The ZTX bipolar transistors are doing two different jobs, the capacitance multiplier Q8, and the cascode Q5.
Q5 is the position that benefits more from low noise, and in Q8 the transistor parameter known as Vearly is utilized. ZTX851 is extremely quiet, and has quite good Vearly, so works nicely in both positions. There’s no need to match, but you might as well since you have so many. (You are a rich man in our Pearl 3 world!)
Because I could only purchase a small number (fewer than 400) of ZTX851, kits will be supplied with ZTX851 for Q5 and ZTX457 for Q8. This will put a slightly more optimized part in Q8, will retain the low-noise 851 for it’s most critical role, and most importantly, allow for more kits to be made as Zetex is currently showing October 2024 dates for 851 restock!
Any of the ZTX parts, 450, 457, 851, 857 will work beautifully in either position. As @hbtaudio mentions, BC550 will work as well. (But watch your pinout!) Wayne has also tried and approved KSC1008YBU.
Q5 is the position that benefits more from low noise, and in Q8 the transistor parameter known as Vearly is utilized. ZTX851 is extremely quiet, and has quite good Vearly, so works nicely in both positions. There’s no need to match, but you might as well since you have so many. (You are a rich man in our Pearl 3 world!)
Because I could only purchase a small number (fewer than 400) of ZTX851, kits will be supplied with ZTX851 for Q5 and ZTX457 for Q8. This will put a slightly more optimized part in Q8, will retain the low-noise 851 for it’s most critical role, and most importantly, allow for more kits to be made as Zetex is currently showing October 2024 dates for 851 restock!
Any of the ZTX parts, 450, 457, 851, 857 will work beautifully in either position. As @hbtaudio mentions, BC550 will work as well. (But watch your pinout!) Wayne has also tried and approved KSC1008YBU.
I don't hope I need them all for the P3.
So yes, if I have received the 851's before Christmas (which I expect) then you are welcome to pickup a few of them
Are we talking about the bipolar NPN in cascodeoperation, like basic "Basisschaltung"?
Textbooks will tell us the truth. In my Pearl 1 (see original schematic) i use unmatched 2SK170BL with increased Rs (R28,29,30,31) up to 33Ohm, split the 2SK389BL source (again, back to original), operating with separate (two) Rs up to 51Ohm ... doesn't match the two channels. End up in marvelous, blameless function. The average dc-voltage-drop across R19 is 8,125V (measured on a real physically build, no simulation). That leaves Q5 in really good workingcondition, i thing /i use BC-550C or B (must look into the housing to verify).
By the way, i never have any problems with ZETEX, knowing since the nice pleasing EQ of original Musical Fidelitys A1 developed by the late Tim de Paravincini.
Question:
Whats the number of dc-drop in the Pearl 3, here UR1 ... anyone measure it?
Textbooks will tell us the truth. In my Pearl 1 (see original schematic) i use unmatched 2SK170BL with increased Rs (R28,29,30,31) up to 33Ohm, split the 2SK389BL source (again, back to original), operating with separate (two) Rs up to 51Ohm ... doesn't match the two channels. End up in marvelous, blameless function. The average dc-voltage-drop across R19 is 8,125V (measured on a real physically build, no simulation). That leaves Q5 in really good workingcondition, i thing /i use BC-550C or B (must look into the housing to verify).
By the way, i never have any problems with ZETEX, knowing since the nice pleasing EQ of original Musical Fidelitys A1 developed by the late Tim de Paravincini.
Question:
Whats the number of dc-drop in the Pearl 3, here UR1 ... anyone measure it?
Kits can only be made and sold one way. To make a SKU without a part that is currently unavailable through normal channels would be folly. When I bought the 851 for the kits, some months ago, they were literally the last available in the normal US distribution channels, (Mouser/DigiKey/Arrow/Newark) and I bought them all for Pearl 3 kits.
