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4P1L DHT Line Stage
4P1L DHT Line Stage
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Old 4th December 2017, 02:03 PM   #1431
Blitz is offline Blitz  Germany
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Hi Ale,

So, I continued my work now more on the pratical side and build a complete new base (heavy+on rubber feet), used NOS Russian sockets this time and build in switches for anode and g3 which allow me to try different combinations.

Here are my impressions:
- G3 at cathode gives a certain "sound". Quiet musical. And that is the sound I am used to at the moment as the sockets I used sofar (from Kevin C.) have this as the build in default.
- G3 at the anode makes the muscial sound veil go away and you have a more honest, but as well less romantic presentation. A bit more clearer as well and better, deeper room. But I need to compare these two modes a bit more to really conclude.
- Anode connected to cathode, so that G2 and G3 become the new Anode: Another step into refinement. More and finer details. But subjectively less loud, less dynamic, less body and soul in the music. Not sure, that I will become a fan of this. I need to gain more experience.

I believe we are here now at a point where you can hear any detail regarding component selection etc. Especially when g2 and g3 become the anode and alle the current go through the two grid-stopper (100ohm) I had still in the game.

Some good news on this mode: You can raise at 150V the total current through the tube to 24mA and g2 will stay in its 1.5W limit. Even going above 1.5W to 1.8W did not make anything red. Ale, so no need to stay at 10mA...

I guess my questions / projects for the next weekend are:
- What is the best sounding g2/g3-stopper ? I used Mills NS(non-inductive)-WW, but I have these under suspicion that they make up for the metallic sound going from g3 to cathode to MEsh, where the sound of these become more and more prominent as more and mor current goes through them.
- Ale, if I saw it right you omitted the grid resistor in MESH completely, right ?
- Shall I try to not connect the anode at all ?
- Put an aquarium onto the tubes (seriously a nano cube)

The disappointing news: I can still clap my hands and get music from the speaker. Not, its not Alexa, its the 4p1l. Even with the heavy sockets, the 5mm Aluminium-plate they are attached to and the rubber-subchassis: These guys are really microphonic like hell. So, I will finish my tests on the right setup and than move on to the 2p29l and the 10y/801A is waiting to challenge those as well...

Best Regards

Frank

Last edited by Blitz; 4th December 2017 at 02:10 PM.
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Old 4th December 2017, 02:32 PM   #1432
RhythMick is offline RhythMick  United Kingdom
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Quote:
Originally Posted by Soundhappy View Post
Hipster or SteamPunk-er Kindest regards
Steampunk Amplifier: 10 Steps (with Pictures)
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Old 4th December 2017, 03:38 PM   #1433
andyjevans is offline andyjevans  United Kingdom
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Hi Frank

I've always connected g2+g3+anode directly. If I read you correctly, there isn't a very good reason to change this?
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Old 4th December 2017, 04:52 PM   #1434
Blitz is offline Blitz  Germany
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Hmm...I believe most people use between 100-300ohm to prevent oscillations...but if you had no issues with connecting directly: I will try this for sure alternatively, the ferrites Rod Coleman suggested might be as well a try...but next weekend I will follow your route...and use BBC Europe on LW to see if there are any oscillations...
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Old 4th December 2017, 07:09 PM   #1435
andyjevans is offline andyjevans  United Kingdom
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Quote:
Originally Posted by Blitz View Post
Hmm...I believe most people use between 100-300ohm to prevent oscillations...but if you had no issues with connecting directly...
I don't know if I have oscillation issues - haven't measured very high frequencies. Maybe I should put some grid stoppers in. This is just for the output stage, PSE, that I'm talking about.
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Old 6th December 2017, 08:51 AM   #1436
frentec is offline frentec  United Kingdom
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Default 4P1L using Grid as Anode.

Hi Blitz,
I have built a version of Ale's 4P1L line stage, this is in the normal anode mode, but am about to alter this & run it in what Ale calls screen mode, I do feel that the actual valve is not as coloured (less romantic) than some others. Does this add more timbre & depth to the sound? I am using Ale's Gyrator Boards & find them to be excellent, are You using Transformer Output?
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Old 9th December 2017, 03:59 PM   #1437
danielyk8 is offline danielyk8  United Kingdom
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Hi all,

I am building my 2P29L, not extactly 4P1L. I am using ALe circuit on his website. Can I ask if I put a 100k pot at input, do L need to adjust the grid leak resistor R9 49k value?
Thanks
Daniel
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Old 10th December 2017, 12:42 PM   #1438
Blitz is offline Blitz  Germany
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Ok, I continue my work on the 4p1l...

So, as I said: You clap your hands and your system claps for you...the microphony of the 4p1l is really bad. Lowering the heater voltage makes it a bit better, but not really stops it. And it sounds not as good imho.

So, I was looking for the ultimate tube damper...and found it:

IMG 1527 — imgbb.com

A heavy piece of brass, I estimate nearly a lb per piece from your friendly plumber store...You wrap the tube in white teflon tape, which makes the brass fit tightly and which as well gives a little vibration dampening...but most importantly now we have MASS around the tube and it is 95% quiet...the rest will be killed in the v2 version of this marvelous damper ("The Blitz Damper" all rights reserved ).

On the listening impression, the short story is:
- getting rid of the resistors was a big step in naturalness, better dynamics etc.
- running the 4p1l with 22mA/194V in both, Mesh with g2 and g3 as anodes vs. both of them plus anode: I believe Mesh gives you more inside without any downside. Regarding Plate dissipation: At 24mA/150V I measured g2 within 1.5W limit. Someone with a lot of experience (Kees) who is using pentodes for the last 10 years this way, told me: As the anode is not used and stays cold, the dissipation at g2 can be 25% higher...which gives us 4.5W dissipattion limit for g2+g3 together. This sounds still very powerful.

Last edited by Blitz; 10th December 2017 at 01:03 PM.
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Old 10th December 2017, 01:13 PM   #1439
Blitz is offline Blitz  Germany
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What I found out as well: It is now so tranparent that it makes anything you do with your PSU EXTREMELY audible. I had a solid stated CCS and a OD3 in (like Lynn Olson in the Karna): Something odd, unnatural, like a hand-brake was still on. Changed this to a LCLC with amorphous chokes (the marvelous stuff from AE50): WOOOOOOOW, it CAN sing !

Last edited by Blitz; 10th December 2017 at 01:16 PM.
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Old 10th December 2017, 01:13 PM   #1440
nikosokey is offline nikosokey  Greece
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IMG 1527 — imgbb.com
excellent idea I will try it.
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Last edited by nikosokey; 10th December 2017 at 01:33 PM.
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