Ram18 Posted January 5, 2021 Share Posted January 5, 2021 10 minutes ago, xlr8or said: The far column in the table below shows the voltage drop for different tube rectifiers. If 5AR4 is giving 325v then you can pretty much work out what a 5U4G and 5Y3 will give. Filter cap uF may also need to be changed. I have never done all these measurements to the tee largely cause I am still inexperienced with tubes. Went with my gut , some reading and observations here and a check with Garry. Now am playing songs on my MP and it sings! Didnt notice the tinkle just now. It is as muon says intermittent. Link to comment Share on other sites More sharing options...
muon* Posted January 5, 2021 Share Posted January 5, 2021 3 minutes ago, Ram18 said: I have never done all these measurements to the tee largely cause I am still inexperienced with tubes. Went with my gut , some reading and observations here and a check with Garry. Now am playing songs on my MP and it sings! Didnt notice the tinkle just now. It is as muon says intermittent. Yeah, side on the side of caution where taking measurements with a powered amp, there are very lethal voltages in there, only do this stuff if you are certain you know what you are doing. And if you know what you are doing always keep one had in ya' pocket. I say this as It's when a voltage (and it doesn't need to be a lot), passes through the heart is when ya' die from electrocution. 1 Link to comment Share on other sites More sharing options...
Ram18 Posted January 5, 2021 Share Posted January 5, 2021 3 minutes ago, muon* said: Yeah, side on the side of caution where taking measurements with a powered amp, there are very lethal voltages in there, only do this stuff if you are certain you know what you are doing. And if you know what you are doing always keep one had in ya' pocket. I say this as It's when a voltage (and it doesn't need to be a lot), passes through the heart is when ya' die from electrocution. Gosh. Tks for the heads and hearts up! I will certainly leave this part to the proffesionals. 2 Link to comment Share on other sites More sharing options...
xlr8or Posted January 5, 2021 Share Posted January 5, 2021 26 minutes ago, muon* said: Yeah I get that, Kirk. I'd like to know what the cathode voltage is in this case Or the Plate voltage relative to ground. Yep - that would be also helpful to know along with heater and grid voltages. 1 Link to comment Share on other sites More sharing options...
xlr8or Posted January 5, 2021 Share Posted January 5, 2021 (edited) There is one tube you can use that can take up to 800v on the plates but finding it is harder than finding hen's teeth. It's the Luxman 6240G made by NEC in Japan in the 1970's. It has the same pinout as the 6CG7, 6FQ7, 6922, 6N1P, 6GU7, 6AQ8 etc. Yahoo Aleado is the only place to get them. Edited January 5, 2021 by xlr8or Link to comment Share on other sites More sharing options...
Ram18 Posted January 5, 2021 Share Posted January 5, 2021 1 hour ago, muon* said: Yeah, side on the side of caution where taking measurements with a powered amp, there are very lethal voltages in there, only do this stuff if you are certain you know what you are doing. And if you know what you are doing always keep one had in ya' pocket. I say this as It's when a voltage (and it doesn't need to be a lot), passes through the heart is when ya' die from electrocution. I did the pencil test. Its the 6H30pi tubes giving the tinkle Link to comment Share on other sites More sharing options...
xlr8or Posted January 5, 2021 Share Posted January 5, 2021 6 hours ago, Ram18 said: I did the pencil test. Its the 6H30pi tubes giving the tinkle If the tinkle sound is annoying you can use these. I personally don't like using tube dampers as they make tubes sound lifeless. However, I understand in this case fitting these maybe necessary. https://herbiesaudiolab.com/collections/tube-dampers Link to comment Share on other sites More sharing options...
gapecans Posted January 5, 2021 Share Posted January 5, 2021 11 hours ago, Ram18 said: Hahaha. Think I guess thats what am experiencing now perhaps. Relative cooling and warming temps giving the tinkling sounds I'm old enough to remember a TV set tinkling on shutdown. It's all part of the sonic bliss. 5 Link to comment Share on other sites More sharing options...
