Higher voltage sub-mini tubes
Hi Wavebourn (or anyone with thoughts on it)
Yes, they are cheap those tubes (see below), but I'm not sure about the total cost of the project, because the JAN6418 are low voltage & can run on a 9V battery.
The ones you quoted are 60V plate, and some other Russian tubes on eBay are 165V or even more, and the power supply can end up costing more than the rest of the tube preamp, as well as being bulky (I'm using them in a guitar pedal & need it to be compact).
Do you have any thoughts on low cost compact higher voltage power supplies? Could you use a Step-Up Voltage Regulator circuit to get 60V from a 9 or 12V supply?
Thanks, John
Hi Wavebourn (or anyone with thoughts on it)
Yes, they are cheap those tubes (see below), but I'm not sure about the total cost of the project, because the JAN6418 are low voltage & can run on a 9V battery.
The ones you quoted are 60V plate, and some other Russian tubes on eBay are 165V or even more, and the power supply can end up costing more than the rest of the tube preamp, as well as being bulky (I'm using them in a guitar pedal & need it to be compact).
Do you have any thoughts on low cost compact higher voltage power supplies? Could you use a Step-Up Voltage Regulator circuit to get 60V from a 9 or 12V supply?
Thanks, John
That's what I use with my 12v battery powered 6418 line stage which feeds a T-amp. Works just fine but I still need to work on reducing microphonics. I got a handful of 6088 tubes in a few months back and I think I'll try them out as well.
So you step the voltage up from 12 to 60V, for a 6418?
Have you tried rubber grommets or bands on the tubes for the microphonics?
I bought a cheap 12v to 48v like this one: DC to DC Converter Pico 12E48S 12V to 48V Hi Rel | eBay and use the 6418 in pentode mode before my passive tone controls and triode mode after them. I use a transistor based buffer to drive the relatively low T-amp input impedance.
I've tried various methods (including grommets) to reduce microphonics but occasionally the tubes still start singing when certain music is playing. When it happens my only recourse is to reduce the volume for a couple of seconds. Because of this I haven't settled on a case for the preamp but maybe I'll find the time to play it with it and come up with a solution in the near future.
I've tried various methods (including grommets) to reduce microphonics but occasionally the tubes still start singing when certain music is playing. When it happens my only recourse is to reduce the volume for a couple of seconds. Because of this I haven't settled on a case for the preamp but maybe I'll find the time to play it with it and come up with a solution in the near future.
Hi Cale
Wow, that DC DC converter's so small, & such a good price. I'll see if the guy'll ship to the UK. Thanks.
Yes I've heard the 6418 can be bad for microphonics, good luck.
Wow, that DC DC converter's so small, & such a good price. I'll see if the guy'll ship to the UK. Thanks.
Yes I've heard the 6418 can be bad for microphonics, good luck.
Hi again and sorry to bring back the discussion to my attempt to make it work.
I replaced the caps with bipolar ceramics and it still didnt work, I then decided to rebuild it from scratch and still no sound comes out of it, only a slight battery hum when i turn my amps volume up.
I am using a 9v battery right now (before i build the psu), the voltages seem to be good, i get 1.25v on pin 5 and about 7.8v on pins 1,2 and i get some kind of alternating voltage of -0.5v - 0.5v on pin 4.
I am not sure whats wrong, is there anything that I am may be missing?
I replaced the caps with bipolar ceramics and it still didnt work, I then decided to rebuild it from scratch and still no sound comes out of it, only a slight battery hum when i turn my amps volume up.
I am using a 9v battery right now (before i build the psu), the voltages seem to be good, i get 1.25v on pin 5 and about 7.8v on pins 1,2 and i get some kind of alternating voltage of -0.5v - 0.5v on pin 4.
I am not sure whats wrong, is there anything that I am may be missing?
Ok it works now!
The missing ingredient was the plate resistors (i used 47k).
* if anyone has the same issue then these are two resistors bypassing the +v into pins 1,2.
First impressions:
- microphonics are very bad, maybe an enclosure and some better grounding is needed. or maybe like moshka mentions I need to play around with the impedance resistors.
- At first the sound was heavily distorted, I guess this circuit is meant for something like a guitar or mic as an input, I had to reduce the volume of my player to get rid of the distortion. So i would suggest a trimpot for both inputs.
- Sound, I have yet to have a good chance to get any real impressions but it sounds good right now. The tubes i am using right now have been warming up for a while in the k272a kit i built previously.
The missing ingredient was the plate resistors (i used 47k).
* if anyone has the same issue then these are two resistors bypassing the +v into pins 1,2.
First impressions:
- microphonics are very bad, maybe an enclosure and some better grounding is needed. or maybe like moshka mentions I need to play around with the impedance resistors.
- At first the sound was heavily distorted, I guess this circuit is meant for something like a guitar or mic as an input, I had to reduce the volume of my player to get rid of the distortion. So i would suggest a trimpot for both inputs.
