Thank you for responding. I did try the pull up/push down "maneuver", but only once since the russian sockets are so incredibly tight. That didn't fix anyting but perhaps you are right. I will try it some more. I have tried changing the tubes between channels as well but that didn't do anything either.
I see that the silver plating on the sockets have some oxidation, but haven't looked closely at pins on the tubes since the noise doesn't seem to follow the tubes. DeoxIT sounds expensive. Is there some other remedies that could be used?
I see that the silver plating on the sockets have some oxidation, but haven't looked closely at pins on the tubes since the noise doesn't seem to follow the tubes. DeoxIT sounds expensive. Is there some other remedies that could be used?
My friend Tony (who also owns a 01a preamp) came around yesterday for a listening session. We ended up comparing the following preamps using my current system including 4P1L PSE, Alpair 10M / FT96H speakers and source mostly used was Starlight CD Transport with Discrete DAC. The 4P1L PSE has no driver stage, so there is actually 2 stages including the preamp in test.
We ended up playing Gwilym Simcock's "Perception" CD as a reference record during the tests. We found it the right one given its dynamics, piano and selection of tracks.
The following preamps were auditioned:
1. VT-25 VT-25 DHT Preamp Update – Bartola Valves
2. 01a 01a Preamp Gen2: Build Complete – Bartola Valves
3. SX-301a (short pin) older version UV-201a preamp test – Bartola Valves
4. 2P29L triode: 2P29L DHT Preamp – Bartola Valves
It was an exciting afternoon where we had a lot of fun. The preamps were easily interchangeable in a matter of 2-3 minutes, so the comparisons were easier to a certain extent.
I won't rank them, as this is quite subjective, but I'd rather share some comments from our listening session:
1. VT-25: I found it to be the best match in my system. However, Tony was slightly inclined for the 01a
2. 01a: The classic 01a is unique. It has a clarity and there is something in the overall tone that it makes it unique.
3. SV-201a: these are very old globe valves with brass bases. We found it very close to the 01a (CX-301a) but with a slight edge on the treble. I'd probably blame the valves. Albeit, the filament resistor and the gyrator components are not my latest preferred choice. I should upgrade this preamp and re-test.
4. 2P29L: this was a great surprise. It simply sounds great and is not microphonic. Quite unusual for an DHT with low current filament. I think is probably one of the only ones I have found that behave like this. They are all mostly very microphonic. This little fellow (albeit there is no glow coming out which will put off many audiophiles) sounds very good. It's quite close to the 01a despite not having the tungsten filaments. I'd put it at my top list of preferred DHTs now. It's dirt cheap (for now) and can also be a great driver given its linearity. Very easy to implement in filament bias.
Well, just some random notes of a great afternoon under the scorching weather here in London
Cheers
Ale
We ended up playing Gwilym Simcock's "Perception" CD as a reference record during the tests. We found it the right one given its dynamics, piano and selection of tracks.
The following preamps were auditioned:
1. VT-25 VT-25 DHT Preamp Update – Bartola Valves
2. 01a 01a Preamp Gen2: Build Complete – Bartola Valves
3. SX-301a (short pin) older version UV-201a preamp test – Bartola Valves
4. 2P29L triode: 2P29L DHT Preamp – Bartola Valves
It was an exciting afternoon where we had a lot of fun. The preamps were easily interchangeable in a matter of 2-3 minutes, so the comparisons were easier to a certain extent.
I won't rank them, as this is quite subjective, but I'd rather share some comments from our listening session:
1. VT-25: I found it to be the best match in my system. However, Tony was slightly inclined for the 01a
2. 01a: The classic 01a is unique. It has a clarity and there is something in the overall tone that it makes it unique.
3. SV-201a: these are very old globe valves with brass bases. We found it very close to the 01a (CX-301a) but with a slight edge on the treble. I'd probably blame the valves. Albeit, the filament resistor and the gyrator components are not my latest preferred choice. I should upgrade this preamp and re-test.
