Slightly OT but since I mentioned it.... I got curious and made a "simple" 2P29L preamp using some Hammond 126C interstages I wasn't using. These are used as plate chokes with a couple of 0.1uF Russian teflon FT-2 output caps in parallel. Usual stuff for me.
Well, guys, this is a serious alternative to a 4P1L line stage. It's lovely - lots of detail, loads of treble and bass. In short, exactly what you would expect from a top DHT. And useful gain as well - should be a mu of around 9. It sounds surprisingly good in this simple implementation. Food for thought - another cheap Russian military tube that sounds great. No microphonic for me either.
Early days - I've only been listening for 15 minutes, but I like what I hear so far.
Well, guys, this is a serious alternative to a 4P1L line stage. It's lovely - lots of detail, loads of treble and bass. In short, exactly what you would expect from a top DHT. And useful gain as well - should be a mu of around 9. It sounds surprisingly good in this simple implementation. Food for thought - another cheap Russian military tube that sounds great. No microphonic for me either.
Early days - I've only been listening for 15 minutes, but I like what I hear so far.
Attachments
Hello andyjevans--
what tube do you prefer...4P1L or 2P29L and why
i have bought the 2P29L but i can see it is a bit difficult to mount on my K&K 4P1L socket print
just today i tried Caddock 15 ohm 30w for the resistor to heater
the sound i absolute nice,,,i use normal Mills 50w,,but i think i prefer the Caddock
Best Bjarne
what tube do you prefer...4P1L or 2P29L and why
i have bought the 2P29L but i can see it is a bit difficult to mount on my K&K 4P1L socket print
just today i tried Caddock 15 ohm 30w for the resistor to heater
the sound i absolute nice,,,i use normal Mills 50w,,but i think i prefer the Caddock
Best Bjarne
Hi Bjarne
I just had the 4P1L into 126B and 2P29L into 126C in my system. The 4P1L was more solid, but the 2P29L had a bit more life and detail, so right now I have the 2P29L in my system. I'll have to A-B it with my 01A/Gyrator line stage and see which I prefer of those. In any case, the 01A replaced the 4P1L and the 26 into 126C so I know that's a preference. Haven't tried 4P1L or 26 into a gyrator yet, or the 2P29L.
I just had the 4P1L into 126B and 2P29L into 126C in my system. The 4P1L was more solid, but the 2P29L had a bit more life and detail, so right now I have the 2P29L in my system. I'll have to A-B it with my 01A/Gyrator line stage and see which I prefer of those. In any case, the 01A replaced the 4P1L and the 26 into 126C so I know that's a preference. Haven't tried 4P1L or 26 into a gyrator yet, or the 2P29L.
Last edited:
Yes - me too. I tried out several Lundahls. They're good and arguably can be smoother, but the Gyrator has more life and detail. I do still like plate chokes as well.
Andy...more life and detail ? Hmmm...I just build a 4p1l line stage and try to understand where my 3D-pin-point holografic presentation is gone which I had before...could be the ll1692a the issue ?
I guess I need to try...as my DAC has fully balanced output, I need minimum two balanced in and on SE out....has anyone done this with Ale's boards ?
I believe Allan K. suggested to connect two triodes on their cathodes and give the second cathode half of B+ on its anode, while the other triode has the mu-follower....makes sense ?
I guess I need to try...as my DAC has fully balanced output, I need minimum two balanced in and on SE out....has anyone done this with Ale's boards ?
I believe Allan K. suggested to connect two triodes on their cathodes and give the second cathode half of B+ on its anode, while the other triode has the mu-follower....makes sense ?
One fundamental thing some people fail to understand is that using transformer loading at signal level requires that tubes and circuit must adapt to the transformer and never the contrary. So there is usually very little choice and very little room for playing, assuming the transformer is good enough for the job....
I don't use balanced any more but when I did some years ago I used the secondary of Hammond 124B as a plate choke, centre tap to HT. Worked very well - it's part nickel.
http://www.hammondmfg.com/pdf/124B.pdf
Last edited:
It is not suitable.
datasheet: TPAS-201 Datasheet - Tamura Corporation of America - Datasheets360.com
I see.
It is low impednace and cannot take DC current. Maybe it could be used in parafeed reversing primary with secondary (i.e. 600R to 300 R) and driven by a proper cathode follower or low plate resistance tube.
After playing several weeks with the same configuration (4P1L into 4P1L), it was pleasing to get back the 01a, in this case a revised UV-201a (short-pin brass base old valves) with a source follower output. Here are the design and build notes
My amp has only one stage of 4P1L PSE and despite being manageable well with a 01a at 3mA in terms of slew rate, I can notice a nice improvement in the overall detail at the treble side. I already praised and enjoy my friend Tony’s 01a preamp which has a simpler follower stage (not this one). It’s revealing to see that the addition of a well implemented source follower stage has no noticeable detriment in the sound. In fact, the 01a works in better conditions which allows it to perform at its best when loaded with a more demanding capacitive load (due to Miller effect).
I will continue to listen to this stage for a while to give firmer impressions.
Cheers
Ale
My amp has only one stage of 4P1L PSE and despite being manageable well with a 01a at 3mA in terms of slew rate, I can notice a nice improvement in the overall detail at the treble side. I already praised and enjoy my friend Tony’s 01a preamp which has a simpler follower stage (not this one). It’s revealing to see that the addition of a well implemented source follower stage has no noticeable detriment in the sound. In fact, the 01a works in better conditions which allows it to perform at its best when loaded with a more demanding capacitive load (due to Miller effect).
