His Master's Noise: A Thoroughly Modern Tube Phono Preamp

Hi, a question about the LEDs.
I have a preohono 2 x ecc83 + 6n6p like CF.
I would like to remove the cathode R of the first two stages and put some LEDs on them.
Are there any LEDs with low voltages, ie below 1.7v of the red LEDs?
So 1.2, 1, 0.8 volts?
Eventually they can be put in parallel to decrease the voltage .. calculating and reasoning as if they were resistors?
I see that to put them in series as possible (to add up the voltages).

Thanks:D
 
I think normal diodes are in the region of 0.7 volts. They don't have to be light emitting. It's just they tend to have larger band gaps.

Leds are also non ohmic.

If you have 2 resistors, a 5k, and a 10k in series and stick 15v across them, you will get 5v, and 10v respectively.

This would also hold if you had 5r and 10r, or 50k and 100k. The voltage drops would still work out the same but the current would vary.

If we changed the voltage accross the pair to say, 30v.the current would double, as would the voltage drop. The 5k resistor would now have a 10v drop. The 10k a 20v drop.

Leds and diodes are different.

Once they turn on, the voltage drop across them stays at the forward voltage drop.

After that the resistance of the device decreases and so you must use a resistor or similar to limit the current.

Let's take the example of a 1.7 volt led. A 30v power source and say the operating current of the led is 10mA.

So, we are over 1.7v, so it's going to light.

Subtract 1.7v from 30v and that will give you the voltage drop across the resistor.

So 28.3v across the resistor.

We need 10mA. In series like this, every device will see 10mA through it.

Using ohms law, R=V/I

28.3v/0.01A (do calc in amps not milli amps)
And that means you need to use a 2830 ohm resistor.

Closest common value is 2700 or 3300 which would give 10.5ma or 8.6ma.
Either would probably be OK.

Then check the resistor isn't going to melt using i2r

0.0105A*0.0105A*2700 ohm = 0.3 watts
0.0086A*0.0086A*3300ohm = 0.24 watts

Either case probably wants a half watt resistor to be safe.

Having said all that. I think you'll lower head room by changing these diodes. Iirc you raise the cathode voltage above the grid instead of putting negative bias on the grid. Unless you know exactly what you are doing I would leave the hmn stock.

Its a fabulous design that sounds amazing and has very low noise. I use mine with a 0.3mV cartridge and I only start to hear hiss out of it once the volume is way past normal listening levels.
 
Through the Mouser site you can select the search for a diode based on "VF".
What I ask myself, thanking for the explanation just written, is:

Can a "Normal" diode perform the function of a LED diode ... in a CVS?
.... or is the led "special" for some feature?

...actually (on Mouser) there are infinite "VF" values ​​even between 0.5v and 1v (normal diode = no led)

Thanks
 
AX tech editor
Joined 2002
Paid Member
A LED is special in that it emits light, which a normal diode doesn't.

You can just try something like an 1N400x, it may be a bit less than 0.8V but your circuit will find a new balance, with slightly higher anode current. You may want to measure that before/after to see how much it changes, and whether that's OK.

Another option would be two Schottky diodes, with the low currents you have they may come out pretty close to 0.85.

Jan
 
Hi Jack, was that a correction or clarification?
It's a clarification -- was reading an article on LED drivers in some trade journal.

the impedance changes with frequency and (obviously) current -- for the IR one-LED used here it's trivial in the range of 10Hz to 100kHz. At 4mA with a 10mV signal it's just a few Ohms change.

It does seem to make somewhat of a difference in the "Red Light District" amplifier which uses a 7x7 array of red LED's. Might have some "self-heating" issues in that one too.
 
Just because I made a list with parts I may use on the next one. :D
Maybe some people will find this useful.

Regards,
Tibi


Part list HMN

Valves
2 buc x d3A Siemens TubeDepot.com | Ericsson D3A Pentode Tube or Siemens D3A goldpin pentode ( 7721 )
2 buc x "Holy Grail" 1975 Reflektor 6N23P SWGP or E88CC JJ E88CC / 6922 gold | JJ Tubes

Sockets
4 buc x 9-PIN tube socket B9A, gold plated contacts
or Ceramic 9 PIN PC Mount | JJ Tubes
Heatsink
4 buc x https://ro.mouser.com/ProductDetail/588-FA-T220-51E
4 buc x https://ro.mouser.com/ProductDetail/588-EA-T220-51E

Conectors
6buc x https://ro.mouser.com/ProductDetail/CUI-Devices/TB001-500-03BE?qs=vLWxofP3U2xc/oleT4B9KQ==
12 buc x https://ro.mouser.com/ProductDetail/CUI-Devices/TB001-500-02BE?qs=vLWxofP3U2zBBnHgU5u3DA==