- Sound, I have yet to have a good chance to get any real impressions but it sounds good right now. The tubes i am using right now have been warming up for a while in the k272a kit i built previously.
Hi Gideon
Which circuit is this? Is this still Moksha's basic Jan 6418 - Triode Circuit?
Dystopian Tone - Products (Vacuum Tubes - Valves)
Which doesn't have any plate resistors in the circuit diagram.
Hi John,
Yes its the one from moshkas' page, the top one out of the three.
The circuit is very similar to the k295 kit from oatley which you can find here:
Oatley Electronics
I am using a 9v battery at the moment but i may build a simple 18v psu for it at some point.
I get 1.25v by using an lm317L with one resistor between adj and out and adj connected to ground.
Have you decided on what to build yet?
Yes its the one from moshkas' page, the top one out of the three.
The circuit is very similar to the k295 kit from oatley which you can find here:
Oatley Electronics
I am using a 9v battery at the moment but i may build a simple 18v psu for it at some point.
I get 1.25v by using an lm317L with one resistor between adj and out and adj connected to ground.
Have you decided on what to build yet?
Hi Gideon
I've just looked at the K295 circuit diagram here at Oatley and yes, if I ignore the power supply, and one of the channels, and the trimmer input pot etc. it's similar to the basic triode circuit, but it does have a 47K plate resistor.
Yes 18V sounds a better plate voltage, the data sheet show typical plate voltage of 15 - 22.5, so 9V seems a bit low, although Oatley do use it in some of their circuits, for the convenience of a 9V battery.
I'm building an Oatley Guitar Preamp K270 to get me started, but I'm breadboarding it rather than use the PCB, so I can experiment with it & attempt to improve the design & learn something at the same time.
Anyway, glad you got it going.
I've just looked at the K295 circuit diagram here at Oatley and yes, if I ignore the power supply, and one of the channels, and the trimmer input pot etc. it's similar to the basic triode circuit, but it does have a 47K plate resistor.
Yes 18V sounds a better plate voltage, the data sheet show typical plate voltage of 15 - 22.5, so 9V seems a bit low, although Oatley do use it in some of their circuits, for the convenience of a 9V battery.
I'm building an Oatley Guitar Preamp K270 to get me started, but I'm breadboarding it rather than use the PCB, so I can experiment with it & attempt to improve the design & learn something at the same time.
Anyway, glad you got it going.
I haven't tried them with really low plate voltage but depending on triode or pentode use I've typically had the best results running them at 20-25v off of a B+ voltage of around 50v.
In pentode mode I get very different distortion results depending on where I set the screen voltage. IIRC somewhere around 24v on the plate with 20-21v on the screens yielded the best results. It's pretty easy to set up the screen voltage off a potentiometer from the B+ tap so you can vary it for best results.
I'm glad you got it working... i'll have to change the schematics to include the plate resistors (i have them in all my circuits - just didnt think they were vital apart from reducing the voltage to the desired level - i made a silly assumption...)
I have a working power supply 12v stepped up to 30v on my website....
Dystopian Tone -Clean Power Supply with 9v & 30v Rails
As for the microphonics you should have 3-4 grommets on the tubes... there is no way to bypass this - some people have tried hot glue melted over the tubes successfully too.
I currently have a 3 stage line preamp laying exposed near my amp using these tubes and i dont have any ringing except when the amp is blasting enough to hurt my ears.... if you build an enclosure - i built one for a customer... i lined the inside with aluminium foil and then stuck cardboard all around it... this worked well even at louder volumes... (3-4 grommets on the tubes as well)
When i say that the change over in impedance resistor helped reduce the microphonics, that is to say the oatley kits i built ring quite a lot even with grommets... where as the change over in impedance resitors causes them to ring at much higher volumes...
My preamps still ring but at really loud volumes. This may also be partly due to how clean your power is.... i aim at a ripple voltage of around 0.1mv on the stepped up stage of the power board i linked to.... this may have some effect on how the tubes funtion as well... i noticed that anything not filtered out of the plate voltage gets amplified... from all kinds of digital jitters (depending on how you step up the voltage) to high frequency hiss and low end hum.
I have a working power supply 12v stepped up to 30v on my website....
Dystopian Tone -Clean Power Supply with 9v & 30v Rails
As for the microphonics you should have 3-4 grommets on the tubes... there is no way to bypass this - some people have tried hot glue melted over the tubes successfully too.
I currently have a 3 stage line preamp laying exposed near my amp using these tubes and i dont have any ringing except when the amp is blasting enough to hurt my ears.... if you build an enclosure - i built one for a customer... i lined the inside with aluminium foil and then stuck cardboard all around it... this worked well even at louder volumes... (3-4 grommets on the tubes as well)
When i say that the change over in impedance resistor helped reduce the microphonics, that is to say the oatley kits i built ring quite a lot even with grommets... where as the change over in impedance resitors causes them to ring at much higher volumes...
