Felipe
Is not clear to me what did you change to produce the noise (if any). It all looks to be the valves if you haven't changed anything (e.g. cables, grounding or ground loops). A quick test would be to place your hand close to the 26 and you other hand to safety earth. If proper screening eliminates the hiss then the valve is better to be replaced. If it continues to be there then you need to trace the source of it somewhere else...
Ale
Is not clear to me what did you change to produce the noise (if any). It all looks to be the valves if you haven't changed anything (e.g. cables, grounding or ground loops). A quick test would be to place your hand close to the 26 and you other hand to safety earth. If proper screening eliminates the hiss then the valve is better to be replaced. If it continues to be there then you need to trace the source of it somewhere else...
Ale
It's been a while since I've last updated my 26 preamp. A minor variation in the filament bias operating point and power supply:
26 Pre-amplifier Gen3 | Bartola Valves
Now back again to revisit the 4P1L, 10Y and 01a versions
Ale
26 Pre-amplifier Gen3 | Bartola Valves
Now back again to revisit the 4P1L, 10Y and 01a versions
Ale
Very interesting Ale!
I'm not using my 26 preamp any more. I just have the 4P1L > 4P1L PSE amp. With 2v in from my ES9023 Dac I get enough volume for my Alpair 10 speakers.
Nice as the 26 preamp is, the sound is cleaner without the extra stage. I never thought I'd move on from the 26 preamp - for me the 26 was the tube that started my whole love affair with DHTs. I remember to this day the moment my jaw dropped on the floor when I first heard it and I believe I said out loud "This is the tube I've been waiting for all my life!"
But there we are - the 4P1L is the tube chez moi these days. 150 of them! And only ever in filament bias, even for the output stage!
I'm not using my 26 preamp any more. I just have the 4P1L > 4P1L PSE amp. With 2v in from my ES9023 Dac I get enough volume for my Alpair 10 speakers.
Nice as the 26 preamp is, the sound is cleaner without the extra stage. I never thought I'd move on from the 26 preamp - for me the 26 was the tube that started my whole love affair with DHTs. I remember to this day the moment my jaw dropped on the floor when I first heard it and I believe I said out loud "This is the tube I've been waiting for all my life!"
But there we are - the 4P1L is the tube chez moi these days. 150 of them! And only ever in filament bias, even for the output stage!
Indeed Andy. I'm going to get the 4P1L back. I remember first time I used it ages ago for preamp and got outstanding results with a mu follower Gyrator as needed the gain in the system at that point. I run it al 20mA which is the minimum for optimal performance of 4P1L. Starved filaments and parallel filament sections is a must for very low microphonic feedback.
I now have an LL1660 gapped at 40mA which can be used for both 10Y and 4P1L line stages
Cheers
Ale
I now have an LL1660 gapped at 40mA which can be used for both 10Y and 4P1L line stages
Cheers
Ale
Hi Ale,
A LL1660 gapped for 40mA will have a too low primary inductance for a 10Y IMHO
Best regards
Thomas
A LL1660 gapped for 40mA will have a too low primary inductance for a 10Y IMHO
Best regards
Thomas
My 4P1L SE amp sounds very good, sweeter than my 300B on the midrange. Noise is minimum, 0.4mVac. I plan building pre amp 4P1L or 5A6 or 26 to compare to current 71A preamp.
Could you post your schematic? There are very few 4P1L amps in circulation, so it's very interesting to see how they are being designed.
Very cheap, very simple Formula: Mullard E180CC- 4P1L with G3 to anode, G2 running in separate winding, C-core OPT 3.5K - 8 Ohms. 5Y3 is rectified. It beats 300B on midrange. Schema is not available and I will try to draw it as detailed as possible.
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Hi!
Did you simulate with the primary inductance of the 1660/40mA? It will have maybe 30Hy or even less.
30mA/250V must be an op point with very low grid voltage. I would not give up the headroom capability of such a tube. But that is only my opinion...
Best regards
Thomas
Did you simulate with the primary inductance of the 1660/40mA? It will have maybe 30Hy or even less.
30mA/250V must be an op point with very low grid voltage. I would not give up the headroom capability of such a tube. But that is only my opinion...
Best regards
Thomas
Hi Thomas,
My simulation was with a 55H Lp. Need to check my notes anyway.
I did some measurements on the bench and with filament starved at 5V/1060mA Vgk=-6V, Vak=255V it does have very good headroom as with Vi=5Vpp, THD with CCS load is less than 0.01%. I could push bias down to -7v, but think 6V peak is enough.
Ale
My simulation was with a 55H Lp. Need to check my notes anyway.
I did some measurements on the bench and with filament starved at 5V/1060mA Vgk=-6V, Vak=255V it does have very good headroom as with Vi=5Vpp, THD with CCS load is less than 0.01%. I could push bias down to -7v, but think 6V peak is enough.
Ale
Hi!
Is that from the negative end of the filament to ground? Yes then it will be ok. Although I wuld prefer more headroom which always proved to sound better in my designs. That's why I run the 10Y in line stages typically at bias voltages of 20-25V
Best regards
Thomas
Is that from the negative end of the filament to ground? Yes then it will be ok. Although I wuld prefer more headroom which always proved to sound better in my designs. That's why I run the 10Y in line stages typically at bias voltages of 20-25V
Best regards
Thomas
