F5 power amplifier

[AndrewT]

the low Idss symptoms and the adjustment to correct such is repeatedly commented on in the F5 builds and Threads.
Seems you did not read about the need to check Idss and make the recommended adjustments.

 

[Nevohteeb]

Dear Andrew,

I don't want to have an argument with you since you help a lot of people here, myself included, and I'm very thankful for that.
Nevertheless, I actually carefully read the F5 manual as well as a lot of posts in this forum before I started the build 4 years ago, but in spite of that, I missed the low Idss symptoms comments. But if you read my post #14795 you'll see that I found the answer myself, on a post about that problem.

So, again, thank you for the help, and I'm sorry if I made you lose some time by my fault.

 

[AESIR]

zetex450/550 replacements ?

Hi F5 Builders

I got some BC550 C / 560 C pairs..can i use them for replacements in F5,insted of the zetex450/550 pair ?

KM

 

[Zen Mod]

yup

mind pinout (I'm lazy to check is it same or not)

 

[ichiban]

Here is an illustration of pin outs

 

[AESIR]

Ok..thank you both !

KM

 

[dutchgfx]

Anyone know a modern replacement for the 2SK170 and 2SJ74?

for the other transistors im using IRFP9240 and IRFP240, is this okay for the MOSFETS?

I can't seem to find any replacement JFETS

 

[Zen Mod]

forum store

 

[dutchgfx]

Those are expensive. Anything else? I will buy if I have too but I would rather build a Beta22 than source $50 transistors

 

[labjr]

The parts in the store aren't matched? What's up with Linear Systems? Are they still unable to supply the parts in any volume?

 

[6L6]

Matched K170/J74 will be available in the store soon.

No, they are not supplying good volume, but were taking what we can get.

 

[Soundhappy]

Matched K170/J74 will be available in the store soon

Diyer dream become reality
DiyAudio store future bestseller

 

[dutchgfx]

So there isn't anything else I can buy to replace the JFETs?

 

[6L6]

Not really.

 

[Defiant]

So there isn't anything else I can buy to replace the JFETs?

It's almost comical to realize that many vacuum tube types have superior availability to these JFETs. Ditto for some medium power lateral MOSFETs - Renesas discontinued the 2SJ76/2SK213 types years ago, and there is no really decent substitute for them.

 

[jacco vermeulen]

It's almost comical to realize that many vacuum tube types have superior availability to these JFETs.

If only they manufactured P-channel valves.

 

[Zen Mod]

those were made , but only for Dutchies

 

[juma]

If only they manufactured P-channel valves.

Unfortunately, all positron-emitting cathodes were used up to build the Death Star and Imperial tube company went bankrupt after that...

 

[juma]

So there isn't anything else I can buy to replace the JFETs?

Sure there is - few cheap BJTs will do the job and won't sound worse than JFETs.
Actually, JFETs are replaced by Q3,Q4 (running at 4.5mA). Q1,Q2 make strictly neutral buffer that polarizes Q3,Q4.
Q5-8 make constant current sources for the input stage.

No need to deprive yourself of a good amp for such a trivial reason - lack of JFETs...

 

[jameshillj]

Maybe some of those Optimized Field Emission Nanotriodes (FENTs)?