@marktd If you meant 1000VA, then that's overkill. It will work, but you have to manage the power-on inrush, which is an added complication. The various soft-start boards will take care of that. 1000VA transformers are quite heavy and will not give you much compared to a 500VA in a two channel setup at 8 ohms because you are limited by the rail voltage. To take advantage of the full 1kVA at 8 ohms you actually need rail voltages of around 85-90 volts. That means 100 volt caps, which definitely adds to the cost. Your supply caps will go from around $30 each to around $60 each. Of course, if you already have the transformer, then go ahead and use it. If you have the boards, then there is a table in the BOM for transformer sizing.
@marktd I am using a pair of 500va 50V transformers with 4 pairs of MJL4xxx output transistors per side. This gives me enormous headroom well above clipping and no sign of DC supply sag. I also have the 5U case to be able to fit the supplies, the softstart, speaker protection and muting and the RIAA preamp, input selector and volume control. My speakers are very inefficient open baffle types but I do not use anywhere near the full power available (unless I play Bach's toccata etc).
So, if I use a pair of 500VA trannies with 45 volt secondaries running 64 volt rails with the NJW3281/0302, do I have less inrush, or the same? I'd really like to use a couple 22000uf 80v screw caps on each side. Is this a reasonable approach? Thank you Ghitus, Johno, Mhuth1776, fvzeppelin.
@marktd "do I have less inrush, or the same?"
Inrush is proportional to the current rating (the VA) of the transformer and the impedance of your household mains circuit. On turn-on there are no magnetic fields in the transformer, just copper wire, so there is a large current surge for several mains cycles while the fields are established to create the magnetic fields and thus the inductive impedance to limit the current. The load on the secondary is not yet visible to the primary (because there are no magnetic fields) and has no influence on the first inrush peak current. Shortly after the inrush the current will fall to a not so high level for several more cycles while the DC supply capacitors charge.
Inrush is highest when the mains is switched on at a voltage peak and another scheme to limit Inrush is to turn-on only at mains zero crossings (but this can be complex or if a SSR, expensive)
Inrush is proportional to the current rating (the VA) of the transformer and the impedance of your household mains circuit. On turn-on there are no magnetic fields in the transformer, just copper wire, so there is a large current surge for several mains cycles while the fields are established to create the magnetic fields and thus the inductive impedance to limit the current. The load on the secondary is not yet visible to the primary (because there are no magnetic fields) and has no influence on the first inrush peak current. Shortly after the inrush the current will fall to a not so high level for several more cycles while the DC supply capacitors charge.
Inrush is highest when the mains is switched on at a voltage peak and another scheme to limit Inrush is to turn-on only at mains zero crossings (but this can be complex or if a SSR, expensive)
The measures needed to start up two 500VA torrid transformers are more or less the same as for one 1kVA torrid transformer. Both require a delay circuit. The price of one 1kVA will be lower as two 500VA. The two 500 VA torrid transformers might be easier to fit in the housing. Also two transformers will enable you to build the amp in dual mono configuration.
To take full advantage of mentioned transformers consider choosing the capacitors a bit higher. Pick some with a low equivalent serial resistance (ESR)
From testing we believe that the NJW0281G / NJW0302G will offer you the lowest distortion.
We also testing these to clipping using 64vdc rails and a 2 ohm non inductive load, no problem. While I won't recommend driving 2 ohms these transistors are very good. If you are prepared to drill more holes feel free to use the MJL3 or 4 series.
Personally I'm running the NJW0281G / NJW0302G with 64v rails driving 8 ohm nominal speakers.
Thanks Stuart that is what I'm thinking will work for me. I there any adavantage to two 500VA transformers vs one 1000va? I'm thinking two 45volt secondaries either way and probably 20-22uf per channel (or more). What I'm not sure about is whether there is an audible benefit to dual mono. Rod Elliott seems to think that if the amp is good, having a fancier power supply won't matter. I just don't know from experience.
There are alot of reasons to go with 2 power supplies. I myself will be using 2 x 500va 45vAC transformers.
They take up less space than a 1KVA and give you the option to stack them and rotate them relative to each other to help cancel out magnetic fields etc.
Im using these caps. 2 per rail.
