spark1
Lunatic Member
Hello. I've been trying to figure out a good replacement for the 2sc871 transistors on the EQ board of a 2000X. Normally I would use KSC1845, but I've read that the gain of the current version (KSC1845FTA) is significantly less than the 871 (which I've seem posted as 600 or thereabouts), which in turn may cause a very noticeable change in the character of the amp's sound.
From what I have read (most notably in a thread by Conrad Hoffman), using 1845s for the input pair should not be an issue. The issue is apparently tied to the second pair on the EQ board. Complicating the topic is Conrad's LTSpice modeling, which seems to show that for a more correct frequency response the gain of the second pair should actually be much lower than that of the 871.
So, I've been trying to identify a better replacement than the 1845FTA...one that will be as close to the 871 as possible without further exaggeration of the low frequencies. Simply put, I want to maintain the character of the 2000X as much as possible.
I am not expert enough to understand all the interactions and variables, but it seems like the KSC1845U would have been a very good sub...but of course they are long obsolete. In my research, I've come across the ZTX694B and ZTX696B.
What would you think about one or the other of these as a good sub for the 871 in this application (other than the difficult pin-out difference)? Would you have any other suggestions?
I originally posted this question in Conrad's thread, but got no responses, and thought that it might be better to start a new thread more specific to my question. Thank you very much for your time.
From what I have read (most notably in a thread by Conrad Hoffman), using 1845s for the input pair should not be an issue. The issue is apparently tied to the second pair on the EQ board. Complicating the topic is Conrad's LTSpice modeling, which seems to show that for a more correct frequency response the gain of the second pair should actually be much lower than that of the 871.
So, I've been trying to identify a better replacement than the 1845FTA...one that will be as close to the 871 as possible without further exaggeration of the low frequencies. Simply put, I want to maintain the character of the 2000X as much as possible.
I am not expert enough to understand all the interactions and variables, but it seems like the KSC1845U would have been a very good sub...but of course they are long obsolete. In my research, I've come across the ZTX694B and ZTX696B.
What would you think about one or the other of these as a good sub for the 871 in this application (other than the difficult pin-out difference)? Would you have any other suggestions?
I originally posted this question in Conrad's thread, but got no responses, and thought that it might be better to start a new thread more specific to my question. Thank you very much for your time.