highcut28 Posted January 6, 2021 Share Posted January 6, 2021 Hi I am the bloke having the hum problem after changing the stock gain settings. Can someone kindly guide me to getting this right. Unfortunately on setting the toggles back to stock standard the way the amp was set, i still get hum! What should i try to do. To reiterate, i havent messed with anything else Thanks Link to comment Share on other sites More sharing options...
xlr8or Posted January 6, 2021 Share Posted January 6, 2021 1 hour ago, highcut28 said: Hi I am the bloke having the hum problem after changing the stock gain settings. Can someone kindly guide me to getting this right. Unfortunately on setting the toggles back to stock standard the way the amp was set, i still get hum! What should i try to do. To reiterate, i havent messed with anything else Thanks You could try swapping the tubes around to see if the hum moves to the other channel. Otherwise, this sounds like an earthing issue and the unit may need servicing. Link to comment Share on other sites More sharing options...
Ram18 Posted January 6, 2021 Share Posted January 6, 2021 7 hours ago, xlr8or said: If the tinkle sound is annoying you can use these. I personally don't like using tube dampers as they make tubes sound lifeless. However, I understand in this case fitting these maybe necessary. https://herbiesaudiolab.com/collections/tube-dampers Thanks for sharing. Will monitor and see how it goes Link to comment Share on other sites More sharing options...
highcut28 Posted January 6, 2021 Share Posted January 6, 2021 19 hours ago, xlr8or said: You could try swapping the tubes around to see if the hum moves to the other channel. Otherwise, this sounds like an earthing issue and the unit may need servicing. i have successfully adjusted to gain to next to lowest. Very weird . i still cannot understand how or why that hum came about or how it is now gone.! It sounds good with volume knob useable from 7 to 12 o clock with current poweramps. I will cautiously get into some tube rolling - when Russian 6N23P valves arrive Any comments on those ? Link to comment Share on other sites More sharing options...
xlr8or Posted January 7, 2021 Share Posted January 7, 2021 (edited) @highcut28 I would seriously stick to 6CG7 and 5Y3 bottles at this stage until more is known about the Mk2 version having addressed the excessively high B+ voltages passing through the plates of the 9-pin minis. The intermittent hum issue you have experienced may possibly relate to the excessively high plate voltages coming through the existing set of 9-pin minis. Edited January 9, 2021 by xlr8or 1 Link to comment Share on other sites More sharing options...
highcut28 Posted January 8, 2021 Share Posted January 8, 2021 16 hours ago, xlr8or said: @highcut28 I would seriously stick to 6CG7 and 5Y3 bottles at this stage until more is known about the Mk2 version having addressed the excessively high B+ voltages passing through the plates of the 9-pin minis. The intermittent hum issue you have experienced may possibly related to the excessively high plate voltages coming through the existing set of 9-pin minis. Thank you Kirk Link to comment Share on other sites More sharing options...
highcut28 Posted January 25, 2021 Share Posted January 25, 2021 (edited) On 07/01/2021 at 7:22 PM, xlr8or said: @highcut28 I would seriously stick to 6CG7 and 5Y3 bottles at this stage until more is known about the Mk2 version having addressed the excessively high B+ voltages passing through the plates of the 9-pin minis. The intermittent hum issue you have experienced may possibly relate to the excessively high plate voltages coming through the existing set of 9-pin minis. Hum returened suddenly after a couple happy weeks. Took a while to diagnose. I use a diy electronic XO for the low pass of semi active drive of a 'JBL 4333'. system The hum was caused by faulty DC supply from PSU to the eXO board. I have sorted that out. System is fine now. So there was nothing at all wrong with the MP. Question: Can i safely use 2 x 6N23P tubes ? These are Reflektor Silver Shields ( will retain the stock Beijing 6N11 at the back So far everything is stock standard) Thanks Edited January 25, 2021 by highcut28 1 Link to comment Share on other sites More sharing options...
Jason Påstorål Posted June 15, 2021 Share Posted June 15, 2021 How's everyone's MP701-MK2? I was supposed to get a Freya+ but there's none available and there's a backlog at Schiit (my friend ordered in February from the official local dealer and still hasn't received his to date). So instead of waiting I decided to give this preamp a shot. I've just recently got one, and I'm about to tube roll for the first time with a Svetlana winged C 5U4G NOS Tube rectifier (black plate), and three EH630pi from Electro Harmonix. Has anyone rolled these tubes for theirs, and what was your experience like? Link to comment Share on other sites More sharing options...
