To tube or not to tube ?

Bernhard · 7th February 2006, 02:05 PM

Hi,

what are the pros and cons of tube I/V ?

Is only tube amplification possible after passive I/V, or also tube I/V that keeps output pin of DAC on virtual ground ?

I read about passive + tube = no feedback = no intermodulation distortion but also I read it is up to 1% harmonic distortion at FS from use of passive or tube ?

Or better discrete silicone ?

Just like to hear some opinions ...

gmarsh · 7th February 2006, 02:47 PM

You can't say "no feedback = no IMD". Any nonlinear system will create IMD, and this includes tubes.

If you're feeling really adventurous and want proof of this, build yourself a diode I/V (that's right, use a forward biased diode without feedback) and measure the intermodulation. I guarantee it won't be zero - heterodyne radio receivers often use diodes in this manner as mixers, and the intermodulation is what makes them work.

poynton · 7th February 2006, 06:28 PM

Quote:

Originally posted by Bernhard
Hi,

what are the pros and cons of tube I/V ?

High voltage, extra transformers, space..............

Quote:

.... tube I/V that keeps output pin of DAC on virtual ground ?

What DAC are you using?

Quote:

Or better discrete silicone ?

Better ask Pammie....

Bernhard · 7th February 2006, 06:58 PM

Quote:

Originally posted by poynton

What DAC are you using?

Don't know yet.

rfbrw · 7th February 2006, 07:25 PM

Active or passive, both are possible.

7th February 2006, 02:05 PM	#1
Bernhard diyAudio Member Join Date: Apr 2002 Location: Munich	To tube or not to tube ? Hi, what are the pros and cons of tube I/V ? Is only tube amplification possible after passive I/V, or also tube I/V that keeps output pin of DAC on virtual ground ? I read about passive + tube = no feedback = no intermodulation distortion but also I read it is up to 1% harmonic distortion at FS from use of passive or tube ? Or better discrete silicone ? Just like to hear some opinions ...

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7th February 2006, 02:47 PM	#2
gmarsh diyAudio Member Join Date: Apr 2004 Location: Halifax, NS, Canada	You can't say "no feedback = no IMD". Any nonlinear system will create IMD, and this includes tubes. If you're feeling really adventurous and want proof of this, build yourself a diode I/V (that's right, use a forward biased diode without feedback) and measure the intermodulation. I guarantee it won't be zero - heterodyne radio receivers often use diodes in this manner as mixers, and the intermodulation is what makes them work.

7th February 2006, 07:25 PM	#5
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	Active or passive, both are possible.

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