Frequency respond of guitar/bassamp's OPT?

hoangduongo · 27th October 2008, 02:48 AM

Hi everyone
I'm currently trying to build a guitaramp, begin with an OPT, and one of the key point here is the Frequency Respond, which decides how much iron/copper you should put in your OPT, and the performance of it as well.
According to GEOFEX here, the low cut for the OPT should be the lowest frequency of the instrument (bass/guitar, ie 41/82 Hz). But I still wonder if Fender/Marshall... follow this guide too, because in some Fender 200W bassamp, I can see the OPT is surprisingly small, giving a different lowcut.
So, the thing I want to ask here, is could anyone give me some data of the Frequency Respond of some brand OPT (which is really rare in my country), or some guide about this issue, so that I can determine the design of my OPT.
Thanks
Cheers

Bone · 27th October 2008, 09:32 AM

The frequency response of the transformer is not determined by the size of it - that determines the power it will handle - but the type of iron in the laminations (core).
A 50VA mains transformer will be approximately the same size as a 50Watt output transformer! Or it was when I was at college.

You could in fact use a rewired mains transformer for bass as the 'better' iron laminations only increase the higher frequency response.

This site - http://www.shure.com/ProAudio/Produc...diotransformer has useful some information on audio transformers.

Tony

27th October 2008, 02:48 AM	#1
hoangduongo diyAudio Member Join Date: Jan 2006 Location: hanoi	Frequency respond of guitar/bassamp's OPT? Hi everyone I'm currently trying to build a guitaramp, begin with an OPT, and one of the key point here is the Frequency Respond, which decides how much iron/copper you should put in your OPT, and the performance of it as well. According to GEOFEX here, the low cut for the OPT should be the lowest frequency of the instrument (bass/guitar, ie 41/82 Hz). But I still wonder if Fender/Marshall... follow this guide too, because in some Fender 200W bassamp, I can see the OPT is surprisingly small, giving a different lowcut. So, the thing I want to ask here, is could anyone give me some data of the Frequency Respond of some brand OPT (which is really rare in my country), or some guide about this issue, so that I can determine the design of my OPT. Thanks Cheers

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27th October 2008, 09:32 AM	#2
Bone diyAudio Member Join Date: Jun 2004 Location: Dorset, UK	The frequency response of the transformer is not determined by the size of it - that determines the power it will handle - but the type of iron in the laminations (core). A 50VA mains transformer will be approximately the same size as a 50Watt output transformer! Or it was when I was at college. You could in fact use a rewired mains transformer for bass as the 'better' iron laminations only increase the higher frequency response. This site - http://www.shure.com/ProAudio/Produc...diotransformer has useful some information on audio transformers. Tony