Power transformer for tube amp requirements

Joshua_G · 9th July 2010, 04:01 PM

I posted a similar post on the Power Supplies forum, however I may get more information here.
I got a quotation for 2 power transformers of 420VA fore tube amps from a manufacturer in India. Their quotation is way cheaper from all others I received, including shipping cost. However, I don't know what specifications to ask the manufacturer, other than voltages and currents. Are there any specifications I should mention? How about the finish?

ray_moth · 10th July 2010, 03:51 AM

You need to state whether each winding needs to be center-tapped.

It might be necessary to specify a range of mains voltages over which it may need to work.

I would specify an electrostatic shield.

Joshua_G · 10th July 2010, 08:18 AM

Thanks.
All the above are specified.
Anything else?

richwalters · 10th July 2010, 01:50 PM

You didn't mention the name of the maker. Are the transformers made to acceptable standards, (insulation between windings and isolation for your safety sake). Anything to hide ? A reputable company should provide primary details.
The reason why I ask is once I encounted a tube amp for repair and found the electrostatic screen was a dummy.-the primary and secondaries were wound bifiliar a dangerous practise !! A damaged primary won't protect the user. Don't always go for the cheapest.

richy

Joshua_G · 10th July 2010, 02:48 PM

The manufacturer is Elent from India: Elent : CVT, Online UPS, Offline UPS, UPS Systems, Servo Controlled Voltage Stabilizers (SCVS), Indian UPS Manufacturers, UPS Exporter Electronic Enterprises, India . I know nothing about the manufacturer. His quotation was $70 per 420VA power transformer (before shipping) or $ 223.75 for 2 transformers including shipping. Other quotations were way higher, 1 was $1,347.00 for 2 transformers including shipping and the other was $1,450 for 2 transformers including shipping.
The other option I have is to order from China R-core custom transformers which will cost me $550 for 2 transformers before shipping.

Being on a very tight budget, I tend to order the transformers from Elent India.
I believe the transformers will be in accord with the specifications I'll give them, I only want to make sure to mention all the relevant specifications.
Right now, as far as I know, the specifications are: primary voltage and power rating, secondary windings voltages and current ratings and voltage insulation between the various windings.

Is there anything more I should specify, or ask for?

nicoch58 · 10th July 2010, 03:21 PM

humm
why not a good and sane tube trafo specialist ? you will use diode tube?.

ae-europe (nl)
budp on forum (usa)
trafomaitc (Serbia)
bartolucci (it)
lundhal

Joshua_G · 10th July 2010, 03:36 PM

Thanks nicoch,
The transformer should be custom made, since AFAIK there is no shelf product with the spec I need. There will be vacuum tube diode rectifiers (2 6CJ3).
Are all the manufacturers you mention produce custom transformers?

Stixx · 10th July 2010, 03:47 PM

Quote:

Are all the manufacturers you mention produce custom transformers?

AE-Europe does for sure, and only custom. Very recommended!

nicoch58 · 10th July 2010, 04:00 PM

no lundhal

the reflect resistence of trafo is very important for diode but you can put a resistor...

nicoch58 · 04:11 PM

what you will build ? cheap or top one ?

http://www.freewebs.com/valvewizard/fullwave.html

9th July 2010, 04:01 PM	#1
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	Power transformer for tube amp requirements I posted a similar post on the Power Supplies forum, however I may get more information here. I got a quotation for 2 power transformers of 420VA fore tube amps from a manufacturer in India. Their quotation is way cheaper from all others I received, including shipping cost. However, I don't know what specifications to ask the manufacturer, other than voltages and currents. Are there any specifications I should mention? How about the finish?

10th July 2010, 03:21 PM	#6
nicoch58 diyAudio Member Join Date: Oct 2004	humm why not a good and sane tube trafo specialist ? you will use diode tube?. ae-europe (nl) budp on forum (usa) trafomaitc (Serbia) bartolucci (it) lundhal __________________ Sic58

10th July 2010, 04:00 PM	#9
nicoch58 diyAudio Member Join Date: Oct 2004	no lundhal the reflect resistence of trafo is very important for diode but you can put a resistor... __________________ Sic58

10th July 2010, 04:04 PM	#10
nicoch58 diyAudio Member Join Date: Oct 2004	what you will build ? cheap or top one ? http://www.freewebs.com/valvewizard/fullwave.html __________________ Sic58 Last edited by nicoch58; 10th July 2010 at 04:11 PM.

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10th July 2010, 03:51 AM	#2
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	You need to state whether each winding needs to be center-tapped. It might be necessary to specify a range of mains voltages over which it may need to work. I would specify an electrostatic shield.

10th July 2010, 08:18 AM	#3
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	Thanks. All the above are specified. Anything else?

10th July 2010, 01:50 PM	#4
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	You didn't mention the name of the maker. Are the transformers made to acceptable standards, (insulation between windings and isolation for your safety sake). Anything to hide ? A reputable company should provide primary details. The reason why I ask is once I encounted a tube amp for repair and found the electrostatic screen was a dummy.-the primary and secondaries were wound bifiliar a dangerous practise !! A damaged primary won't protect the user. Don't always go for the cheapest. richy

10th July 2010, 02:48 PM	#5
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	The manufacturer is Elent from India: Elent : CVT, Online UPS, Offline UPS, UPS Systems, Servo Controlled Voltage Stabilizers (SCVS), Indian UPS Manufacturers, UPS Exporter Electronic Enterprises, India . I know nothing about the manufacturer. His quotation was $70 per 420VA power transformer (before shipping) or $ 223.75 for 2 transformers including shipping. Other quotations were way higher, 1 was $1,347.00 for 2 transformers including shipping and the other was $1,450 for 2 transformers including shipping. The other option I have is to order from China R-core custom transformers which will cost me $550 for 2 transformers before shipping. Being on a very tight budget, I tend to order the transformers from Elent India. I believe the transformers will be in accord with the specifications I'll give them, I only want to make sure to mention all the relevant specifications. Right now, as far as I know, the specifications are: primary voltage and power rating, secondary windings voltages and current ratings and voltage insulation between the various windings. Is there anything more I should specify, or ask for?

10th July 2010, 03:36 PM	#7
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	Thanks nicoch, The transformer should be custom made, since AFAIK there is no shelf product with the spec I need. There will be vacuum tube diode rectifiers (2 6CJ3). Are all the manufacturers you mention produce custom transformers?

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