Hi guys n' gals!
westerday i put together a tubebuffer more or less as an experimental platform, and i could use some tips&tricks to make it sound better, i think it sounds pretty OK already, but i'm sure theres plenty of modifications that will make things even better,
here's the schematic:
http://home.swipnet.se/dice/tubemania/buffer_sch_L.jpg
and a picture of the guts:
http://home.swipnet.se/dice/tubemania/IMG_3422_L.jpg
westerday i put together a tubebuffer more or less as an experimental platform, and i could use some tips&tricks to make it sound better, i think it sounds pretty OK already, but i'm sure theres plenty of modifications that will make things even better,
here's the schematic:
http://home.swipnet.se/dice/tubemania/buffer_sch_L.jpg
and a picture of the guts:
http://home.swipnet.se/dice/tubemania/IMG_3422_L.jpg
First, you need a ground reference on the tubes' grids. Take a 470K resistor from the grid to the common. Now since you've got the cathode resistors returned to common, it would probably be better to return the grid resistors to some reference voltage, somewhere in the neighborhood of 40-50% of the B+, with the cathode resistors sized to get you your desired plate current.
Second, voltage multipliers are not reputed to have great regulation. And you've got a circuit which, inherently having mediocre PS rejection, needs a stable, quiet DC rail. Splitting and regulating the filament rails isn't important at all in comparison with getting the B+ right- proper raw supply, regulation, filtering.
Second, voltage multipliers are not reputed to have great regulation. And you've got a circuit which, inherently having mediocre PS rejection, needs a stable, quiet DC rail. Splitting and regulating the filament rails isn't important at all in comparison with getting the B+ right- proper raw supply, regulation, filtering.
Hi,
I'm more than happy to second you on that one....
Fortunately it doesn't take too much to get it started; just a powerxformer with 2*120VAC secondaries (or thereabout), a pair of FWBs, some filtering caps and resistors to make an ordinary Pi filter would already adorn the circuit with a dedicated PS per channel.
Chances are I can have something cooking along the intitial lines within a couple of hours....Way too hot to sleep anyway.
Cheers,
I'm more than happy to second you on that one....
Fortunately it doesn't take too much to get it started; just a powerxformer with 2*120VAC secondaries (or thereabout), a pair of FWBs, some filtering caps and resistors to make an ordinary Pi filter would already adorn the circuit with a dedicated PS per channel.
Chances are I can have something cooking along the intitial lines within a couple of hours....Way too hot to sleep anyway.
Cheers,
Hi,
Because this is DIY, not CIY ( copy it yourself)...
Either way, if it's a buffer that's needed then, sure there are plenty to be found even here on the forum.
If some gain is still needed, I think I posted a schematic of mine using a plate follower direct coupled to a cathode follower only a week or so ago...
Ah...Found it on my own HD:
Cheers,
P.S. Mr. Triatic, if the pic of the innards of the preamp is showing shiny plates for the Chinese ECC88/6DJ8s then they are really Chinese 6N1Ps NOT true ECC88s. This implies that the Zout of that stage is even higher than for a European ECC88 or Russian 6922.
Because this is DIY, not CIY ( copy it yourself)...
Either way, if it's a buffer that's needed then, sure there are plenty to be found even here on the forum.
If some gain is still needed, I think I posted a schematic of mine using a plate follower direct coupled to a cathode follower only a week or so ago...
Ah...Found it on my own HD:
Cheers,
P.S. Mr. Triatic, if the pic of the innards of the preamp is showing shiny plates for the Chinese ECC88/6DJ8s then they are really Chinese 6N1Ps NOT true ECC88s. This implies that the Zout of that stage is even higher than for a European ECC88 or Russian 6922.
Attachments
hi guys, thanks for ur help!
-yes, this is DIY, not CIY... hence all my mistakes..
