Good price on mains Tx for tube gear
« on: January 07, 2019, 08:01:24 AM »
Just got a pair of these , very handy voltages for tube stuff ,

https://www.ebay.ie/itm/273622786975?ul_noapp=true

Theres a few other versions of this transformer out there , but this one is a good bit cheaper , 54 pounds sterling for two including shipping by DHL , this one also has foil interwinding screens ,where many modern transformers dont include this  . The seller also says custom voltages can be done to order . 


ruffrecords

Re: Good price on mains Tx for tube gear
« Reply #1 on: January 07, 2019, 12:33:38 PM »
Nice find. For HT supplies I use these:

https://www.tme.eu/en/details/58-0100-230-s/toroidal-transformers/talema/

TME supply a range of VA ratings and secondary voltage.

heers

Ian

www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

My3gger

Re: Good price on mains Tx for tube gear
« Reply #2 on: January 07, 2019, 02:52:24 PM »
I'm buying and using only toroid transformers from two local sources in Slovenia (EU), prices are almost the same, both have magnetic shield around transformer. One does static shields between pri and sec, also insulated secondaries (hope i'm using correct name) not found in most toroids. Cost for this is around 2eur per tap and little more for static shield.

One example of unshielded:
Primary: 230V
Sek. 1: 220V/50mA
Sek. 2: 7,5/8V/1,5A
Sek. 3: 45V/40mA
Price:20eur

A friend who makes power amps told me both winders save on copper which seeems a problem for him. I'm ordering trafos with 2x max VA and never had a problem, even 1,5x is ok. Maybe because i tell them told trafos go into small signal audio devices they like and show interest in what i'm doing...

Don't you have cheap winders like this in England or US? Eastern Europe has plenty of shops with high quality toroids for audio, prices are low. I can give you contacts, or help get them for testing which would be free for at least 2 tube preamps or compressor. They speak English too.

Cheers

Re: Good price on mains Tx for tube gear
« Reply #3 on: January 07, 2019, 04:59:09 PM »
I also saw the R cores , some specifically wound for tube voltages , I was tempted but Im unsure about interwinding insulation,anyway it was more like 60-70 euros each for these including shipping  ,

Ill most likely order extra screening cans  for these E-I ones in the end , Im also planning to run them at around 50% maximum current for lower noise ,

Transformer winding isnt much of a thing here anymore , cost of labour means and transformers or motors under a couple of hundred euros are simply replaced . Aside from simple 1:1 transformers you cant really get anything off the shelf for tube stuff here in Ireland .

Im planning on running both these transformers with an Ebay dual 6x4/silicon diode bridge board , that will form the Ht supply  of a stereo SE 6L6/6AU6  board also off ebay , I would like to try a seperate regulated  dc heater  supply for each amp too, just to keep it  mono block from the ground up so another transformer is required , dual 8 volt windings plus possibly a subsidiary Ht winding specifically for early high gain stages . The Pri/Sec shielding on transformers is nice if you can get it ,but it seems like something many transformer makers are  not too bothered about anymore . Ive my eye on a couple of nice oil filled chokes Id like to use between the psu and the output transformer ,I might also wind a smaller low current choke for the 6L6 screen /6AU6 anode supply , mainly for the extra decoupling it will give . From the view point of guitar tone ,something was lost when the man suggested a resistor could taken the place of a choke , a kind of roundness and bounce back when the amp is overdriven , almost all the great guitar amps make use of the choke for screen supply , I found most modern guitar amps to get very brittle at maximum output .

I might be interested in trying some transformers from eastern europe ,for the money its good value even compared to off the shelf or simple dual secondary type stuff  , Id also be very interested in the possibillity buying materials like lams and bobbins
from there , I work in a winding shop already ,so I have access to all the copper I need ,but its almost exclusivly motors we handle in our shop ,

 Maybe if you pass me along the details im pm My3gger , I'll shoot them a work email later on in the week .

