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4P1L DHT Line Stage

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#341
dirkwright said:
Can I ask, what is the purpose of R1 (1K)? I've seen this often when people use this CCS, but it does not appear to be necessary. The resistor does not improve the performance or serve any other function that I'm aware of. Why's it there?
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It does a couple things. First, it isolates stray CCS capacitance from the plate (and thus from the output signal). Second, it takes some heat off of the CCS.
 
#343
jpak said:
Andy or Ale, I read on Ale's blog that 4p1l gain stage (preamp) with 4p1l power amp is "too much of a good thing"; a bit too bright or revealing in nature? Apologies if this is twisting your words.

Do you guys still feel this is the case, or have there been advances in your 4p1l preamp circuits?
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We had a day of listening which included Ale, and we heard solid solid state class A, SIT class A, PP6B4G, SE300B and PSE4P1L amps in my home. General concensus was the SIT amp pleased most of us. The solid state amp and the 300b (which was a good one with Lundahl OPT) came bottom. The PP 6B4G amp with 4P1L drivers and 26 inputs all balanced was well liked as being clean and transparent but ultimately not quite as good on vocals. The SIT amp did just about everything well and was smooth and detailed. My PSE amp at that stage was driven by a 26 preamp but since then I've driven it straight off a new ES9023 DAC with 2v output which is cleaner and preferable.

In the original form, the sound was immediate, detailed and dynamic. What we wondered about since it was 4P1L into 4P1L was whether there was a slight edge due to multiplying odd order harmonics in two identical stages. I was less concerned with this than Ale. I rated the 4P1L amp on a par with the SIT amp and better than the rest. Ale preferred the SIT amp at the time but hasn't heard my 4P1L amp lately.

The multiplication effect, however perceptible it is, only applies to 2 stages of 4P1L, and should have no effect on a single line stage.
 
#346
andyjevans said:
We had a day of listening which included Ale, and we heard solid solid state class A, SIT class A, PP6B4G, SE300B and PSE4P1L amps in my home. General concensus was the SIT amp pleased most of us. The solid state amp and the 300b (which was a good one with Lundahl OPT) came bottom. The PP 6B4G amp with 4P1L drivers and 26 inputs all balanced was well liked as being clean and transparent but ultimately not quite as good on vocals. The SIT amp did just about everything well and was smooth and detailed. My PSE amp at that stage was driven by a 26 preamp but since then I've driven it straight off a new ES9023 DAC with 2v output which is cleaner and preferable.

In the original form, the sound was immediate, detailed and dynamic. What we wondered about since it was 4P1L into 4P1L was whether there was a slight edge due to multiplying odd order harmonics in two identical stages. I was less concerned with this than Ale. I rated the 4P1L amp on a par with the SIT amp and better than the rest. Ale preferred the SIT amp at the time but hasn't heard my 4P1L amp lately.

The multiplication effect, however perceptible it is, only applies to 2 stages of 4P1L, and should have no effect on a single line stage.
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I agree with Andy's comments here. This is a very subjective point of view and I'm not keen to create a debate at all. Simply 4P1L is a fantastic valve. From it's characteristics to its sound in every role in the system. From line-stage to output stage. You may want to build an amp or pre with it and make your own conclusions. I'm yet to try 4P1L in pentode as driver 🙂

Ale
 
#347
mogliaa said:
I agree with Andy's comments here. This is a very subjective point of view and I'm not keen to create a debate at all. Simply 4P1L is a fantastic valve. From it's characteristics to its sound in every role in the system. From line-stage to output stage. You may want to build an amp or pre with it and make your own conclusions. I'm yet to try 4P1L in pentode as driver 🙂

Ale
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I think Ale, Thomas and I share a love for the 46 and 801/10Y. We're pretty agreed on this. What stops me using them, though I have plenty, is that they are expensive in a day-to-day setup (I leave my amp on 24hrs) and they are harder to implement in filament bias. Ale has done it with the 46, and Thomas routinely does it with the 10Y, as I have also done. There's also the 26 but I've gone over to more beefy tubes with more current, since they are good as drivers and even outputs. The great thing about the 4P1L is that it's cheap, I have loads of them, and it sounds great as well.

All these tubes have decent gain. I've nothing sonically against the 2a3 or 300b but they're quite impractical in filament bias, they're expensive and they require more than 2 stages because of the reduced gain.

So for all these reasons I've chosen to use the 4P1L. It has the gain, the sound, filament bias and can be left on 24hr a day. That's my story and I'm sticking to it!

The other possibility is transmitting tubes with higher gain in a 2-stage amp. I love the idea, but I'm not going up to high voltages when I can use the 4P1L at less than 300v. Ale's more courageous than me.......
 
#348
Just wondering when the price of 4P1L will go up, after all this praise...😉
I, like Ale and Andy, am very fond of this wonderfull little tube. The PSE with 4p1l driver is a total success. I am building a second one with slight changes. Cant wait to hear the differences in sound, if any.
Indeed the 4p1l in place of driver or line stage can be quite microphonic. However, having a good stash to select from might help as a starting point. Then a good operating point, optimal starving filament, socket suspension and rings will definetely manage the microphony.
Andy, running the amp 24hours? Do you get any sleep..? 😉
Best,
Radu
 
#350
Abszero said:
Andy, running the amp 24hours? Do you get any sleep..? 😉
Best,
Radu
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I like to listen to music as I fall asleep. By now I can tell you what music sends you to sleep and what doesn't! Top of the list for me is modern gospel. You know - Jesus Loves You and so on. Definitely comforting. I'm not a believer, but I love modern gospel. Debussy piano music is good. And Meistersinger. Die Frau Ohne Schatten and Bluebeard's Castle is not good.... Zavod is really not good....

I've left my 4P1Ls in 24/7 for at least 6 months and they still worked fine. I didn't measure emissions, though. I imagine the input stage would be less affected.
 
#351
andyjevans said:
I like to listen to music as I fall asleep. By now I can tell you what music sends you to sleep and what doesn't! Top of the list for me is modern gospel. You know - Jesus Loves You and so on. Definitely comforting. I'm not a believer, but I love modern gospel. Debussy piano music is good. And Meistersinger. Die Frau Ohne Schatten and Bluebeard's Castle is not good.... Zavod is really not good....

I've left my 4P1Ls in 24/7 for at least 6 months and they still worked fine. I didn't measure emissions, though. I imagine the input stage would be less affected.
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This is excellect news. Over 4000 hours! Thank you.
 
#355
Nightpuma said:
Hi Merlin,

Well that is not so difficult;-) I am looking for experiences with tube vendors both indside and outside ebay
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Hi Nightpuma,
I bought them from different vendors. I started with gstube.com where they have nice sockets too. I bought also from tubes-store.com and siberian shop. Recently I had un unpleasant experience with sovtube.com. They sent me nasty looking tubes ( all tested good but a lot of dents and aluminum oxide). Never bought from ebay.
Hope this helps.
Best,
Radu
 
#360
P9270188.jpg

get dressed!
Continued after striptease 😀 http://www.diyaudio.com/forums/tubes-valves/190857-4p1l-dht-line-stage-34.html#post3878052
 
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