Search found 10804 matches

by Nick
Fri Nov 17, 2017 2:04 pm
Forum: Everyones Projects
Topic: 811a SET amp.
Replies: 274
Views: 20501

Re: 811a SET amp.

pre65 wrote:
Fri Nov 17, 2017 1:49 pm
According to the data sheet for a 76 max current is 5ma.
I can't find that limit on any data sheet I have seen. Though TBH, 5ma looks like a good op point. Maybe a little less to preserve the thing a bit more.

and I dont think a 76 needs a grid stopper. Its a relatively docile valve.
by Nick
Fri Nov 17, 2017 1:43 pm
Forum: Everyones Projects
Topic: 811a SET amp.
Replies: 274
Views: 20501

Re: 811a SET amp.

What I mean (and didn’t say clearly) was a simple CCS would probably do just as well as a cascaded one.
by Nick
Fri Nov 17, 2017 1:16 pm
Forum: Beginners
Topic: Dual rail +/- 80v power supply.
Replies: 9
Views: 75

Re: Dual rail +/- 80v power supply.

Thanks Nick, although I can't see from the circuit where those numbers came from ? Not claiming equivilance: At the question period after a Dirac lecture at the University of Toronto, somebody in the audience remarked: "Professor Dirac, I do not understand how you derived the formula on the top lef...
by Nick
Fri Nov 17, 2017 12:07 pm
Forum: Beginners
Topic: Dual rail +/- 80v power supply.
Replies: 9
Views: 75

Re: Dual rail +/- 80v power supply.

pre65 wrote:
Fri Nov 17, 2017 11:58 am
Thanks Ed.

I was more thinking of the mosfet follower likely current draw.

Ohms law gives you that. 20ma I think I remember, 104v across 5k
by Nick
Fri Nov 17, 2017 12:05 pm
Forum: Everyones Projects
Topic: 811a SET amp.
Replies: 274
Views: 20501

Re: 811a SET amp.

I would be tempted to argue that the cascade CCS is a bit questionable as the minimum load the the driver valve sees will always be in parallel with 200k, so always 200k or less.
by Nick
Fri Nov 17, 2017 11:53 am
Forum: Solid State
Topic: P6 AMP REVIEW
Replies: 11
Views: 95

Re: P6 AMP REVIEW

Bigman80 wrote:
Fri Nov 17, 2017 10:47 am
were these the ones at the bakeoff?
Yes
by Nick
Wed Nov 15, 2017 2:28 pm
Forum: Everyones Projects
Topic: WAD Phono2 power supply.
Replies: 97
Views: 4326

Re: WAD Phono2 power supply.

Well, the voltage dropped across that will be the input voltage - the zener voltage.

Generally I would avoid strip board for power supplies. point to point or PCB gives you better control.
by Nick
Wed Nov 15, 2017 1:31 pm
Forum: Everyones Projects
Topic: WAD Phono2 power supply.
Replies: 97
Views: 4326

Re: WAD Phono2 power supply.

That looks like the cap charging current. What you need to make sure is that the wires from the bridge go to the +ve and -ve of the first cap and nowhere else, and everything from that both +ve and -ve come from the cap. The idea is that the charging current in the first cap will create a voltage ac...
by Nick
Wed Nov 15, 2017 12:54 pm
Forum: Valves
Topic: ETF 2017 ( Thomas Mayer )
Replies: 32
Views: 363

Re: ETF 2017 ( Thomas Mayer )

3D printed it is some kind of plastic. It depends on how expensive the printer was... https://all3dp.com/ferrari-using-3d-printing-to-develop-piston-innovation-for-f1-2017/ wow... but does this application warrant the expense of the metal process(there seem to be 2 distinct methods, one involving s...
by Nick
Wed Nov 15, 2017 10:57 am
Forum: Everyones Projects
Topic: WAD Phono2 power supply.
Replies: 97
Views: 4326

Re: WAD Phono2 power supply.

Where is your 0v point connected? Can you show the actual wiring and connections especially where the 0v point is in relation to the link between the bridge rectifier and the -ve of the first cap?
by Nick
Tue Nov 14, 2017 9:01 pm
Forum: Everyones Projects
Topic: WAD Phono2 power supply.
Replies: 97
Views: 4326

Re: WAD Phono2 power supply.

shane wrote:
Tue Nov 14, 2017 8:47 pm
Tomorrow’s job, dig out ‘scope from darkest recessed of shed. Then see if I can work it.
Make sure the scope is on AC input and probably x10 probe to protect the from end from the voltages.
by Nick
Tue Nov 14, 2017 8:31 pm
Forum: Valves
Topic: ETF 2017 ( Thomas Mayer )
Replies: 32
Views: 363

Re: ETF 2017 ( Thomas Mayer )

3D printed it is some kind of plastic.
It depends on how expensive the printer was...

https://all3dp.com/ferrari-using-3d-pri ... r-f1-2017/
by Nick
Tue Nov 14, 2017 6:44 pm
Forum: Everyones Projects
Topic: WAD Phono2 power supply.
Replies: 97
Views: 4326

Re: WAD Phono2 power supply.

That all sounds fine, however we dont know if those are steady DC voltages or have ripple. Try measuring the AC voltages at each point (assuming you don;t have a scope).
by Nick
Tue Nov 14, 2017 3:21 pm
Forum: Everyones Projects
Topic: WAD Phono2 power supply.
Replies: 97
Views: 4326

Re: WAD Phono2 power supply.

Does the zener string have its own load resistor, or is it meant to be added?
by Nick
Mon Nov 13, 2017 11:48 am
Forum: Everyones Projects
Topic: 811a SET amp.
Replies: 274
Views: 20501

Re: 811a SET amp.

Well, the old C4S would be a good example.