I was thinking that I might get more gain with the Aikimo circuit. I guess I can go with the SRPP and switch from 6N23Ps to 12AX7 if I feel like the gain needs to be increased.
The hiss is definitely from the preamp itself. The CAT SL1 has a good S/N ratio but all models that I have owned have had "some" hiss when no music is playing regardless of the source equipment that is input. I used to short all of the unused inputs but quit doing that many years ago because I didn't think I heard any significant improvements doing that. There was even a note in the user manual advising to try changing the 12AU7 input tubes if the hiss became louder. BTW: the preamp seemed to eat the 12AU7s for breakfast. I am glad to not have to keep buying them.
All of the earliest models used ECC82 / 12AU7(A)s for the input tubes in the line stage. Ken Stevens decided that changing those tubes to 6922s (Sovtek were installed at the factory) would improve S/N and reduce the hiss. He first did that with the SL1 Signature MkIII (my current model). I can say that the hiss is much less with the 6922s but always can still be heard from a short distance with no music.
According to designer Ken Stevens, the 6922 is a better input tube than the 12AU7, and allows the SL-1's noise level to be reduced from -92dB to -112dB (unweighted)
I probably should clean my tube sockets and tighten the spring clips because I haven't done that in a long time and have rolled a lot of tubes trying to find the ones that sound best to me. I should give the volume control a good cleaning too. I have found that to decrease noise in the past.
I should have asked in my previous post. Can you please make a schematic for an SRPP circuit using a 10 ohm I/V resistor and using the 6N23P tube?
https://www.tubeampdoctor.com/media/pdf/24/19/71/tad-datenblatt_rt-6922_190912_version_1_0.pdf
have some usa air force in input, indeed they are amazing, 1meg grid resistor then 12au7 for drivers of SET 845.
I have only good things to say of the American version of the 6dj8
6922 + 5687, amazing combo...
have some usa air force in input, indeed they are amazing, 1meg grid resistor then 12au7 for drivers of SET 845.
I have only good things to say of the American version of the 6dj8
6922 + 5687, amazing combo...
@MarcalvdG
I found this schematic. What do think about using this and using a 33ohm I/V resistor with 6N23P? I would need to change the PS because the only transformer is not center tapped.
I found this schematic. What do think about using this and using a 33ohm I/V resistor with 6N23P? I would need to change the PS because the only transformer is not center tapped.
@MarcelvdG
Here is datasheet for the transformer I have:
https://www.antekinc.com/content/AS-1T150b.pdf
It is rated at 0.33A @150V x 2 and 3A @ 6.3v x2
Here is datasheet for the transformer I have:
https://www.antekinc.com/content/AS-1T150b.pdf
It is rated at 0.33A @150V x 2 and 3A @ 6.3v x2
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You mean the E88cc/6923, cca is not 300 mA for the heater ?
In my book only the ECC88 has the highish 365 mA...
Btw if audioxcel has some E810F, they are even quieter....
I woul read the first link to a thread I gave. More simplier than the SRPP of the paper and what T Loesch used after. Add a 5687 indeed, be happy.
Grid stopper 10R to 100R,
I/v between 27 to 50, 50R if the pre is hissing at more than 10H00. Filtering I/v silver mica or tin foil according the R value.
10 R is too low for an 6n23/Ecc88/ 6dj8
10R cathode to ground , B+ : -75 to 90 V according the tonal you prefer.
A good DC output cap 2,2 uF like the neutral tin foil from SCR or better. And voila.
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I know for a fact (tried several times) that 91R works perfectly with 6N2P.... = gain matches for a decent output.
33 ohm = 1/3 of signal strength used with a tube with much less gain......... What does your math-teacher say??
Distortion goes through the roof when you load a TDA1541A with such a high resistance, see post #111.
https://www.diyaudio.com/community/...ac-to-feed-a-phono-preamp.426544/post-7993129
https://www.diyaudio.com/community/...ac-to-feed-a-phono-preamp.426544/post-7993129
Perhaps the MarcelvdG approach is the only sane approach to a situation like this.
Marcel, up to 50R is good enough for ears, no one has complained ever with that and the ECC88/6DJ8 and the TDA1541. The 6N23 non EV is too risky for the nouse and 10R too weak indeed with a 33 Mu. One can use the 12ax7 but irs transconductance is less goid than the ECC88/6DJ8 iirc.
Better if 27 to 36 R, ou are rigth indeed. but with a pre after only. My understanding is audioxcel's is hissing...(made from 6922? Ahaha... swap it for 7308 in the pre after having checking the heater voltage... hiss solved)
Better if 27 to 36 R, ou are rigth indeed. but with a pre after only. My understanding is audioxcel's is hissing...(made from 6922? Ahaha... swap it for 7308 in the pre after having checking the heater voltage... hiss solved)
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The non sense begun with the phono stage idea that is interesting only conceptually but a bad idea sound wise and technically for the current output of a dac chip...
This is a rolling opa and tube thread and it is not like we knew nothing about what is working or not with the TDA chip... I assume audioxcel shows enough of incertitude and I surmise it will end by a short and the death of expensive cd player. This is my sanity bill for J-P who is also in the re launch loop of the insane he highligths.
@audioxcel: we know well the tda1541. There is over things to chase to improve it.
Use the good opa or better use the spidf output of the cd player to a good tda1541A like the boxed Aya5 from Audialonline.com or a second hand AMR cd. Sold one of the 3 cd player to affoard it.
You said it yourself: 78, time to profit to the good sound: Best advice ever imho. Well YMMV.
Good luck.
ECC83 will not be that able to drive anything with normal impedances. It is probably best to keep to the schematics with the recommended parts. Add more variables and the solutions are farther away. If the RIAA thing is completely out of the equation more possibilities exist.
I recall a proven circuit for tube IV and TDA1541A by Thorsten Lösch. And of course the Adagio by the same person. It would be a shorter path to success to build things that were built and tested to function correctly if one does not have that knowledge oneself.
https://darklanternforowen.wordpress.com/2017/09/26/adagio-tda1541a-non-oversampling-dac/
I recall a proven circuit for tube IV and TDA1541A by Thorsten Lösch. And of course the Adagio by the same person. It would be a shorter path to success to build things that were built and tested to function correctly if one does not have that knowledge oneself.
https://darklanternforowen.wordpress.com/2017/09/26/adagio-tda1541a-non-oversampling-dac/
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