Could you post a pic of some of the toroids you had made up ?

iampoor1

Re: Good price on mains Tx for tube gear
« Reply #4 on: January 07, 2019, 05:47:29 PM »
The only low cost power cordial transformers avaliable in the US with tubey modelsis antek

http://www.antekinc.com

Of course we have edcor too, but they don't wind torodiaks, and their power transformers are quite abit more expensive than antek. Output transformers are a different story of course:-)

My3gger

Re: Good price on mains Tx for tube gear
« Reply #5 on: January 08, 2019, 09:50:28 AM »

I also saw the R cores , some specifically wound for tube voltages , I was tempted but Im unsure about interwinding insulation,anyway it was more like 60-70 euros each for these including shipping  ,

Ill most likely order extra screening cans  for these E-I ones in the end , Im also planning to run them at around 50% maximum current for lower noise.

Transformer winding isnt much of a thing here anymore , cost of labour means and transformers or motors under a couple of hundred euros are simply replaced . Aside from simple 1:1 transformers you cant really get anything off the shelf for tube stuff here in Ireland .

I might be interested in trying some transformers from eastern europe ,for the money its good value even compared to off the shelf or simple dual secondary type stuff  , Id also be very interested in the possibillity buying materials like lams and bobbins
from there , I work in a winding shop already ,so I have access to all the copper I need ,but its almost exclusivly motors we handle in our shop ,

 Maybe if you pass me along the details im pm My3gger , I'll shoot them a work email later on in the week .

Could you post a pic of some of the toroids you had made up ?

Interesting, i will do my best for what you asked. Interwinding insulation for this toroids (writing about better winder imo) is specified at more than 4KV. I notice very low V drop when LT is loaded at about 70%, for example 7,5V winding into LDO at 1V drop gives 5,8V plugged anywhere for years. HT is fine too, since i'm using cap multipliers tube builds have lower perceived noise than solid state, so i don't always bother measuring noise. Beside, they don't heat like some others.
Static shield between pri and sec comes with ground wire, magnetic is a few turns of core material. Can't remember what exactly they do about tap shielding, my guess is the same thing as for pri:sec, drain to the same ground.?

Winder i like best is electrical engineer who likes audio, i'm happy to get you in contact with him (call seems to be better before sending specifications or questions...). I'm sure he can and is willing to wind high quality toroids when provided with correct details, sometimes i get his suggestions because they do supplies beside toroids.
It really interests me what are best practices when winding audio power toroids, despite good results with non shielded. Signal OTs were used in lots of German gear, i asked here a few times but no one gave any directions. I've seen how windings are distributed because of capacitances, pics didn't show shielding which should help further.

We tend to rewind EI trafos and motors which cost a lot less than couple hundred of eur, of course it depends who is repairing... Power trafos for audio stuff are always ordered custom localy, except for audiophiles ) One more thing i noticed is that we still have lots of practical knowledge and more stuff is getting repaired, compared to richer countries.
I searched EI lams for small signal output trafos, all are too thick made of iron, we don't even dream of 49Ni or similar. Best were old M lams no one has now, bobbins were not a problem in small quantity. No one really makes low level OTs, i've seen a power OTs. Never asked for power trafo materials or finished ones, toroids work very well and are cheap.

« Last Edit: January 08, 2019, 10:16:31 AM by My3gger »

Re: Good price on mains Tx for tube gear
« Reply #6 on: January 08, 2019, 11:54:34 AM »
Just got a pair of these , very handy voltages for tube stuff ,
https://www.ebay.ie/itm/273622786975?ul_noapp=true
Did you have to pay import VAT?

pucho812

Re: Good price on mains Tx for tube gear
« Reply #7 on: January 08, 2019, 02:40:12 PM »
been looking at all of this.

