"Say Hello! to my new little friend"
- Thread starter brickbuster
- Start date
Rob DeFries
Active Member
Heater voltage is ok.
It seems it does work with the + to the ground. Which is odd. It has some 2 ohms resistance
Does the rectifier still get hot?
It seems it does work with the + to the ground. Which is odd. It has some 2 ohms resistance
Does the rectifier still get hot?
gr33nhorn
Active Member
I am planning to replace the coupling caps in this schematic, the stock "audiophiler" caps are 1uF 400V. I am planning to upgrade to 2.2uF, but options in 400V are few and far in between. most of the good stuff is in 250V. I see a few folks have replaced them with 250V caps, but from a circuit design point of view, I like to use caps which run at half their rated voltage, and I am not sure how the voltage levels run in a tube - In a transistor, I can figure out the bias voltages & calulate the voltage the cap sees, and figure out how much I need, but with tube circuits, I am lostI believe this is preamp stage schematic:
Can someone help?
Little Bear has different schematic, browse back a little and see.
BTW I don't think the heater+ connected to ground is a chinese design mistake, it is more like a trick to try and keep voltages low enough for the 200V electrolytics and with some transformers they sell with these amps this seems to fail. So the 200V rating is a very chinese design-mistake, not the fact they deduct heatervoltage from B+ voltage.
Volumepot in output is a mistake. Radiostations somehow interfering into signal I read about imo is caused by lack of gridstopper resistors, so one could call that design mistake too, probably easy enough fix.
BTW I don't think the heater+ connected to ground is a chinese design mistake, it is more like a trick to try and keep voltages low enough for the 200V electrolytics and with some transformers they sell with these amps this seems to fail. So the 200V rating is a very chinese design-mistake, not the fact they deduct heatervoltage from B+ voltage.
Volumepot in output is a mistake. Radiostations somehow interfering into signal I read about imo is caused by lack of gridstopper resistors, so one could call that design mistake too, probably easy enough fix.
Regarding hum, try replacing the 2200uF capacitor for a 10.000uF capacitor:
Merlin Blencowe (online The Valve Wizard)
DC Heaters
Sometimes no amount of good wiring, balancing and heater elevation will bring hum down to acceptable levels. In that case we may have to resort to DC heater power, which unfortunately adds complexity. It must be clean DC; dirty DC can sometimes cause more hum.
Usually, most hum is picked up by the input valve. A cheap trick is to supply only the input valve heater with DC while the rest still receive AC. You still need a surprisingly large amount of reservoir capacitance to get the ripple voltage down to acceptable levels; at least 4700uF for one 300mA heater.
Merlin Blencowe (online The Valve Wizard)
DC Heaters
Sometimes no amount of good wiring, balancing and heater elevation will bring hum down to acceptable levels. In that case we may have to resort to DC heater power, which unfortunately adds complexity. It must be clean DC; dirty DC can sometimes cause more hum.
Hey all, left channel appears to have died on my Sainsmart. It's very quiet and muddy. Been in use maybe 3-4 months. Would first step be to check voltage from the transformer? I have tried 2 new tubes, tried re-tightening the connections from the transformer to the board. I fear my Sainsmart is dead already...I sure hope not. If I take the Sainsmart out of the chain, everything plays normally, so I know the issue is in the Sainsmart.
yes there should be equal value resistor there like r14. in earlier schematics you find them as input to ground resistors, 10k value. these set inputimpedance to that lowish value, without it probably is a megaohm or more? that could mean there is a little more hiss in that channel when result is negative, it could also mean gridcurrent goes to your source now when tube gets a little instable with for example cdlevel inputs?? could be positive too, the channel could sound better if source has trouble driving the 10k inputimpedance 
Thanks natger, good to know. I was considering picking up some GE 5670's, do you know how the 6n3p-ev compares?
Last edited:
There probably are many different 6n3p-ev's and 5670's. And the chinese might supply boards with different 6n3's too
I for example have Oekrain factory tubes American or Russian might be better ? But difference with chinese is a difference you normally won't find between cheapest cdplayer and a high end cdplayer, or cheap amp and a Krell or Audio Note amp. The difference is huge for audio. It is more like comparing a nobrand $5 speaker with some Kef or AndrewJones Pioneer if your in US. Something like that.
I for example have Oekrain factory tubes
American or Russian might be better ? But difference with chinese is a difference you normally won't find between cheapest cdplayer and a high end cdplayer, or cheap amp and a Krell or Audio Note amp. The difference is huge for audio. It is more like comparing a nobrand $5 speaker with some Kef or AndrewJones Pioneer if your in US. Something like that.
