Hello Joshua
A LCR-RIAA-Filter is not so expensive. Please have a Look at the Filter from Gerd Reinhöfer in Germany:
LCR-RIAA
He sells the complete Filter or the single Induktors. Here you can find a picture of the Induktors in his device for the ETF-2013:
FORUM - Bilder vom ETF2013
Best Regards
Michael
Hi Joshua,
first of all i have to say thank you for this great thread.
I`m experimenting with lcr RIAA too. With not so much success i have to say.
I use the coils from Lundahl for the lcr - network. the curve look pretty good on the analyzer ( +/- 0,1dB) but sounds dull when you hear it.
My first tube is a 5842 with a Lundahl 1692A 3,5:1 at 18mA.
I chose this tube because of the really low microphonics.
Have anyone experience with the 5842 as first tube?
The D3a´s (Siemens) i have here are very microphonic and i can´t think that they are good at this place.
Excuse my horrible germlish.
Good luck with your projekt,
Hilmar
first of all i have to say thank you for this great thread.
I`m experimenting with lcr RIAA too. With not so much success i have to say.
I use the coils from Lundahl for the lcr - network. the curve look pretty good on the analyzer ( +/- 0,1dB) but sounds dull when you hear it.
My first tube is a 5842 with a Lundahl 1692A 3,5:1 at 18mA.
I chose this tube because of the really low microphonics.
Have anyone experience with the 5842 as first tube?
The D3a´s (Siemens) i have here are very microphonic and i can´t think that they are good at this place.
Excuse my horrible germlish.
Good luck with your projekt,
Hilmar
Indeed, I chose SUT followed by 2 active stages, 1st stage tube D3a, triode strapped, transformer loaded, followed by 600R LCR. I'll decide upon the 2nd tube after making some calculations. However there will be no CCS and no cathode follower. The power supply will also be decided later. Probably it will have tubes rectifiers, followed by LCLCRCRC filtering. Heaters supply will be DC, filtered and current regulated.
Hi Hilmar,
I built lot's of LCR RIAA EQ'ed phonos. None if them sounded dull. Also many LCR phonos from other people which I had a chance to listen to didn't sound dull.
I have built 4 phono stages with the D3a so far, several people built D3a phono kits from me and none have any problems with micro phonics. Care needs to be taken that the tube does not start oscillating at HF. Such self oscillation can have audible effects which appear like micro phonics.
The D3a is used by many people in phono preamps with different circuits. Most report positive results.
Best regards
Thomas
I built lot's of LCR RIAA EQ'ed phonos. None if them sounded dull. Also many LCR phonos from other people which I had a chance to listen to didn't sound dull.
I have built 4 phono stages with the D3a so far, several people built D3a phono kits from me and none have any problems with micro phonics. Care needs to be taken that the tube does not start oscillating at HF. Such self oscillation can have audible effects which appear like micro phonics.
The D3a is used by many people in phono preamps with different circuits. Most report positive results.
Best regards
Thomas
Hello Joshua
When using the D3a, please have a good look at the Datasheet from Telefunken:
http://frank.pocnet.net/sheets/128/d/D3a.pdf
There is a parameter called +Ubg1 = 10V
That means, you have to provide +10V for the grid of the tube. This is for better stability over the time, because you can use a Rk with higher value (470 Ohm) than without.
Best Regards
Michael
Hi Thomas,
i believe you that your amps sounds fantastic but htis is the experience i had.
i had Gridstoppers (1kohm) at g1 and the D3a wired as a triode. I controlled Hf-oscillation with my Osci and there where nothing. So can you give me an advice how to cure the "ping" when i stomp alittle at the tube?
Did you ever try the Lundahl coils?
In my power and line amps i allways use Lundahls with great results as input, interstage and output. The LCR-network is new to me and maybe i do something completly wrong.
Have you experience with the 5842 ?
Keep on with your great work,
Hilmar
i believe you that your amps sounds fantastic but htis is the experience i had.
i had Gridstoppers (1kohm) at g1 and the D3a wired as a triode. I controlled Hf-oscillation with my Osci and there where nothing. So can you give me an advice how to cure the "ping" when i stomp alittle at the tube?
Did you ever try the Lundahl coils?
In my power and line amps i allways use Lundahls with great results as input, interstage and output. The LCR-network is new to me and maybe i do something completly wrong.
Have you experience with the 5842 ?
Keep on with your great work,
Hilmar
Hi Hilmar
Most tubes will give some noise when you actually hit them. But that is not a very practical test IMHO.
As much as I like most of the Lundahl stuff. Those coils were not very good and that's also why they are not made any more. That was a one time production batch. I found the inductance to vary from coil to coil a lot.
But still they should not cause the preamp to sound dull if you got the frequency response right as you say.
Many things can influence the sound, maybe it was something else in the circuit?
Difficult to say.
Parasitic oscillations can be at very high frequencies, probably beyond the capabilities of your scope. And additionally the capacitance of the scope probe can kill such oscillations while trying to measure them.
Best regards
Thomas
Don't stomp the tube
Most tubes will give some noise when you actually hit them. But that is not a very practical test IMHO.
As much as I like most of the Lundahl stuff. Those coils were not very good and that's also why they are not made any more. That was a one time production batch. I found the inductance to vary from coil to coil a lot.
But still they should not cause the preamp to sound dull if you got the frequency response right as you say.
Many things can influence the sound, maybe it was something else in the circuit?
Difficult to say.
Parasitic oscillations can be at very high frequencies, probably beyond the capabilities of your scope. And additionally the capacitance of the scope probe can kill such oscillations while trying to measure them.
Not much really, I briefly played around with it many years ago. Certainly a tube which I will get back to some time in the future as I still have plenty of them
Best regards
Thomas
Hi Thomas,
Is it recommended to supply the control grid with +10V on D3a?
Under what circumstance it may be recommended?
What I got from the datasheet is that it is intended to protect the tube from over-current in the event of brief cut-offs, when the cathode resistor is bypassed with a capacitor >10uF.
Is that correct?
Is it relevant to a phono stage circuit?
'Stomping' the tube may serve only as comparison between different tubes. As Thomas said, there will always be some noise.
Probably a stopper resistor between the g2 and the anode is also needed. Best is to connect it right at the tube socket. The g1 stopper resistor should also be connected right at the tube socket. If there are still RF oscillations, you can try ferrite beads around the stopper resistors leads which are connected to the grids' tube socket.
Another way which may work, in order to detect possible RF oscillation, is to connect a capacitor of about 1nF (and appropriate voltage rate) between the anode and cathode, right at the tube socket. If in that test the 'microphonics' will go away, you have RF oscillation.
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