To be more precise: FUGLY!I like the build of the Aleph J boards, and the general concept of a common chassis and power supply that can be used for multiple amp designs.
I do, however, see much use of smaller boards that are not really necessary. Things like "soft start" and "speaker protection" PCBs don't make it into the production FirstWatt amplifiers, presumably for a very good reason. Among the build reports we have seen over the years, these little add-ons seem to cause more problems than they solve. I'm sure they don't do anything positive for the sound quality. Hopefully there is a build option to eliminate these items, or better yet, not include them as the default.
I do, however, see much use of smaller boards that are not really necessary. Things like "soft start" and "speaker protection" PCBs don't make it into the production FirstWatt amplifiers, presumably for a very good reason. Among the build reports we have seen over the years, these little add-ons seem to cause more problems than they solve. I'm sure they don't do anything positive for the sound quality. Hopefully there is a build option to eliminate these items, or better yet, not include them as the default.
TungstenAudio,
I totally get what you are saying, such is the spirit of DIY. In fact, we could argue that the panel engraving, etc…are all superfluous as well. The engravings don’t help the sound at all!
Whether the usual CL-60 thermistor or a dedicated softstart, I would need one of them especially with my choice of an 800VA toroid. The ISS board has momentary switch options, LED, 12V triggers, etc…and will immediately work should there be a short power outage.
I have used the Guardian-86’s in other designs and with/without them there is no sonic difference to my ears. Moreover the designer has demonstrated the incredibly low infringement they have on the THD on even his best design; I would encourage you to contact him if you are doubtful as such (that is if you believe in measurements in being a guide). The Guardian-86’s provide insurance, you may not want that, and that is your choice.
Oh…I do like to support other vendors as well
Best,
Anand.
I totally get what you are saying, such is the spirit of DIY. In fact, we could argue that the panel engraving, etc…are all superfluous as well. The engravings don’t help the sound at all!
Whether the usual CL-60 thermistor or a dedicated softstart, I would need one of them especially with my choice of an 800VA toroid. The ISS board has momentary switch options, LED, 12V triggers, etc…and will immediately work should there be a short power outage.
I have used the Guardian-86’s in other designs and with/without them there is no sonic difference to my ears. Moreover the designer has demonstrated the incredibly low infringement they have on the THD on even his best design; I would encourage you to contact him if you are doubtful as such (that is if you believe in measurements in being a guide). The Guardian-86’s provide insurance, you may not want that, and that is your choice.
Oh…I do like to support other vendors as well
Best,
Anand.
The use of low RDson MOSFETs for solid state relays as speaker protection, if properly implemented, can work very well and indeed, has no audible (or measurable) effect on the sound quality or distortion. And get this, both Tomchr and myself noticed a very slight reduction in THD with the SSR in place!
Use of a smart soft start circuit helps reduce the massive in rush current, while eliminating the full-time resistive heater that the NTC becomes after steady state is reached. Those are burning hot circa 150C from my own measurements for a Class A amp.
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A not-insignificant additional benefit of including a soft start PCB is: almost all of them let you use a low-voltage, low current ON/OFF switch. A lot of DIYers, including me, really like circular illuminated "anti vandal" pushbutton switches which are only rated for 12VDC or 24VDC operation. They're meant for vending machines, pontoon boats, that sort of thing. These relative weaklings can't switch the mains of a 200VA transformer (never mind Anand's 800VA!) , but they certainly can switch a 5V DC relay control circuit, on a soft start board.
MJ,
Yes! I used a Bulgin on mine, it’s what I had on hand, but as you point out, there are several varieties and colors (along with dual color illuminated LED’s) to boot. Beats the usual “rocker” imho.
Moreover depending on your electrical configuration, mounting this circuit at the rear panel (near the power inlet) has the benefit that AC mains wiring need not be run to the front panel where the pushbutton is.