4. 2P29L: this was a great surprise. It simply sounds great and is not microphonic. Quite unusual for an DHT with low current filament. I think is probably one of the only ones I have found that behave like this. They are all mostly very microphonic. This little fellow (albeit there is no glow coming out which will put off many audiophiles) sounds very good. It's quite close to the 01a despite not having the tungsten filaments. I'd put it at my top list of preferred DHTs now. It's dirt cheap (for now) and can also be a great driver given its linearity. Very easy to implement in filament bias.
Well, just some random notes of a great afternoon under the scorching weather here in London
Cheers
Ale
Hi Ale,
2P29L is a very nice surprise. I've built a module that uses all low filament current DHT in the 50mA-150mA range and I've never got one that is not very microphonic. The most microphonic was the CX-199.
Too bad that the 2P29L can only be used up to a certain output voltage.
Cheers,
Radu
2P29L is a very nice surprise. I've built a module that uses all low filament current DHT in the 50mA-150mA range and I've never got one that is not very microphonic. The most microphonic was the CX-199.
Too bad that the 2P29L can only be used up to a certain output voltage.
Cheers,
Radu
Hi Radu.
I believe the 2P29L can do 250V: http://www.mif.pg.gda.pl/homepages/frank/short/054/2/202.pdf . Perhaps a bit more as most of the Russian valves. I haven't tried though.
I was surprised as I was expecting same microphonic feedback as most of low filament current DHTs. I'm actually using it with my "Mule" preamp which is simply an Ikea chopping board and the sockets are bolted to it without damping.
Unfortunately the CX-199, as you say, is very microphonic. I do liked the sound of it, a nice contender.
If I get time, I will do some tests on the 2P29L as driver. Too many projects, not enough time!
I have also around the 2P29P and the 2P27L and 2P27P to test in the list. I'd expect some differences between them of course.
Cheers
Ale
I believe the 2P29L can do 250V: http://www.mif.pg.gda.pl/homepages/frank/short/054/2/202.pdf . Perhaps a bit more as most of the Russian valves. I haven't tried though.
I was surprised as I was expecting same microphonic feedback as most of low filament current DHTs. I'm actually using it with my "Mule" preamp which is simply an Ikea chopping board and the sockets are bolted to it without damping.
Unfortunately the CX-199, as you say, is very microphonic. I do liked the sound of it, a nice contender.
If I get time, I will do some tests on the 2P29L as driver. Too many projects, not enough time!
I have also around the 2P29P and the 2P27L and 2P27P to test in the list. I'd expect some differences between them of course.
Cheers
Ale
Too bad you didn't put a 4P1L preamp in with the others.
I don't have any 2P29L. I'm probably happy with my 01As, and I have plenty. But as a slightly higher current tube I'd like to know how the 2P29L compares with the 4P1L. I'm guessing you like it better as a single stage.
Also, what is a 4Z1L? I have one - can't find any data. It's a metal loctal as well.
I don't have any 2P29L. I'm probably happy with my 01As, and I have plenty. But as a slightly higher current tube I'd like to know how the 2P29L compares with the 4P1L. I'm guessing you like it better as a single stage.
Also, what is a 4Z1L? I have one - can't find any data. It's a metal loctal as well.
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Ale,
That is a very sad reality...too many valves to experiment with and very little time.
I had the opportunity to play with the majority of the popular DHTs lately and indeed I have preferences, but I haven't got one that was not sounding good.
I'll buy some of these 2P29Ls before the price is skyrocketing..
)
Cheers,
Radu
That is a very sad reality...too many valves to experiment with and very little time.
I had the opportunity to play with the majority of the popular DHTs lately and indeed I have preferences, but I haven't got one that was not sounding good.
I'll buy some of these 2P29Ls before the price is skyrocketing..
)Cheers,
Radu
Hi Andy,
We should do an amp/preamp shooting together soon, I spoke about it with Tony.
The 4Z1L is low current IHT: http://www.mif.pg.gda.pl/homepages/frank/short/054/1/153.pdf, is this the one you have?