I will continue to listen to this stage for a while to give firmer impressions.
Cheers
Ale
It's hard to rank all of them as I have used them over a wider timeframe and makes it difficult to do a fair comparison. However, at this point my preferences are as follows:
1) VT25 and 01a: both come at top of the list to me. Blaming or not thoriated tungsten filaments can be, but I find a clarity of sound and detail above the other DHTs. The 01a has probably it's unique tone but the VT25 is more neutral.
2) 4P1L - it was revealing to me to implement this stage again with the gyrator after so many years of experimenting with other DHTs. Again, this valve sounds superbly. A bit more challenging on the microphonic noise, however it can be managed with some care to very good levels. It can drive any load, which is great. Also the higher anode current is better for bass response of the gyrator
3) 2P29L - a great discovery. I liked it sound a lot as you found as well. Unfortunately my mule system mutated to fit the 4P1L so can't play it again. Will have to build another version
4) 26 - classic
5) CX-112a very nice. It can provide more driving due to its current capability compared to the 01a. It's neutral and sounds very good. No thoriated sound magic though...
6) CX-299 - I loved the sound of it, but fragile and very microphonic unfortunately.
Well, this is very subjective of course, but you know my system and in the past we both have reached to similar impressions so it may be a good list for others to take into account.
I was disappointed recently with the 3B7 and the 2J27L. There are other ones to try still, but not enough time am afraid!
Cheers
Ale
1) VT25 and 01a: both come at top of the list to me. Blaming or not thoriated tungsten filaments can be, but I find a clarity of sound and detail above the other DHTs. The 01a has probably it's unique tone but the VT25 is more neutral.
2) 4P1L - it was revealing to me to implement this stage again with the gyrator after so many years of experimenting with other DHTs. Again, this valve sounds superbly. A bit more challenging on the microphonic noise, however it can be managed with some care to very good levels. It can drive any load, which is great. Also the higher anode current is better for bass response of the gyrator
3) 2P29L - a great discovery. I liked it sound a lot as you found as well. Unfortunately my mule system mutated to fit the 4P1L so can't play it again. Will have to build another version
4) 26 - classic
5) CX-112a very nice. It can provide more driving due to its current capability compared to the 01a. It's neutral and sounds very good. No thoriated sound magic though...
6) CX-299 - I loved the sound of it, but fragile and very microphonic unfortunately.
Well, this is very subjective of course, but you know my system and in the past we both have reached to similar impressions so it may be a good list for others to take into account.
I was disappointed recently with the 3B7 and the 2J27L. There are other ones to try still, but not enough time am afraid!
Cheers
Ale
Ok, guys...I need your help: I just changed the configuration of my line-stage opt (LL1692A-PP) http://www.lundahl.se/wp-content/uploads/datasheets/1692A.pdf from 1.75+1.75:1 (Push-pull-->SE), Alt N. to 1:75+1,75:2+2...and from a perfectly working operations have now horrible, loud white noise with some nasty hizzzzzzz on top !
What is going on here ?
So, the primary is untouched, two 4p1l playing into it with approx. 27mA/170V as LTP with a ccs in the tail.
I want to have a fully differential/balanced chain as my Dac is balanced, my power amp is http://www.triodedick.com/monobill/monobill schema versterker.GIF...
I have not a lot of experience with IT...so I guess I made somewhere a stupid mistake. What I did:
- Changed the input stage to accept positive and negative input, one 330k grid to ground for each grid (so 660k from grid to grid).
- Instead using xlr, I used my cinch cable to get plus and negative signal to the amp. I am using one ground cable to connect ground Line stage to power amp, so that the reference for the signal is there.
The hizz noise is immediately as well recognizable, even when the power amp is out, you can hear the resonance from the OPT...it seems to oscillate hefty and the windings seem to move...but I triple checked that Alt M. is comfigured as it should be.
So, are these Modes only good if a powertriode is following immediately between driver and powertriode ? Not foe a balanced linestage ? Or should I omitt the 330k grid to ground resistors of the input tube of the power amp, so that the grids get grounded through the secondaries of the OPT ?
What is going on here ?
So, the primary is untouched, two 4p1l playing into it with approx. 27mA/170V as LTP with a ccs in the tail.
I want to have a fully differential/balanced chain as my Dac is balanced, my power amp is http://www.triodedick.com/monobill/monobill schema versterker.GIF...
I have not a lot of experience with IT...so I guess I made somewhere a stupid mistake. What I did:
- Changed the input stage to accept positive and negative input, one 330k grid to ground for each grid (so 660k from grid to grid).
- Instead using xlr, I used my cinch cable to get plus and negative signal to the amp. I am using one ground cable to connect ground Line stage to power amp, so that the reference for the signal is there.
The hizz noise is immediately as well recognizable, even when the power amp is out, you can hear the resonance from the OPT...it seems to oscillate hefty and the windings seem to move...but I triple checked that Alt M. is comfigured as it should be.
So, are these Modes only good if a powertriode is following immediately between driver and powertriode ? Not foe a balanced linestage ? Or should I omitt the 330k grid to ground resistors of the input tube of the power amp, so that the grids get grounded through the secondaries of the OPT ?