4P1L diff driver gain is not too much, with parafeed OPT the overall gain is about 20dB.
If you use 01A as input tube (about 17dB with Ale's gyrator), the gain is -about- 70, so you need some attenuating.
Attachments
I started out with three stages, but with my Mark Audio Alpair 10s in a smallish room I found that PSE 4P1Ls are just enough as outputs, so ended up with 2 stages, first being the 01A Gen 2. I feed them with a ES9023 DAC and it needs all the output that gives - around 2v probably. Nice to manage with 2 stages if you can, and in my case all filament bias. I use twin 4P1L outputs, but three is possible or you can go PP and double up. Wise to wire the 4P1L filaments in series here, so less heat generated in the cathode resistors.
Intersting schematic...may I ask why you have introduced two 100ohm resistors between the ccs and the cathodes ? I have build as well a diff pair 4p1l-preamp, but connected the ccs straight to the cathodes...so try to learn from you...
Resistors in those positions can be used to control the (differential) gain, if needed - i.e. lower gain with increased resistance.
If you want maximum gain, no resistor is needed.
If you want maximum gain, no resistor is needed.
Right...plus I guess they introduce a local NFB / reduce maybe a bit distortion plus gives a bit of auto-bias / protection if one tube fails...right ?
Yes, a little degenerative feedback.
The bias protection may help a little, but 40mA tail-current in one 4P1L will drop most of the supply voltage in the anode-resistor, already.
The bias protection may help a little, but 40mA tail-current in one 4P1L will drop most of the supply voltage in the anode-resistor, already.
New Thread?
YES!! I have the headset, oldish, in the draw with a handful of Coleman boards and 4P1L's...
The Newbie
YES!! I have the headset, oldish, in the draw with a handful of Coleman boards and 4P1L's...
The Newbie
I would wire the ll1660pp in standard PP way, i think the 5k plate resistors are giving too low loadline= more THD. 🙁 It lowers also the gain.
If REALLY want to use OPT in "parafeed", then why not add gapped chokes ...
Or 2x Ua + SiC 1700 fet gyrators...driving the 1660 as fake-parafeed
If REALLY want to use OPT in "parafeed", then why not add gapped chokes ...
Or 2x Ua + SiC 1700 fet gyrators...driving the 1660 as fake-parafeed
Hi Rod,
I'd just like to say thanks for a great circuit. Just finished building the Bartola 01a line stage with your filament regulators. It's a wonderful combination and the regulators worked without any hassles.
John
I'd just like to say thanks for a great circuit. Just finished building the Bartola 01a line stage with your filament regulators. It's a wonderful combination and the regulators worked without any hassles.
John
Hello,
Rod just told me my 2 regulators for my 5687 line preamp have been send.
Right now i am using LM350 with Lundahl LL1694 choke input.
For the pair of regulators, each supplying 6,3 volt 0,9A to one 5687 i will use the same transformer ( split bobbin EI ) SBYV28-100-E3 diodes. The LL1694 will be wired for 40 mH so i will need around 300mA through a bleeder resistor just to be sure.
Morgan Jones did publish on Linear Audio about snubbers across diodes. In ther end he concluded that 1nF with 1Kohm in series across the secondairy will work perfect in most cases. 1nF should be something like silver mica or just any cap what the resistor power rating, kind of resistor?
Kind greetings, Eduard
Rod just told me my 2 regulators for my 5687 line preamp have been send.
Right now i am using LM350 with Lundahl LL1694 choke input.
For the pair of regulators, each supplying 6,3 volt 0,9A to one 5687 i will use the same transformer ( split bobbin EI ) SBYV28-100-E3 diodes. The LL1694 will be wired for 40 mH so i will need around 300mA through a bleeder resistor just to be sure.
Morgan Jones did publish on Linear Audio about snubbers across diodes. In ther end he concluded that 1nF with 1Kohm in series across the secondairy will work perfect in most cases. 1nF should be something like silver mica or just any cap what the resistor power rating, kind of resistor?
Kind greetings, Eduard
Hello Eduard,
Snubber across the transformer secondary is OK, yes.