Signal Capacitors
2 buc x https://www.hificollective.co.uk/catalog/castdcag010-01uf-630v-duelund-cast-silver-stock-p-9417.html or https://www.hificollective.co.uk/content/jcw-050-01uf-600vdc-jupiter-copper-foil-paper-wax-capacitor or https://www.hificollective.co.uk/ca...jupiter-beeswax-paper-caps-cryoed-p-9830.html
2 buc x https://www.hificollective.co.uk/ca...al-path-tin-foil-polypropylene-capacitor.html
2 buc x https://www.hificollective.co.uk/catalog/axo230-01uf-400v-auricap-capacitors-p-10036.html
4 buc x https://www.hificollective.co.uk/ca...50vdc-claritycap-csa-range-polypropylene.html
2 buc x https://www.hificollective.co.uk/catalog/ccsa080-claritycap-range-polypropylene-p-2465.html

Power supply caps
4 buc x https://ro.mouser.com/ProductDetail/Vishay-Roederstein/MKP1840410634?qs=tXmISY13bxc4SxIkg6BQWQ==
4 buc x https://ro.mouser.com/ProductDetail/KEMET/F461BS224J630L?qs=CBysBIMljtjbAsW4LNhtHg==
8 buc x https://ro.mouser.com/ProductDetail/Nichicon/UTT1C221MPD1TA?qs=OSAjuGjmRDOLJbS9%2BwAL2Q==
6 buc x https://ro.mouser.com/ProductDetail/KEMET/ESU476M400AM5AA?qs=gt1LBUVyoHmcGH/Sx3A9qA==
2 buc x https://ro.mouser.com/ProductDetail/Nichicon/UPW2C101MHD?qs=iBYEVWNtbS6%2BP1Y%2BdUf0nA==
2 buc x https://ro.mouser.com/ProductDetail/Vishay-BC-Components/MAL215919471E3?qs=POvGejmMzm9eCh8NPZIyJw==
4 buc x https://ro.mouser.com/ProductDetail/EPCOS-TDK/B41888C5478M000?qs=nadT/cWsIvCiax0mLoR6SQ==


Resistors
16 buc x https://www.hificollective.co.uk/content/prp-14-265-300r-025w-pr9372-metal-film-resistor
8 buc x https://www.hificollective.co.uk/catalog/prp14330-025w-pr9372-metal-film-resistor-p-8875.html
2 buc x https://www.hificollective.co.uk/content/prp-14-220-120r-025w-pr9372-metal-film-resistor
4 buc x https://www.hificollective.co.uk/catalog/prp14690-025w-pr9372-metal-film-resistor-p-8918.html
2 buc x https://www.hificollective.co.uk/content/prp-14-230-150r-025w-pr9372-metal-film-resistor
4 buc x https://www.hificollective.co.uk/catalog/prp14210-100r-025w-pr9372-metal-film-resistor-p-8860.html
2 buc x https://www.hificollective.co.uk/catalog/prp14205-025w-pr9372-metal-film-resistor-p-8859.html
2 buc x https://www.hificollective.co.uk/content/prp-14-390-3k3-025w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/catalog/prp14485-025w-pr9372-metal-film-resistor-p-8894.html
4 buc x https://ro.mouser.com/ProductDetail...=sGAEpiMZZMtlubZbdhIBIO9L4riy6rIvaK9afVxQj6o=

Power supply resistors
2 buc x https://ro.mouser.com/ProductDetail/Vishay-Dale/NS02B1K800FE12?qs=0n%2BW/EG%2BKm5gl%2B%2Byel4qKw==
2 buc x https://www.hificollective.co.uk/content/prp-12-430-6k8-05w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-12-440-8k2-05w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-12-535-51k-05w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-12-595-160k-05w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-12-610-220k-05w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-12-550-68k-05w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-1-570-100k-1w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-12-510-33k-05w-pr9372-metal-film-resistor
2 buc x https://www.hificollective.co.uk/content/prp-14-220-120r-025w-pr9372-metal-film-resistor
4 buc x https://www.hificollective.co.uk/content/prp-12-290-470r-05w-pr9372-metal-film-resistor


Semiconductor
12 buc x https://ro.mouser.com/ProductDetail/Microchip-Technology/DN2540N5-G?qs=F9TAcTrDwItjOowozNtDSg==
2 buc x https://ro.mouser.com/ProductDetail/Lumex/OED-EL-1556SN?qs=CpNDN/cFIdfdtftRZYPzCQ==
2 buc x https://ro.mouser.com/ProductDetail/Lumex/SSL-LX5093SRC-DU?qs=S5aV3aBO9PflSj8qWp7eiA==
2 buc x https://ro.mouser.com/ProductDetail/VCC/A1A?qs=rHu0DOexXLD2XDJrE%2BAsOw==