Wish there was more toroidal options available.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

BluegrassDan

Re: Good price on mains Tx for tube gear
« Reply #8 on: January 08, 2019, 06:19:44 PM »
Has anyone tried Edcor PSU transformers? I just received a quote from them for EIs with multiple secondaries just north or $60 USD.

scott2000

Re: Good price on mains Tx for tube gear
« Reply #9 on: January 08, 2019, 06:42:17 PM »
Has anyone tried Edcor PSU transformers? I just received a quote from them for EIs with multiple secondaries just north or $60 USD.

I have a XPWR009-120  I'm waiting to use..... can't say how it'll work but it's very slick looking  (little bit orange peel looking on some of casing but nice) and pretty beastly in size and weight .... I was kinda taken back by how large it actually is.... 
« Last Edit: January 08, 2019, 06:55:08 PM by scott2000 »


pucho812

Re: Good price on mains Tx for tube gear
« Reply #10 on: January 08, 2019, 06:53:32 PM »
Has anyone tried Edcor PSU transformers? I just received a quote from them for EIs with multiple secondaries just north or $60 USD.

yes. I have a few DIY tube builds with edcor's.   work very well.  I also use them for I/O
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

pvision

Re: Good price on mains Tx for tube gear
« Reply #11 on: January 08, 2019, 07:40:36 PM »
Wish there was more toroidal options available.

Same here. I've been going round in circles...

Nick Froome

Re: Good price on mains Tx for tube gear
« Reply #12 on: January 08, 2019, 07:47:59 PM »
The one thing about toroids is that sometimes wires with very different potentials cross close to each other , when your dealing with multisection secondaries windings for instance how will your 6.3v winding hold up with elevated grounds relative to its twin 6.3 v winding with 0V ground .There are a lot of unknowns which could play well or badly with your particular arrangement
I think a lot of the subtleties (relating to audio)  devised in the day of the El lam havent been passed down the line to Toroid manufactures .

The R core looks interesting as  each bobbin seems to be wound in  mirror image fashion relative to its counterpart , so noise could cancel to a high degree .

I might try a  230v volt toroid   and thread in  a couple of Lt sections  with  a little bobbin shuttled through the O  ,probably only a couple of dozen turns would be needed , you could add screening as required , be very easy in any case to do a test with any particular toroid ,ten turns of a suitable wire gauge and you'd get a good idea from the output voltage what turns would be required for 2x3.15,  6.3 ,7.5 etc.Wind more than the turns you need then strip off turns to get your voltage to nominal, if you had  all the needed materials to hand the job would be down to a matter of minutes per transformer  ,certainly a lot easier than requesting a custom job from the winder each time plus you can screen and magnetically shield to your own spec  .I might check if there are any old toroids in scrap tomorrow for a test.

How do  toroids work  out as inductors,  psu filter choke and anode load choke ,

handy core turns  calculator here ,
http://www.giangrandi.ch/electronics/trafo/trafo.shtml
 






BluegrassDan

Re: Good price on mains Tx for tube gear
« Reply #13 on: January 08, 2019, 08:18:52 PM »
yes. I have a few DIY tube builds with edcor's.   work very well.  I also use them for I/O

How are they regarding noise compared to toroids - both physical noise and electrical?

Re: Good price on mains Tx for tube gear
« Reply #14 on: January 09, 2019, 03:52:30 AM »
Toroid transformers are very easy to wind yourself, I've wound a few now with good results. I got my toroids cheap off ebay for about £30 -  big 625VA low voltage high current secondaries, took off the secs , left the primary on and rewound to what I wanted. I overwound them and didn't use all their capacity. There is one downside with toroids though when winding  low voltage  6.3v heater windings for example. As toroids have more V per turns it's hard to get 6.3v loaded bang on, so you might have to compromise with something like  6v or 6.7v.

I've heard good things about these lads - https://sklep.toroidy.pl/en_US/index if winding your own doesn't appeal.