Vishay/BC 338 series is good for snubber use:
BFC233860102 | Vishay 1nF Polypropylene Capacitor PP 300 V ac +-20% Tolerance Through Hole MKP 338 Series | Vishay
Carbon composition for the resistor (non-inductive):
CBT50J1K0 NEOHM - TE CONNECTIVITY, Through Hole Resistor, 1 kohm, 350 V, Axial Leaded, 500 mW, +- 5%, CBT Series | Farnell element14
Snubber across the transformer secondary is OK, yes.
Vishay/BC 338 series is good for snubber use:
BFC233860102 | Vishay 1nF Polypropylene Capacitor PP 300 V ac +-20% Tolerance Through Hole MKP 338 Series | Vishay
Carbon composition for the resistor (non-inductive):
CBT50J1K0 NEOHM - TE CONNECTIVITY, Through Hole Resistor, 1 kohm, 350 V, Axial Leaded, 500 mW, +- 5%, CBT Series | Farnell element14
Hello Rod,
I will see what i have in stock. I do have some self healing Rifa caps but it appears the new ones are more reliable.
Being on the sec side they also have to be self healing. Even with choke input AC voltage will be below 20 volts.
For the sensing resistor i need 1,1 ohm because 5687 draws 0,9 A.
Will it need readjustment too after installing a new tube after all it is not a DHT?
Greetings, Eduard
I will see what i have in stock. I do have some self healing Rifa caps but it appears the new ones are more reliable.
Being on the sec side they also have to be self healing. Even with choke input AC voltage will be below 20 volts.
For the sensing resistor i need 1,1 ohm because 5687 draws 0,9 A.
Will it need readjustment too after installing a new tube after all it is not a DHT?
Greetings, Eduard
Hello Eduard, Yes, it's always best to check that the heater voltage is correct, if you want the triode to have a long lifetime. 6.20-6.30V for preference.
Hello Rod and the others,
I hope the regulators will be delivered today.
The sensing resistor in my set up need to be 1,1 ohm. I have some 2,2 ohm to put in parallel. Do they need to be soldered at both sides of the circuit if not i can use use some cheap wirewounds untill Mills mra 12 will arrive. And installing will be a peace of cake
greetings, Eduard
I hope the regulators will be delivered today.
The sensing resistor in my set up need to be 1,1 ohm. I have some 2,2 ohm to put in parallel. Do they need to be soldered at both sides of the circuit if not i can use use some cheap wirewounds untill Mills mra 12 will arrive. And installing will be a peace of cake
greetings, Eduard
The PCB has some extra terminals for large-size R1, marked with a * in the silk-screen - so you can use those for the Mills.
All the holes are plated, so you can solder to one side only, if required.
All the holes are plated, so you can solder to one side only, if required.
Hello,
Got the Mundorf 22000µF caps plus the bleeder resistor ( necessary because of choke input) from the UK today. Your parcel posted one day before will hopefully arrive tomorrow.
In the past i did install 12 watt Mills where used to be a 2 watt in a pre amp. It was a BIG difference. Probably the difference between the supplied ones and the Mills in the R1 position will not be that big. Did find 1,1 ohm 10 watt Mills in the USA closer so far i could only find 2,2 ohm 12 watt to mount in parallel.
The circuit now is very basic LM350. Which got a choke input added a year ago.
Maybe your circuit is less inflenced by adding choke input but i will do it from the start!
Greetings, Eduard
p.s if anyone knows a supplier of mra 10 or 12 1,1 ohm please let me know
Got the Mundorf 22000µF caps plus the bleeder resistor ( necessary because of choke input) from the UK today. Your parcel posted one day before will hopefully arrive tomorrow.
In the past i did install 12 watt Mills where used to be a 2 watt in a pre amp. It was a BIG difference. Probably the difference between the supplied ones and the Mills in the R1 position will not be that big. Did find 1,1 ohm 10 watt Mills in the USA closer so far i could only find 2,2 ohm 12 watt to mount in parallel.
The circuit now is very basic LM350. Which got a choke input added a year ago.
Maybe your circuit is less inflenced by adding choke input but i will do it from the start!
Greetings, Eduard
p.s if anyone knows a supplier of mra 10 or 12 1,1 ohm please let me know