Low Noise Transistors: ZTX851 versus ZTX689B Noise Performance

Where we discuss new analog design ideas for Pro Audio and modern spins on vintage ones.
User avatar
mediatechnology
Posts: 4520
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Low Noise Transistors: ZTX851 versus ZTX689B Noise Performance

Post by mediatechnology » Wed Nov 20, 2019 5:48 pm

Wow. My guestimate of 5.5 was pretty close.

The ZTX689 may be better overall as a mic preamp simply due to its higher gain (lower Ibias) and lower Cob.

Thank you Bill and Hans!
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

al2002
Posts: 1
Joined: Mon May 04, 2020 9:36 pm

Re: Low Noise Transistors: ZTX851 versus ZTX689B Noise Performance

Post by al2002 » Mon Jun 29, 2020 3:32 pm

Is any rbb data available for the pnp ZTX 789? Also, has anyone measured the hfe variations for a batch of 689/789s? Would be useful to know.

Thanks in advance.

User avatar
mediatechnology
Posts: 4520
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Low Noise Transistors: ZTX851 versus ZTX689B Noise Performance

Post by mediatechnology » Thu Jul 02, 2020 3:42 pm

I would have to work backwards from the noise measurements but the rbb' of the ZTX789 is between the 5Ω rbb' of the ZTX689 and the 2SB737's 2Ω rbb'.

I don't have enough ZTX789 to get a meaningful hFE spread.
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

Post Reply