@SY-> i know that the PSU isn´t good, but i couldnt finda any suitable HT-transformer, so i thought i should try to double it six times, which gives me about 150Volt and i have a drop about 25-30 V in the PSU-filter, (since the ECC88 are spec. to 130V ?) and use the filter to reduce hum, although i can´t hear any hum in my speakers so obviously it works
The split and reg. of the filaments are due to my transformer choice, i didn't have another..8-/
@fdegrove-> yes, i guess it amplifies about 6dB or so.. i would gladly lower the amplification a bit.
yes, these tubes are Golden Dragon, i also have a pair of Billington gold, but there isn't very much that differs between them regarding sound..
--
now i changed the capacitors at the output to better ones, that helped, i also put an inductor i series with the resistor in the PSU-filter
-do you think i should pick the output signal on the cathode side instead? (like ordinary buffers..?)
i experienced some ringing/slicht echo in voices earlier, i wonder what caused these oddities?
now my amp have been "on" for about 20 hours, with no degradation of sound, without any fire or blown-up capacitors,
-thats good!
my main goal with this amp/buffer is to learn me more about construction, i do have some experience, but not as much as needed.. so even more help is truly appreciated..
PS @fdegrove, your muting seems a little bit rough for the tube?
-yes, this is DIY, not CIY... hence all my mistakes..
@SY-> i know that the PSU isn´t good, but i couldnt finda any suitable HT-transformer, so i thought i should try to double it six times, which gives me about 150Volt and i have a drop about 25-30 V in the PSU-filter, (since the ECC88 are spec. to 130V ?) and use the filter to reduce hum, although i can´t hear any hum in my speakers so obviously it works
The split and reg. of the filaments are due to my transformer choice, i didn't have another..8-/
@fdegrove-> yes, i guess it amplifies about 6dB or so.. i would gladly lower the amplification a bit.
yes, these tubes are Golden Dragon, i also have a pair of Billington gold, but there isn't very much that differs between them regarding sound..
--
now i changed the capacitors at the output to better ones, that helped, i also put an inductor i series with the resistor in the PSU-filter
-do you think i should pick the output signal on the cathode side instead? (like ordinary buffers..?)
i experienced some ringing/slicht echo in voices earlier, i wonder what caused these oddities?
now my amp have been "on" for about 20 hours, with no degradation of sound, without any fire or blown-up capacitors,
-thats good!
my main goal with this amp/buffer is to learn me more about construction, i do have some experience, but not as much as needed.. so even more help is truly appreciated..
PS @fdegrove, your muting seems a little bit rough for the tube?
PSU
Hello ,
A better psu could be made from a pair of tranies connected back to back (pri/sec:sec/pri) .
'Billington gold'
...ooof ! Better check these aren't 6ES8's , Mr Billington's audio valves tend to be , well , errr , iffy to say the least . The valves to go for are PCC88's rather than ECC88's which are now commanding silly prices . Mullard , Siemens PCC88 etc are still cheap and can use current sourced heating . If your circuit has strange ringing or microphony , check the layout and add grid stoppers if required . Have fun !
cheers
316a
Mr. Triatic said:hi guys, thanks for ur help!
-yes, this is DIY, not CIY... hence all my mistakes..
@SY-> i know that the PSU isn´t good, but i couldnt finda any suitable HT-transformer, so i thought i should try to double it six times, which gives me about 150Volt and i have a drop about 25-30 V in the PSU-filter, (since the ECC88 are spec. to 130V ?) and use the filter to reduce hum, although i can´t hear any hum in my speakers so obviously it works
The split and reg. of the filaments are due to my transformer choice, i didn't have another..8-/
@fdegrove-> yes, i guess it amplifies about 6dB or so.. i would gladly lower the amplification a bit.
yes, these tubes are Golden Dragon, i also have a pair of Billington gold, but there isn't very much that differs between them regarding sound..
