AP Chock
Hi Andy, just tried the AP 40mH chock from you, very very nice. I also used sic diode bias to -8.3v and found better than -7v. For 8.3v I only used 8x diodes. Cheers
Daniel
Hi Andy, just tried the AP 40mH chock from you, very very nice. I also used sic diode bias to -8.3v and found better than -7v. For 8.3v I only used 8x diodes. Cheers
Daniel
PS Choke
Hi Frank,
It's going back a while, but You mentioned that You went from CLCLC to CLC on HT power arrangements, was this as Lundahl recommend in differential mode? I am using Lundahl.
Hi Frank,
It's going back a while, but You mentioned that You went from CLCLC to CLC on HT power arrangements, was this as Lundahl recommend in differential mode? I am using Lundahl.
Another 4P1L is born, still needs a few tweaks before i button it up but it's 90% done. Big thank you to KevinC and Ale for your help and inspiration!
Layout is based around the Siberian Gen 3 schematic with Kevin's shunt regular supply, Rod Coleman regulators running filament bias, and CCS plate loads with a capacitor coupled output instead of some iron. Its big and hot and sounds fantastic, just like the F4 amp its driving
Thanks all!
Just reading through this thread again as i found a couple of gyrator boards i never implemented. Was surprised to find my post that i wrote after i built this pre amp, 5 years ago
Looking at my notes, i lifted the hood once in 2018 to check the bias, how is that for a testament of reliability and how good this thing sounds.
No exaggeration, it has been used every single day for the last five years, for 5-6 hours a day. Still love it so thanks again Ale and Rod for your contribution!
p.s. Gyrators, Lundahl, or leave it alone for another five years?
Attachments
Hello Ireland,
I like the way you mounted the two split bobbin transformers!.
You dont have much space for improvement.
If that is a choke in the center. You could try a Lundahl choke. How much henry, current and DCR is that choke if it is one? I like them a lot but i hate the flimsy soldering tags that they use on a lot of models. They need careful soldering.
Greetings, eduard
I like the way you mounted the two split bobbin transformers!.
You dont have much space for improvement.
If that is a choke in the center. You could try a Lundahl choke. How much henry, current and DCR is that choke if it is one? I like them a lot but i hate the flimsy soldering tags that they use on a lot of models. They need careful soldering.
Greetings, eduard
Just reading through this thread again as i found a couple of gyrator boards i never implemented. Was surprised to find my post that i wrote after i built this pre amp, 5 years ago
Looking at my notes, i lifted the hood once in 2018 to check the bias, how is that for a testament of reliability and how good this thing sounds.
No exaggeration, it has been used every single day for the last five years, for 5-6 hours a day. Still love it so thanks again Ale and Rod for your contribution!
p.s. Gyrators, Lundahl, or leave it alone for another five years?
I’d leave it as-is. Why do you want to change it? If you need more gain, you can try the gyrator load / mu-follower circuit. Easy to implement and revert if you don’t like it.
Nice to see you still love the preamp. A great one indeed.
Cheers
Ale
CLC vs CLCLC for 2P29L
Hi Flikoman,
I'm using filament bias(using diodes) with 2P29L using Ale's Gyrator Boards, but I have been playing with HT PSU, with varying results regarding sound quality, I was using CLCLC but I have now changed to CLC, this in my case has made a vast difference everywhere, I have not gone down the road with LCLC & listening to the sound I have, I may not. I had 2.7uF 20h, 45uf 10h 45uf, I now have 2.7uf 20h 90uf (linked the two 45uf's together). Everything just became free & open with bags of air & sparkle, choke is lundahl 1673, Rectifier is EZ81, All caps are film, either Mundorf or Clarity.
Hi Flikoman,
I'm using filament bias(using diodes) with 2P29L using Ale's Gyrator Boards, but I have been playing with HT PSU, with varying results regarding sound quality, I was using CLCLC but I have now changed to CLC, this in my case has made a vast difference everywhere, I have not gone down the road with LCLC & listening to the sound I have, I may not. I had 2.7uF 20h, 45uf 10h 45uf, I now have 2.7uf 20h 90uf (linked the two 45uf's together). Everything just became free & open with bags of air & sparkle, choke is lundahl 1673, Rectifier is EZ81, All caps are film, either Mundorf or Clarity.
