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 Post subject: Re: KT120 Oddblocks
PostPosted: 31 Aug 2016, 11:43 
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Joined: 29 Oct 2014, 12:32
Posts: 95
Location: Russia Komi republic
A few pages ago, I wrote about the components that are applied. maybe it's a little help.

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 Post subject: Re: KT120 Oddblocks
PostPosted: 02 Sep 2016, 22:07 
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Joined: 03 Aug 2016, 19:28
Posts: 2
How high of a DC voltage rating does the switch between the LM317HV's adjust lead, the second resistor and ground need to be? Is LM317HV just measuring between ground and just pushes a lower voltage or does it need to handle 600V DC?

Also, would it be OK to use a 50 Ohm resistor instead of two 100 Ohm? My plan was to use a 2+ watt 50 ohm.

Lastly, in the power supply, are ground and neutral tied to chassis?

Adam


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 Post subject: Re: KT120 Oddblocks
PostPosted: 03 Sep 2016, 07:00 
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Joined: 29 Oct 2014, 12:32
Posts: 95
Location: Russia Komi republic
Also, would it be OK to use a 50 Ohm resistor instead of two 100 Ohm? My plan was to use a 2+ watt 50 ohm.
No. If we take the figure of 300 mA in a circuit, the 50 ohm resistor reduces the voltage to 0,3mA * 50V = 15V (meaning little change depending on the current). Thus, the resistor will be 15V * 0.3mA = 4.5Vatt power. By installing two 100 ohm resistors we divide the power between them almost equally.
Also, these 2 resistors act as a fuse in case something goes wrong with lm317 current source (I just had such a history, the lamp has lost vacuum burned lm317 and burned 2 100 ohm resistor. They saved the rest of the details) .

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 Post subject: Re: KT120 Oddblocks
PostPosted: 03 Sep 2016, 10:44 
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Joined: 07 Dec 2015, 14:21
Posts: 135
cadamwil wrote:
How high of a DC voltage rating does the switch between the LM317HV's adjust lead, the second resistor and ground need to be? Is LM317HV just measuring between ground and just pushes a lower voltage or does it need to handle 600V DC?


It sees probably like 15v across it.

cadamwil wrote:
Also, would it be OK to use a 50 Ohm resistor instead of two 100 Ohm? My plan was to use a 2+ watt 50 ohm.


Yes but don't use a 2 watt resistor, use at least a 10 watt resistor. These are nice and cheap, use some thermal paste and bolt it to the chassis: http://www.mouser.com/ProductDetail/ARC ... JYLGryE%3d

cadamwil wrote:
Lastly, in the power supply, are ground and neutral tied to chassis?


Safety ground/earth is tied to the chassis. The neutral is not tied to the chassis.


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 Post subject: Re: KT120 Oddblocks
PostPosted: 03 Sep 2016, 11:41 
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Joined: 24 Oct 2010, 07:05
Posts: 312
cadamwil wrote:
I am looking at adding another circuit I am working on to do a turn on from 12v
If I understand you right you want your monoblocks to be switched by an external 12V voltage? It's simple: just use a relay instead of power switch.
cadamwil wrote:
check AC mains voltage for high or low voltage conditions.
You need RMS to DC converter and a microprocessor with an ADC input.
cadamwil wrote:
are ground and neutral tied to chassis?
It depends on what ground you had in mind. Mains' ground ties to the chassis. Signal ground does not. Please collaborate more on "Neutral"?
cadamwil wrote:
How high of a DC voltage rating does the switch between the LM317HV's adjust lead, the second resistor and ground need to be?
It is rather low. In the range of 1.2V.


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 Post subject: Re: KT120 Oddblocks
PostPosted: 03 Sep 2016, 17:22 
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Joined: 04 Jun 2008, 20:59
Posts: 4285
Location: Arizona, USA
Hi, I'm glad to see others answering some of the questions since I don't check all the threads every day. Thanks for the assists. I do have a thought about using 50 ohm pots vs 25 ohm ones in the cathode circuits. They will add a small but measurable impedance between the cathodes. The design really works best with zero impedance there. 25R is sufficiently low as to be insignificant. As you increase it relative to the effective impedance to ground you will start to introduce problems. It is true that there is a large leeway there, but when going for max performance and sound quality anything IMO that degrades it is undesirable. YMMV.

The nominal voltage across the sense resistors is 1.25 volts.

The grounding system is covered in several posts. Essentially the chassis is at AC mains earth level. The chassis in turn is separated from the amps internal signal and power supply grounds by the X2 capacitor and its parallel resistor. Internal to the amps I keep the signal grounds separate from the power supply ones and tie them together at a single point normally at the ground tab of the input jack. Yes I know that some power will flow through portions of the signal ground. There is no way to avoid having the cathode current from going there. Just make sure that the parts that carry the most current have the shortest leads and use larger gauge wires for them. Failure to do so will introduce ground based noise.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 08 Sep 2016, 12:52 
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Joined: 18 Jun 2016, 06:52
Posts: 28
Hi Bruce, I'm having some trouble with the delay circuit. LM555 and the relay are working, but there is almost no delay (one or two seconds). I've checked everything over and over again but I can't find a mistake. Did you get a 30 seconds delay with the 220K/220uF combo in the schematics, or do I need much higher values?


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 Post subject: Re: KT120 Oddblocks
PostPosted: 08 Sep 2016, 14:09 
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Joined: 04 Jun 2008, 20:59
Posts: 4285
Location: Arizona, USA
Hi, that combination gives about 75 seconds. Check that the capacitor is good and there is no short between the cap and ground. Verify the resistor value as well. Check the polarity on the anti spike diodes on the relay as well. If the one is backwards the relay will activate on power up.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 08 Sep 2016, 16:40 
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Joined: 18 Jun 2016, 06:52
Posts: 28
Thanks Bruce for your fast reply.

For a moment I thought you had saved me, because indeed the relay activates on power up. I changed the polarity of the diode and waited for two minutes after switch on, but nothing happened. So it must be something else.


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 Post subject: Re: KT120 Oddblocks
PostPosted: 08 Sep 2016, 21:11 
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Joined: 04 Jun 2008, 20:59
Posts: 4285
Location: Arizona, USA
Hi, Curious. Does the amp work if you jumper the contacts (directly apply B+ to the circuit)?

Good listening
Bruce

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