Hello All,
Awhile back I bought a pair of these for a 211 project. I was somewhat skeptical because of the price ($74USD each), but I took a chance and bought them based on a few positive comments I found when researching interstage transformers.
As usual, there are a lot of opinions floating around but not much data (or measurements) to show you how the device performs.
I built a test circuit (gain of 100) to give me approximately 300VP-P to see how the 126B would perform. Test circuit consists of SRPP 6SN7GT / 6BX7GT with 6BX7GT sections paralleled, running 30mA's thru the 126B.
6BX7GT Operating Parameters:
B+: 275VDC
Voltage across tube: 247.5VDC
5VDC loss across 126B
22.5VDC bias
750 Ohm cathode resistor, bypassed with 100uF cap
I terminated the secondary with 100pF and 560kOhm for testing. I also removed the 560kOhm resistor and the frequency response was still flat with no peaks or ringing.
Attached are a few measurements.
Awhile back I bought a pair of these for a 211 project. I was somewhat skeptical because of the price ($74USD each), but I took a chance and bought them based on a few positive comments I found when researching interstage transformers.
As usual, there are a lot of opinions floating around but not much data (or measurements) to show you how the device performs.
I built a test circuit (gain of 100) to give me approximately 300VP-P to see how the 126B would perform. Test circuit consists of SRPP 6SN7GT / 6BX7GT with 6BX7GT sections paralleled, running 30mA's thru the 126B.
6BX7GT Operating Parameters:
B+: 275VDC
Voltage across tube: 247.5VDC
5VDC loss across 126B
22.5VDC bias
750 Ohm cathode resistor, bypassed with 100uF cap
I terminated the secondary with 100pF and 560kOhm for testing. I also removed the 560kOhm resistor and the frequency response was still flat with no peaks or ringing.
Attached are a few measurements.
Attachments
many thanks, is what I was looking for...I'm gonna use them instead of coupling capacitors for my dac...I have only one doubt...my amplifier is 10k input impedance and my dac is 1k3 output impedance...I guess the 126b is ok
Hi, hope someone can help,
I'm using 2 Tx 126b instead capacitors on my dac, I have some uA so Amperage should'nt be an issue. 230V dc and around 1.8V ac.
I'm sure I respected the wire colors,
Bnr-Blu Primary, Brw Hot and Blu Ground
and Green-Blk Secondary, Green Hot and Blk Ground, but at the secondary I have 0.5V dc, no ac and lot of noise.
many thanks
Vito
I'm using 2 Tx 126b instead capacitors on my dac, I have some uA so Amperage should'nt be an issue. 230V dc and around 1.8V ac.
I'm sure I respected the wire colors,
Bnr-Blu Primary, Brw Hot and Blu Ground
and Green-Blk Secondary, Green Hot and Blk Ground, but at the secondary I have 0.5V dc, no ac and lot of noise.
many thanks
Vito
When using the Hammond interstages, you must observe the following wire connections:
Primary - Brown (B+), Blue (Plate)
Secondary - Black (Grid), Green (Ground)
If you connect the secondary with the green and black backward, you will get very poor frequency response.
Nick
Primary - Brown (B+), Blue (Plate)
Secondary - Black (Grid), Green (Ground)
If you connect the secondary with the green and black backward, you will get very poor frequency response.
Nick
Thanks THD+N, this is a great advice, I will keep in mind when I will build a tube amplifier, in fact, after some research I've discovered I made a mistake, following the announce of this kind of transformer " interstage transformer to replace capacitor " I thought it was possible to replace coupling capacitors in my dac with these transformer....obviously is not the case....to learn sometimes we have to make some mistakes....
Thanks for the advice to connect the interstage right, now the sound is very clear and open, before to much bass and dumb
I have a homepage of my amps on roehrenfieber.com, have a look and please give me feedback how you like it, Josef