Jason Påstorål Posted June 26, 2021 Share Posted June 26, 2021 Hey guys, what are your ways of replacing the caps? What steps do you take and what do you keep in mind to keep safe in replacing them? Link to comment Share on other sites More sharing options...
xlr8or Posted June 26, 2021 Share Posted June 26, 2021 5 hours ago, Pashmeister said: Hey guys, what are your ways of replacing the caps? What steps do you take and what do you keep in mind to keep safe in replacing them? @muon* would be the best person to answer this. In summary, avoid grasping them in the body and instead handle the wired ends, watch out to not apply too much heat while soldering them in and study the circuit beforehand to determine the best mounting requirements; in particular, if the new cap has larger dimensions. Obviously, ensure the unit is switched off and the caps are discharged before opening up the unit and desoldering the existing caps and replacing them with the new ones. One way of discharging the caps is to unplug the unit from the AC mains and power on/off the unit a few cycles to remove any stored charge. Link to comment Share on other sites More sharing options...
Guest crankit Posted June 26, 2021 Share Posted June 26, 2021 6 hours ago, Pashmeister said: Hey guys, what are your ways of replacing the caps? What steps do you take and what do you keep in mind to keep safe in replacing them? I made a discharge tool with 470 ohm 5W resistor if I recall, gets the job done Link to comment Share on other sites More sharing options...
muon* Posted June 26, 2021 Share Posted June 26, 2021 It's a no brainer with the replaceable caps in these, just fix them in place as the originals are with a zip tie and make sure the posts that hold the leads are screwed down firmly on the leads. If you know the outer foil end of the new caps, direct them so the outer foil end is to the lowest impedance side. In a signal coupling situation that means outer foil end to the previous stage, and if decoupling to ground the outer foil end to ground. Link to comment Share on other sites More sharing options...
MrBurns84 Posted June 28, 2021 Share Posted June 28, 2021 @Pashmeister I got a cheap capacitor discharging tool that does the job nicely. As @muon* pointed out its easy to replace the caps. Just as a safety precaution, i remove the power cable from preamp and leave it overnight. Using the discharge tool i touch the leads in .wait 2 seconds..and then untouch them. Its a pain but from my experience with the 2-4uf output caps, this takes less than 10 seconds effort to complete until its fully discharged. What you need to be really careful off are the bypass capacitors on the preamp. These take a lot longer (2-3mins) to discharge fully as I use 10uf values here. From what the designer told me, his caps are connected where the outer foil goes to ground. 1 Link to comment Share on other sites More sharing options...
muon* Posted June 28, 2021 Share Posted June 28, 2021 MP could have included drain resistors on those caps and that would have meant they drain quickly as soon as you turn it off, I added drain resistors to the input and output caps in a Yaqin Buffer as it didn't have them out of the box. 2 Link to comment Share on other sites More sharing options...
JB82 Posted July 30, 2021 Share Posted July 30, 2021 Hey guys, I'm having trouble with my MP-701 that I've just bought, soundstage is way off to the left, but when I switch left & right outputs it only moves the soundstage slightly towards centre but still on the left. I've just been checking out the pictures in this thread and noticed that my wires between the XLR outputs and RCA are hooked up differently to others in this thread, mine both go to the outside RCA. Could this be related to the issue I'm having? Link to comment Share on other sites More sharing options...
Searching for Magic Posted July 31, 2021 Share Posted July 31, 2021 The XLR is not fully balance with the MP. It share with the single ended input and output. I had the same issue before. What I did was disconnect all the cables, took the tube out and swap with another tube. Put everything back and back to normal. Not too sure why. But happened with me twice now. 1 Link to comment Share on other sites More sharing options...
JB82 Posted July 31, 2021 Share Posted July 31, 2021 Thank you but I've already rotated the tubes a few times without success. My XLR is wired differently to all the other pictures I've seen, I'm wondering if that has something to do with it? Extremely frustrating when you receive a new item Link to comment Share on other sites More sharing options...
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