I hate to start a new thread as my first post on the forum, but I really am beginning to spin my wheels. My question is in line with a few other posts, but they are kind of old now, so hopefully, this isn't too duplicative.
I'm looking to build my first DIY amp. I'm fairly handy, so the process of building an amp is not intimidating to me. I majored in physics, so I'm not scared away by more complicated designs. I don't have electronics experience, but I want to learn. That said, I don't want to build anything, unless I understand what all of the parts are doing/how the circuit works. As a result, I'm attracted to Mr. Pass's designs, because of the articles he wrote about the circuits, which (for the most part, I think), I can follow. (Not to mention, for a few years, I have really wanted to buy a Pass Labs amp and have been intrigued by First Watt amps.)
I have a pair of Focal Kanta 2s, which can be a bit of a tough load to drive; the amp has to be very comfortable with 4 ohm loads (see Stereophile's measurements; the impedance is "nominally" 8 ohms, but it can drop below 3 ohms: Focal Kanta No.2 loudspeaker Measurements | Stereophile.com). I had originally thought to buy a couple of ACAs and set them up in a dual mono configuration, because they are made for newbies, but I'm concerned that they just won't have the grunt to drive these speakers. Based on what I've been able to glean from posts on this forum and other websites, going with a push pull output stage is the way to go. This would mean F5, F5 Turbo, F6, or Burning Amp (with complimentary output). So if the ACA won't work, which of the builds would you recommend? (I tend to listen to music between 80-90 dB at the listening position at 8ft from the speakers, so I imagine there are only a few watts going through the speakers; that being said, I am also a believer that having some overhead is important). (I also don't necessarily need a full parts kit available at diyaudiostore.com or anything like that - though, if there isn't one available, I'm sure you'll be hearing from me again with help on parts selection.)
I'm looking to build my first DIY amp. I'm fairly handy, so the process of building an amp is not intimidating to me. I majored in physics, so I'm not scared away by more complicated designs. I don't have electronics experience, but I want to learn. That said, I don't want to build anything, unless I understand what all of the parts are doing/how the circuit works. As a result, I'm attracted to Mr. Pass's designs, because of the articles he wrote about the circuits, which (for the most part, I think), I can follow. (Not to mention, for a few years, I have really wanted to buy a Pass Labs amp and have been intrigued by First Watt amps.)
I have a pair of Focal Kanta 2s, which can be a bit of a tough load to drive; the amp has to be very comfortable with 4 ohm loads (see Stereophile's measurements; the impedance is "nominally" 8 ohms, but it can drop below 3 ohms: Focal Kanta No.2 loudspeaker Measurements | Stereophile.com). I had originally thought to buy a couple of ACAs and set them up in a dual mono configuration, because they are made for newbies, but I'm concerned that they just won't have the grunt to drive these speakers. Based on what I've been able to glean from posts on this forum and other websites, going with a push pull output stage is the way to go. This would mean F5, F5 Turbo, F6, or Burning Amp (with complimentary output). So if the ACA won't work, which of the builds would you recommend? (I tend to listen to music between 80-90 dB at the listening position at 8ft from the speakers, so I imagine there are only a few watts going through the speakers; that being said, I am also a believer that having some overhead is important). (I also don't necessarily need a full parts kit available at diyaudiostore.com or anything like that - though, if there isn't one available, I'm sure you'll be hearing from me again with help on parts selection.)
The F5 is certainly the "safe" answer, as it increases power into 4 ohm loads, unlike most FW designs. But many have had success with the Aleph J into 4 ohm loads. Since the power supply for both the F5 and Aleph J are the same, I'd recommend that you build both sets of boards, use the same chassis and power supply, and see which you like better. 🙂
Oh, and while I'm here, let me plug my Aleph J build guide, which might be useful. 🙂
Oh, and while I'm here, let me plug my Aleph J build guide, which might be useful. 🙂
You don't need to look solely at the impedance,
it's better to look at the impedance in combination with the needed voltage swing.
