Leach has taken the Mains Protective Earth direct to Chassis.
He has also taken the Safety Connection from transformer Centre Tap direct to Chassis. This has taken with it the first two smoothing capacitors of the PSU to that same Chassis bolt.
All these connections are referred to in his description and on his schematics as Central Ground and shown with the "E" symbol.
You will find that all the amplifier "grounds" are NOT taken to Chassis.
There is ONLY one chassis connection shown on the amplifier and it is from the Speaker Return terminal Output Zobel.
The amplifier does not get taken to Chassis.
DF has stated
He has also taken the Safety Connection from transformer Centre Tap direct to Chassis. This has taken with it the first two smoothing capacitors of the PSU to that same Chassis bolt.
All these connections are referred to in his description and on his schematics as Central Ground and shown with the "E" symbol.
You will find that all the amplifier "grounds" are NOT taken to Chassis.
There is ONLY one chassis connection shown on the amplifier and it is from the Speaker Return terminal Output Zobel.
The amplifier does not get taken to Chassis.
DF has stated
This is no different from what Leach suggests for the Lo Tim. Both Leach and DF are saying the same thing. The amplifier grounding does not go to chassis.
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to increase the quiescent ripple voltage and with it the risk of hum at the amplifier output when no audio signal is present.
up to you, i use it in my amps and never had problems....
one thing though, the film bypass caps at the big filter caps are not going back there...
if you build something that works to your satisfaction, who can argue with that?
i would rather listen to someone who actually build things than to someone who likes to argue and talk....
one thing though, the film bypass caps at the big filter caps are not going back there...
if you build something that works to your satisfaction, who can argue with that?
i would rather listen to someone who actually build things than to someone who likes to argue and talk....
Both statements are true.
Both statements are coloured by the bias of the Member.
You have to assess the relative merits and decide which is/are important to you.
With the case screwed together, how long will the amp take to discharge the PSU down to a volt or two? I find this is all done in well under a minute. Some exceptional very low bias power amplifiers could take over two minutes to get down to that couple of volts, whereas a ClassA amp or pre-amp could be done in less than 15seconds
How long does it take after power OFF, remove the amp from the rack, unplug all the cables and unscrew the covers to be able to measure the residual voltage on the PSU?
How much does the extra current increase the ripple?
Will the amplifier attenuate that extra ripple?
Will the ripple be audible/measureable?
You have to choose.
LoL is not appropriate, This is a serious matter. You have to learn how to assess the information you are given. It's sorting the wheat from the chaff. It's not always black and white, i.e. lies & truth. It's about recognising what is important to you as a thinking, active Member of DIYaudio.
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If your amplifier is humming because bleed down resistors are installed, the issue is the amplifier, not the bleed down resistors. They serve a purpose.
I've been adding rail shut downs to my supplies, so without the bleed down resistors they would stay dangerous for a long time.
I've been adding rail shut downs to my supplies, so without the bleed down resistors they would stay dangerous for a long time.
ripple is a natural consequence of current draw....
there is a good explanation of ripple calculations here: powersupplies
what percentage of total current draw is that bleeder?
how good your amp in terms of power supply ripple rejection?
if your amp is class A drawing say 1A of current, surely 10mA of extra bleeder is peanuts...
there is a good explanation of ripple calculations here: powersupplies
what percentage of total current draw is that bleeder?
how good your amp in terms of power supply ripple rejection?
if your amp is class A drawing say 1A of current, surely 10mA of extra bleeder is peanuts...
i agree....normally when the power switch is turned to off,
the amplifier bleeds down the psu, but it also depends on the amplifier itself,
how fast it can discharge the caps....
Golden
TY this made my day
"Bleeders? we don't need no stinkin' Bleeeders"
low power Class A can do with out ( due to high quiescent current draw & 24 Vdc levels are considered safe)
For high power Class AB where nominal +/-60V = 120V , bleeders are almost a must have . esp. for DIY ... got yer hands in there so manually discharging all caps becomes tedious. 2W-5W is chosen for practical size and it still may take a few minutes to be safe.
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since this is a rebuild, as i have torn it down, those caps are not coming back in there....
Yes, that will be fine. Just be aware that it is actually a very short bus, not a star, so you need to get the order of connections right.number7 said:
I use a bus, not a star. Every real star is actually a very short bus, so you can't really avoid having to think about the order of connections.
I have seen people use a 6-connection star tag, bolted to the chassis, for their 'star'. As you can't be sure exactly how this connects to the chassis (how many points, how far apart?) you can't be sure to what extent the currents travelling across the tag couple to the chassis. A single tag would be fine, but how do you get all the required connections onto one small tag? Putting several tags on one bolt means that again you have a bus, connected to the chassis at one end. What if the chassis connection should not be at the end but somewhere in the middle? What if it works OK when first built but subsequent fault-tracing etc. means the tags get re-assembled in a different order?AJT said:
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