ruffrecords
Well-known member
That one certainly looks to have had some input from me. The SRPP is a topology I often use. Where did you find that? Any idea how old it is?
Cheers
Ian
Tube DI Box
- Thread starter ruffrecords
- Start date
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Cheers
Ian
rock soderstrom
Tour de France
This means you don't have any problems with interference, that's true. But it needs more space and gets quite warm with just one tube. Here is a current PCB design on Eurocard (2 pieces on board). This is a "luxury" version, more flexible, also for other circuits. If you get serious, you might be able to halve the footprint. The "Ruud" switcher is definitely more compact and flexible!
PermO
Well-known member
Cool idea !
But, to start with, it has to be really really good... it will have to sound amazing as there's so many of these things out there allready.
So it should sound better than the Alembic Tube DI.
And I have my doubts running a tube from a wallwart using an upconverter will be that... though I have been looking into these things and you can get pretty small ones that take 5V in and put out 100V DC... but these will cost over $ 100,- not sure about the amount of hash they will introduce.
That SRPP DI with a big transformer is a better candidate I guess...
Why bring it down to Mic level ? ..it's an active device ! It should provide gain and take the mic pre out of the equation.
I've been playing with 12au7 on 12.6V plate voltage, and they will run, they will work, and they will defenitely not sound "hifi" I spend a couple weeks experimenting, listening to get a decent sound from that and the best thing I could come up with was a stereo bus saturator (it has a topic on GDIY) that does not completely destroy your material and is actual a device I use occasionally (paralel on a bus) to add extra harmonic content to a source.
I will be following this with interest, but with the latest version of my Instrument Line Amplifier I don't think I will ever have the need for another DI
But, to start with, it has to be really really good... it will have to sound amazing as there's so many of these things out there allready.
So it should sound better than the Alembic Tube DI.
And I have my doubts running a tube from a wallwart using an upconverter will be that... though I have been looking into these things and you can get pretty small ones that take 5V in and put out 100V DC... but these will cost over $ 100,- not sure about the amount of hash they will introduce.
That SRPP DI with a big transformer is a better candidate I guess...
Why bring it down to Mic level ? ..it's an active device ! It should provide gain and take the mic pre out of the equation.
I've been playing with 12au7 on 12.6V plate voltage, and they will run, they will work, and they will defenitely not sound "hifi" I spend a couple weeks experimenting, listening to get a decent sound from that and the best thing I could come up with was a stereo bus saturator (it has a topic on GDIY) that does not completely destroy your material and is actual a device I use occasionally (paralel on a bus) to add extra harmonic content to a source.
I will be following this with interest, but with the latest version of my Instrument Line Amplifier I don't think I will ever have the need for another DI
L´Andratté
Well-known member
found it: old thread
I would be super interested in such a thing for live recording for Bass and Keys DI. Obviously compact is preferred, but even an Avalon U5 isn’t *TOO* big when you’re already dealing with amps and mixers and the like anyhow.
BIASKING
Member
Just ran across this thread. In case anyone is still interested, this might be a good option:
https://www.electronics-lab.com/project/hv-nixie-dc-dc-switching-power-supply/
https://www.electronics-lab.com/project/hv-nixie-dc-dc-switching-power-supply/
ruffrecords
Well-known member
Yes, I have come across quite a few 555 based Nixie drivers. Nice to see one based on a "proper" SMPS chip and on a ready made PCB.
Cheers
Ian
ruffrecords
Well-known member
In not surprised the Reverb tank enthusiastically picks up hash from the switcher ,positioned directly above the output transducer .
You probably will get lower noise by making a close fitting metal lid for the underside of the tank , as any gaps will tend to allow in garbage .
It would seem to me a switcher PSU needs at the very minimum good metal screening from areas containing tube circuits , otherwise the noise floor is a seething mess .
As I recently noticed with the EQP-KT , the RF garbage enters the circuit via multiple paths , both the input transformer and the EQ inductor contribute , each adding its own spectrum of phasey harmonic overtones to the party ,
In the past Ive used any mains transformer that came to hand for projects , mainly reclaimed stuff , one offs ,
Now Ive settled on my own version of a universal tube mic/preamp supply ,
It doesnt have switchers , it doesnt have voltage doublers and it doesnt piggy back transformers ,
It uses two separate transformers , one HT one LT , it has strong metal screening all round .
And everything runs just warm to the touch .
I think I'll include a standby switch of sorts , basically a series resistance and a bleed resistor in the HT supply that slows the charging of the caps right down , after a suitable ramp up period a front panel switch can bypass the resistors to get upto the full HT , it seems to be the simplest solution , without involving relays or transistors or anything else than can go wrong .
There is always the human element , but in any case its not like a normal standby where the tubes might run for hours or days with no HT applied ,
You probably will get lower noise by making a close fitting metal lid for the underside of the tank , as any gaps will tend to allow in garbage .
It would seem to me a switcher PSU needs at the very minimum good metal screening from areas containing tube circuits , otherwise the noise floor is a seething mess .
As I recently noticed with the EQP-KT , the RF garbage enters the circuit via multiple paths , both the input transformer and the EQ inductor contribute , each adding its own spectrum of phasey harmonic overtones to the party ,
In the past Ive used any mains transformer that came to hand for projects , mainly reclaimed stuff , one offs ,
Now Ive settled on my own version of a universal tube mic/preamp supply ,
It doesnt have switchers , it doesnt have voltage doublers and it doesnt piggy back transformers ,
It uses two separate transformers , one HT one LT , it has strong metal screening all round .
And everything runs just warm to the touch .
