I've built 2 so far, but haven't yet tried Ale's gyrator. One uses a Hammond 126C just as plate choke with a FT-3 cap. the other uses a LL1635/5mA. Both sound nice, but I need to drive a 4P1Lx2 output stage with the 01A stage, so will have to look at a solid state buffer stage, as Ale describes in Tony's 01A preamp.
Sound is very detailed but needs more fullness and weight - it's a bit thin with 3mA attempting to drive a parallel 4P1L output stage.
Sound is very detailed but needs more fullness and weight - it's a bit thin with 3mA attempting to drive a parallel 4P1L output stage.
Hi Andy
Looks like we almost on the same line. Lol
Yes with such a small current & high output impedance it will
sound lightweight unless a tube or ss buffer with higher current
is added. You should try the Buf03 . When build with the right parts
& power supply, it is very very neutral & has a certain warmth.
Im building this stage with colemean regs as well as ales gyrator
cause I need the max mu in this stage & I want it to be quiet too
Pls do try the Buf03 you'd be surprise with it
Cheers
Looks like we almost on the same line. Lol
Yes with such a small current & high output impedance it will
sound lightweight unless a tube or ss buffer with higher current
is added. You should try the Buf03 . When build with the right parts
& power supply, it is very very neutral & has a certain warmth.
Im building this stage with colemean regs as well as ales gyrator
cause I need the max mu in this stage & I want it to be quiet too
Pls do try the Buf03 you'd be surprise with it
Cheers
Hi Andy yes its not manufactured now but you still can buy them in Ebay.
Circuit is very very simple. If you don't mind pls google Aunt Corey Buf03
preamp in stereophile. Use only +- 15 as opposed to articles 18v also build
it in mono mono with seperate power supplies to each Buf03. This makes huge
difference
Circuit is very very simple. If you don't mind pls google Aunt Corey Buf03
preamp in stereophile. Use only +- 15 as opposed to articles 18v also build
it in mono mono with seperate power supplies to each Buf03. This makes huge
difference
About one year ago I want to modify my (CCS loaded) #26 preamp to switchable 01/26 one.
Tested 01 in my -breadboard- test equipment (filament bias, R.C. regulators, CCS load, SSHV as B+), the sweep was very interesting: the HF rolloff was very prominent. :-o
The cause of rolloff was the few meters of RG58 coaxial cable (my scope was in the other side of the room) due to the preamp poor driving capacity at HF.
At this time Ale also tested 01 preamp. Discussed with him this symptom, suggested to use his gyrator. I tried it, but the result was the same, the gyrator loaded 01 driving capacity at HF remains limited, and output impedance not decreased significantly.
Later Ale experienced the same (http://www.bartola.co.uk/valves/dht-pre-amplifier/01a-preamp-gen2/), so suggest to use low output resistance source follower after 01.
I like 01 tube, but want to use it without lesser sand (I use source followers to drive grid current hungry output tubes), so I started my -never ending?- experimenting with gyrators.
I don't want to modify my daily used #26 preamp, so built 10y/801 one and tried to use several gyrators (Ale's gyrator with different FETs, and another gyrators).
At summer I felt little urge to develop, but cool autumn is coming.
Simulations is hopeful (2SK170, J310, DN2540, BF862, 2N439x, AOT1N60), but "the truth is out there".
Tested 01 in my -breadboard- test equipment (filament bias, R.C. regulators, CCS load, SSHV as B+), the sweep was very interesting: the HF rolloff was very prominent. :-o
The cause of rolloff was the few meters of RG58 coaxial cable (my scope was in the other side of the room) due to the preamp poor driving capacity at HF.
At this time Ale also tested 01 preamp. Discussed with him this symptom, suggested to use his gyrator. I tried it, but the result was the same, the gyrator loaded 01 driving capacity at HF remains limited, and output impedance not decreased significantly.
Later Ale experienced the same (http://www.bartola.co.uk/valves/dht-pre-amplifier/01a-preamp-gen2/), so suggest to use low output resistance source follower after 01.
I like 01 tube, but want to use it without lesser sand (I use source followers to drive grid current hungry output tubes), so I started my -never ending?- experimenting with gyrators.