Hmmm. Thanks Jim. I was hoping the comments/criticisms were based on real-world experience and testing of the circuit in question. I like theory and conjecture as much as anyone (i’m an architect, so that’s my happy place, but also why i’m not rich), but i need hands-on empiricism when it comes to the mysteries of electricity…
Hello 'Jim', hello 'spoiler',
hands on - and what is the /your problem (with my question) ?
@spoiler,
not yet - but i am in the position to do it immediately. What proves it for you personally?
Please anser my friendly question (don't thing to much, do it) if you can. If you don't want, its ok for me - i have qualified
experience, can calculate, can measure ...
"Nichts für ungut",
HBt.
hands on - and what is the /your problem (with my question) ?
@spoiler,
not yet - but i am in the position to do it immediately. What proves it for you personally?
Please anser my friendly question (don't thing to much, do it) if you can. If you don't want, its ok for me - i have qualified
experience, can calculate, can measure ...
"Nichts für ungut",
HBt.
Last edited:
The ZTX bipolar transistors are doing two different jobs, the capacitance multiplier Q8, and the cascode Q5.
Q5 is the position that benefits more from low noise, and in Q8 the transistor parameter known as Vearly is utilized. ZTX851 is extremely quiet, and has quite good Vearly, so works nicely in both positions. There’s no need to match, but you might as well since you have so many. (You are a rich man in our Pearl 3 world!)
Because I could only purchase a small number (fewer than 400) of ZTX851, kits will be supplied with ZTX851 for Q5 and ZTX457 for Q8. This will put a slightly more optimized part in Q8, will retain the low-noise 851 for it’s most critical role, and most importantly, allow for more kits to be made as Zetex is currently showing October 2024 dates for 851 restock!
Any of the ZTX parts, 450, 457, 851, 857 will work beautifully in either position. As @hbtaudio mentions, BC550 will work as well. (But watch your pinout!) Wayne has also tried and approved KSC1008YBU.
Hello All,
I do this for the fun of it.
So far I have assembled a bread board of the P3 input stage sans the JFETS. The transistors; Q5 and Q8 are ZTX 851. The breadboard has screw terminals for swapping out the capacitors C6 and C7.
I have found the missing voltage injector to use with the Bode-100 VNA for PSRR plots. (Misplaced in my past boxing and moving adventure.)
I think that I will refabricate the first stage breadboard with additional screw terminals to also allow swapping of the NPN transistors.
Even possibly try out the KSC1845. I have a stash to try with other DiyAudio projects.
Thanks DT
fine ;-)Hmmm. Thanks Jim. I was hoping the comments/criticisms were based on real-world experience and testing of the circuit in question. I like theory and conjecture as much as anyone (i’m an architect, so that’s my happy place, but also why i’m not rich), but i need hands-on empiricism when it comes to the mysteries of electricity…
Your are an architect, i am an engineer (only trust in physics).
Is this enough information about my person?
Jim,
you can answer for me and spoiler can attentive read my post. If i had a PEARL 3 on my desk, i can measure myself and don't ask the forum.
Jim,
are you so kind and do me the favor? It is a very quick thing to measure the voltage V(R1). across R1 = 750 Ohm. If you tell me what type of Q1,2,3,4 is installed, BL,GR,V ... i can easy calculate the result myself ... additionell measurement (the voltagedrop) is wise too.
Thank you,
HBt.
You seem quite defensive. I was simply asking a question about whether you’d built the Pearl 3 already, as it seems that you had a lot of criticisms of the design. As someone who is just learning about how one builds equipment, but with 50+ years of listening to music through all variety of equipment, i just wanted to know how you could be so sure there were flaws in the design without having built one, listened to it, and measured the actual device in question.
I don’t have a problem per se with your questions, other than you seem quite certain that the design is flawed, without having tested the design in the real world. I think i stated clearly that i think theory is great, but it is meaningless until applied, and at that point, it should be tested empirically. Major flaws in concept can certainly be caught in modeling, but at this stage i give the benefit of the doubt to Wayne, due to his long history of remarkable designs. He’s earned that respect from me, and because of it, i will build the Pearl 3 first as he intends. I will question it, and my own hearing, if it doesn’t achieve its stated goals.