Hard to compare as haven't tried any other capacitors or preamp other than 26 with an OT.
Have to say they sound really nice....
Well, fixed the Salas HV regulator. Set the shunt to nearly 70mA. Had to tweak the current set resistor to two 33 ohm in parallel (simulation suggested a 33 ohm resistor though).
Now the 50Hz and 100Hz peaks are even lower than before
did a quick listening test against the 26 preamp. Had to use the CD since the gain of the 4P1L stage is a tad too much for my system when using the RIAA preamp as well. Played Bach's organ works just to listen to the difference at the bass.
Both configurations are different. My 26 preamp is loaded with a LL1660 and also has Rod Coleman's filament boards and filament bias. I tried my best pair of RCA CX-226 which have a distortion level of 0.03%
First impressions:
1. The 4P1L is definitely a great match to the 26 preamp.
2. The 26 preamp has a slightly better bass response. I may need to tweak the 4P1L gyrator as suggested earlier to improve this. Also will do a frequency response test to confirm if there is a significant difference.
3. 4P1L sounds slightly brighter in my opinion.
4. The CX-226 can also be microphonic. I don't have these valves suspended as I have the 4P1Ls, however the decay of the ringing is faster than 4P1Ls when you tap them. You really need to turn the volume up and tap them hard to get them ringing though.
Have to do more side by side testing, but so far, "the Siberian" has proved to be a cracking line stage and at a really low budget!
Cheers,
Ale
Now the 50Hz and 100Hz peaks are even lower than before
did a quick listening test against the 26 preamp. Had to use the CD since the gain of the 4P1L stage is a tad too much for my system when using the RIAA preamp as well. Played Bach's organ works just to listen to the difference at the bass.
Both configurations are different. My 26 preamp is loaded with a LL1660 and also has Rod Coleman's filament boards and filament bias. I tried my best pair of RCA CX-226 which have a distortion level of 0.03%
First impressions:
1. The 4P1L is definitely a great match to the 26 preamp.
2. The 26 preamp has a slightly better bass response. I may need to tweak the 4P1L gyrator as suggested earlier to improve this. Also will do a frequency response test to confirm if there is a significant difference.
3. 4P1L sounds slightly brighter in my opinion.
4. The CX-226 can also be microphonic. I don't have these valves suspended as I have the 4P1Ls, however the decay of the ringing is faster than 4P1Ls when you tap them. You really need to turn the volume up and tap them hard to get them ringing though.
Have to do more side by side testing, but so far, "the Siberian" has proved to be a cracking line stage and at a really low budget!
Cheers,
Ale
Attachments
Have been listening to both preamps for a while now. Have regularly played same record with one preamp and then switch to the other and played it back again. Sometimes particular songs which I know quite well and my ears would notice a subtle difference between both preamps.
Today, I played a couple of times "Closing Time" from Tom Waits. The 4P1L is as good or even better than my 26. Bass is tight, crystal clear and overall great response to dynamics. I also have to say that the microphonic feedback of this valve is not noticeable. I can't distinguish any coloration in the sound and also can hear the ringing if I tap the glass properly at high volume with no music playing - not a realistic scenario!
Final veredict from my side: 4P1L is a perfect choice for a low budget! I used same power supply though and probably 90% of the total budget is on the power supply!
Anyone fancy a listening test in London?
Today, I played a couple of times "Closing Time" from Tom Waits. The 4P1L is as good or even better than my 26. Bass is tight, crystal clear and overall great response to dynamics. I also have to say that the microphonic feedback of this valve is not noticeable. I can't distinguish any coloration in the sound and also can hear the ringing if I tap the glass properly at high volume with no music playing - not a realistic scenario!
Final veredict from my side: 4P1L is a perfect choice for a low budget! I used same power supply though and probably 90% of the total budget is on the power supply!
Anyone fancy a listening test in London?
Why is it a realistic choice only for small budgets. Are there any more expensive direct heated tubes that will perform significantly better? 
BTW, thanks for sharing your experience. It's nice to see such good performance. The 4P1L is quite a winner. I wonder how people will find it subjectively.
BTW, thanks for sharing your experience. It's nice to see such good performance. The 4P1L is quite a winner. I wonder how people will find it subjectively.
I suppose 46 or 10Y/801a is a great choice as well. Also a good pair of globe CX-226/326s are really pricey! Why not going for this lovely russian DHT?
I think that if the same effort is spent on the power supply the difference between a 4P1L preamp and a 46 preamp might be minuscule.
Perhaps I will generate with this an increase on the price of the 4P1L now?
I doubt it. There is no shortage of them on eBay.
*4P1L* can be a nice tricks
but too late
Why? Only drawback is microphony which can be managed effectively...
Agree. My HT supply is a Mesh Telefunken AZ1, CLCL stage with oil caps and salas shunt, that's why all budget is burnt here! Lt supply includes Rod Coleman Regulators...
Testing new pair of Fullmusic 45/n
An externally hosted image should be here but it was not working when we last tested it.
Aha, this is the point I wanted to make. IMHO, the 26 has a bit of an advantage here; easier to find an IT that can do low current.
Yes, fully agree but: compare the cost of an LL1660 against a MOSFET gyrator
Or just wind your own choke for the 4P1L. That's easy and can be down on the cheap.
That's way beyond my skills, I wish I could do that!
Missed this part. I guess I look like a lunatic now until someone else comes up with a similar experience. So looking forward to someone else who is willing to try the 4P1L in filament bias, lower filament current, suspended valve sockets and gyrator loaded to see what his/her feedback is
Hi Anatoliy,
Traced some curves on both 4P1L and 12P17L to compare both triode strapped performance. See attached.
12P17L is really linear albeit it has greater gm than the 4P1L. Valve book says gm=6 for 4P1L and gm=8 for 12P17L.
I thought you may find the 12P17L plot useful.
Also plotted the 4P1L with filaments running at 500mA which is how I used them on my Siberian Preamp. You can see that curves are flatter than when filament current is 660mA (both filaments in parallel).
Cheers,
Ale
