Interstage transformer for balanced amp question

Tyimo · 12th March 2008, 06:51 PM

Hi!
I would like to use an interstage transformer (or line output transformer) between my tube preamp and a balanced mosfet power amp as a phase splitter.
The tube preamp has ca. Zout 100R and the Mosfet amp has Zin 90Kohm /+-channel.
What would be the ideal transformer parameters for this combination?? What imp or voltage ratios?
I thought on something like the Jense JT-10K61-1M with 4:1
or a toroid....

Greets:
Tyimo

bear · 13th March 2008, 09:48 PM

It really doesn't matter.

The transformer is merely a ratio device.
If you don't need any "voltage gain" then the ratio needs to be 1:1 wrt each part of the secondary that is going to be used separately, unless they are recombined and that sum = "one". Otherwise the full secondary is a step up.

If you have extra headroom/gain then the ratios don't matter much at all - but not sure why you want/need a "phase splitter"??

The only issue wrt the actual transformer is the driving impedance, if it is sufficiently low then the frequency response should be preserved when driving a low Z primary (not a lot of inductance) ... but the effective impedance will be the reflection of the secondary load... which in some instances will need to be loaded to maintain the transient response (prevent ringing) if the actual load (the amp) is high - Z.

If ur trying to use this to bridge two amps, beware that you may well exceed the current capability or even the voltage swing of the output stages on many amps when bridging... also beware of the possibility of grounds that do not want to be connected together.

_-_-bear

andyjevans · 13th March 2008, 11:06 PM

I really lke the Hammond nickel 124b in step-down, but this would require you to use a push pull preamp stage. Could be worh it. If you could get your hands on four 26 or 01A that would be really good. And even a pair of the cheap 3a5 would be excellent.

Tyimo · 14th March 2008, 06:58 PM

Hi Bear!
Thanks!

Quote:

If you have extra headroom/gain then the ratios don't matter much at all - but not sure why you want/need a "phase splitter"??

I would like to use the interstage transformer as a SE/Balanced converter for my SE tubre and Balanced Mosfet amp combo.

Tyimo

12th March 2008, 06:51 PM	#1
Tyimo diyAudio Member Join Date: Nov 2002 Location: Hungary	Interstage transformer for balanced amp question Hi! I would like to use an interstage transformer (or line output transformer) between my tube preamp and a balanced mosfet power amp as a phase splitter. The tube preamp has ca. Zout 100R and the Mosfet amp has Zin 90Kohm /+-channel. What would be the ideal transformer parameters for this combination?? What imp or voltage ratios? I thought on something like the Jense JT-10K61-1M with 4:1 or a toroid.... Greets: Tyimo

13th March 2008, 09:48 PM	#2
bear diyAudio Member Join Date: Apr 2002 Location: New York State USA	It really doesn't matter. The transformer is merely a ratio device. If you don't need any "voltage gain" then the ratio needs to be 1:1 wrt each part of the secondary that is going to be used separately, unless they are recombined and that sum = "one". Otherwise the full secondary is a step up. If you have extra headroom/gain then the ratios don't matter much at all - but not sure why you want/need a "phase splitter"?? The only issue wrt the actual transformer is the driving impedance, if it is sufficiently low then the frequency response should be preserved when driving a low Z primary (not a lot of inductance) ... but the effective impedance will be the reflection of the secondary load... which in some instances will need to be loaded to maintain the transient response (prevent ringing) if the actual load (the amp) is high - Z. If ur trying to use this to bridge two amps, beware that you may well exceed the current capability or even the voltage swing of the output stages on many amps when bridging... also beware of the possibility of grounds that do not want to be connected together. _-_-bear __________________ _-_-bear http://www.bearlabs.com ...ur feeback please - like/dislike my what I have written? PM/email tnx. --

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13th March 2008, 11:06 PM	#3
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	I really lke the Hammond nickel 124b in step-down, but this would require you to use a push pull preamp stage. Could be worh it. If you could get your hands on four 26 or 01A that would be really good. And even a pair of the cheap 3a5 would be excellent.

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