Sorry, creepy hand pics will have to do. I connected everything as per page 26 in the manual, and measuring as pointed out a few pages below that with the con lead on the PG side and the red one on the V (- or +). Thanks in advance.
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I'm beginning to doubt my sanity here - AC 1 and AC 2 both give a figure of around 154-155-ish. I don't think that's supposed to happen...
Seems either the transformer is defective or the DVOM is...
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I've had that problem a while ago with another project.
It seems that i had both the secondaries crosswired and that gave some very strange readings.....
Take a new ac measurement between the two secondaries, perhaps they made a mistake with colourcoding the secondaries.
I can't even get a reading of the mains, the meter just comes up blank, even though I can get readings of AC1 AC2 and V-PG.
I tested the meter on some standard duracell AA's, reading 2.00 V.
I'd feel really stupid if it's just a dinky meter.
My meter only runs up to 300Vac.
Still stumped why my readings are so high on the secondaries.
If your DMM is only suitable for less than 300Vac, then check your probes.
They should have a safety rating on them.
All the DMM I have bought in the last 5years have a 600Vac rating to CAT III
They came with probes that have a dual rating: Cat III to 1000V and Cat IV to 600V
The only probes that don't have a safety rating on them came with the DMM I bought ~ 1986, but it shows a 750Vac max for the AC voltage.
They should have a safety rating on them.
All the DMM I have bought in the last 5years have a 600Vac rating to CAT III
They came with probes that have a dual rating: Cat III to 1000V and Cat IV to 600V
The only probes that don't have a safety rating on them came with the DMM I bought ~ 1986, but it shows a 750Vac max for the AC voltage.
How does one implement such a resistor? In parallel between the 2 channels at the headphone jack?
attach the two resistors in series. That gives you 101r
Attach the 100r to the Hot/Flow output.
Attach the 1r to the Cold/Return output.
The headphone Hot/Flow output comes from the junction of the 100r & 1r
The headphone Cold/Return output comes from the amplifier Cold/Return.
This way the headphones see a source impedance of a tiny bit less than 1r
and the amplifier sees a load a bit higher than 100r
If the 100W amplifier were turned up to just reach clipping the 100r will dissipate less than P=28.2V²/100r = 8W
Use at least 16W of resistor for this arrangement to get 40dB of attenuation from a 100W amplifier.
Use your own values to determine your attenuation and impedances and dissipations.
Attach the 100r to the Hot/Flow output.
Attach the 1r to the Cold/Return output.
The headphone Hot/Flow output comes from the junction of the 100r & 1r
The headphone Cold/Return output comes from the amplifier Cold/Return.
This way the headphones see a source impedance of a tiny bit less than 1r
and the amplifier sees a load a bit higher than 100r
If the 100W amplifier were turned up to just reach clipping the 100r will dissipate less than P=28.2V²/100r = 8W
Use at least 16W of resistor for this arrangement to get 40dB of attenuation from a 100W amplifier.
Use your own values to determine your attenuation and impedances and dissipations.
1875 or 3875?
Hi Peter,
As you had the chance to listen to lm1875 and lm3875 in the same configuration and setup, could you tell me the main differences in sound between them? the output power is not a big issue, since my speakers are 96 dB efficient. Sorry for my poor English. Thanks in advance!
Hi Peter,
As you had the chance to listen to lm1875 and lm3875 in the same configuration and setup, could you tell me the main differences in sound between them? the output power is not a big issue, since my speakers are 96 dB efficient. Sorry for my poor English. Thanks in advance!
The centre tap is part of the capacitor charging circuit.
The centre tap must go to the smoothing capacitors.
No where else.
And keep the loop areas very small. That means use a twisted triplet from transformer to rectifier and from rectifier to smoothing capacitors and from smoothing capacitors to amplifier.
The centre tap must go to the smoothing capacitors.
No where else.
And keep the loop areas very small. That means use a twisted triplet from transformer to rectifier and from rectifier to smoothing capacitors and from smoothing capacitors to amplifier.
If you are using my rectifier boards, which are part of the amp kit discussed here, then center tap of transformer secondary does not connect there (wire bridge between OG pads on amp boards).
My rectifier boards are actually designed to work with dual secondaries transformers, not center tapped units, however, there is a mod for that, when center tap transformer can also be used: http://www.diyaudio.com/forums/chip...oid-wiring-peter-daniels-kit.html#post1196283
In either case, secondary wires from transofrmer connect to rectifier boards and not to the wire bridge on amp boards.
Hi Peter,
As you had the chance to listen to lm1875 and lm3875 in the same configuration and setup, could you tell me the main differences in sound between them? the output power is not a big issue, since my speakers are 96 dB efficient. Sorry for my poor English. Thanks in advance!
I didn't really have much chance to listen extensively to this amp as I rushed to sent it to the customer who requested that chip configuration.
To me, it's a bit too low in power and as such not practical. People say LM1875 sounds even smoother, but I can't really confirm it.
Is this is how all the wiring should be done ?
Please excuse shoddy MS Paint job
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despite quoting the text of my advice you are again asking for my opinion, so I'll repeat my opinion
Is that an audio sector PCB?
It states "technofreek.com"
I think you are in the wrong section.
AND keep the loop areas small. That means no single wires trailing randomly across the enclosure.
Is that an audio sector PCB?
It states "technofreek.com"
I think you are in the wrong section.
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