Massive over specced transformers

There is also the issue of availability too. Sometimes, like as with the BB3 and BBu have a 50VA and 130VA traffo respectively. Thats because even though we need way less, they will only make O-Core transformers with a minimum core size so we end up with beastly transformers. Thankfully, it worked in our favour.

There is a point where the size of the transformer becomes pointless, and using a 1kVa traffo to draw 0.6mA is absolutely pointless and causes more issues than it fixes.

Truth is, in HiFi, there is no hard and fast rule with these things. There is a trade-off for everything.

For example:

Putting massive transformers into phonostages means higher levels of flux and a greater degree of difficulty stopping that flux affecting the performance of the unit. That's why the Avalon has 2 tiny transformers in it. If having bigger ones was beneficial, it would have them. The BB3 and BBu have the best type of transformer for the job, but they have to be massively over spec on size due to the availability of the core. Using EI transformers was equally as good and were 30VA smaller, but the hum was uncontrollable. Performance wise, the size made no difference.

And just because you can't hear a hum in a phonostage doesn't mean it isnt having a negative effect. People ask if i could get a BB3 into a smaller case. Well of course i could, but any smaller means the traffo starts to raise the noise floor, which you don't want.

However, putting MAHOOSIVE transformers into power amps is usually a good thing.

Yep! Just think of the heat sinks you could stuff on the outside of any case you buy. Massive heatsinks to go with massive Tx's. Could be a "thing", maybe Tx envy i.e. mine's bigger than your's?

Can you expand, just purely interested in your thoughts. No agenda for arguments!

Theu are many schools of thought here, bt look at the basics you ony have 50 cycles a second to play with with so your recharge time between cycles is pretty big compared to say 50,000 cycles a second. Ever wondered why the main smoothing tanks of a quality SMPS are much samller?

Think about this, recharging the caps takes 10,000 tiems less to achieve to the distance per say between top up cycles is very small in comparsion to a Linear power supply.

However linear (if correctly designed) will be much quieter and more robust. Although with the new GaN and SiC devices the power density factor of SMPS is now quite something no problem to generate 100 amps in quiet ridiculiously small footprints but the penalty is high switching freqeuncies and increased RF output.

Why would you need a big trasformer?, well depends on what voltage/current you require along with how many secondary taps you require for your power supply. Also need to take into account voltage drop across the diodes and how much head room you really need as energy can only be converted so the wasted power is turned into heat!

Now I am about to start a brand new linear power supply for the Wadia I will be using a 120Va two 15Vac secondaries and a 200Va twin 9Vac secondaries the former for the analogue stage the latter for the digital stage, but I am going to break into the board to give a seprate 5Vdc for the digital signal processing and synthetic PLL.

here are the Tx I will be using

Does it warrant using bigger Tx's in this case not really if you look at the maximum total current draw on each circuit the analogie might just peak at 650ma possibly and the digital for the dac and clocks around 350ma Max the other 5volt rail maybe 500ma but it will totall seperated form the other digital rail. The out put from each rail can easily exceed this by a factor of 6+

Voltage headroom around 30%. Regulation tighter than a ducks ass on speed at the start of open season. Plus a reserve of a 1/4 of fad on the dual rail and 120K on each of the 5Vdc rails

Bruce what i was hinting at look at each application 6 times could be Considered overkill for that application

The original Tx had 3 taps and was 60Va and it sounded great

Would I have used 300Va for each no, after modelling several ideas via red expert spice etc


Then actually producing a real world prototypes I settled for those sizes of transforms.

I have a 5kw  programmable mains regenerator so I can have real world deliver any ac voltage from 3 to 600Vac with significant current. So i can simulate pretty much any Tx that you could wish to use in any audio application


Recently I used a 1.2Kva for a dac streamer package with 5 high power rails. That was a touch overkill but that application could handle it

My own mononblocks which are 600wrms have pair of 1.2Kva Tx's in each mono's they really need that size no, but i would suggest they sound would not be as desirable

I have the ability to rea, world model power supplies without having to have a dozen or so various voltage transformers on the self although I do have around 50 they are all allocated for production products

Heat disappation via the diodes and regulator if you are looking for say a 12Vdc rail then you IMHO will require a minimum AC secondray voltage (if you wish for a safe headroom) of 12Vac this will gve you somewhere around 17Vac unregulated voltage before entering the half bridge/Full bridge or FET based ac<>dc converson system you employ.

The incoming DC voltage into the regulator will be around 16 to 17.2Vac on average. So you regulator will need to drop say 5 volts, that has to be converted into heat.

Also you need to factor in the actual current draw at the point of circuit introduction (this includes, any wiring, connectors and board layouts)

In reality a 12Vdc cicruit may drop as low as 11.6Vdc when under load (we call this the sag or droop recovery when the line voltage has recovered to a satisfactory level) so ideally a 12Vdc rail would ideally be set around 12.35Vdc

Now if you have a small load on that circuit say around 250ma constant at max then you can happily use say a 10 or possibly 9vac secodnary tap.

Transient response factor also plays a large part in designing power supplies as deos how quiet the supply rail voltage ACTUALLY needs to be.

This is where smps are better simply as they have a great power denisty than LPS, but the reserve they have is pretty poor, hence why laptop psu's when tested under load perform perfectly well for their purpurse. But having to get them them fill large capacitance from cold so to speak they just do not cut it.

I recently built a 6 amp 12 volt smps for a gent to power his 12 volt audio dac, it just couldn't fill the caps up enugh to deliver constant operation despit the product only requiring 620ma while in use.

DO also remember you may not be able to purchase the exact voltage of transformer you require and so compromises have to made in that area. We are fortunate we have a small transformer winding company we have as part of our small group of companies so its is not an issues for ourselves.