There are other choices as well, such as AMB’s ε24, but this is sans a softstart.
Best,
Anand.
Yes! I used a Bulgin on mine, it’s what I had on hand, but as you point out, there are several varieties and colors (along with dual color illuminated LED’s) to boot. Beats the usual “rocker” imho.
Moreover depending on your electrical configuration, mounting this circuit at the rear panel (near the power inlet) has the benefit that AC mains wiring need not be run to the front panel where the pushbutton is.
There are other choices as well, such as AMB’s ε24, but this is sans a softstart.
Best,
Anand.
Agreed. Unlike relays which will degrade over time and start to have an audible (and measurable) degradation of the signal. In addition, relays often arc over at high current, so they may not offer the protection of your speakers that you're looking for. You can see some spectacular examples here: Speaker DC protection with relays
And get this, both Tomchr and myself noticed a very slight reduction in THD with the SSR in place!
I haven't seen your measurements (my bad), but we seem to agree. See attached measurement of the Guardian-86.
I'm not a fan of hot components inside amps. In particular not in DIY builds when "hot" means temperatures exceeding 60-70 ºC. It wouldn't take much for a wire to come into contact with the hot component and now you may have a safety risk. Furthermore, the thermal mass of those inrush limiters is significant, so it'll take a while (several minutes!) for them to cool down to the point where they can limit the inrush current again. This means that you'll likely blow a fuse if the power glitches while the amp is on. That's not my idea of a good user experience.
I would argue that a soft start is mandatory - at least if the VA rating of the power transformer exceeds 200-300 VA. Up to that point you can usually get away with oversizing the fuse a little. You still have to make sure that your mains switch can handle the inrush current, however. You can read my thoughts on soft start design here: The Ultimate Guide to Soft Start Design – Neurochrome
As Mark points out, another nice feature of using a soft start is that some soft starts (both his and mine, for example) allow for the use of a low-voltage switch, including the nice-looking anti-vandal switches for the power switch.
Speaker protection is something I'd consider to be optional in a DIY build. I would consider it mandatory in a commercially available amp. I used to go without speaker protection - mostly because I didn't have such a circuit in my portfolio - but have more recently opted to include it in my custom builds. Why? Because they don't add much to the overall cost of the project but add a lot of peace of mind. And ... <tada.wav> ... they add no contribution to the sonic signature of the amp and have no negative measurable impact on the output of the amp.
Nice build, Anand.
Tom
Attachments
Very nice build Anand!
Maybe some day I’ll be able to go to your place for a day of music listening, that would be cool!
I totally agree with the use of softstart and speaker protection. Speakers are not cheap and for me it adds peace of mind. I also use Neurochrome’s products in my build, really like them.
Congrats on your very nice build and enjoy the music!
Do
Maybe some day I’ll be able to go to your place for a day of music listening, that would be cool!
I totally agree with the use of softstart and speaker protection. Speakers are not cheap and for me it adds peace of mind. I also use Neurochrome’s products in my build, really like them.
Congrats on your very nice build and enjoy the music!
Do
wcwc,
I am getting a little ahead of myself but I didn't come up with the NPXP to just take the Aleph J board of course. There are a multitude of boards that can be used in this large 5U enclosure and many/most do not have a differential input stage. I do not use single ended sources only balanced and/or differential. So I needed a very clean Diff->SE converter and the THAT 1200 is one of the most transparent I have encountered (more transparent than high end input transformers from the usual suspects such as Lundahl, Jensen, etc...). The THAT 1200 was developed by Bill Whitlock of Jensen transformers. The CMRR is very high with this design even with source impedances that are unbalanced. Moreover, it provides RFI and ESD protection as well. All that is needed is a +/-10V to +/- 18V dc supply @10mA (max) and the common LM317/337 combo will do; of course I went all out with Jan's excellent Silent Switcher V3. You will see that I mounted it to the Neurochrome ISS board as it is a very light board.
