That's £53. Now a 300VA airlink (to be comparable) is £28, but if you add the electrostatic shield its £35, leaving £18 for rectifier, caps and mounting hardware. Given how easy it is to up spec these things unless you have parts lying around you could easily blow that £20 on 4 bling electrolytics.
And of course ignoring the fact that you would generally not be able to resist upping the toroid to 500VA, just in case.
Having an amp that remains reference grade across a number of PSU options gives choices. That is good.
And of course ignoring the fact that you would generally not be able to resist upping the toroid to 500VA, just in case.
Having an amp that remains reference grade across a number of PSU options gives choices. That is good.
Wow. I was thinking about building a simple DIY tube amp, but for the same money I can easily buy everything I need to build a stereo pair of Modulus-86. Actually, I already have some of the components...
The M86 just went to the top of my list (after a garage door and new sliding door in my kitchen).
Thanks for all your hard work on this, Tom.
The M86 just went to the top of my list (after a garage door and new sliding door in my kitchen).
Thanks for all your hard work on this, Tom.
One does not use a 500VA transformer with a pair of 35W chipamps.
160VA is just fine for the 35+35W
160VA is just fine for the 35+35W
One can do the math... Taming the LM3886 - Power Supply Design. The numbers are for one channel.
Assuming a reasonable crest factor, Andrew is right. A 160 VA transformer is enough to power the Modulus-86 to full power into 4 Ω, assuming a 10-ish dB crest factor. Anything beyond 200 VA would be overkill for a stereo Modulus-86 intended for music reproduction, unless you use two Modulus-86 boards in a bridge configuration.
~Tom
Assuming a reasonable crest factor, Andrew is right. A 160 VA transformer is enough to power the Modulus-86 to full power into 4 Ω, assuming a 10-ish dB crest factor. Anything beyond 200 VA would be overkill for a stereo Modulus-86 intended for music reproduction, unless you use two Modulus-86 boards in a bridge configuration.
~Tom
The Bling Electrolytics would provide similar or worse performance than a stock Panasonic or CDE electrolytic cap. As mentioned earlier, a few bucks buys you a 22000 uF, 35 V electrolytic can from CDE with good ripple current specs and rated for +85 or +105 ºC operation.
Supply budget:
Antek AS-2222: $32
KBPC2504 diode bridge: $3.12
22000 uF, 35 V electrolytic can: $4.28/each -> $8.56 total
TOTAL: $43.68
You're quite welcome. Thanks for the recognition. I'll be happy to supply boards once you're ready to start building.
~Tom
Why would one assume that is what I am building? I'm not.
Anyway, if Naim can put 1kVA transformers in a pre-amp I can if I want over engineer my solution.
You were comparing the costs to a previous post that gave a cheaper solution.
I happen to agree that the cheaper solution does not suit everyone.
But if you compare on "cost" then it would be wise to use a linear (non switching) PSU that is operationally adequate AND similar in cost.
A while ago I decided to buy a pair of 105W switching PSUs with the intention to compare performance to a 120VA transformer fed PSU, with it's largish capacitors.
The pair special offer cut price Switchers were dearer than the transformer + caps + rectifier AND could not be fitted inside the chassis that could accommodate the linear PSU.
The big advantage of the switchers is that they are double insulated and for beginners they don't need to worry about wiring errors on the mains side.
I did an apples with apples, was merely pointing out that human nature will always tempt to go to the next size up when faced with options. It's programmed into us at a genetic level. Tom has the advantage of lower prices and taxes to order stuff so he can make a linear more cheaply than I could.
This looks like a great project. I have a finned case and transformer saved for something very much like it. 🙂
Would it be possible to add a volume control in between the balanced line receiver and the controlling opamp?
Would it be possible to add a volume control in between the balanced line receiver and the controlling opamp?
You can over-engineer your solution if it makes you feel better. Been there, done that... 🙂 All Andrew and I are pointing out is that you actually don't have to. But hey... It's your money and time.
~Tom
Well, there you go!
That is possible. You would have to cut a trace and pay attention to what you're doing to ensure that you get good performance when you're done. In particular, you need to ensure that the volume pot connects to the signal ground at a good spot.
Should you opt to buy a pair of boards, I'll be happy to guide you through the modification via email. If you can look at pictures and follow instructions, you'll be fine.
~Tom
This will be my reference amp for probably a decade, I want to make sure it can cope with whatever I decide to do on the speaker front. If that means it costs £20 more on the PSU that is needed for right now I can live with that and sleep happily.
And it's great to see. All too often discussion on DIY Audio tends to take the form of being unsure of requirements and therefore overbuilding until doubt feels assuaged. Works in cases where more of something doesn't degrade performance. But it doesn't foster the development of design skills and the assumption more is better isn't always correct.
I find there's substantial value in not needing to accommodate high mains or overvoltage conditions in the thermal design as well. It's also nice not to be designing to handle, say, a 70% mains brownout corner; the regulation means available swing is more or less guaranteed, which in turn means rail voltages can be lowered and heatsinks made a little smaller.
Looks like at least three of us missed that gene. 😉
I very much doubt it. Read ' The drunkards walk' which talks quite a bit about the anthropology around how rubbish we are at making purely logical decisions. It was not a good strategy when we were evolving. Technology even in my 46 years has moved on a lot faster than our species can evolve to cope with it.
When I consider what was state of the art during my undergraduate course its almost laughable what is available now. Some technologies have gone from research, to mass market to near extinction in that time (cold cathode emitters for example) yet we still have no fusion or room temperature semiconductors. Hey ho.
Back on track, the difference in price between 225VA and 500VA toroids is £13. one is undersized for the peak power requirements but would work due to crest factor, the other is a tad oversized but not insanely so and would give me headroom should I want to bridge the bass channel. A waste or £13 well spent? That is a trade off for me to make. Odd that everyone assumed this is a 2 channel chassis I am building.
Dan Ariely's "Predictably Irrational" is a good read along the same lines.
If sizing the components for continuous sine wave operation or beyond makes you happy, I'm certainly not going to get in your way.
~Tom
If sizing the components for continuous sine wave operation or beyond makes you happy, I'm certainly not going to get in your way.
~Tom
I'm looking forward to it.
One question;
Since I am not planning to use differential connections and I have no need for bridging, is it possible to omit the THAT1200 entirely?
You can. I recommend leaving it in, though. That way, you have the option to convert to differential at a later date. It also makes bridging two boards a possibility. All you have to do for a bridging is to swap the two input wires and connect the speaker at the two (+) output terminals. Those options go away if you remove the THAT1200.
~Tom