I don't have anything higher than 4.7uF caps in a 100V+rated cap at the moment. Might need to order some parts again. + shipping these $1 parts orders get expensive lol. Might hold off for a while as along as it's not causing any harm.
Doesn't have to be a huge cap. Try it with the 4,7uF and see if you hear a difference. And ofcourse..not hurry..or need. 🙂 Just something to one day try.
Wow, it's getting quieter and quieter. I just found a 22uF/100V cap and put it in. Previously there was a little bit of a buzz in gain mode with the pot at 50%. Buzz totally gone now. I'm not sure how they are related but apparently they were. Like when your back hurts, but you really needed a good hamstring stretch rather than work directly on the back.
Ok, if I'm going to get this anal, there is a very faint low frequency oscillation happening somewhere. It's faint, like the pitter patter of a chicken running, maybe 10Hz- very faint. Just in one channel, and only in the gain tube that is furthest away from the input jack. Not the best layout, but between the pot and the grid stopper is 15cm of wire. Thinking maybe I need to just increase that value a bit? Currently it's at 1K exactly as the original schematic.
I feel it's definitely a layout issue. Just added a bit more decoupling at the B+ to ground at that tube, and that didn't help. I also swapped tubes around to no avail.
I'm amazed at the improvement, since I first got it semi working to now. This thing got way quiet.
Ok, if I'm going to get this anal, there is a very faint low frequency oscillation happening somewhere. It's faint, like the pitter patter of a chicken running, maybe 10Hz- very faint. Just in one channel, and only in the gain tube that is furthest away from the input jack. Not the best layout, but between the pot and the grid stopper is 15cm of wire. Thinking maybe I need to just increase that value a bit? Currently it's at 1K exactly as the original schematic.
I feel it's definitely a layout issue. Just added a bit more decoupling at the B+ to ground at that tube, and that didn't help. I also swapped tubes around to no avail.
I'm amazed at the improvement, since I first got it semi working to now. This thing got way quiet.
Last edited:
Since you use an AC heaters supply, DC reference lifting reduced cathode to heater leakage currents so much so, that far less hum and buzz couples between them now.
Regarding other small nuisances remaining, ok maybe it's about something to fix in the layout indeed, but exchange the tubes between their now places first. To exclude it's not about one of them being more "vocal".
Grid stoppers usually damp whines. Must be located directly on the base's grid pin with a short trimmed leg. You may up that 1K to 2.2K but if it will not prove useful for pitter patter return it to 1K because we don't want to lose some more bandwidth for nothing in the gain section. Volume pot's Zout (1/4 nominal kΩ at 1/2 signal division point) plus grid stopper always creating an RC low pass filter with the stage's Miller capacitance. Assuming negligible source equipment Zout. Else it has to be added too.
Regarding other small nuisances remaining, ok maybe it's about something to fix in the layout indeed, but exchange the tubes between their now places first. To exclude it's not about one of them being more "vocal".
Grid stoppers usually damp whines. Must be located directly on the base's grid pin with a short trimmed leg. You may up that 1K to 2.2K but if it will not prove useful for pitter patter return it to 1K because we don't want to lose some more bandwidth for nothing in the gain section. Volume pot's Zout (1/4 nominal kΩ at 1/2 signal division point) plus grid stopper always creating an RC low pass filter with the stage's Miller capacitance. Assuming negligible source equipment Zout. Else it has to be added too.
I can't be sure ofcourse. But I think I got that as well. I used current production tung-sol 6v6. To summarize...perhaps try some tube rolling to see if that noise goes away.
Thanks Salas and Bas, I will try a few things next week. I have already moved the tubes around, and the pitter patter does not follow the tube.
Btw, I'm also using the current production tung-sol. I tried an RCA metal can, and a JJ and those do not have that particular noise, but are more microphonic. Maybe it's something with this particular reissue then, although they generally sound pretty great.
Anyway, this is more of a tiny nuisance, not an emergency, so will take my time. Thanks for all your feedback
Btw, I'm also using the current production tung-sol. I tried an RCA metal can, and a JJ and those do not have that particular noise, but are more microphonic. Maybe it's something with this particular reissue then, although they generally sound pretty great.