I think I'll include a standby switch of sorts , basically a series resistance and a bleed resistor in the HT supply that slows the charging of the caps right down , after a suitable ramp up period a front panel switch can bypass the resistors to get upto the full HT , it seems to be the simplest solution , without involving relays or transistors or anything else than can go wrong .
There is always the human element , but in any case its not like a normal standby where the tubes might run for hours or days with no HT applied ,
IBarfoot
Member
- Joined
- Sep 25, 2018
- Messages
- 7
I would most definitely be interested in a valve DI too, I would go for a balanced output using a good transformer though.
Whilst it wouldn’t be classed as compact a simple linear power supply either internal or external strikes me as a simple solution.
Whilst it wouldn’t be classed as compact a simple linear power supply either internal or external strikes me as a simple solution.
BIASKING
Member
rock soderstrom
Tour de France
I am also not surprised as I have already built a few spring reverbs. It's a worst case scenario, a good test, the output transducer tells you very clearly what works and what doesn't.
I did that yesterday, but it doesn't help that much. Essentially, the problem is the same as with a mains transformer, but (you are right) the annoyance factor is tonally greater.
I agree, the PSU switcher transmits heavily noise without shielding.It has a particular effect on inductors, pure tube circuits get less of it (in my tests so far).
The question I am investigating is how best to do this and which materials have the best shielding performance for that kind of interference.
The circuit board gets quite warm at 600mA heater current, so it needs passive ventilation.
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Wavelength
Well-known member
Well I do this thing with the NMT0572SC and a 12AU7A and a hammond 8ma/150H (156C) inductor for a USB DAC, I build. Put the inductor in the cathode as a cathode follower... oh what the hell drew it up as I am home doing taxes, yuck. So you can find the NJM2396F63 on eBay it's a great 6.3V regulator or do something different like ok 9-6.3V/~150ma = 18ohms ~3.5W would be good and give you 6.3V into the 6C4WA basically 1/2 of a 12AU7A. The NMT0572 is a great DCDC converter which I have hundreds of products. @5.5V gives you 80V. I would use a 500K volume pot all the 1M ones even the best suck the top end like crazy. Suggestions for 600:600? I could board this up as I have a gig for acoustic next month and was thinking of a SS DI but I like this idea better.
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Rob Flinn
Well-known member
Personally I don't like using wallwarts at all, especially for things that will get moved around a lot & don't live in a rack. I don't find them to be a professional solution.
L´Andratté
Well-known member
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Worst case scenario is a good staring point ,
At least it means matters can only improve !
Id reccomend trying the switcher module inside a
single gang metal clad electrical back box with a blanking panel on the front .
These are readily available at your local electrical supplier .
The knock outs can be used to mount cable glands but also as vents if you need air flow ,
AC wallwarts arent all that easy to find now ,
and even with a voltage trippler your probably going to end up needing a 48v transformer ,which arent commonly found .
As far as I can see the 220/110v 20va shaver transformer is the cheapest and most available source for a HT supply you can find and if anyone knows better ,let us know .
It can easily supply 50ma , which should be more than enough for even power hungry preamps ,
It could outlast a switcher supply by half a century ,
Likewise ,
Low voltage transformer based chargers/supplies are easily found these days in the recycle heap , so its easy for me to grab one of the correct voltage and current rating as I need it .
I found an old Altec Lansing 15V 800ma supply recently , the kind from desktop multimedia speakers ,
Its just right for the EQP-KT LT supply ,
I broke away the wallwart housing and mounted up the transformer with Galvo band inside the another dual gang back box .
At least it means matters can only improve !
Id reccomend trying the switcher module inside a
single gang metal clad electrical back box with a blanking panel on the front .
These are readily available at your local electrical supplier .
The knock outs can be used to mount cable glands but also as vents if you need air flow ,
AC wallwarts arent all that easy to find now ,
and even with a voltage trippler your probably going to end up needing a 48v transformer ,which arent commonly found .
As far as I can see the 220/110v 20va shaver transformer is the cheapest and most available source for a HT supply you can find and if anyone knows better ,let us know .
It can easily supply 50ma , which should be more than enough for even power hungry preamps ,
It could outlast a switcher supply by half a century ,
Likewise ,
Low voltage transformer based chargers/supplies are easily found these days in the recycle heap , so its easy for me to grab one of the correct voltage and current rating as I need it .
I found an old Altec Lansing 15V 800ma supply recently , the kind from desktop multimedia speakers ,
Its just right for the EQP-KT LT supply ,
I broke away the wallwart housing and mounted up the transformer with Galvo band inside the another dual gang back box .
ruffrecords
Well-known member
That's OK but I have to ask, what would you like? Surely not a mains cable either so are you asking for it to be battery powered?
Cheers
Ian
ruffrecords
Well-known member
ruffrecords
Well-known member
I have been playing with LTpice this evening to see just what you can achieve with a very simple CF circuit:
The results are quite encouraging. With a standard 10K:600 output transformer the insertion loss is just over 14dB. The response is flat down to 20Hz and 3dB down at 10Hz. Distortion with a 1V input is about 0.2% mostly second harmonic. Input impedance is comfortably over 1Meg. HT current is just under 6mA so well within reach of Nixie driver designs. I have added some additional smoothing just in case. The circuit works well right down to 90V on the plate.
Cheers
Ian
The results are quite encouraging. With a standard 10K:600 output transformer the insertion loss is just over 14dB. The response is flat down to 20Hz and 3dB down at 10Hz. Distortion with a 1V input is about 0.2% mostly second harmonic. Input impedance is comfortably over 1Meg. HT current is just under 6mA so well within reach of Nixie driver designs. I have added some additional smoothing just in case. The circuit works well right down to 90V on the plate.
Cheers
Ian
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