Quest For a Toroidal Transformer

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kroyin

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Hi,

If this helps anybody. I had a requirement for 2x225VA toroidal transformers for my Pass F5 project with the 230V AC input and 18-0-18V center tapped output and 5 Amps continuous current rating.

---Searched locally in Kolkata, could not source one.

---Contacted Delta Transformers Delhi & they wont ship 1~2 pieces to Kolkata

---Contacted Miracle (toroidal.com). Got a quote for 1x225VA @ 3393/- (incl taxes & shipping) with the following specs (112 OD, 57 HT, 2.2 KG)

---Contacted Torotrans (toroidal.com). Got a quote for 1x225VA @1485 (incl taxes & shipping) with the following specs (125 OD,50 HT, 6.25 A, 2.5 kg). Very nice gentleman called Mahesh.

--Contacted Toroid Engineers (toroidengineers.com). Got a quote for 1x225VA @2000 (ex factory) with the following specs (175 OD,70 HT, 6.25 A).Even nicer gentleman called Dayanand who told me that 90% of his trafo's are used in audio applications.

---Contacted SVTronicks (svtronicks.com). Got a quote for 1x225VA @1300 (ex factory) with the no specs (i should asked for it). Subramaniam is nice but took 3 days to give me a quote.

So i went ahead & ordered form Torotrans

---Arrived in 7 days post payment via surface courier
---Impressive hunk of wire. Feels heavy
---Supplied with rubber washer (crib:: should give full mounting hardware)

Performance

---No load AC voltage @ secondary is ~20V. Post DC rectification 27V on both rails.

---With F5 fully biased, DC rails are +24.8V/-25V (bingo, near perfect)

---No hum, no rattle, no hiss (total silent)

----Solid soundstage (even with cheap Chinese caps).


I'll take some photos over the weekend.
 
bro, let us know more about your project, F5 source, chassis and heatsink etc.
Final result, and not to forget nicer pics.

Waiting, till the time adding this thread to subscription.

kroyin said:
Hi,

If this helps anybody. I had a requirement for 2x225VA toroidal transformers for my Pass F5 project with the 230V AC input and 18-0-18V center tapped output and 5 Amps continuous current rating.

---Searched locally in Kolkata, could not source one.

---Contacted Delta Transformers Delhi & they wont ship 1~2 pieces to Kolkata

---Contacted Miracle (toroidal.com). Got a quote for 1x225VA @ 3393/- (incl taxes & shipping) with the following specs (112 OD, 57 HT, 2.2 KG)

---Contacted Torotrans (toroidal.com). Got a quote for 1x225VA @1485 (incl taxes & shipping) with the following specs (125 OD,50 HT, 6.25 A, 2.5 kg). Very nice gentleman called Mahesh.

--Contacted Toroid Engineers (toroidengineers.com). Got a quote for 1x225VA @2000 (ex factory) with the following specs (175 OD,70 HT, 6.25 A).Even nicer gentleman called Dayanand who told me that 90% of his trafo's are used in audio applications.

---Contacted SVTronicks (svtronicks.com). Got a quote for 1x225VA @1300 (ex factory) with the no specs (i should asked for it). Subramaniam is nice but took 3 days to give me a quote.

So i went ahead & ordered form Torotrans

---Arrived in 7 days post payment via surface courier
---Impressive hunk of wire. Feels heavy
---Supplied with rubber washer (crib:: should give full mounting hardware)

Performance

---No load AC voltage @ secondary is ~20V. Post DC rectification 27V on both rails.

---With F5 fully biased, DC rails are +24.8V/-25V (bingo, near perfect)

---No hum, no rattle, no hiss (total silent)

----Solid soundstage (even with cheap Chinese caps).


I'll take some photos over the weekend.
Click to expand...
 
:-) Om, at this moment i have 1 channel (mostly as a Proof Of Concept) with Jim's Audio (ebay) boards. I'll intend to go through few iterations and then use new boards & components for the final build. This is what i had posted on diyaudio...pictures will come but right now things are ugly :-)
-------------------------------------------------------------------------
Thanks to all got 1 channel working...
R11&R12 --- .623V
VGS9240---4.39V
VGS240---3.87V
Offset --- 25mV(1 2.2k...will experiment)
R3/R4--5.02V/4.51V
Rails -- +24.8V/-25V

Heatsink warm...washers on top of mosfet hot...readings taken after 3 hours.
Coming from AVR's the difference is as evident as bald pate v/s shaggy mane (never missed the other channel)
--------------------------------------------------------------------------
 
Hi,

This is good stuff. I am planning on F5 with Jims, but have not yet started. Now I am encouraged.:yahoo:

I have always been wondering why there is such a variation in Toroid prices. being in Bangalore, I had bought a couple for my earlier projects from Miracle - toroidal. They were expensive but seemed to work. Then thanks to Om I got the Rcore from Svtronics, that also is doing an excellent job. maybe I am missing something between these guys or they are just pricing themselves as they please...
 