Andy.

pucho812

Re: Good price on mains Tx for tube gear
« Reply #15 on: January 09, 2019, 03:54:55 AM »
How are they regarding noise compared to toroids - both physical noise and electrical?

not sure, my x-formers were mounted on the outside.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

alexc

Re: Good price on mains Tx for tube gear
« Reply #16 on: January 09, 2019, 04:22:02 AM »
I ping therefore I am

Re: Good price on mains Tx for tube gear
« Reply #17 on: January 09, 2019, 03:40:47 PM »
Had a dig around today today found a couple of old toroids ,unfortunately the primaries were damaged , so probably not worth rewinding as there only 100-200 watt cores anyway .

Another easy way to find a big  EI core is from an older microwave oven , the secondaries can be carefully chiseled out  without seperating the lams and bobbin , then a new wire can be threaded through easily. You'd most likely need to fill any unused  window space  with packers of some kind to stop the coil vibrating or moving when turned on . If you  made up 6-8 strands of smaller gauge wire into one bundle  you could very easily make several heater supplies on a microwave oven core, enough to power a whole rack of gear, just the price of the new copper and you save a lump of iron from landfill ,I might give that idea a try on my lunch break tomorrow, come to think of it might just be doable with high temp double insulated multiway mains cable instead of magnet wire ,all to be decided once I get volts/turn on the core .

Thanks for the link Dr Wobble ,turns out they have loads of toroid inductors and they seem to be able to do pi wound too .
« Last Edit: January 09, 2019, 03:55:23 PM by Tubetec »

Re: Good price on mains Tx for tube gear
« Reply #18 on: January 10, 2019, 04:27:13 PM »
I extracted a microwave oven transformer today from scrap , easy job to hacksaw the HV secondary either side of the core then use a drift to bash the remains of the coil out , What your left with is a really good quality transformer ready to be re-wound or threaded with new LV secondary windings . I didnt get a chance to do the ten turns test but Im fairly certain its 1 volt per turn , so 6 and a half turns for 6.5 volts ,its that easy . I have a window area of about 15x25mm to work with , there are some strips of lam dividing primary and secondary. I might just leave them in place as it probably does good for screening theres also a lot of glassfibre based paper insulation to be cleared away  , I can replace it with a nomex slieve before I pull the new wire through .

I looked at the various different multicore mains cables ,none is rated much above about 150C , the insulation would take up a huge amount of space  and not really be upto short circuit  meltdown , another possible option would be braided screened four wire mains cable which is about 8mm in diameter .75mm cross section per conductor, it limits the amount of current to 1.5-2 amps per winding ,  I might settle a single strand of thick   magnet wire run through fibre slieveing , and do a few seperate coils side by side , I saw a neat trick where you wind the coils with a curved wooden spacer in place between the core face and inside edge of the coil , it allows air to circulate and also means theres no need for tight radius bends in the wire at the edge of the core , everything is then secured with cable ties .The fact that the winding projects beyond the the edge of the core  means screening wrap or foil  could easily be wound round also

Its a real pity I didnt think of trying this before , theres no shortage of broke down microwaves waiting to give up their treasure and a  hefty lump is it too  , still when you do off signal chassis Psu you might as well throw some heavy weight iron at it , it'll work all the better and quieter with light loads and you can trim the turns to get the close enough to the  volts you need. Any guidance on the winding geometry and screening aspects greatly appreciated  .

Re: Good price on mains Tx for tube gear
« Reply #19 on: January 12, 2019, 06:51:52 AM »
Found some 4mm sq stranded hook up wire ,  silicone and glass fibre insulation,resistant to fuel, oil and heat  so probably good enough for this job  , should be good for at least 10 amps which is way less than I need from it , I probably have space  I might just be able to squeeze three Lt windings in there ,I wont ever draw 10 amps per winding ,so hopefully the thick wire will make  any voltage drop under load small  . Im still unsure about adding screening between and around  LT windings ,if its needed or not for lowest noise . Will post back later when Ive wound and tested it


 

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