Toroidal Transformers in B'lore

[roadkill]

Hello Bangalorean DIYers,
I posted some time ago asking where I can pick up a toroid core transformer in bangalore. Well, now I know. Miracle transformers will supply them in single-piece quantities, and even courier them to your home (for just Rs. 30!). I ordered a 225VA 25Vx2 toroid (model no M225 50) from them, it cost me Rs. 915 (MRP). Total charge including shipping was Rs. 1225.
Website: www.toroidal.com
Since then, they updated their site, they also offer encapsulated transformers, good for preamp supplies and such (small, starts at just 2VA!!!).
I've only unpacked the toroid, will check it out tomorrow (spent the day at URock ). It will end up feeding five gainclones (LM3886). Yes I know it's underpowered, but I wont be using it near full amplitude. Besides, I will be using a powered sub.
Hope this post helped!

[ashwin]

roadkill,

thanks for that info! I see that they also offer audio output transformers for tube amps. I didn't know that kind of thing was still being manufactured! So now I can play around with tubes for a while

Any particular reason (apart from size) you're using torroidals instead of EI?

- Ashwin

[tcpip]

Originally posted by roadkill
Miracle transformers will supply them in single-piece quantities, and even courier them to your home (for just Rs. 30!).

This is fantastic news! I presume they'll ship anywhere in India. I don't even know of any toroidal tranny guys with ready-made list of models in Bombay, let alone B'lore. I keep hearing that there are guys who make toroids in Bombay, but I've yet to meet anyone who can (i) sell retail, (ii) has a range of standard specs. And the fact that these chaps have a Website is an added blessing. Bolton doesn't yet have a Website, and probably never will, for instance.

Great news! Thanks.

The price premium is interesting, though. I bought a 26-0-26V, 5A (that makes it a mite more than 250VA?) E+I transformer through Angshu's good offices from a guy called "Guru" in Delhi, and that cost me Rs.550. (I too plan to power some gainclones or P3As with it.) Your toroid is twice as expensive. But I guess I can now make my chassis slimmer.
Toroids should be ideal for low-current ratings (500mA or less?) for preamps, where I can really cram things tight and not worry about EMI. For poweramps, I'm quite often more open to E+I, specially if toroids cost this much extra.

Tarun

[roadkill]

ashwin, I used a toroid mostly for the size reduction. I am planning to try a cabinet design featured in Elektor, where they bolt on aluminium sheets to a pair of heatsinks. The heatsinks form the side walls, and the sheets form the top, bottom, rear and front panels. The largest heatsink extrusions I could find did not have enough height to fit an E-I of 225VA. Then there are other issues, like less EMI, simple means of mounting, etc.

tarun, the rumours must be true I've been to Lamington rd only thrice, there's this very dank-looking bridge you have to pass under if you're getting off at the local station, there was a hole-in-the-wall shop which had toroids. I didnt have enough money to buy them at the time (it was the last time I was there, on my way out... argh!) He also had C-core trannys, which apparently can be made smaller than a regular E-I, tho not as slim as a toroid. EMI is less, too, and there won't be a problem with inrush current like toroids have. Freight to mumbai would probably cost a bit more than just Rs. 30, it weighed about 3 kgs in all.

[ashwin]

Originally posted by roadkill
The largest heatsink extrusions I could find did not have enough height to fit an E-I of 225VA. Then there are other issues, like less EMI, simple means of mounting, etc.

Hmm, I have the same problem, my 15-0-15V/5A is about 5" high. But the place where I bought the heatsink did have some tall extrusions (6-7" IIRC) which I intend to try. Where did you get your heatsinks from? I got mine from an Al shop at the entrance to SP road (from the town hall side).

- Ashwin

[roadkill]

ashwin,
I got my heatsinks from Cee Pee electronics (near Vishal). They're fairly expensive, too, so I guess I could try the place you mentioned. What's it called? Hope they're anodized ones...

[ashok]

Ashwin,
Where did you find the audio transformers for tubes on the Miracle web site ? I checked and seem to have missed them.

I have had a few dealings lately with them and they did not have any transformers for tubes. However they do have line level ( 70 V and 100V ) audio transformers for audio distribution purposes. I am not sure if you can use these with tubes . Their specs may not be suitable. On the other hand have you discovered that they can be used as tube OPT's ? If so that's great. Let us know.
Cheers.

[ashwin]

Originally posted by roadkill
ashwin,
I got my heatsinks from Cee Pee electronics (near Vishal). They're fairly expensive, too, so I guess I could try the place you mentioned. What's it called? Hope they're anodized ones...

My place was called Maruti Metals. Not an electronics shop, more an Al extrusions shop. But the Al was expensive.

Originally posted by ashok
Ashwin,
Where did you find the audio transformers for tubes on the Miracle web site ? I checked and seem to have missed them.

I have had a few dealings lately with them and they did not have any transformers for tubes. However they do have line level ( 70 V and 100V ) audio transformers for audio distribution purposes. I am not sure if you can use these with tubes . Their specs may not be suitable. On the other hand have you discovered that they can be used as tube OPT's ? If so that's great. Let us know.
Cheers.

Well, I'm not a tube expert, so you may be right. I assumed that they were OPTs because of the following quote on their page:

"Audio Line Matching Transformers 40


EDIT: dunno how this incomplete post happened...

[ashwin]

Originally posted by roadkill
ashwin,
I got my heatsinks from Cee Pee electronics (near Vishal). They're fairly expensive, too, so I guess I could try the place you mentioned. What's it called? Hope they're anodized ones...

roadkill, my place was called Maruti Metals. Not an electronics shop, more an Al extrusions shop. But the Al was expensive.

Originally posted by ashok
Ashwin,
Where did you find the audio transformers for tubes on the Miracle web site ? I checked and seem to have missed them.

I have had a few dealings lately with them and they did not have any transformers for tubes. However they do have line level ( 70 V and 100V ) audio transformers for audio distribution purposes. I am not sure if you can use these with tubes . Their specs may not be suitable. On the other hand have you discovered that they can be used as tube OPT's ? If so that's great. Let us know.
Cheers.

Well, I'm not a tube expert, so you may be right. I assumed that they were OPTs because of the following quote on their page:

"Audio Line Matching Transformers 40 HZ TO 20,000 HZ

The purpose of this Transformer is to match the Impedance of the loudspeaker or a number of loudspeakers to the optimum load of the tube or transistor. In other words, the transformer transforms the Impedance of the speaker, so that the impedance which it presents to the primary winding is equal to the load of the Output stage active element (tube to transistor)."

On their home page, click products -> transformers -> Audio Line Matching Transformers.

So what's the deal? Are they OPTs or not?

Why would you need a 70/100V rated transformer for audio distribution? I thought the 70/100V was for the high anode voltage of a tube stage.

- Ashwin

[ashok]

Why would you need a 70/100V rated transformer for audio distribution

Same reason as High Voltage power transmission. It cuts down on losses in the interconnecting wire. Higher voltage means lower current . So IxR loss drops.

70 and 100 volts distribution transformers are used universally .

I have been quite blind to the fact that if they made those transformers , I could get them to make units to our specs.
There is however a difference between OK transformers and superb transformers. We need to explore that possibility.
I did not read the blurb that followed it on the web page. I will follow up on this and let you know what transpires. If we can get some modified units I will test them out and see what we get.

Cheers.