Lets keep this thread to toroids...i'll open a fresh F5 threads once i get pics of my fugly uni channel setup :-)
 
kroyin said:
If this helps anybody. I had a requirement for 2x225VA toroidal transformers for my Pass F5 project with the 230V AC input and 18-0-18V center tapped output and 5 Amps continuous current rating.
Click to expand...
Am seeing your post just now. Invaluable. I am not allowed to thank you through the button any more, it seems, so I'm just writing thanks! :)
---Contacted Delta Transformers Delhi & they wont ship 1~2 pieces to Kolkata
Click to expand...
This part surprised me. I have NEFT'd them full payment and they have sent me two transformers by road transport to New Bombay, well packed. It was a bloody 13-kg heavy carton, with two R-core transformers, each 500VA, each with eight secondary windings. I have had great experience dealing with them -- this was my second order to them.

---Contacted Miracle (toroidal.com). Got a quote for 1x225VA @ 3393/- (incl taxes & shipping) with the following specs (112 OD, 57 HT, 2.2 KG)
Click to expand...
I've dealt with them in the past. Very good chaps. Expensive.

--Contacted Toroid Engineers (toroidengineers.com). Got a quote for 1x225VA @2000 (ex factory) with the following specs (175 OD,70 HT, 6.25 A).Even nicer gentleman called Dayanand who told me that 90% of his trafo's are used in audio applications.
Click to expand...
I just called them up just for some air-core coils (for crossovers) and Mr Dayanand was really nice and encouraging to talk to. Let's see how it goes.

Thanks again for the list.
 
Jims Audio!

kroyin said:
.... with Jim's Audio (ebay) boards.
Click to expand...
Even you've discovered this chap? :D I was so excited to see his products. I find his offerings quite different from the typical Chinese audio PCB seller, and I've exchanged some emails with him, bought a few power soft-start modules from him, etc. Seems like a good chap. I intend to build one or two amps from him once the Darbari gets done.
 
Maybe slightly OT, but Jim's Audio has been around for years, selling bare boards, kits (generally reasonable) and boutique components (generally pricey). I bought a couple of Symasym clone kits from him years ago, and they worked OK but needed numerous mods/upgrades to unlock their full potential. He does have a fair number of bare boards and kits of well-known classic circuits most of the time.
 
Sharing contact details of Transformer manufacturer in Mumbai. I searched for quite some time and then found them.

Though I have never dealt with him as I found a ready-made one and purchased it. The person is talkative and helpful.

He had quoted Rs. 750 for a 28-0-28 3 Amp transformer. I wanted one for a 7294 mono amp kit which I got from Aliexpress then.

Electromatiks in Malad (East) 022-2873-2527

When I told him that I need it for an audio amplifier he enquired whether its a valve amplifier and also suggested the option of Toroidal. So I am guessing he is knowledgeable regarding where his products get used..

Hope this helps someone...

regards,
Jawed, Mumbai.
 
FWIW, I quote from Jonathan Carr of lyraaudio:

Toroidal transformers have good regulation and low output impedance, but OTOH high interwinding capacitance. High interwinding capacitance means wide bandwidth coupling between the primary and secondary windings. This may not be what you want in an audio power supply, as it implies that all kinds of noise as well as 50/60Hz can pass through the power supply. If you decide to use a toroidal transformer, I would specify an additional electrostatic shield between the primary & secondary windings, as this helps reduce the primary-secondary noise transmission issue somewhat.

EI (frame) core, C-core and R-core transformers usually have split-bobbin primary and secondary windings, which cuts down on interwinding capacitance and makes it considerably more difficult for non-50/60Hz noise components to pass in and out of the power supply. Here you can also specify an additional electrostatic shield between the primary & secondary windings for less noise transmission, but this is not as important as it is when using a toroidal transformer for power supply applications. OTOH, EI, C and R-cores are usually physically larger and heavier for a given VA rating (at a given flux) than a toroidal, and this can have a direct impact on the size and weight of the amplifier chassis.

At the end of the day, it is possible to make a good-performing and good-sounding power supply using toroidal, EI, C-core or R-core transformers. But the cost and implementation issues will differ if you are trying to make any sort of optimized design.
Click to expand...
 
I've heard it said that everything upwards of an amplifier [CDP, DAC, Pre-amp etc] should use R-Core's. I wonder why.
 
All kind of transformers do some kind of line and load regulation. May be to a different degree for respective types.

For Amplifiers with line level input low gain - its does not matter V noise floor. Power amps are immune to main noise unless well designed filtering is absent. So toroidal works better from price v/s performance ratio.

R-core are better saved for low signal level handling like preamplifiers and phono preamplifiers, tuners, DACs etc.

I know it does not harm using r-core everywhere, but its not required always to spend that much.

I prefer torotrans Pune for my toroidal transformer needs which is cost effective and good quality. The owner is technically knowledgeable person and gentleman.
 
Sv Tronics
No. 2, Arinagar Anna Street, Kottur,,
Chennai, 600085
Phone: (2) 441-3199
Fax: 044-24404281
Email: [email protected]

This is your best bet and only one needed (at least according to me),Mr Subramaniam,Proprietor is a thorough gentlemen and will be more then happy to do the job !

The Best part is,They are the most economical Toroid transformer makers in the Entire south India (perhaps all over India too).

I had the mobile number but somewhere misplaced,if the above contact details don't workout do post here,I'll try to search and give the mobile number.
 
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