Power supply semiconductor
4 buc x https://ro.mouser.com/ProductDetail/Analog-Devices/LM329AZPBF?qs=ytflclh7QUXicoXY7fSAVA==
2 buc x https://ro.mouser.com/ProductDetail/Analog-Devices/LT317ATPBF?qs=hVkxg5c3xu%2BWmN6GS8grZg==
2 buc x https://ro.mouser.com/ProductDetail/Analog-Devices/LT337ATPBF?qs=hVkxg5c3xu%2BRClNVSSW3pQ==
4 buc x https://ro.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/MPSA42?qs=UMEuL5FsraDu/9ZWGlN1JQ==
4 buc x https://ro.mouser.com/ProductDetail/ON-Semiconductor/TIP50G?qs=xZq1yRCsb1daw3NBBsHj0g==
8 buc x https://ro.mouser.com/ProductDetail/Vishay-Semiconductors/1N4001-E3-53?qs=N4vtoAxH/SqgF/ds26xYYA==


Trafo and balast coil
2 x PetraToroid with secundary 240Vac/100mA 2 x 9Vac/2A
2 x https://ro.mouser.com/ProductDetail/546-158Q

Rectification
4 x Saligny LC evotronix.eu
2 x Saligny HVHF evotronix.eu
 
Hi all. I am having very little luck with the measurements of my implementation of this phono preamp. The measurements I have obtained are not even comparable to those obtained by Stuart, in fact mine are really bad. Could someone share their measurements on this forum?

There are no variations from the circuit designed by Stuart, except for adjusting some resistors to get the right values of voltage on the regulators and current on the CSS. A Partidge 977 step-up transformer (6:1) has also been used. Static measurements right channel (left is similar):

B+ = 249V, B++ = 155V, I (CSS1) = 20.60mA, I (CSS2) = 10.55mA, I (CSS3) = 10.72mA.

Va(D3a) = 114.5V, Vk(D3a) = 1.11V, Va1(ECC88) = 78.2V, Vk1(ECC88) = 1.79V, Vk2(ECC88) = 78.9V.

First of all, I would like to characterize my measurements as there is also the possibility that the methodology or procedure is incorrect, especially considering how difficult it is to measure this type of preamplifiers.

The equipment used was an external EMU-0404 soundcard (very low distortion and noise) and a Thinkpad T420 laptop (i5, 8GB RAM). Software: MI (sample at 48kHz, FFT: 16384, Wnd: rectangle, ~1kHz signal adjusted for no leakage)

The SW was calibrated, and for the THD measurement a 1mV, 1kHz tone, has been applied to the input (simulating the output of an EMT TSD-15 cartridge), as a result, 1.01V was obtained at the output. Next are the graphs:

- The first graph shows the output of the EMU-0404 with nothing connected to the input.
- The second graph shows the output of the step-up transformer (in the circuit) with input shorted.
- The third graph shows the output at the anode of D3a with input shorted.
- The fourth graph shows the output of the phono with input shorted.
- The fifth graph shows the phono output with 1kHz signal at the input.
- The sixth and last graph shows the frequency response (white noise, averaged at the output) using passive iRIAA from Jim Hagerman.

Thanks!
 

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With simulating the 1mv output, did you take a stronger signal then attenuate via resistors like stuarts setup? Im wondering how clean that 1khz test signal is.

You may also want look at the 1mV sqr signal on your fft directly and a scope. Does the signal look ok. Bear inthe mind the riaa will filter quite a bit of the squarness out. Dont worry, I dont think vinyl can really reproduce a proper square anyway, think about what the cutting head and stylus would have to do

I notice that you had the fft for no input connected and the output of the transformer. What about connecting your test leads to each other. Are they picking up noise?

If theres no hum on the output or dc. Have you tried hooking it up to your turntable? Does it sound ok or really bad. That might be a better test to ascertain whether its the phono stage or the test setup. Maybe theres noise from a smps creeping in.
 
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B+ = 249V, B++ = 155V, I (CSS1) = 20.60mA, I (CSS2) = 10.55mA, I (CSS3) = 10.72mA.
The D3a is quieter when it is run cooler. TavishDad did a comprehensive survey of triode noise, and ranked D3a triode strapped at 7mA quietest of the lot. I think that somewhere in this long thread, SY may have concluded the same. You'll also find that maybe one in five D3a's may be noisy.
The SW was calibrated, and for the THD measurement a 1mV, 1kHz tone, has been applied to the input (simulating the output of an EMT TSD-15 cartridge), as a result, 1.01V was obtained at the output.

