F5X -- the EUVL Approach - The Build Thread

[fitzfish]

Patrick,

Business demands seem to keep my responsiveness here slow. My sincere apologies.

I will check all of the questions posted and update the BOM with corrections or clarifications where needed.

Information for measuring JFETs is here. The chart with details for selecting various JFET Idss values and the corresponding degen and drain resistors is here.

I'll post the bias article for those who need it already here ASAP.



Dave

[ramallo]

I started today mounting the amplifier, and probably this are a dumb questions:

-K1530/J201 (close to unobtainium) or K3497/618 (I have the GB set)?.

-Cascode or not? (16V supply)

-Optional Protection Circuit or not? (Main amplifier board)

-CRC or regulated?.

-Anybody have the R45, R46 for sale? (SUSUMU 5R1 OHM 0805 SMD 1%), the minimum in Mouser are 5000 units

Probably this questions had a answer in the multiple threads, but I'm very doubtful. I'm sorry in advance.

Cheers

[NicMac]

> K1530/J201 (close to unobtainium)
In a week or so I will be posting good news with respect to the unobtaniun. Please follow this thread.

> K3497/618 (I have the GB set)?.
These are for the regulated supply. In the works. Keep.

> Cascode or not? (16V supply)
Not. Benefit not fully tested at this moment. In the works.

> Optional Protection Circuit or not? (Main amplifier board)
Your call I guess......

> CRC or regulated?.
CRC until the new regulated supply has been fully tested.

> Anybody have the R45, R46 for sale? (SUSUMU 5R1 OHM 0805 SMD 1%), the minimum in Mouser are 5000 units
Ask ashaw. There is a GB for small components and I believe this is one of them.

[EUVL]

> K1530/J201 (close to unobtainium)

You will be catered for by 3 gentlemen who have taken on this enormous task of procuring 1000 FETs and matching them by curve tracing at 16V 2A 60°C.
Just count the hours, say 10 minutes a FET.

> K3497/618 (I have the GB set)?.

Keep them for now. The first tester who tried both prefers K1530/J201 in the amp.

> Cascode or not? (16V supply)

If you have to have an answer today then cascode.
But since you can add it in later easily, I would build standard to start with.
Why spoil your joy with experimenting progressively ?



> Optional Protection Circuit or not? (Main amplifier board)

If you ask me definitely.
I have expensive speakers.

> CRC or regulated?.

CRC until the new regulated supply has been fully tested, as Nic said.

The first tester also preferred Regulator.
But he is going to build it all in the case and report later.
How late depends on his workload. But the regulator sinks are expensive.

Again since this can be upgraded later without too much work, why not start with CRC first ?

> Anybody have the R45, R46 for sale? (SUSUMU 5R1 OHM 0805 SMD 1%), the minimum in Mouser are 5000 units

Not true.
You can get 1 piece also :

DK #RL12S5.1FCT-ND 0.29 Euro a piece.



Patrick

[ramallo]

Nice,

Thanks to both of you.

[AndrewT]

I am using a pair of 10r in parallel.
They cost 1p each coming to ~0.024 euro for the 5ohm equivalent.

[AndrewT]

What are the radial 1r0 resistors for?

[alazira]

Originally Posted by AndrewT

What are the radial 1r0 resistors for?

If you mean the Fukushima's, then they are for the CRC.

[oneoclock]

Bad news. I measured resistor 47 Oh. R9, R16, R29 R32.

7 are very close to 47 Oh.
1 measures 39 Oh. (the bottom in the photo). I think a lot difference. I do not trust and have to measure all. 8<((

[EUVL]

May I suggest you post at the GB thread with your measurement of all 8 resistors, plus details of the equipment and method used.

This issue is a GB issue which is best sorted out at the GB thread.
It probably will have a better chance also of drawing the attention of the right people who can resolve this.


Patrick