My preamps still ring but at really loud volumes. This may also be partly due to how clean your power is.... i aim at a ripple voltage of around 0.1mv on the stepped up stage of the power board i linked to.... this may have some effect on how the tubes funtion as well... i noticed that anything not filtered out of the plate voltage gets amplified... from all kinds of digital jitters (depending on how you step up the voltage) to high frequency hiss and low end hum.
9v you will have some loss with the jan 6418's as i signal going in will be louder than signal going out... As for distortion... lower B+ or attentuate incoming signal with a pot or resistor.... try 100k first move your way up to 300k as necessary.... input volume attenuation is essential as with 18v you are driving the signal quite a lot.
Someone posted earlier that the Oately kits use 9v on some kits.... this is mainly to get clean power with small capacitors and to get the clarity and warmth of having a tube stage... the only time this would work though is if there is an opamp or FET stage after the initial 9v tube stage... i was planning at one stage (i think i will most likley still do it) make a headphone amp around an opa2134 circuit i found online with a 9v tube stage on the input... 16v caps are much cheaper (especially when you get to 10000uf) than 35v caps.... the only reason of running a 30v rail is to get amplification out of the Jan 6418's... if you are happy to replace the gain stage with an opamp, 9v is sufficient on the tube stage to get that analog sound out of the circuit
hey Moshka,
Thanks and no worries, I wouldn't have gotten this far without your articles and tips!
i had the feeling that the plate resistors was the issue but kind of left it as the last test in the debugging so to not bring down the voltage 🙂
I am now running it from a 19v laptop external battery source and it sounds much better and the microphonics are totally gone. Its also lying bare next to my laptop.
in the next "boy is sleeping, wife is reading" hole in the weekend I will build a power supply with the lm317 for voltage adjustment like you suggested.
Thanks and no worries, I wouldn't have gotten this far without your articles and tips!
i had the feeling that the plate resistors was the issue but kind of left it as the last test in the debugging so to not bring down the voltage 🙂
I am now running it from a 19v laptop external battery source and it sounds much better and the microphonics are totally gone. Its also lying bare next to my laptop.
in the next "boy is sleeping, wife is reading" hole in the weekend I will build a power supply with the lm317 for voltage adjustment like you suggested.
Hope you enjoy the sound as much as i do.... have my RIAA preamp turned on right now with a Pioneers PL-707 deck gifted to me last night... massive difference than plugged into the RIAA port of the amp i'm using...
I thought my amp was blown this morning... i tried plugging in my kenwood surround receiver i purchased for DVD surround sound... its amazing how even plugging the tube preamps into different amps will produce completely different sound... on the Kenwood sound is lifeless whereas plugged into my 1970's JVC solidstate amp the sound is brilliant... what i'm trying to say is don't be afraid to pull out the old amp sitting in the garage or shed as one might be pleasantly surprised by the tonal differences compared to modern hifi equipment... i've been messing around with these tubes and vinyl for the last 2 years and now i have difficulty listening to music in the car or at other peoples houses....
I thought my amp was blown this morning... i tried plugging in my kenwood surround receiver i purchased for DVD surround sound... its amazing how even plugging the tube preamps into different amps will produce completely different sound... on the Kenwood sound is lifeless whereas plugged into my 1970's JVC solidstate amp the sound is brilliant... what i'm trying to say is don't be afraid to pull out the old amp sitting in the garage or shed as one might be pleasantly surprised by the tonal differences compared to modern hifi equipment... i've been messing around with these tubes and vinyl for the last 2 years and now i have difficulty listening to music in the car or at other peoples houses....
Unless you're using some sort of buffer after the 6418 stage it would make sense that it would sound completely different depending on what it's plugged into. The 6418 barely has enough oomph to drive anything on its own.
I simply meant that modern equipment doesn't sound as good as older equipment... whatever the reason... i picked up an old amp for 10$ at a local market that to me sound 10 times better than an amp i paid around 1000$ for... if one is building a tube preamp to enjoy msuic in its entirety i'm simply suggesting trying them on older amps as newer digital amps may rob the analog signal of its texture therefore not allowing for the full appreciation of the preamp's effect on music...
About 10 years ago i picked up an old amp and speakers at a market for 50$ or so and in my stupidity traded it to a friend for a 350watt pioneer amp then fairly new... not until recently have i been able to come close to replicating the sound that came out of it.... just something about the detail & frequency response of older equipment that is lacking in most likley all but a few very expensive modern amps eg Harmon Kardon etc
About 10 years ago i picked up an old amp and speakers at a market for 50$ or so and in my stupidity traded it to a friend for a 350watt pioneer amp then fairly new... not until recently have i been able to come close to replicating the sound that came out of it.... just something about the detail & frequency response of older equipment that is lacking in most likley all but a few very expensive modern amps eg Harmon Kardon etc
Hello all!
Dystopian tone doesn't seem to exist anymore, so does anyone have any of the schematics for the circuits discussed in this thread?
Dystopian tone doesn't seem to exist anymore, so does anyone have any of the schematics for the circuits discussed in this thread?