Yes, shame I couldn't compare with the 4P1L. I need to rebuild my 4P1L with gyrator load so I can compare it.
These are all great DHTs and you can't get wrong with any of them.
Cheers
Ale
After listening for some time to the 2P29L, I tried the 2Ж27Л / 2Z27L. It was a simple upgrade and worth trying:
2?27? / 2Z27L DHT Preamp – Bartola Valves
Despite it measures really well and sounds great, I found it a bit tiring after listening to it for some time. There is something in the treble that I don’t like. Specially when listening to any brass arrangements. I did not measure any significant H3, so am puzzled. Well that is why listening tests provide the ultimate veredict!
I then went back to the 4P1L as my Gen4 setup:
4P1L (4?1?) Siberian Gen4 – DHT Preamplifier – Bartola Valves
Same concept, slightly adjusted operating point and choices in the gyrator. This has been my optimal configuration after trying so many DHTs over the last years.
The sound is fantastic, better than before incarnation. Definitely the gyrator load is the best in my view. Detail, clarity and flat response up to 3MHz. It does sound very well in my system and I like the 4P1L into 4P1L. Before I heard a similar setup in Andy's previous system and there was something in the treble which we didn't like. It was a transformer coupled version as well as a choke loaded one we tried. Anyhow, the system wasn't the same. I do like this 4P1L version and will keep it for some time to get further impressions on its sound.
Cheers
Ale
2?27? / 2Z27L DHT Preamp – Bartola Valves
Despite it measures really well and sounds great, I found it a bit tiring after listening to it for some time. There is something in the treble that I don’t like. Specially when listening to any brass arrangements. I did not measure any significant H3, so am puzzled. Well that is why listening tests provide the ultimate veredict!
I then went back to the 4P1L as my Gen4 setup:
4P1L (4?1?) Siberian Gen4 – DHT Preamplifier – Bartola Valves
Same concept, slightly adjusted operating point and choices in the gyrator. This has been my optimal configuration after trying so many DHTs over the last years.
The sound is fantastic, better than before incarnation. Definitely the gyrator load is the best in my view. Detail, clarity and flat response up to 3MHz. It does sound very well in my system and I like the 4P1L into 4P1L. Before I heard a similar setup in Andy's previous system and there was something in the treble which we didn't like. It was a transformer coupled version as well as a choke loaded one we tried. Anyhow, the system wasn't the same. I do like this 4P1L version and will keep it for some time to get further impressions on its sound.
Cheers
Ale
Andy,
The fact that you can run higher current is key to make this circuit to operate at its best. This is possible with the 4P1L and the 10Y/VT-25. It can be done with other DTHs, but gain is lower around 3-4. Unfortunately the 01a can only do 3-4mA. I may try some day the EML20 but need to save for that.
With higher current, the lower FET can perform better as the output impedance is 1/gm. Gm is dependent to drain current. The more the better.
I suggest you try the 2P29L with the BSH111BK/IXTP08N100D pair. That is the best gyrator I've tried so far.
Cheers
Ale
The fact that you can run higher current is key to make this circuit to operate at its best. This is possible with the 4P1L and the 10Y/VT-25. It can be done with other DTHs, but gain is lower around 3-4. Unfortunately the 01a can only do 3-4mA. I may try some day the EML20 but need to save for that.
With higher current, the lower FET can perform better as the output impedance is 1/gm. Gm is dependent to drain current. The more the better.
I suggest you try the 2P29L with the BSH111BK/IXTP08N100D pair. That is the best gyrator I've tried so far.
Cheers
Ale
Hi Ale,
I have bought gyrator boards from you month ago and i got schematic for 4p1l preamp.
I see that you have done so many modifications that i can not follow anymore...
So please if you can take one minute and clear me some things that i can finally made best version of this preamp not to modify it every week.
Schematic in last page shows some differences according from that you send me.
1.Another fet...i will unsolder BF no problem... can i use bss138 or any other fet instead bsh111 or is bsh111 best choice?
