'E'-Choke

[richardcooper2k]

Could a VR tube be used in some way (instead of C1 ?) to give a regulated constant voltage output relative to earth ?

[Mike H]

Certainly it could. Or a Zener chain. R2 value will need to be selected as appropriate, replace ZD1 with a wire link and omit VDR1 & R3 & C1, as not needed.

[Neal]

Hmmm, gone back to the standard choke. Was loving the extra detail but ultimately found the presentation tiring and although the Bass was better with the added caps it is still missing some drive and depth.

I've another problem though which I perhaps should post in another thread, as this amp is SS rectifier the HT hits 500v quickly and stays there for 10s before the heaters get to work. During this time the decoupling caps are 50v over spec and are starting to complain...

Anybody know of a simply soft start cct to limit HT until the heaters are up?

[Mike H]

What these are across the HT supply rails I presume? Simplest way I know of is put a valve rectifier in, and to make sure with an inrush limiter on its heater

Or, double up the caps in series. I've even done a relay control starting with a lower HT tap on the secondary.

All of which are more complicated so it is a problem I'm still struggling with at the design stage.

Hmmm, gone back to the standard choke. Was loving the extra detail but ultimately found the presentation tiring and although the Bass was better with the added caps it is still missing some drive and depth.

Can't help you with that!

[richardcooper2k]

Hmmm, gone back to the standard choke. Was loving the extra detail but ultimately found the presentation tiring and although the Bass was better with the added caps it is still missing some drive and depth.

I've another problem though which I perhaps should post in another thread, as this amp is SS rectifier the HT hits 500v quickly and stays there for 10s before the heaters get to work. During this time the decoupling caps are 50v over spec and are starting to complain...

Anybody know of a simply soft start cct to limit HT until the heaters are up?

Hi Neal, have you tried replacing C1 with a film cap ?
This restored tone and depth for me
See top of page 10 of this thread

[Andrew]

Neal,

You could use a simple cap and resistor constant and a zener as avalanche, when the cap charge over the zener use a Darlington pair to switch on a solid state relay.

Nick had some nice boards to do this plus relay muting, the timer was done with a PIC, or similar on his. Which reminds me I need to sort with Nick for the two he has for me. But the attached works fine too.

cheers,

Andrew

[Mike H]

Ah the power controller is a sophisticated, no-nonsense way of doing it. Flashy as well

In a literal sense even

Hi Neal, have you tried replacing C1 with a film cap ?

Or a smaller value film cap in parallel?

If it helps I have a 4.7uF audio polyprop on the end of the HT supply? It's in parallel with the F&T 50uF

I make it page 11

[richardcooper2k]

yes, sorry page 11

[Neal]

Thanks Richard, I'll give it a try but its a lack of deep bass that I noticed.

Thanks for the cct Andrew, very neat....i may just wire a 'standby' switch in for the HT as a short term measure...

[Mike H]

Ah could that mean that PSU resonance (step response) was "helping" boost the low bass? E-choke totally blocks step response type resonances.

You could try substituting the choke for a resistor and see if that drops the bass in the same way, just as a sperrymint