Fripppel
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« Reply #90 on: January 10, 2016, 12:37:10 PM » |
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Hello, I would like to thank you all for sharing. I started mine yesterday and realized that I have 7,2V instead of 6,3V. Will this be a problem? Also, I do have some hum, any thoughts of how I best minimize this?
Regards Fredrik. Sweden
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« Last Edit: January 10, 2016, 02:30:34 PM by Fripppel »
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fasterbyelan
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"If the first watt sucks, who wants another one?"
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« Reply #91 on: January 10, 2016, 05:24:27 PM » |
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Hello, I would like to thank you all for sharing. I started mine yesterday and realized that I have 7,2V instead of 6,3V. Will this be a problem? Also, I do have some hum, any thoughts of how I best minimize this?
Regards Fredrik. Sweden
Are you referring to the heater voltage? Karl |
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KarlLenco -cause it's got soul! My audio world here_______________________________________________________________________________________________
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Fripppel
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« Reply #92 on: January 10, 2016, 07:52:26 PM » |
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I am referring to Voltage from psu to ria. It's supposed to give DC 6,3V but instead gives DC 7,2V. Is it likely that I get rid of som hum if I get right voltage here, white any green cables.  Can it be that I use a choke instead of the original component? This is my first tube build so I'm not very good at these things. It sound really promising so far anyway. Regards Fredrik  |
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ZZMoko
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David
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« Reply #93 on: January 10, 2016, 08:45:19 PM » |
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Where about are you measuring do you have a photo so I can copy and see what mines reading.
It looks like you have used the kit of caps supplied for the PSU but have different ones in the valve board....what did you use?
Mine also has a constant hum but a lot of time these can be earthing problems or a stray signal wire not properly connected somewhere so I'm just starting trying to track mine down as well.
It would be interesting to hear what difference fitting a choke would make and how you would go about choosing one and fitting it....but all the original builders don't seem to reply to any queries us beginners have.
Over on my thread Chris/Nigel/Malcolm have been a huge help in getting mine finished and it's great when people share their knowledge and experiences.
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Garrard 401 & Jelco 750L Ortofon Classic GMII E SPU, MusicMaster GE VRII,Kerr McCosh System, Squeezebox, Beresford Caiman and JBL 4425 speakers
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rg3117
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« Reply #94 on: January 15, 2016, 10:18:40 PM » |
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Work in progress...   The tubes are on their way. I have chosen 12AX7LPS Sovtek valves. By the way, I found this pin underneath the circuit, anybody knows what it is for ? A grounding pin?  |
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ZZMoko
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David
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« Reply #95 on: January 15, 2016, 11:04:37 PM » |
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It's for putting in the ground hole on the PCB so you can attach leads more easily to it
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rg3117
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« Reply #96 on: January 15, 2016, 11:20:44 PM » |
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Thanks! I ran out of solder, it will have to wait until tomorrow.  |
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ZZMoko
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« Reply #97 on: January 15, 2016, 11:25:30 PM » |
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I'm glad I sounded so knowledgeable...but I had to ask exactly the same question on my thread hence I now appear clever  |
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odermatt
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« Reply #98 on: January 16, 2016, 09:40:01 AM » |
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Everything between 5,9 and 6,4V for heaters might be ok but 7,3V is a bit "on steroids"....
so for Startup and testing it is ok.
-Startup and measure if you have 0,9V to much put a resistor in series with the + of 6,3V like 0,9V/0,9A(for three tubes like data sheet) 1 Ohm say a 5Watt type a thingy.
Best regards
Peter
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J-ROB
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« Reply #99 on: January 16, 2016, 04:18:51 PM » |
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Frippel,
odermatt gave you a solution for the high heater voltage. You will kill your tubes fast on 7.x volts! Get yourself a 1 ohm resistor.
As for hum....this is a sensitive high gain circuit and you have meters of twisted wire going to the input. This is like a hum antenna. The input wiring should be as short as possible.
Put the circuit in a metal box, keep the power trans as far as possible from the amplifier board, make those input wires short, THEN you can evaluate your project for hum.
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needlekiller
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« Reply #100 on: January 16, 2016, 05:29:42 PM » |
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ehrm, the 7,3 volt , do you checked it without valves? the psu for the heater with no load can produce higher-output!
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uli
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ZZMoko
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David
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« Reply #101 on: January 17, 2016, 11:05:21 AM » |
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Does anyone have a diagram/photo of where to read the heater voltages as I never checked mine and now I'm slightly worried?
Also I posted this over in my build thread but what does adding a choke do to the performance of a phono stage?
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ecosprog
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« Reply #102 on: January 17, 2016, 12:19:52 PM » |
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Does anyone have a diagram/photo of where to read the heater voltages as I never checked mine and now I'm slightly worried?
Also I posted this over in my build thread but what does adding a choke do to the performance of a phono stage?
Just check where you connected the heater supply to the PCB. |
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Fripppel
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« Reply #103 on: January 17, 2016, 08:20:15 PM » |
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Sorry for not being available sooner. I checked Psu Voltage with tubes operating. I have now put the resistors in place. I had to put two 0.47ohms 3w in series since I didn't find any oner and now I get 6.22V which is fine. Also, I have shortened all the wires and tried to put the transformer farther away and got rid of most of the hum  . What is left to do now is to find a proper box. Do you guys know if it is always better to use a separate box for the psu or internal shielding in between will be sufficient against hum? I really like the sound, I've compared it to the ifi and I like this a lot better. Thank you all for great support, I appreciate it a lot  |
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« Last Edit: January 17, 2016, 08:26:23 PM by Fripppel »
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ZZMoko
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David
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« Reply #104 on: January 18, 2016, 12:35:57 AM » |
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Do you have a photo of the resistors in place as l can't really imagine how you fix them in place....just in case I need to bring my voltage down.
As long as the case is fairly big and you use a good sized piece of shielding I think you can make one case work....just look how small the original 834 stage is and users are very happy with that
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