Poor frequency response with DIY re-amp box

[Flundran]

I have this Hammond 20K:600R transformer that i bought a while ago, used. Today I built a re-amp box, for converting a balanced line level signal to unbalanced guitar-level signal. This is the schematic I used:

I seem to poor high frequency response. It starts to roll off at about 2.5KHz and at 15KHz I am -8dB down. If I take the measurements directly over the 600R resistor I get the same results. Have I missed something in my design? Or is the transformer broken?

/Flundran

 

[Curtis]

What happens if you disconnect the 600R resistor and measure straight across the transformer's unconnected output?

 

[Flundran]

Hi Curtis,

Same result.. It has to be the transformer, right? I just read the Hammond datasheet and it should have straight response from 30Hz-30kHz (+/-1dB).

 

[bernbrue]

Hi,
maybe a stupid hint, but did you connect pin 2&3 and 6&7 of the transformer?
regards
Bernd

 

[cannikin]

[quote author="bernbrue"]Hi,
maybe a stupid hint, but did you connect pin 2&3 and 6&7 of the transformer?
regards
Bernd[/quote]

Hahaha good one bernbrue ... it took me a minute to figure it out!

Nice one :thumb: :thumb: :thumb: :thumb: :thumb: :thumb: :thumb:


your transformer is wired backwards

 

[Curtis]

Hehe, I see now. Double-check the way you've wired your transformer. The schematic you've drawn and the Hammond pinout don't line up.