--
now i changed the capacitors at the output to better ones, that helped, i also put an inductor i series with the resistor in the PSU-filter
-do you think i should pick the output signal on the cathode side instead? (like ordinary buffers..?)
i experienced some ringing/slicht echo in voices earlier, i wonder what caused these oddities?
now my amp have been "on" for about 20 hours, with no degradation of sound, without any fire or blown-up capacitors,
-thats good!
my main goal with this amp/buffer is to learn me more about construction, i do have some experience, but not as much as needed.. so even more help is truly appreciated..
PS @fdegrove, your muting seems a little bit rough for the tube?
Hello ,
A better psu could be made from a pair of tranies connected back to back (pri/sec:sec/pri) .
'Billington gold'
...ooof ! Better check these aren't 6ES8's , Mr Billington's audio valves tend to be , well , errr , iffy to say the least . The valves to go for are PCC88's rather than ECC88's which are now commanding silly prices . Mullard , Siemens PCC88 etc are still cheap and can use current sourced heating . If your circuit has strange ringing or microphony , check the layout and add grid stoppers if required . Have fun !
cheers
316a
Hi,
That's the plate voltage for a cascode service as per the Sylvania 6DJ8 datasheet.
The original Philips ECC88 can take as much as 250VDC on the plate.
In general you often see a B+ of around 250VDC for an audiocircuit using the ECC88 which is fine as heater to cathode insulation is rated at 150VDC with cathode positive and 100VDC with respect to a negative cathode.
Maybe both are Chinese 6N1Ps anyway...
The sonic difference between these and a true quality ECC88 is nothing short of unbelievable, upto the point where you'd wonder if you're still listening to the same track...
Depending on when you bought them from Billington they could be anything but I still have to see it live up to the wild claims they make for them.
Just like 316A, I too have a pretty strong opinion on whatever tube comes from that particular vendor and that's about all I'm going to put in writing about it...
If you do you won't have any useful gain and you'd need to reconfigure the circuit as a cathode follower.
The circuit I posted has gain from the first triode section and the second section lowers the Zout to be able to drive lowish input impedances and longer (read more capactive) cable lengths.
Not at all, it's 100% fine. All it does is short the output.
Cheers,
That's the plate voltage for a cascode service as per the Sylvania 6DJ8 datasheet.
The original Philips ECC88 can take as much as 250VDC on the plate.
In general you often see a B+ of around 250VDC for an audiocircuit using the ECC88 which is fine as heater to cathode insulation is rated at 150VDC with cathode positive and 100VDC with respect to a negative cathode.
Maybe both are Chinese 6N1Ps anyway...
The sonic difference between these and a true quality ECC88 is nothing short of unbelievable, upto the point where you'd wonder if you're still listening to the same track...
Depending on when you bought them from Billington they could be anything but I still have to see it live up to the wild claims they make for them.
Just like 316A, I too have a pretty strong opinion on whatever tube comes from that particular vendor and that's about all I'm going to put in writing about it...
If you do you won't have any useful gain and you'd need to reconfigure the circuit as a cathode follower.
The circuit I posted has gain from the first triode section and the second section lowers the Zout to be able to drive lowish input impedances and longer (read more capactive) cable lengths.
Not at all, it's 100% fine. All it does is short the output.
Cheers,
now iv'e done some modifications to the psu, i really have to find another solution to get the voltage higher without the triple doubler..
i have done some measurements and with a "squarish" input it delivers square output with a disappearingly small cut of the corner at the rising cycle but none at the falling cycle
when measuring the frequency response the curve whas surprisingly flat, although it starts dropping right after 24kHz sharp..
its fun how some scrap really can turn out to something almost useful
by the way, the timing between the channels are almost perfect, too bad the signal is inverted..
i have done some measurements and with a "squarish" input it delivers square output with a disappearingly small cut of the corner at the rising cycle but none at the falling cycle
when measuring the frequency response the curve whas surprisingly flat, although it starts dropping right after 24kHz sharp..
its fun how some scrap really can turn out to something almost useful
by the way, the timing between the channels are almost perfect, too bad the signal is inverted..
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