Anyway, this is more of a tiny nuisance, not an emergency, so will take my time. Thanks for all your feedback
I'd give the Russian 6P6S a try. They sound best to me. I tried several 6V6's but the 6P6S' were the winners. (Entirely subjective of course)
Thanks for the recommendation, I'll give them a try. There were a few consecutive pages early on with some subjective testing of various tubes, so nice to add these to the mix.
Some Measurements
Attached are some measurements I made with a Quantasylum QA400. The device has a dynamic range of 105db, so disregard anything below that. Input impedance of the unit is 100K.
QA400 not supported anymore, so had to bust out the windows 7 laptop. For some reason I couldn't get the markers to work all the time, so you'll have to eyeball some of the numbers.
One thing that surprised me just a bit was the LF rolloff was a little more than I expected. I used a higher bleeded than the schematic, so maybe I go back to the original. I lowered it because on startup/shutdown I got a lot of noise and burps. Just ordered some relays and timers, so will cure that the old fashioned way 🙂
Also, for gain mode I used the potentiometer at the input of the preamp to lower the output so as not too overload the analyzer which cannot accept more than 2V RMS in.
Attached are some measurements I made with a Quantasylum QA400. The device has a dynamic range of 105db, so disregard anything below that. Input impedance of the unit is 100K.
QA400 not supported anymore, so had to bust out the windows 7 laptop. For some reason I couldn't get the markers to work all the time, so you'll have to eyeball some of the numbers.
One thing that surprised me just a bit was the LF rolloff was a little more than I expected. I used a higher bleeded than the schematic, so maybe I go back to the original. I lowered it because on startup/shutdown I got a lot of noise and burps. Just ordered some relays and timers, so will cure that the old fashioned way 🙂
Also, for gain mode I used the potentiometer at the input of the preamp to lower the output so as not too overload the analyzer which cannot accept more than 2V RMS in.
Last edited:
Not bad at all especially when its an AC heated between four tubes combo build. Time for a 555 err.. timer.
Where do you think the 120Hz peaks are coming from? Rectifier? I'm using a Maida though.
Heater noise should be straight 60Hz, right?
Heater noise should be straight 60Hz, right?
Yes but 120Hz is 60Hz's 2nd harmonic so if not interference related maybe harmonically related
Nick, I just so happen to have a donor chassis with a working SSHV2 and 5k OPTs installed. Any guidance on how I could do an EL84 linestage?
Cheers,
Greg
What kind of ratio output transformers? Made for 8Ω output?
Something like this is needed: SINGLE ENDED Tube to line Output Transformer 15K/600 Ohms
Something like this is needed: SINGLE ENDED Tube to line Output Transformer 15K/600 Ohms
Another instance of the Salas 6v6. This time with 6p1p-ev. And 21st century Maida based regulator. Currently running trials in my kid's bedroom system. Slightly lower than the recommended b+340V. 305VDC. Power switch and fuse rather clumsily set up...but whatever...it works.
DC heaters. Heater elevated to around 65VDC with the 'thingy' by Morgan Jones (Was on the board so I decided to use it despite its detractors who claim it has not advantages over a voltage divider.)
DC heaters. Heater elevated to around 65VDC with the 'thingy' by Morgan Jones (Was on the board so I decided to use it despite its detractors who claim it has not advantages over a voltage divider.)
Attachments
Last edited:
Interesting alternative equivalent tube. Maybe good in microphonics. Because noval. Do I see the edge of a Svetlana original wing?
Yes on all counts. I'll know for sure, once I have it in my main system (re microphonics). (It is a non-issue in my son's system) ps the 40 odd mA it draws is peanuts for the regulator. Heat sink not getting warm at all.
Last edited:
By the way, maybe its a photo artifact, those two brown capacitors (Nippon?) on the upper board look like bulging.
Photo artifact I suppose...though they look like the normally do...the caps. Not sure which brand...they are pp orange drop like caps.
Attachments
Last edited: