Hi Andy,
I agree with hpeter regarding the impedance of the OT.
I've just finished a 45 amp that I will post soon. I'm using James 6115HS and have the option to switch between 5k and 7K. Despite reducing a bit the output power, the 7k sounds more pleasant, just because of reduced distortions. However, both 5k and 7k have the predominant second harmonic.
Best,
Radu
I agree with hpeter regarding the impedance of the OT.
I've just finished a 45 amp that I will post soon. I'm using James 6115HS and have the option to switch between 5k and 7K. Despite reducing a bit the output power, the 7k sounds more pleasant, just because of reduced distortions. However, both 5k and 7k have the predominant second harmonic.
Best,
Radu
Back to 01A preamps. Just built a nice sounding version of Ale's Gen 2 preamp.
Filament supply worked out nicely - 50VA 18+18v transformer into Hammond 159Y 600mH, 750mA, choke input. Gives exactly 15v into Rod Coleman boards for filament bias. I'm a believer in choke input here - smoother sound.
Filament supply worked out nicely - 50VA 18+18v transformer into Hammond 159Y 600mH, 750mA, choke input. Gives exactly 15v into Rod Coleman boards for filament bias. I'm a believer in choke input here - smoother sound.
Attachments
Question about resistors - Ale's Gen 2 preamp uses a 20 ohm cathode resistor in filament bias, which should be at least 2W. Basic good quality is Welwyn vitreous enamel wirewound W22, 7W
Has anybody tried out some more exotic ones?
- Audio note tantalum 2W:
Audio Note Tantalum Resistors | Hifi Collective
Audio Note Resistors | Hifi Collective
Audio Note Tantalum Non-magnetics Resistors | Hifi Collective
Dueland standard and CAST 10W
Duelund Standard Graphite Silver Resistors | Hifi Collective
Duelund CAST Graphite Silver Resistors | Hifi Collective
Mundorf Supreme
Mundorf M-Resist Supreme 20 W | Hifi Collective
Mills wirewound non-inductive 5W
Mills | Hifi Collective
Ohmite Audio Gold wirewound 5W
Ohmite Audio Gold Resistors | Hifi Collective
Kiwame Carbon film 2W
Kiwame | Hifi Collective
Pathaudio 10W
Pathaudio Resistors 10 Watt 1% | Hifi Collective
Shinkoh tantalum 2W
Shinkoh Tantalum Resistors | Hifi Collective
TKD metal film 2W
TKD 2W Metal Film Resistor | Hifi Collective
Has anybody tried out some more exotic ones?
- Audio note tantalum 2W:
Audio Note Tantalum Resistors | Hifi Collective
Audio Note Resistors | Hifi Collective
Audio Note Tantalum Non-magnetics Resistors | Hifi Collective
Dueland standard and CAST 10W
Duelund Standard Graphite Silver Resistors | Hifi Collective
Duelund CAST Graphite Silver Resistors | Hifi Collective
Mundorf Supreme
Mundorf M-Resist Supreme 20 W | Hifi Collective
Mills wirewound non-inductive 5W
Mills | Hifi Collective
Ohmite Audio Gold wirewound 5W
Ohmite Audio Gold Resistors | Hifi Collective
Kiwame Carbon film 2W
Kiwame | Hifi Collective
Pathaudio 10W
Pathaudio Resistors 10 Watt 1% | Hifi Collective
Shinkoh tantalum 2W
Shinkoh Tantalum Resistors | Hifi Collective
TKD metal film 2W
TKD 2W Metal Film Resistor | Hifi Collective
If you use 20R bias resistor, the dissipation is 1.25W.
In my practice 2W resistor is at the border for 1.25W dissipation, especially if you use it within the box.
IMHO at least 3-5W is necessary.
For example Mills 5W tend to deep browning even at 50% of nominal dissipation. At 100% sometimes "elongate" the resistance and stay that way.
Very good resistors, but I use 12W ones up to 5-6W dissipation!
I use tantalum (Shinkoh) 2W resistors as cathode resistors. If the dissipation is greater than 1-1.2W, I use two parallel resistors.
Kiwame -and my favorite WW resistor Welwyn- chargeable to the limit, and does not change. I use these resistors "everywhere".
Mundorf Cast graphite is unique resistor, I now order ones to try in Rod Coleman regulator.
IMHO TKD is better in power supplies or bias equipments (I use these resistors in Ale's gyrator).
In my practice 2W resistor is at the border for 1.25W dissipation, especially if you use it within the box.
IMHO at least 3-5W is necessary.
For example Mills 5W tend to deep browning even at 50% of nominal dissipation. At 100% sometimes "elongate" the resistance and stay that way.
Very good resistors, but I use 12W ones up to 5-6W dissipation!
I use tantalum (Shinkoh) 2W resistors as cathode resistors. If the dissipation is greater than 1-1.2W, I use two parallel resistors.
Kiwame -and my favorite WW resistor Welwyn- chargeable to the limit, and does not change. I use these resistors "everywhere".
Mundorf Cast graphite is unique resistor, I now order ones to try in Rod Coleman regulator.
IMHO TKD is better in power supplies or bias equipments (I use these resistors in Ale's gyrator).
Hi - very useful. Ale's Gen 2 starves the filaments at 200mA so the dissipation is more like 0.9W. I'd prefer a 5W part as you say, but a bit interested in some of these more exotic ones that just go up to 2W. Maybe just for testing in the first instance - I can parallel up later if they're audibly better.
So as a cathode resistor, would you expect Dueland CAST or Tantalum to sound better than Welwyn W series? I'm guessing Mills would not be a step up...?
So as a cathode resistor, would you expect Dueland CAST or Tantalum to sound better than Welwyn W series? I'm guessing Mills would not be a step up...?
As cathode resistor Mills and Welwyn also good, but a Welwyn is more "hifi", and Mills is more "calm". BTW I prefer ww resistors in anode or cathode circuit, better than metal film or carbon resistors.
Shinkoh is better (very good -extended- bandwith with 3D imaging) in this position, if it is unblocked (I usually avoid R//C in cathode).
I have not tried graphite resistor in this position.
Shinkoh is better (very good -extended- bandwith with 3D imaging) in this position, if it is unblocked (I usually avoid R//C in cathode).
I have not tried graphite resistor in this position.
Ayrton-Perry means a type of bifilar winding technique, as you say. Where did you source your resistors, and what make? The kind of winding may not be obvious unless explicitly stated. I imagine these were vitreous enamel surplus stock? Harder to get these days.
Well, I got the clip leads out and am testing cathode resistors for the Gen 2 preamp. This may well be the road to madness. It means listening for tiny differences - really tiny, since the differences so far are not striking. Sometimes it's simply a gut reaction with no obvious explanation. I've tried 4 kinds so far:
1. Dale Stackable wirewound 10R, 20W, surplus stock off ebay. Ale and I bought a bunch but they're sold out a while ago. These were maybe the most neutral, and the ones I've used up to now especially in 4P1L inputs and outputs. On this occasion I found them to be neutral, as stated, but slightly "uninvolving". This is simply gut reaction - I can't put my finger on why.
2. Welwyn W22 20R vitreous enamel wirewound. These were probably the clearest. I was feeling a suspicion of something edgy - again on the level of a gut reaction. They were slightly more "involving" and lively than the Dales.
3. Russian 51R marked C5-5-10. These are 50mm long in the body and I assume 10 watts. They look ceramic. I paralleled two with a 3W 82R wirewound of good quality. The sound in this case was the most mellow, smooth and pleasant, though the treble seemed to be all there without being compromised. Gut reaction was positive. Nothing edgy here. i missed some of the positive qualities of the Welwyns. Safe choice.
4. Unnamed wirewounds marked C1 C or CI C. 5W, hollow construction. These were good too, quite an immediate sound. Similar sound to the Welwyns - clear with a suspicion of edginess. I preferred the Welwyns.
My 4P1Lx2 output stage is clear with a suspicion of edginess, so the Welwyns might simply be the most faithful, and the Russian wirewounds might be slightly rounding the sound.
No obvious conclusion here. I've left the Russian wirewounds in for now. Slightly more "likeable" to my ears and in my system.
1. Dale Stackable wirewound 10R, 20W, surplus stock off ebay. Ale and I bought a bunch but they're sold out a while ago. These were maybe the most neutral, and the ones I've used up to now especially in 4P1L inputs and outputs. On this occasion I found them to be neutral, as stated, but slightly "uninvolving". This is simply gut reaction - I can't put my finger on why.
2. Welwyn W22 20R vitreous enamel wirewound. These were probably the clearest. I was feeling a suspicion of something edgy - again on the level of a gut reaction. They were slightly more "involving" and lively than the Dales.
3. Russian 51R marked C5-5-10. These are 50mm long in the body and I assume 10 watts. They look ceramic. I paralleled two with a 3W 82R wirewound of good quality. The sound in this case was the most mellow, smooth and pleasant, though the treble seemed to be all there without being compromised. Gut reaction was positive. Nothing edgy here. i missed some of the positive qualities of the Welwyns. Safe choice.
4. Unnamed wirewounds marked C1 C or CI C. 5W, hollow construction. These were good too, quite an immediate sound. Similar sound to the Welwyns - clear with a suspicion of edginess. I preferred the Welwyns.
My 4P1Lx2 output stage is clear with a suspicion of edginess, so the Welwyns might simply be the most faithful, and the Russian wirewounds might be slightly rounding the sound.
No obvious conclusion here. I've left the Russian wirewounds in for now. Slightly more "likeable" to my ears and in my system.
For #26 and 10Y (10-15W dissipation!) I use 10R 50W (aluminium housed) Vishay NH (non inductive Ayrton-Perry, bought from Mouser 8.5 EUR). http://www.vishay.com/docs/30201/rhnh.pdf
I also have some 10R 10W NS type (Vishay - RS, NS - Wirewound Resistors, Industrial, Precision Power, Silicone Coated, Axial Lead) Ayrton-Perry (good up to 350 °C) which is enough cheap (2-3 EUR), but never tried as filament bias resistor.
I also have some 10R 10W NS type (Vishay - RS, NS - Wirewound Resistors, Industrial, Precision Power, Silicone Coated, Axial Lead) Ayrton-Perry (good up to 350 °C) which is enough cheap (2-3 EUR), but never tried as filament bias resistor.
Some years ago I have a test: noise measuring (- #26 - preamp on breadboard, filament bias, Rod Coleman regulator).
The object was minimizing 50-100Hz components on the R.C. regulator output (with changing of raw supply values).
Surprisingly I encountered barrier, the 50Hz hum not diminished below few (3-4) mV (on 10V DC).
DHT preamp is oversensitive of filament bias noise, so it was unacceptable. I don't understand this thing, the same preamp in my equipment was dead silent (100uV at 50Hz).
After some speculation I decoded the origin of the problem: the filament bias resistor!
In the test equipment the filament bias resistor was the old 10W (Tesla) wirewound, which was inductive, so in the windings -as in the coil- induced radiated hum (and some radio station
).
Conclusion: the physics know one's stuff. Don't use there simple coil type resistor!
The object was minimizing 50-100Hz components on the R.C. regulator output (with changing of raw supply values).
Surprisingly I encountered barrier, the 50Hz hum not diminished below few (3-4) mV (on 10V DC).
DHT preamp is oversensitive of filament bias noise, so it was unacceptable. I don't understand this thing, the same preamp in my equipment was dead silent (100uV at 50Hz).
After some speculation I decoded the origin of the problem: the filament bias resistor!
In the test equipment the filament bias resistor was the old 10W (Tesla) wirewound, which was inductive, so in the windings -as in the coil- induced radiated hum (and some radio station
).Conclusion: the physics know one's stuff. Don't use there simple coil type resistor!
I think I put a Sfernice (Vishay) but it was almost two years ago. Not quite sure. I'd have to "open the hood" to check.
01a Gen2 - new build
I built another 01a preamp with slight modifications on the components:
The gyrator FETs are DN2540+BF862. Filament bias is changed slightly to accommodate the Russian NOS wirewound that Andy recommended. These sound amazing. We did a comparison with a set of alligator clips with Andy and they do sound better than other wirewound in our opinion.
Output caps are teflon FT-3. Rest as usual.
More info here:
01a Preamp Gen2: Build Complete – Bartola Valves
Cheers
Ale
I built another 01a preamp with slight modifications on the components:
The gyrator FETs are DN2540+BF862. Filament bias is changed slightly to accommodate the Russian NOS wirewound that Andy recommended. These sound amazing. We did a comparison with a set of alligator clips with Andy and they do sound better than other wirewound in our opinion.
Output caps are teflon FT-3. Rest as usual.
More info here:
01a Preamp Gen2: Build Complete – Bartola Valves
Cheers
Ale
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Hi Guys
Advice pls. Been researching the above tube. Notice that aside from 01A numbering,
I see SX 201A, UX 201A, CX 301A etc. Are they all the same tube type.
Many Thanks
-------------------------------------------------------------------
Pls excuse, I may have posted this a while ago. So for the curious & others, a summary of 5V toobz.
Advice pls. Been researching the above tube. Notice that aside from 01A numbering,
I see SX 201A, UX 201A, CX 301A etc. Are they all the same tube type.
Many Thanks
-------------------------------------------------------------------
Pls excuse, I may have posted this a while ago. So for the curious & others, a summary of 5V toobz.I just found this interesting page that Vinylsavor had linked from his page on the UX201A:
RCA UV-200 and UV-201 Series Tubes
Good stuff.
Cheers
Matt
RCA UV-200 and UV-201 Series Tubes
Good stuff.
Cheers
Matt
Hi Guys
Advice pls. Been researching the above tube. Notice that aside from 01A numbering,
I see SX 201A, UX 201A, CX 301A etc. Are they all the same tube type.
Many Thanks
-------------------------------------------------------------------
They are not. Brass based and tipped enveloped types have different characteristics, most notably Rp
LH/S
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I built another 01a preamp with slight modifications on the components:
The gyrator FETs are DN2540+BF862. Filament bias is changed slightly to accommodate the Russian NOS wirewound that Andy recommended. These sound amazing. We did a comparison with a set of alligator clips with Andy and they do sound better than other wirewound in our opinion.
Output caps are teflon FT-3. Rest as usual.
More info here:
01a Preamp Gen2: Build Complete – Bartola Valves
Cheers
Ale
Great stuff, always love this... quick question - when are you going to find a way to direct couple the 01A to the driver of the output tube and avoid the capacitor altogether.
To be honest, Ludwig is winding down to out. You guys get it so right and then completely **ck it up.. sorry, its beyond theory,... its a fact.
Lets talk about a resistor, get **ked you're just a dumb kunt.
Just.. wow (despair)... but you know ... with expectations come (_fill in the blank_)
LH/S
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