Tested wiring and grounding I get only 2.3x gain ! I contacted cinemag and they send me a new schematic but wired as 1:3 transformer! Any thoughts?
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same case with just one specimen , or it is same with both?
presuming that you're building stereo ....... not mono , not multichannel 🙂
presuming that you're building stereo ....... not mono , not multichannel 🙂
Loose wire! Now its working 1:3 as stated by cinemag! Next stage has 100K input impedance its the M2 clone!
check again ...... without loose wire 
decent drive and appropriate loading .....
decent drive is , say , everything up to 75R and appropriate loading at autoformer output - no less than 20K
decent drive and appropriate loading .....
decent drive is , say , everything up to 75R and appropriate loading at autoformer output - no less than 20K
check again ...... without loose wire
decent drive and appropriate loading .....
decent drive is , say , everything up to 75R and appropriate loading at autoformer output - no less than 20K
I am using complementary 2sk170V/2sj74V @12mA using a 50R pot so output impedance should be very low.
Tomorrow I will listen to the 1:3 setup....
Guys I managed to configre the cmoq-4 for 1:4 autoformer test and it sounds wonderful! Cinemag propably send me a phase reversed sample so the colors in datasheet dont match the transformer! 🙂
No problem!
No problem!
What would be the disadvantage of using a 10k:10k autoformer rather than a 600:600?
Wouldn't the 10k input allow us to skip the jfets on the input?
Wouldn't the 10k input allow us to skip the jfets on the input?
most probably adding too much to Rout
think about Rdc of windings ...... even if there isn't simple adding of Rdc in Rout figure , there still is substantial consequeance
think about Rdc of windings ...... even if there isn't simple adding of Rdc in Rout figure , there still is substantial consequeance
That makes sense, especially as a utility preamp, you don't want to high of an Rout.
I should have clarified- I am thinking of using this into a hiZ input, such as the Salas 6V6 buffer to get just a little bit of a boost.
I should have clarified- I am thinking of using this into a hiZ input, such as the Salas 6V6 buffer to get just a little bit of a boost.
can we use below audio transformer iron preamp:
(LM-NP-1001-B1L - Audio Transformer, 600 ohm, 600 ohm, Through Hole, LM-NP-1000 Series)
http://in.element14.com/bourns/lm-np-1001-b1l/transformer-line-matching-1-1/dp/1929741
its power level is given as "- 45.0 to + 3.0 dBm"
not much clear with its current or voltage ratings.. can use this for preamp for 6db gain..?
(LM-NP-1001-B1L - Audio Transformer, 600 ohm, 600 ohm, Through Hole, LM-NP-1000 Series)
http://in.element14.com/bourns/lm-np-1001-b1l/transformer-line-matching-1-1/dp/1929741
its power level is given as "- 45.0 to + 3.0 dBm"
not much clear with its current or voltage ratings.. can use this for preamp for 6db gain..?
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I suspect it is not of quality to be on par with rest of concept
however - it's cheap enough , just try it
however - it's cheap enough , just try it
Could you please tell what parameters to look for selecting a transformer for voltage gain in preamp.. from the iron pre it seems to be a 600ohm:600hom.. ie. 1:1 turn ratio (can we look for a 1:2 turn ratio for gain more than 6db).. what other parameters do we need to look for
it needs to be linear ...... not just on paper , as many of these small and cheap thingies are
connected as autoformer , 1:1 is becoming 1+1 , having 2V/V gain , which is 6db
if you take 1:2 , it is becoming 1+2 , giving 3V/V gain , which is 9.5db
there is waste number of possible xformers ....... if you take 600CT:600CT , that's practically 4 windings of 150R (nominally) ......
you can use that one as 1:1+1+1 , resulting in 1+3 , having gain of 4V/V , which is 12db
and that's where I think you need to stop with gain , because Rout of entire shebang is really going up
connected as autoformer , 1:1 is becoming 1+1 , having 2V/V gain , which is 6db
if you take 1:2 , it is becoming 1+2 , giving 3V/V gain , which is 9.5db
there is waste number of possible xformers ....... if you take 600CT:600CT , that's practically 4 windings of 150R (nominally) ......
you can use that one as 1:1+1+1 , resulting in 1+3 , having gain of 4V/V , which is 12db
and that's where I think you need to stop with gain , because Rout of entire shebang is really going up