Caps
They take up less space than a 1KVA and give you the option to stack them and rotate them relative to each other to help cancel out magnetic fields etc.
Im using these caps. 2 per rail.
Caps
I seem to be coming to the same conclusion regarding power supply. It helps to know others have tried it.
Hello Gents,
It's probably a bit out of my league or comfort zone at the moment but I like reading the wolverine threads. Here's some noob questions:
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It's probably a bit out of my league or comfort zone at the moment but I like reading the wolverine threads. Here's some noob questions:
- Its only and amplifier and I need seperate preamp...correct?
- Whats the input stage board for actually and why is it a seperate board?
- The wolverine amplifier "starts" after the reservoir caps basically so I need both a transformer and some rectifier circuit board as well...correct?
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Oh and in addition...what am I looking at in terms of costs on average including the housing, input / output terminals, transformer/PSU pcb? around € 700,- ?
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1. A separate preamp is only needed if your source is not powerful enough or you need some extra gain. But especially with the 22k input circuit you should be fine without
2. There are many different design out there for the input stage. To my knowledge the idea was to give the builder the option to add their own input stage.
3. Correct (or you choose a SMPS)
The complete price really depends on a lot of choices.
You can choose 20€ or 200€ speaker binding posts for example. An other example would be the often used Delux case from modushop, which is (in the 4u 300mm size) 280€. It's an incredible case with all holes predrilled, but there are definitely cheaper options.
I would guess that many builds are somewhere in the neighborhood of 1000-2000€ without super crazy builds or going "budget" everywhere
2. There are many different design out there for the input stage. To my knowledge the idea was to give the builder the option to add their own input stage.
3. Correct (or you choose a SMPS)
The complete price really depends on a lot of choices.
You can choose 20€ or 200€ speaker binding posts for example. An other example would be the often used Delux case from modushop, which is (in the 4u 300mm size) 280€. It's an incredible case with all holes predrilled, but there are definitely cheaper options.
I would guess that many builds are somewhere in the neighborhood of 1000-2000€ without super crazy builds or going "budget" everywhere
Thx a lot. I'll be using the SMSL Sankkrit MK-2 DAC as output device which has around 2 volt output voltage. I guess that would be enough?
I'm now considering building one🙂
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I'm now considering building one🙂
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In this tread 'Wolverine' usually refers to a power amplifier. As it has no source selection or volume control you need at least one additional device that can provide these services for itself and other sources.
In this thread 'input stage' revers to the small PCB containing the long tailed pair, current source, cascode, current mirror, voltage amplifier and VAS current source. They are on a separate PCB as this will enable designers/builders to develop other amplifier setup. There are some 9? different IPS designs published by ostripper in the Slewmaster - CFA vs. VFA "Rumble" thread, most of them conceptual. Wolverine is the most matured one of them, and by far the best documented. An other interesting one is the Spookyamp (Georgia Tech "Leach" topology), based on the HK 990. I might build this one myself if I ever find the time for it.
Rectifier PCB is a choice, not a requirement. Often the reservoir capacitors and rectifier are mounted on the amp chassis.
Building an amplifier of excellent quality requires excellent quality parts, so its costly. 700 is more the price for a singe channel. DIY is not necessary cheaper then factory build.
Yes, building this amp is not cheap. Nevertheless I believe that, after all the distortion measurements and the comparisons that have been done, it can quietly compete with commercial devices which are much more expensive.
Gaetano.
Gaetano.
Ok...thx for the replies. Hell of a project to take on.....for me at least. I did refurbish a couple of H/K PM's. Currently working on a PM665-VXi which is nice but this Wolferine beast is next level....what a project......🙂. On the PSUpart. Does this beast run better on a good transformer snubber caps rectifier setup or is SMPS the preferred option......ie: don't want to start a discussion......
thx
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thx
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I recommend a conventional PSU with torrid transformer(s) and big reservoir capacitors (screw terminals) connected together with massif bars aluminium or brass. Mainly for its known good transient response and low Z, others might recommend a SMPS. Usually people recommend what they (have) build themself. This Poland manufacturer of torrid transformers might be worth to investigate. https://sklep.toroidy.pl/
At the SMPS front, Micro Audio's Cobra-S2 has often been recommended (and I think someone of the Wolverine team also measured it with very good results).