Since your Focal Kanta's have a high sensitivity of 91dB, the amplifier voltage swing required will be rather low.
An 8ohm 88db speaker will need double voltage swing to play as loud,
so power demands for both speakers will be the same, it's ohm's law.
But there are some amplifiers where the distortion rises more with 4 ohm and halve output voltage compared to others.
A good guide is the First Watt Amplifier Comparison Chart
You should also do this speaker voltage test to see how much power you need.
it's better to look at the impedance in combination with the needed voltage swing.
Since your Focal Kanta's have a high sensitivity of 91dB, the amplifier voltage swing required will be rather low.
An 8ohm 88db speaker will need double voltage swing to play as loud,
so power demands for both speakers will be the same, it's ohm's law.
But there are some amplifiers where the distortion rises more with 4 ohm and halve output voltage compared to others.
A good guide is the First Watt Amplifier Comparison Chart
You should also do this speaker voltage test to see how much power you need.
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If you want an amp with some grunt, the BA2/3 with a 6 deep output stage https://www.firstwatt.com/pdf/art_ba2.pdf https://www.firstwatt.com/pdf/art_ba_3.pdf or a Stasis amp New Stasis front end are probably the best candidates; but an F4 https://www.firstwatt.com/pdf/prod_f4_man.pdf can easily drive my Apogee Stage's 3 ohm load; if you build an F4, this will leave you with plenty of scope to play with 'front ends' to get the 'sound' your looking for.
I have 4 Ohm Tekton Moabs. I have built the F4, F5, F6 and Aleph J. You can see more detailed comments on my impressions of them here Anyone put 2 Pass amps in 1 chassis with 1 PSU? . None of them seemed to have any issues with the 4 Ohm load but I don't know how I would know if they did unless they sounded terrible which they haven't. And the specs on the Aleph J say it only outputs 13 watts into a 4 Ohm impedance but that has been my favorite build so far.
The Focal Kanta 2s deserve the best you can build. My recommendation would be the Aleph J, with a proper dual-mono power supply. Don’t worry too much about single-ended vs push-pull. Very fine amplifiers can be built either way.
The Aleph J is known for handling ‘difficult’ loads well. With the extra capacity afforded by a dual-mono PSU, one can build up the voltage and bias current as necessary. A high bias Class A amp will meet the needs of your speakers. Their efficiency of 91dB will help make the most of what the amp deliveres.
The Aleph J is known for handling ‘difficult’ loads well. With the extra capacity afforded by a dual-mono PSU, one can build up the voltage and bias current as necessary. A high bias Class A amp will meet the needs of your speakers. Their efficiency of 91dB will help make the most of what the amp deliveres.
The M2X is a lot of fun with the different input boards and it is rated 40W in 4 ohm as I remember. It should be more than enough.
Also I think you would be surprised how loud ACA would be able to play. I had my ACA's with me to a friend to test them on Snell C speakers. I was quite surprised by the performance. They could play louder than my ears liked and with good bass control. Many have built this amp so maybe one close to you could bring it to you for at test.....
Also I think you would be surprised how loud ACA would be able to play. I had my ACA's with me to a friend to test them on Snell C speakers. I was quite surprised by the performance. They could play louder than my ears liked and with good bass control. Many have built this amp so maybe one close to you could bring it to you for at test.....
+1 on Aleph J for your needs. Yes, it’s not a lot of power but it’s a really sweet sounding amp. I run my less sensitive Martin Logan Montis on much less with my flea watt tubes and they are usually enough for my listening, even with my jet engine destroyed hearing they are enough.
Thank you all for your quick and thorough responses. They all helped me to get my brain moving in the right direction again.
Flohmann, I like the idea of going with a design where I can easily swap out boards to get a new amp. Takes the pressure off of my initial choice.
Flohmann, I like the idea of going with a design where I can easily swap out boards to get a new amp. Takes the pressure off of my initial choice.
You rightfully plugged it. I somehow missed that build guide. You did a fabulous job with it.