2.Why are diodes on bsh fet sometimes oriented face to face sometimes back to back when i see different schematics at your page..what kind of diodes are they... ?
3. 100nf capacitor is sometimes connected after 10R sometimes before 10R?
4. no 300 Ohm grid resistors on any schematic till now...i will use it, any recommendation what kind...dale holco, takman, AN? Can be from 180-300R? if i don*t have exactly 300R.
5. another change in voltage for coleman reg (9,45v)... i have bought 2pcs 12Vac-1.3A transformers and 2pcs 15vac-1.3A transformers...which is best to use?
6.For B+ raw supply you presented choke supply at your page. can you post any schematic for raw supply before gyrators. I have bought 220V-150mA and 200V-150mA transformers ...which one to use ? No raw supply with tubes please....
I will use potentiometer on input. What is the best value for input pot?
Thank you for all your answers. That i can finally make your preamp and listen to music.
I have bought gyrator boards from you month ago and i got schematic for 4p1l preamp.
I see that you have done so many modifications that i can not follow anymore...
So please if you can take one minute and clear me some things that i can finally made best version of this preamp not to modify it every week.
Schematic in last page shows some differences according from that you send me.
1.Another fet...i will unsolder BF no problem... can i use bss138 or any other fet instead bsh111 or is bsh111 best choice?
2.Why are diodes on bsh fet sometimes oriented face to face sometimes back to back when i see different schematics at your page..what kind of diodes are they... ?
3. 100nf capacitor is sometimes connected after 10R sometimes before 10R?
4. no 300 Ohm grid resistors on any schematic till now...i will use it, any recommendation what kind...dale holco, takman, AN? Can be from 180-300R? if i don*t have exactly 300R.
5. another change in voltage for coleman reg (9,45v)... i have bought 2pcs 12Vac-1.3A transformers and 2pcs 15vac-1.3A transformers...which is best to use?
6.For B+ raw supply you presented choke supply at your page. can you post any schematic for raw supply before gyrators. I have bought 220V-150mA and 200V-150mA transformers ...which one to use ? No raw supply with tubes please....
I will use potentiometer on input. What is the best value for input pot?
Thank you for all your answers. That i can finally make your preamp and listen to music.
Well, I don't have much spare time am afraid so I will answer as much as I can. You may get some extra help from the people out here.
I'd suggest you build it with the BF862 and set the current to 25mA. If you like it, you can then upgrade it to BSH111BK. Soldering the BSH111BK in the Rev06 requires a lot of skill in SMD soldering as you need to mount it in 45 degrees. I have now Rev07 boards which fit the BSH111BK.
I've written before in my blog some observations regarding the lower FETs. Take a look and study a bit more.
In the BSH111BK, the diodes are included inside the transistor case, so no need to add them so you should not solder D1 and D2. You should always include D3 which protects the FET. These are normal 15-18V zener type as described in the BOM.
As they are back to back Zeners its irrelevant if you place them anode to anode or cathode to cathode.
If I ever terminated 10R sensing resistor before C1, it has been a typo. In the board C1 terminates before 10R resistor. Having said that, it does not make any difference in the performance of the circuit should you decide to implement a point to point circuit.
No, not need to be exact 300R. I previously used ferrite beads and have recently added it given the high bandwith of this amplifier stage which may enter into oscillation if you don't take the right measures.
There is plenty of advice in this forum around grid stoppers, just do a search.
Make sure you solder the resistor at the solder tag of your socket.
No change, just filament voltage is slightly different as I didn't have at hand 15R resistor for the type of wirewound I wanted to use. The coleman regulator you purchased (if for starved 4P1L 500-550mA) should work just fine. You need to set it up to 550mA. I suggest you get yourself familiarised with the Rod Coleman Regulator documentation, it provides a lot of good information. Also the info on what raw supply to use for a 15V DC input. Rod is also able to advise as needed.
There are so many ways to build up a 15V DC supply, that you need to work that yourself based on the transformers and/or chokes you purchased or are willing to buy.
