Nope, transformer geometry must be optimal for certain max wattage and primary inductance. You can take 60W transformer for 50W amplifier, but not 60W for 10W amp.
Low wattage PP amps usually require higher primary impedance, typically:
15 - 20W -> 8 - 10K
30 - 40W -> 5 - 6.6K
50 - 60W -> 3.3 - 4.3K
80 - 100W -> 1.5 - 2.2K
So if one takes 100W 1.5K for EL84/6P14P amp, the result will be abysmal.
Monolith Magnetics SiFe
Anyone know what core material is used in Monolith Magnetics Summit line for push pull? I read SiFe however it seems that's quite vague. Is that equivalent to M3, M6, etc?
Shipping and taxes
What sort of shipping and tax costs should I expect from Europe? It helps that Monolith Magnetics has export pricing specials. Japan is way too expensive and hard to get. USA is EI-core without potting mostly. Since I like aesthetics I am branching out.
AE-Europe
I guess Tribute is NLA for new DIY'ers so that leaves AE-Europe. Any experiences with AE and pricing?
Linearity, Distortion & 10khz square wave
All are important but if you could pick two which two would be the most telling of quality?
First-Watt or Tube amp experiences
I am stuck between two First Watt F4's (50w mono class-A amplifier) and Pete's 50w engineer tube amp. Both cost the same since it will cost around $300 each for the chassis and heatsink alone for the F4.
FYI - The First Watt F4 has no feedback and no gain (preamp dependent I know).
Anyone know what core material is used in Monolith Magnetics Summit line for push pull? I read SiFe however it seems that's quite vague. Is that equivalent to M3, M6, etc?
Shipping and taxes
What sort of shipping and tax costs should I expect from Europe? It helps that Monolith Magnetics has export pricing specials. Japan is way too expensive and hard to get. USA is EI-core without potting mostly. Since I like aesthetics I am branching out.
AE-Europe
I guess Tribute is NLA for new DIY'ers so that leaves AE-Europe. Any experiences with AE and pricing?
Linearity, Distortion & 10khz square wave
All are important but if you could pick two which two would be the most telling of quality?
First-Watt or Tube amp experiences
I am stuck between two First Watt F4's (50w mono class-A amplifier) and Pete's 50w engineer tube amp. Both cost the same since it will cost around $300 each for the chassis and heatsink alone for the F4.
FYI - The First Watt F4 has no feedback and no gain (preamp dependent I know).
Shipping and taxes are a big determining factor. There are quite a few US transformers I would like to try (power as well as OPT) but shipping and import duty make them immediately less interesting. I would expect the same when shipping in the opposite direction....
Sometimes I get transformers when visiting a different continent though. I did that while in Japan a couple of years ago for work/business.
Don't forget Plitron. The exchange rate is in your favour and some argue that these are the absolute best to get for PP...
Ian
Sometimes I get transformers when visiting a different continent though. I did that while in Japan a couple of years ago for work/business.
Don't forget Plitron. The exchange rate is in your favour and some argue that these are the absolute best to get for PP...
Ian
Yeah, shipping is the real killer. As far as Plitron is concerned from what I can gather they are close to the absolute best a person can buy. The problem is that without an active bias balancing circuit the user can run into issues with saturation very quickly. Which is why hardly anybody uses Plitron in comparison to C and EI. I am curious why we don't see R-core output transformers and what their flaws would be. And more than that why a winder never just did it for kicks and reported back.
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Physically you could compare them with c-cores.
Their "flaw" is that they are gapless, so they must be treated like gapless toroids.
Besides to wind with r-cores you need special winding gear as the round bobbins are wound while on the core.
Their "advantage" is speed: round bobbins can be wound with higher speed than rectangular ones.
Are you sure?
Another advantage is the decreased wire length and thus reduced winding capacities.
Best regards!
Yes, I am sure.
See what winding machine is needed to wind r-cores:
https://www.youtube.com/watch?v=-WfdSUKo6qU
You are right that with equal iron area (Afe) the winding length is reduced with some 10%.
It might be interesting when these cores were readily available in cut halves so that normal winding machines can be used and airgaps can be applied.
See what winding machine is needed to wind r-cores:
https://www.youtube.com/watch?v=-WfdSUKo6qU
You are right that with equal iron area (Afe) the winding length is reduced with some 10%.
It might be interesting when these cores were readily available in cut halves so that normal winding machines can be used and airgaps can be applied.
Nope. Output transformer are designed with certain core cross-section area in mind, no matter it is rectangular or round. If one have smaller cross-section area, thus, it will require more turns for defined flux density.
Nope - see pieter T's answer:
For a given area, the circle is the geometric shape with the smallest circumference.
Best regards!
Digikey has free shipping on orders over $200CAN which includes Hammond transformers in Canada and the US. Digikey is also in Europe and I think you will find their shipping very reasonable on the Hammonds.
It looks like they list everything Hammond makes. They do not stock them but it does not take long for them to get them.
It looks like they list everything Hammond makes. They do not stock them but it does not take long for them to get them.
I just sent Monlith an email to help clear up a few questions over core material and options when selecting a custom transformer.
"Engineer's Amplifier" 50 watt monoblock
As far as building a custom transformer is concerned should I go with Monolith's B-8/5K 5k (2-175,000 Hz) rated to 90-110ish watts? Or get a custom transformer wound to 4.3K like the original? How much wattage would I give up with 5K?