Once again a schematic with values found here and with powersupply, to clarify it is normal, no problem there except 180uF electrolytics should really be 250V
Tube can't drive the output volumecontrol, even when you connect a poweramplifier that has no trouble with the 50k pot, the tube itself has a problem driving it. If moving it to inputside is too much work one can improve things easier by bypassing the 510r resistors with sufficient size capacitor (bass). Without the capacitors the amp has more negative feedback, but the global feedback is so huge already that that hardly changes anything, gain also only slightly increases because of the huge global feedback.
Ok I really like adding some SS to the outputtube, instead of the capacitor bypassed resistors, I really really like the LED's better than electrolytic's with the 510R. But the leds are a SS diode, so some will dislike it because of that It is a constant voltage sink, the ones I used are ~1.6V red, very low intensity, low ~constant resistance of about 6 ohms, 0805 smd
(Replaced the "Rubycon" 200V for Nichicon 250V same value, replaced the "Panasonic" for 10.000uF Nichicon too, and replaced the 100k load resistors inputtube for 33k like second stage, replaced the 4k7 cathoderesistors inputtube for 2k2, thus feedback is a little lower, gain a little higher, but inputtube no longer is operating in very unstable area. Oh also added some bypass PPfilm to 250V electrolytics and high voltage side of all load resistors, my loadresistors are flameproof too, just for peace of mind)
It is a constant voltage sink, the ones I used are ~1.6V red, very low intensity, low ~constant resistance of about 6 ohms, 0805 smd
(Replaced the "Rubycon" 200V for Nichicon 250V same value, replaced the "Panasonic" for 10.000uF Nichicon too, and replaced the 100k load resistors inputtube for 33k like second stage, replaced the 4k7 cathoderesistors inputtube for 2k2, thus feedback is a little lower, gain a little higher, but inputtube no longer is operating in very unstable area. Oh also added some bypass PPfilm to 250V electrolytics and high voltage side of all load resistors, my loadresistors are flameproof too, just for peace of mind)
Hey Guys
So have we come to the conclusion that the heater+ to the ground is fine?
I am going to be using this transformer http://www.ampmaker.com/store/240V-6.3V-toroid-power-transformer.html with 2k3 2w dropping resistor's and upgrade the electrolytic's to a higher voltage. So I just need to know if I should do any of the heater mods mentioned before or leave it.
thanks
So have we come to the conclusion that the heater+ to the ground is fine?
I am going to be using this transformer http://www.ampmaker.com/store/240V-6.3V-toroid-power-transformer.html with 2k3 2w dropping resistor's and upgrade the electrolytic's to a higher voltage. So I just need to know if I should do any of the heater mods mentioned before or leave it.
thanks
I have killed my transformer (the supplied chinese) and learned my lesson.
In case of using own/homebrew powersupply I would recommend any of the previously mentioned mods, either the "3 hole drill"-mod or whatever makes sure not having heater-plus on circuit/(or: audio)-ground.
Your trafo looks fine, just what the guanzo needs. Of course the +B 320V is little too much indeed, anything between 130 and 170 Volt for the stock audio circuit is ok.
Lowering the trafo-voltage and upgrading the electrolytics is the way to go. I suggest you try reaching around 210-250 V and use 450V rated caps.
(But be aware that your new torroid-trafo will be not strong enough to drive dual-tubing (2 x 2 tubes in parallel)
In case of using own/homebrew powersupply I would recommend any of the previously mentioned mods, either the "3 hole drill"-mod or whatever makes sure not having heater-plus on circuit/(or: audio)-ground.
Your trafo looks fine, just what the guanzo needs. Of course the +B 320V is little too much indeed, anything between 130 and 170 Volt for the stock audio circuit is ok.
Lowering the trafo-voltage and upgrading the electrolytics is the way to go. I suggest you try reaching around 210-250 V and use 450V rated caps.
(But be aware that your new torroid-trafo will be not strong enough to drive dual-tubing (2 x 2 tubes in parallel)
Thanks for the reply Olk, I have just realised the original transformer has two 6.3v & 170v secondaries that feeds the circuit. My transformer only has one each, can I just feed them in parallel to the preamp or do any changes need to be made? I cant check as my preamp has not arrived yet.
Also have you found any sonic benifits running x 2 tubes in parallell compared to one.
Thanks
Also have you found any sonic benifits running x 2 tubes in parallell compared to one.
Thanks
Original transformer has one 6.3V and one 170V secondary. The heatervoltage is referenced to the highvoltage circuit just in one place, + and - are correct everywhere. Connect the two in several places and nice groundloops might occur and then anything could happen. If your going for higher voltages, tubes might perform better, more linear there ?, but also have a look at elevating heater. Then you do have to mod the current circuit, because you only want one connectionpoint between the circuits.
