMPS1200A700 seems made for 2 amps. Why not opting for this one, once available again, for stereo applications (and then presumably 1 only would be enough, halving the PSU costs)?
Or am I just mislead by the layout of the specs sheet and the way ther power output is declared?
Thanks!
I heard hiss and hum. My guess is ground loop or interconnect cable...
Since it has frequency 50/100 Hz you could easily spot it with a scope if you have one, or you can borrow one. This way you can compare input and output of both channels. If the hiss is in the input of one channel only, then your crossover could be faulty.
Other way is to swap amps and cables between channels and observe when will the hiss and hum will move. When it does, that is the faulty part.
After you swap left and right channel amps and cables and the hiss is still present from the same tweeter it is time to consider active crossover. BTW what is your active crossover?
Cresnet, Hose4 thanks for the input.
I am using a Najda as a digital crossover with an amenero for usb input from a computer.
I don't think the Najda itself is directly causing the issue as the noise is exactly the same when the crossover is on or off. The cabling to / from could be introducing a ground loop or be the entry point for interference.
If I unplug the tweeter amp input cable then the buzz disappears from the tweeter but is now present on the two midrange speakers instead which is a bit strange. If I plug the tweeter input cable back in then the noise returns to only be audible from the tweeter.
The way the system is set up now it is not too easy for me to take a picture of that that would show anything other than the components themselves.
Computer to Najda. Najda to two separate amplifiers. One four channel First One for mid / tweeter and another two channel amp for woofers. Speakers are Linkwitz LX521.
Interconnects are as short as possible made out of mic cable with shield and one wire connected to ground with the other central conductor for signal.
Speaker cables are four core speakons one cable for mid / tweeter the other for woofers.
I am using a Najda as a digital crossover with an amenero for usb input from a computer.
I don't think the Najda itself is directly causing the issue as the noise is exactly the same when the crossover is on or off. The cabling to / from could be introducing a ground loop or be the entry point for interference.
If I unplug the tweeter amp input cable then the buzz disappears from the tweeter but is now present on the two midrange speakers instead which is a bit strange. If I plug the tweeter input cable back in then the noise returns to only be audible from the tweeter.
The way the system is set up now it is not too easy for me to take a picture of that that would show anything other than the components themselves.
Computer to Najda. Najda to two separate amplifiers. One four channel First One for mid / tweeter and another two channel amp for woofers. Speakers are Linkwitz LX521.
Interconnects are as short as possible made out of mic cable with shield and one wire connected to ground with the other central conductor for signal.
Speaker cables are four core speakons one cable for mid / tweeter the other for woofers.
I think you are using a SMPS to power up the amplifiers?
I still recommend a picture, because it will show whats going on.
I recommend that you conduct the below test
1- Disconnect all output signals from the DSP to all amplifier modules
2- Start connecting one output from the DSP to each amplifier
3- Check if you have buzz if one module is connected
4- If GND (220VAC) is connected to the system, it could be the problem.
Once you identify the source of the problem, or at least when it appears exactly. then it can be fixed from there.
Regards
GND loop interference for sure. For multichannel amp as active speaker is, you have to have only one reference GND for all the amp's channels because active crossover has only one GND. Solution is to connect both main GND-s (active crossover and SMPS out GND) together and rout only +IN signal wire from active crossover channels to each amp's channel input without input GND wire (no connection), thus GND loop is broken and no hum present.
SMPS1200A180, 2 x 45 V (1-4 FO S, 1-2 FO M)
SMPS1200A400, 2 x 65 V (1-4 FO S, 1-2 FO M, 1-2 FO L)
SMPS1200A700, 2 x 85 V (1-2 FO L)
Other solutions not recomended. Consider SMPS's output power and current, not just output power. Mind you not to choose wrong SMPS1200 according to its output voltage ratings, otherwise your amp will say goodbye.
LC thanks for the information. I can think of two ways to achieve the setup you describe.
My four channel amp has each amp module's ground connected to the same SMPS ground point.
1. I could leave only one signal ground connection in the interconnects instead of having four separate ones as now.
2. I could connect smps ground to the screen of one interconnect and remove the screen/ground connections from all other interconnects.
It would not be too hard to do either of these and it should eliminate a few loops. Which would you choose?
Thanks