I don't want to modify my daily used #26 preamp, so built 10y/801 one and tried to use several gyrators (Ale's gyrator with different FETs, and another gyrators).
At summer I felt little urge to develop, but cool autumn is coming.
Simulations is hopeful (2SK170, J310, DN2540, BF862, 2N439x, AOT1N60), but "the truth is out there".
And this is one of the reasons that I choose to use the Buf03 cause input impedance is infinite which will make it a very light load for the 01A . The other benefit is high current drive & 2 ohm output impedance. Right now I've been listen just to the Buf alone & it really sounds impressive. Will know if HF is roll off the minute I hook up the 01As
ver
ver
Well, not YET!
I prepared by collecting some 01A's and am aiming for a balanced preamp. Currently running a 4P1L pre using THE gyrators plus a Coleman-like heater thing, with a MOSFET follower to drive the output transformer, cause I (currently) don't need the gain.
To me this sounds really nice so far & visiting acoustical observers did not complain.
I'm in the transition towards a complete balanced set-up. First thing to obtain is a RIAA, a preamp with gain (01A) and a dual mono amp based on a silicon "triode" the 2SK82 SIT. It'll be based on my current amp: a parafeed hybrid SET with a 4P1L driving the 2SK82.
Ulruch
I never really understood the concept of pre/power amplifiers if the system was not using phono font end. All you need to do is couple the output of 01A to the next stage with an inch or two of wire, and be done with it. Hybrid mu-follower is good for this and DC coupling is always possible, but may require redesign of the following stages.
LH/S
LH/S
Yes - I agree, but you can use different chassis. I've now separated the output stage of my amp (4P1L PSET) from the line (=driver) stage so it's more convenient to try different versions of the line stage. I just have 2 stages. But they're right next to each other so minimal interconnects, and work off the same HT.
I've tried out 4P1L, 26 and 01A line stages and the 01A wins. Not by much - the others are good - but by enough to prefer it. Just a bit more detail, air and realism.
I will be building 3 versions of a 01A line stage
1. Ale's gyrator
2. Plate choke using 126C
3. Interstage coupling, using LL1635/5mA and LL1660/5mA
So far I have the LL1635 version up and running and very pleased indeed with the basic sound.
So, your final implementation of 01A will have it as a 'line stage' on a separate chassis to your '2 stage power amp' ?..
LH/S
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No - I only use 2 stages total. This is possible with 4P1L outputs because they have a mu of 11.
I previously put both stages in the one chassis, with outboard PSU and filament supplies. I've now separated the output stage (2x4P1L) chassis from the input stage chassis. You can call the input stage any version of "driver", "line stage", whatever...... It's just the one stage that drives the output stage. Short interconnects, and the chassis are side by side. Gives me the ultimate flexibility in finding out my favourite input stage and my favourite output stage. At present this is 01A input into 2x4P1L outputs with LL1664/70mA OPT. I also flirt with 1x4P1L output into LL1682/50mA, which has its virtues especially with human voice, but isn't as solid overall as the dual 4P1L version.
I previously put both stages in the one chassis, with outboard PSU and filament supplies. I've now separated the output stage (2x4P1L) chassis from the input stage chassis. You can call the input stage any version of "driver", "line stage", whatever...... It's just the one stage that drives the output stage. Short interconnects, and the chassis are side by side. Gives me the ultimate flexibility in finding out my favourite input stage and my favourite output stage. At present this is 01A input into 2x4P1L outputs with LL1664/70mA OPT. I also flirt with 1x4P1L output into LL1682/50mA, which has its virtues especially with human voice, but isn't as solid overall as the dual 4P1L version.
4P1L likes at least 30mA in outputs, though 25mA isn't impossible. But the LL1682 is 8K into 8 ohms. The anode impedence of the 4P1L is around 2K so that would be quite a mismatch. two 4P1L really need 3K to 4.5K, somewhere there. I'm happy with the LL1664/70mA, it's perfect without going into Hashimoto, Monolith etc. I also have a LL1620/80mA which can be configured for 3K or 5K, but that doesn't sound as good as the LL1664.
... in conjunction with the bias voltage of the output stage which determines the output swing across the OPT primary - but I take your point.
LH/S
if every half watt counts , then yes.
with higher imp. you get better distortion profile,more pleasing.