Either way though it's probably best to go custom 60w. Lowers shipping costs and helps inductance since C-Core reaches maximum inductance at max power. Any suggestions on what path I should take?
"Engineer's Amplifier" 50 watt monoblock
As far as building a custom transformer is concerned should I go with Monolith's B-8/5K 5k (2-175,000 Hz) rated to 90-110ish watts? Or get a custom transformer wound to 4.3K like the original? How much wattage would I give up with 5K?
Either way though it's probably best to go custom 60w. Lowers shipping costs and helps inductance since C-Core reaches maximum inductance at max power. Any suggestions on what path I should take?
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Power rating has to be compared on the same basis (i.e. at the same frequency). A generic 60W transformer is usually rated at power line frequency. At lower frequency headroom decreseas. The primary voltage one can apply is inversely proportional.
The B-8/5K is rated such that it will start to saturate for 30W @21Hz. That means saturation will occur for 61W @30Hz and 170W @50Hz.
Unless you want full power down to 20Hz the B-8/5K is perfect for the "Engineer's Amplifier" 50 watt monoblock. The Hammond 1650N is specified for 60W at unknown frequency. Being quite lighter than the Monolith I would assume that 60W are true at 50Hz. Personally, I would not bother with custom stuff.
The difference between 5K and 4.3K is not going to make a significant difference.
Awesome thanks 45.
Monolith Magnetics got back to me and it appears their FeSi core is grain oriented cold rolled M6X. I checked Automatic Electric Europe and they also use M6X. I am sending them a request for a quote. Unless their price is significantly better than Monolith it's unlikely I'll switch. Monlith's spec sheet is a bit hard to resist and cosmetically pleasing.
Regarding M6X, what is this material and how does it differ from M6?
Monolith Magnetics got back to me and it appears their FeSi core is grain oriented cold rolled M6X. I checked Automatic Electric Europe and they also use M6X. I am sending them a request for a quote. Unless their price is significantly better than Monolith it's unlikely I'll switch. Monlith's spec sheet is a bit hard to resist and cosmetically pleasing.
Regarding M6X, what is this material and how does it differ from M6?
Specs are really good for PP 300B. Yet you have to take into account that their PP transformer are quite low-power.
5K PP (B8-5K) units rated core saturation 21Hz at 30W RMS - way to low for 50W amplifier. In other words, it translates into around 25W real-life RMS without noticeable distortions at LF.
2Hz are at 1W / -3dB - meaningless parameter, have no practical use.
This is data from manufacturer's PDF data sheets downloadable from web site.
Unless you have high-sensitivity speakers, there is a certain risk to drive them into saturation.
BTW, 310 Euro / pc for 25/30W transformer is not a bargain. This is 620 Euro + shipping to USA. IMHO there are enough domestic companies capable to do similar job for comparable or even less money.
5K PP (B8-5K) units rated core saturation 21Hz at 30W RMS - way to low for 50W amplifier. In other words, it translates into around 25W real-life RMS without noticeable distortions at LF.
2Hz are at 1W / -3dB - meaningless parameter, have no practical use.
This is data from manufacturer's PDF data sheets downloadable from web site.
Unless you have high-sensitivity speakers, there is a certain risk to drive them into saturation.
BTW, 310 Euro / pc for 25/30W transformer is not a bargain. This is 620 Euro + shipping to USA. IMHO there are enough domestic companies capable to do similar job for comparable or even less money.
Okay I thought I was set. Now this wattage is confusing me. Let me word it this way: If you were to build the Engineer's 50W push-pull amplifier what specs would you provide a winder? Using meaningful parameters
By the way quality matters to me and my DIY Transmission line revelator speakers are flat to 30hz. Planning stages: Horn loaded Tuba HT/Table Tuba horn loaded subwoofer, possibly a DAC with PC (REW) room correction and sub crossover.
Yes, $600-ish dollars is expensive and trust me my conscious is bugging me. Truth of the matter is if I purchase something I want it to potentially last my lifetime. Seems like a much better proposition than the latest $770 iPhone which always seems to die when the 2yr contract expires. I tend to be very frugal and purchase very few but nice things in my life.
P.S. - I have nothing against USA transformers but potted cosmetics and C-core do matter to me.
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OK, here it is:
1) 60W at 20Hz, flux density B = 1.20 .. 1.30 T (enough headroom till core saturation).
2) 4.3K primary, 43% UL (big+ in case you will move to KT88/6550 amp sometime later). 4/8 Ohm secondary.
3) Minimum inductance 68H, need to be measured also at low signal level, e.g. 1V/100 Hz, grain-oriented silicon steel have quite low permeability at small flux density. As flux grows, permeability go up.
4) You are right with C-core selection, ribbon thickness 0.23 - 0.27mm, grade M3 or M4, preferably HiB. M6 is last choice if nothing else available. Small air gap could be fine to counter DC idle current imbalance.
5) Leakage inductance <= 8.5mH.
6) Resonant frequency > 100 KHz.
7) Nomex or teflon insulation between layers.
8) Split bobbin/symmetric winding not necessary.
Cages can be bought at Aliexpress or elsewhere, drill ventilation holes at backside, and go to nearby auto repair shop for powder coating (Dupont have huge selection of available colors). Potting not required.
I think cost around $400 - $500 for a pair without cage is a fair price. Somewhere on this forum buried thread with list of USA/Canada winders.
In case of questions and/or feedback from manufacturers, feel free to post here.
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