If you want to use silicon only, you can use same supply but you will get higher output voltage due to voltage drop by HV schottky/SiC diodes is much smaller than the dampers. You can read about how to use PSUD2 to design or see if anyone here has some cycles to design the supply for you.
Is all about noise/load compromise. Your choice but anything between 47k and 100k should work fine.
Thank you for all your answers. That i can finally make your preamp and listen to music.
Hope this helps. The design is so flexible that you can play easily with it once you built the PCB and test it carefully to avoid damaging the FETs. You can then tweak the operating point as you please. Also the gyrator can accommodate a wider range of raw HT, but the penalty is on the power dissipated in the TOP FET which requires a bigger heatsink the more HT you put on it.
Cheers
Ale
Hi Ale,
Thanks for all the work you have put into this project. I have your gyrator boards and most of the parts for a 4p1L pre-amp but keep getting distracted by other projects!
A quick question - what is the approx. minimum voltage you need to have across the gyrator for correct operation? I would like to have the lowest practical PS voltage as it is just easier with the transformer I have.
Thanks,
Rod
Thanks for all the work you have put into this project. I have your gyrator boards and most of the parts for a 4p1L pre-amp but keep getting distracted by other projects!
A quick question - what is the approx. minimum voltage you need to have across the gyrator for correct operation? I would like to have the lowest practical PS voltage as it is just easier with the transformer I have.
Thanks,
Rod
Thank you Ale.
Answers are all i need. I do preamp for my friend and i don*t have time that he will come to me every week to do some modicifications. I totaly trust your design becauss you spent a lot of time with it. I will do best versiion available and going on with other projects. Maybe i got idea to do 4p1l soekris dac output because raw output is poor. What is minimum gain that i can get it with 4p1l without any feedback? A can do attenuation and some filtering on input to get around 3-3.5vrms out. I saw Lampizator did thar maybe worth trying. Thank you again Davorin
Answers are all i need. I do preamp for my friend and i don*t have time that he will come to me every week to do some modicifications. I totaly trust your design becauss you spent a lot of time with it. I will do best versiion available and going on with other projects. Maybe i got idea to do 4p1l soekris dac output because raw output is poor. What is minimum gain that i can get it with 4p1l without any feedback? A can do attenuation and some filtering on input to get around 3-3.5vrms out. I saw Lampizator did thar maybe worth trying. Thank you again Davorin
Hi Daovrin,
The gain of the 4P1L in triode mode is about 8-9. With the gyrator load you get close to this gain (mu) or about 19dB. This may be too much gain in your system, I don't know. Generally most of the solid state amps and/or integrated systems are designed for 2Vrms sensitivity. However you have the option to control volume digitally which is an advantage but I don't know whether the DAC will sound better at lower level. You can try this easily and listen to it to make an informed decision.
Cheers
Ale
Hi Rod,
I believe this has already been covered many times before, but here you go.
Assuming you have a 2Vrms (2.82 Vpeak) maximum input and that you're biasing the valve at 150V. You probably have about 170V maximum at idle at the source of the top MOSFET (DN2540/IXTP08N100D). You need at least 25V across the source - drain of the top MOSFET (Vds) to operate effectively an minimise the capacitances (Crss/Coss). For the IXTP08N200D, if you check the data sheet you will see that minimum voltage is 10-15V. With a gain of 8-9 of the 4P1L, the output will swing to 25Vpeak maximum. That means you will need 170V+25V+25V=220V. This would be the safest minimum raw HT voltage. If you're not going to operate the 4P1L at full swing, then you can adjust accordingly and reduce the HT level.
Cheers
Ale
Hi Ale, Yes, plenty of design information for raw DC available.
For 15V dc for Filament Bias with 4P1L, there is a special Design Note, with all the build details and parts:
http://lyrima.co.uk/pdf/FilamentBias_Supply.pdf
Other documentation for V7 Regulators is listed:
Rod Coleman DHT Filament Regulator