That's pretty much my PSU - low value cap, choke and then 47uF doubled. All caps are polypropylene motor run. I use a separate PSU for the input stage of my 2-stage amp and I like to use a mesh rectifier like AZ1.
Using a separate PSU for the input allows the output PSU to just provide around 140mA (70+70) which is easier on all the components. Sounds nice too, and can be designed for just the voltage needed, e.g. 200v. Plus I may want to use driver tubes with 30mA of current. That's certainly desirable with a 4P1L. I use plate chokes.
Using a separate PSU for the input allows the output PSU to just provide around 140mA (70+70) which is easier on all the components. Sounds nice too, and can be designed for just the voltage needed, e.g. 200v. Plus I may want to use driver tubes with 30mA of current. That's certainly desirable with a 4P1L. I use plate chokes.
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CLC vs CLCLC for 2P29L
Hi Andy,
Yes as before, I've tried a lot of different approaches & valve types, but the little 2p29L running on AM Gyrator boards is hard to beat for me, it's an amazing find, but you have to play around with operating points & biasing. I'm going to give my filament supply a go with LCLC next, atm I'm running CRC on Rods PSU boards & V5 regulators, although I have no audible noise, I don't think it will detract from what I'm hearing. I do have terrible mains fluctuation here in France, they turn windmills on and off all the time here.
Hi Andy,
Yes as before, I've tried a lot of different approaches & valve types, but the little 2p29L running on AM Gyrator boards is hard to beat for me, it's an amazing find, but you have to play around with operating points & biasing. I'm going to give my filament supply a go with LCLC next, atm I'm running CRC on Rods PSU boards & V5 regulators, although I have no audible noise, I don't think it will detract from what I'm hearing. I do have terrible mains fluctuation here in France, they turn windmills on and off all the time here.
The 2P29L is a smoother sound to my ears than the 4P1L. A little "boring" maybe and doesn't have the treble sparkle of an 01A or the rich mids of a 26, but it doesn't have that brightness that can become aggravating with the 4P1L. It certainly has value as a choice, particularly running 17mA through it. I haven't used it for a while since I'm currently focussing on 10Y and 01A. Like that thoriated sound. Maybe I should pull out the 2P29L again and give it a whirl driving EL12n outputs which I'm playing around with.
The 4P1L has a good treble response - it's all there. Maybe its the "disembodied" mids that I'm not comfortable with - prefer a fatter sound or at least a neutral one with plenty of tone and body to instruments and voices. I've always found the 4P1L a little "thin". Needs high current of course, it's very thin under 20mA. I can't exactly put my finger on it but I hear something with the 4P1L I'm not entirely comfortable with. May of course be my implementations of it introducing resonances or distortion.
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I used a 4P1L pre for 5 years or so in my system and loved it, cant say i would ever call mine thin sounding.
Currently have CX-301A build up and running and its 100% going to replace the 4P1L. There is a delicacy to the 01a i have just fallen in love with..
I am surprised that Frentec is hearing much difference is power supply setup when the bulk filtering is in front of active regulator boards, wouldn't have thought there would be much difference once the ripple is low enough?
I stuck to solid state rectification on mine with SiC diodes into a 270uf-10H-270uf filter, Salas SSHV2 regulators boards, then into Ales Gyrator boards. If my modelling is right it should have about 1mv ripple before the regulators.
When i have this build done i might revisit the 4P1L and update it, or convert it to 2P29L out of curiosity
Currently have CX-301A build up and running and its 100% going to replace the 4P1L. There is a delicacy to the 01a i have just fallen in love with..
I am surprised that Frentec is hearing much difference is power supply setup when the bulk filtering is in front of active regulator boards, wouldn't have thought there would be much difference once the ripple is low enough?
I stuck to solid state rectification on mine with SiC diodes into a 270uf-10H-270uf filter, Salas SSHV2 regulators boards, then into Ales Gyrator boards. If my modelling is right it should have about 1mv ripple before the regulators.
When i have this build done i might revisit the 4P1L and update it, or convert it to 2P29L out of curiosity