Bigbottle Phonostage Builders thread

[Bigman80]

Would you deliver to Denmark ??

I have some well matched BF861c, which i use if they are of interest?

 

[Vivant]

Neil, the board will work with a lower HT but the treble end of the RIAA may be a little off.

Resistor R9P should have a voltage of around 10V across it when operational.
Measure the voltage drop and report back.

 

[nielsek]

Neil, the board will work with a lower HT but the treble end of the RIAA may be a little off.

Resistor R9P should have a voltage of around 10V across it when operational.
Measure the voltage drop and report back.

Across it's 9,2V. Drop from 216v to 207v.

 

[Vivant]

That's good, the current is correct.

I am guessing your mains transformer has a poor regulation figure.
Try the phono stage and see what you think.

 

[Scotty38]

That's good, the current is correct.

I am guessing your mains transformer has a poor regulation figure.
Try the phono stage and see what you think.

My transformer is on order now regardless but how do you make sure poor regulation isn’t an issue?

 

[Ryssen]

Just in case anyone is interested, I'm selling off some very closely matched BF862, Whichbwere ordered from Farnel a few years ago when this project started.

£10 a pair, delivered in the UK

View attachment 841625

Is the BF862 involved in the power supply,or is it in the stepup for the MC pickup?

 

[Bigman80]

Is the BF862 involved in the power supply,or is it in the stepup for the MC pickup?

The BF861c that is used, is for the MC

 

[nielsek]

That's good, the current is correct.

I am guessing your mains transformer has a poor regulation figure.
Try the phono stage and see what you think.

It sounds better than my receiver's built in preamp, other than that it's hard to compare. I will keep playing with different cartridges.
I'd really appreciate if someone could point me in the right direction for measuring transformer's regulation figure. I paid good money for that and would like to get it sorted.

 

[Bigman80]

It sounds better than my receiver's built in preamp, other than that it's hard to compare. I will keep playing with different cartridges.

I'd really appreciate if someone could point me in the right direction for measuring transformer's regulation figure. I paid good money for that and would like to get it sorted.

What do you think you have a problem with the transformer?

 

[Scotty38]

What do you think you have a problem with the transformer?

Oli see Alan’s post, he suggested perhaps an issue with regulation so a question was how do we know?

 

[Bigman80]

Oli see Alan’s post, he suggested perhaps an issue with regulation so a question was how do we know?

Oh, ok....sorry, there so much here that I couldn't find it.

OK....I'll try and find it.

 

[Scotty38]

No probs it’s just a few back...

 

[Vivant]

It sounds better than my receiver's built in preamp, other than that it's hard to compare. I will keep playing with different cartridges.
I'd really appreciate if someone could point me in the right direction for measuring transformer's regulation figure. I paid good money for that and would like to get it sorted.

Easiest thing is to measure the HV winding (165V) with and without the valves fitted.
I think you said you had 175V AC and around 230V HT, was that without the valves fitted?
You said the HT was lower with valves fitted, measure the transformer voltage. If it doesn't alter much the transformer is OK, the problem is elswhere.

 

[Bas Horneman]

The BF861c that is used, is for the MC

Ohhh...so if I just want MM. I could leave out that part?

 

[Ryssen]

Im belive there was a switch onboard tu use,just in case will want to try MC in the future.
Just my thought...

 

[Bas Horneman]

Must be Ryssen...

 

[Scotty38]

Yep, flicking the switch to MM removes the extra stage needed for MC.

 

[Vivant]

If you wanted you could omit the relays, just have to link two holes on each side.

For MM only you can omit the fets, Q2L &R, plus R7L &R, R8L &R, R4P and C3P.

 

[Bas Horneman]

Thanks all!

 

[nielsek]

Easiest thing is to measure the HV winding (165V) with and without the valves fitted.
I think you said you had 175V AC and around 230V HT, was that without the valves fitted?
You said the HT was lower with valves fitted, measure the transformer voltage. If it doesn't alter much the transformer is OK, the problem is elswhere.

with valves: HV=176V AC, C4P 219V DC
w/o valves: HV=177V AC, C4P 239V DC
So my problem is elsewhere?