The HMN has tremendous overload margin so you can use a larger input signal than 1mV.

Best of all, HMN is a very, very nice sounding phono-pre.
 

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mrdave45, I think the 1kHz test signal is quite good (THD 0.006%). I attach a graph of it. This signal is passed through a reverse RIAA module (obviously this does not affect the sine 1kHz signal), which additionally has a voltage divider that provides an attenuation of 60dB, so the signal that was originally 1V goes to 1mV, from here it enters the HMV. This is similar to the method used by Stuart, except that my attenuator is not balanced and the impedance at the output of the attenuator is about 60 ohms (a bit high, Stuart's attenuator was 15 ohms).

One test I should do is to connect the input to the actual cartridge and see what happens. Maybe I can do it tomorrow. About testing the HMV in my system, I haven't really wanted to play music through it until the measurements I get are somewhat acceptable... perhaps tomorrow.

What I really don't understand (and don't like at all) is the noise pattern you see at the output of the phono preamp; it's a perfect ramp from -120dB at 20kHz to -50dB at 20Hz. Is that usual? What can it be due to?

jackinnj, I have several pairs of D3a and the result is similar in all of them, so I guess we can eliminate the valve from the equation. As for the input signal, I think it's a good idea. I will use a higher input voltage and maybe I can avoid the noise limitations of the test equipment.
 

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I spent a lot of time playing with the loading of the transformer with mine.
It looks like your cartridge has a 24ohm coil and if the tone arm is balanced, you definitely want to set the whole thing up to run balanced if possible. You should also make sure you use a 24 ohm resistor for your simulation if your cartridge is indeed 24ohm.

I experimented for quite a time trying different loading resistors to filter the ringing whilst trying to maintain output level and played with zobel networks too.
I can't quite remeber how I made my signal balanced though. I think I used three resistors, 2 higher ohmage ones either side of the simulation resistor (15ohm in my case I think).

It might be worth disconnecting the transformer and with suitable loading resistor and injecting a single ended test signal into the first tube stage and check that its not loading or not balancing the signal.
Is your transformer set up for a balanced input or is one winding connected to ground? You will get a much much lower noise floor running balanced.
Just for reference, in my system, I would consider playing a record pretty loud with the volume control about 2 o clock.
Whilst not playing, I only start to hear hiss out the speakers on the second to last click of the volume control.
Sorry I cant be more help diagnosing this. I've never really done much fft as my kit isn't good enough to have been much use.
 
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I ‘finished’ my hmn recently. It’s really great. I tried sy’s suggestion to lower the currents to 10 ma for d3a and 5ma for each of the j8’s. I gave it some time but went back to the original currents, with greater appreciation for the original’s qualities. I am gonna put a distortion analyzer on it and work up the data to find the sweet spot ala Signore N. Pass. - it deserves the analysis. Has anyone tried this? The changes in the sound character by varying a few things and the demonstrated headroom & robust circuit makes me want to flesh it out and see if all the triodes are singing in tune.
 
mrdave45, I think the 1kHz test signal is quite good (THD 0.006%). I attach a graph of it. This signal is passed through a reverse RIAA module (obviously this does not affect the sine 1kHz signal), which additionally has a voltage divider that provides an attenuation of 60dB, so the signal that was originally 1V goes to 1mV, from here it enters the HMV. This is similar to the method used by Stuart, except that my attenuator is not balanced and the impedance at the output of the attenuator is about 60 ohms (a bit high, Stuart's attenuator was 15 ohms).

One test I should do is to connect the input to the actual cartridge and see what happens. Maybe I can do it tomorrow. About testing the HMV in my system, I haven't really wanted to play music through it until the measurements I get are somewhat acceptable... perhaps tomorrow.

What I really don't understand (and don't like at all) is the noise pattern you see at the output of the phono preamp; it's a perfect ramp from -120dB at 20kHz to -50dB at 20Hz. Is that usual? What can it be due to?

jackinnj, I have several pairs of D3a and the result is similar in all of them, so I guess we can eliminate the valve from the equation. As for the input signal, I think it's a good idea. I will use a higher input voltage and maybe I can avoid the noise limitations of the test equipment.

Hi what is this FFT software? Have tambien a hardware?
Gracias!
 
Sometimes you will get fritzy stuff in the high freq end of an FFT from light fixtures, LF harmonics of SMPS power supplies. In fact Analog Devices has a white paper in which one of their engineers in France figured out that a fluorescent light fixture was modulating some "clear" diodes used as a clamp. Trivial, I can't hear any effect but have observed same.

My HMN is temporarily out of commission -- power supply issues.
 
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