Next "main" amp board will be the Aleph J Zen, then XRK Alpha 20 (Aksa Lender P-Mos Hybrid Aleph), XRK Alpha Nirvana, F6 variants, M2 variants, F5 variants, etc...
I will experiment with directly going from the XLR jack to the Aleph J and report back here on the sonics in the future.
Best,
Anand.
I am getting a little ahead of myself but I didn't come up with the NPXP to just take the Aleph J board of course. There are a multitude of boards that can be used in this large 5U enclosure and many/most do not have a differential input stage. I do not use single ended sources only balanced and/or differential. So I needed a very clean Diff->SE converter and the THAT 1200 is one of the most transparent I have encountered (more transparent than high end input transformers from the usual suspects such as Lundahl, Jensen, etc...). The THAT 1200 was developed by Bill Whitlock of Jensen transformers. The CMRR is very high with this design even with source impedances that are unbalanced. Moreover, it provides RFI and ESD protection as well. All that is needed is a +/-10V to +/- 18V dc supply @10mA (max) and the common LM317/337 combo will do; of course I went all out with Jan's excellent Silent Switcher V3. You will see that I mounted it to the Neurochrome ISS board as it is a very light board.
Next "main" amp board will be the Aleph J Zen, then XRK Alpha 20 (Aksa Lender P-Mos Hybrid Aleph), XRK Alpha Nirvana, F6 variants, M2 variants, F5 variants, etc...
I will experiment with directly going from the XLR jack to the Aleph J and report back here on the sonics in the future.
Best,
Anand.
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Anand,
Good luck with your journey, and wish you lots of fun on the way! I have my 2in1 project coming up, more on that later.
Sorry if this has been already asked before - what speakers are you pairing with these plethora of amps (in one box, huh!)?
p.s Guys, maybe this is the way to WAF nirvana... SWMBO sees only one big amplifier... but actually there are many.
Good luck with your journey, and wish you lots of fun on the way! I have my 2in1 project coming up, more on that later.
Sorry if this has been already asked before - what speakers are you pairing with these plethora of amps (in one box, huh!
)?p.s Guys, maybe this is the way to WAF nirvana... SWMBO sees only one big amplifier... but actually there are many.
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Great amp you've built there Anand!
I'm about to place an order with Toroidy myself and hadn't considered custom quad secondaries (now seeing yours I'm quite tempted...), do you see any benefits to it over the saved space? Do you think there's much difference to the sound vs a transformer for each channel?
I'm about to place an order with Toroidy myself and hadn't considered custom quad secondaries (now seeing yours I'm quite tempted...), do you see any benefits to it over the saved space? Do you think there's much difference to the sound vs a transformer for each channel?
Elliot,
I ordered it with quad secondaries to make the wiring neat and clean. And yes, it saves space.
But I also upsized the size of my Toroidy. Here is why. If you look at the dimensions of a 600VA and 800VA they are the same. The 800VA is more expensive though. To top it off, in a Class A amplifier, you have a current draw that is high and also constant. Constant. That's important to remember. In addition, this is transformer that is encapsulated. Encapsulation increases heat production. You want less heat production, more reliability and more longevity, not the opposite. So if you can upsize the core, minimize heat and use the same space, why not? As is, the Toroidy in my NPXP is at about 30-35 degrees C, so cool as a cucumber. I can also increase the current draw if I need to. Room for expansion for future projects. In my mind, an 800VA is very much nearly, dual 400VA's especially if you are careful about grounding, minimizing ground loops, etc...the devil is in the details..always
. Have I done a sonic 1:1 comparison? No I have not. I would be surprised if they are substantially different though, given that my build also had dual power supplies. The final reason I ordered a single large Toroidy was I could place it close to the middle of the chassis and it makes the chassis more balanced from a weight distribution standpoint. This becomes important if you are moving the chassis around which will happen often with this build.
Best,
Anand.
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