Tungsten, I think this is the way I'm going to go. You all convinced me. I'll save the more modular BA and M2X designs for future builds.
Poseidon, I did notice your post. That is quite a beautiful beast you built. It did get me thinking that adding a 12V trigger would be a nice quality of life thing to add. This being my first build, though, I think I'll keep it simple - shoot for building a solid, quality amp with no people, electronic components, or speakers dying in the attempt.
You might take a look at the "amplifier comparison chart" at firstwatt.com. Compare the 4 ohm and 8 ohm numbers of the amplifier in question.
It's not just a 4 ohm load, but also low sensitivity (83-85 db/w/m, depending on whose measurements you prefer). The Aleph J is a 13 watt amp into 4 ohms.
Will it work? If you are listening near-field at reasonable volume, I suspect it will sound great. But unlike with a higher powered amp, you'll likely need to live within those limits with the Aleph J. For example, I love my Aleph J with Falcon LS3/5a speakers (15 ohm, 83db/w/m), but mostly for nearfield listening at moderate volumes.
If you want more flexibility with your LS50s, you'll want a higher-powered amp. You might consider building a Hypex-based Class D amp -- they are easy to build, have a big community, and deliver high power easily. I had one based on the Hypex NC252mp module, and it sounded surprisingly good for the money.
Its great you have considered the load ( speakers ) and the amp required to effectively drive this load .
The magnitude of the impedance curve of the Kanata 2's drops down to 3.0 ohms - plus there are significant swings in the phase angle .
These speakers are a difficult load for an amp .
I think of like this - Its current that is needed to create a magnetic field in the voice coils ,
So a power supply big enough to supply that current is needed and the supply needs to have a low Zout .
If the power supply is undersized , especially with a difficult load , the voltage rails will droop and bass will suffer .
Suggest selecting a Pass Labs design that has a low Zout , so the current from the power supply can get
to the load .
.
I like the F5 for this sort of thing, and you can always parallel another pair of output
transistors for roughly twice the output current. And if you use the Harris parts you
can get a mild negative phase 2nd harmonic.
transistors for roughly twice the output current. And if you use the Harris parts you
can get a mild negative phase 2nd harmonic.
I was going to suggest the f6 as I have used that to power some pretty tough loads. Including, magnapans, Acoustat, Martin Logan request, von schweikert, vanderstein to mention a few. However, Mr Pass makes a great point about being able to add output devices to the F5.
I guess what it comes down to is what flavor you would like in your sound.
The f6 would work. I would suggest swapping the MOSFETs for IRFP150's. Otherwise check out the F5. Alephs are great but have a higher part count which isn't a huge deal. I do like the sound of the Aleph quite a bit though. Probably my favorite sound of the three mentioned above.
Maybe Randy's boards for the Aleph 30/40 amplifier would be a good choice.
I guess a good step would be to share some thoughts as to what you want from your sound.
I guess what it comes down to is what flavor you would like in your sound.
The f6 would work. I would suggest swapping the MOSFETs for IRFP150's. Otherwise check out the F5. Alephs are great but have a higher part count which isn't a huge deal. I do like the sound of the Aleph quite a bit though. Probably my favorite sound of the three mentioned above.
Maybe Randy's boards for the Aleph 30/40 amplifier would be a good choice.
I guess a good step would be to share some thoughts as to what you want from your sound.
Thank you all for replies! 13W @ 4Ohms, yeah I saw that before. Might be rough with those notoriously inefficient speakers.
I built a F5Tv2 for a friend, but that is way too big for my current situation 🙁 Fun build though, thank you!
Thanks Papa! What do you mean by negative phase 2nd harmonics? Guess I need to read about that more.I like the F5 for this sort of thing, and you can always parallel another pair of output
transistors for roughly twice the output current. And if you use the Harris parts you
can get a mild negative phase 2nd harmonic.
I built a F5Tv2 for a friend, but that is way too big for my current situation 🙁 Fun build though, thank you!
I know the NC series pretty well, indeed they sound really good. The new MERUS series from Infineon is pretty amazing too.