This is my second tube project and i really would like to hear some opinons from you experienced guys out there, about the schematic i gotten:
Does it look good? Any values that need to be overlooked? Any room for improvments?
An externally hosted image should be here but it was not working when we last tested it.
Does it look good? Any values that need to be overlooked? Any room for improvments?
The 1660 is presumably wired 4.5:1, right? Looks fine although i am not particularly fond of non-bypassed cathode resistors. Consider replacing the resistor with a couple of NiCds as well.
analog_sa:
yes 4.5:a SE to line output.
What type of NiCd do you reccomend?
The person i got the schematic from used anoher value POT, im going to use as seen 250K, i dont have to change any values because of that? the one i had on mind was the 100k
yes 4.5:a SE to line output.
What type of NiCd do you reccomend?
The person i got the schematic from used anoher value POT, im going to use as seen 250K, i dont have to change any values because of that? the one i had on mind was the 100k
Is this a linear pot being log-faked by the 100k resistor? Then you would also need to reduce the resistor value in order to get a smooth pot action. Or just use a log pot and remove the resistor.
The batteries i currently use are NIMH and come from 900mA/h cellphone batteries. I use 2 cells for 2.4v bias.
The batteries i currently use are NIMH and come from 900mA/h cellphone batteries. I use 2 cells for 2.4v bias.
Hi,
i have built this nice pre-amp (called: Euridice) with the LL1660/18mA. In the normal connection the output level is too much. IMHO you don' t need 4,5:1.
Batterie biasing is a good way...
Greetings Barossi
i have built this nice pre-amp (called: Euridice) with the LL1660/18mA. In the normal connection the output level is too much. IMHO you don' t need 4,5:1.
Batterie biasing is a good way...
Greetings Barossi
analog_sa:
To be honest i dont know the type of the pot, its an alps black beauty marked: 643t 250KX2
I will look it up.
barossi&analog_sa:
As i understood you both are using batteries instead of cathode resistor. What have you compared with and what was the results?
To be honest i dont know the type of the pot, its an alps black beauty marked: 643t 250KX2
I will look it up.
barossi&analog_sa:
As i understood you both are using batteries instead of cathode resistor. What have you compared with and what was the results?
Not me. I generally dislike batteries in the cathode. Better than resistors, just not good enough. As i use a TVC my battery is in series with the input - it does not get recharged very effectively in this position but it also does not pass much (any?) current so it's sonics contribute a lot less colourations.
It's pointless talking about the sonic results if the PS is not shown. I use 83 rectifier with low DCR transformers and chokes (Lundahl) and Cerafine caps.
It is not essential. I guess it's only purpose is to keep negative bias for the tube if the wiper goes AWOL.
If you decide to use NiCd battery for this, just make sure it can stand the current. Look in the datasheet what charging current is OK.
It is also possible to use battery for bias and no cathode resistor at all.
For bypassing the cathode resistor, it is good to use tanthal electrolytics I´m told.
It is also possible to use battery for bias and no cathode resistor at all.
For bypassing the cathode resistor, it is good to use tanthal electrolytics I´m told.
Hi,
Sure, at the expense of using either a coupling cap or a xformer at the input.
That may have been the case about 15 years ago. Those are solid tantalum, I don't think there's any electrolyte inside of those. I'm not even sure they're still produced.
In any case the insulation voltage was no higher than 35VDC IIRC.
Nowadays excellent electrolytic caps such as the BGs will outperform any tantalum cap hands down.
Cheers,😉
Sure, at the expense of using either a coupling cap or a xformer at the input.
That may have been the case about 15 years ago. Those are solid tantalum, I don't think there's any electrolyte inside of those. I'm not even sure they're still produced.
In any case the insulation voltage was no higher than 35VDC IIRC.
Nowadays excellent electrolytic caps such as the BGs will outperform any tantalum cap hands down.
Cheers,😉
barossi:
How do you recomend me to wire the LL1660? What B+ do you have over the LL1660?
Im going to build the powersupply monowise and this is what i had in mind:
The rectifierpart is going to be hybride as found on lundahl site and not as in picture.
I already have the parts.
Id be very glad to get feedback on it, perhaps any values i can add/modify.🙂
C1,C2 = MKP
C3 = 1x MKP 2x Electrolytic
C4 = do i need it at all? any suggestions here?
This is the linestage itself:
🙂
How do you recomend me to wire the LL1660? What B+ do you have over the LL1660?
Im going to build the powersupply monowise and this is what i had in mind:
An externally hosted image should be here but it was not working when we last tested it.
The rectifierpart is going to be hybride as found on lundahl site and not as in picture.
I already have the parts.
Id be very glad to get feedback on it, perhaps any values i can add/modify.🙂
C1,C2 = MKP
C3 = 1x MKP 2x Electrolytic
C4 = do i need it at all? any suggestions here?
This is the linestage itself:
An externally hosted image should be here but it was not working when we last tested it.
🙂
Hi,
here you can find the datas:
http://www.lundahl.se/pdfs/datash/1660.pdf
connection is ALT S.
The voltage should be 170-180V. So you will have 165-175V on the anode!
Greetings Barossi
P:S: I add a foto of the signal Test-Board!
here you can find the datas:
http://www.lundahl.se/pdfs/datash/1660.pdf
connection is ALT S.
The voltage should be 170-180V. So you will have 165-175V on the anode!
Greetings Barossi
P:S: I add a foto of the signal Test-Board!
Attachments
barossi:
Beautiful test rig! I see you also have balanced outputs, is possible to use both types connectins "ALT S"?
Beautiful test rig! I see you also have balanced outputs, is possible to use both types connectins "ALT S"?
fdegroove, I have tried a lot of capacitors on the cathode and the tantalums always sound better then electrolytics, BG and Oscon, but of course there ara a lot of different types... I will use batterys in the next preamp.
time:
what do you think about the powersupply?
check your mail later tonight i will send some pics =)
what do you think about the powersupply?
check your mail later tonight i will send some pics =)
I wouldn't ever put nicads or any other battery in the signal path - which includes the cathode.
You might choose to use fixed grid bias with a battery - but that is a different circuit and a different idea and implementation.
Consider using an adjustable current source in the cathode - that's a jfet and a resistor... *way better* than any battery. Or you can buy a "current diode" which is merely a jfet in a two lead package selected for a particular current...
Tantalum caps are ng - unless you like that soupy tantalum sound. Use a film cap for bypassing
The 220R resistor's function is as a "grid stopper". The 417a is a VHF tube - designed to work into the 100s of Mhz. You don't want it oscillating, which it will do. So you want not one 220 ohm resistor, you want 3 (iirc) one on each pin that comes out for the grid - check the basing diagram - mounted as close as possible to the grid pin and all coming together with identical length leads, the body of the resistor as close as reasonable to the grid pins.
Set up the current in the 417a for the requisite high end of the tube's current range - they seem to sound better that way...
Consider running the output side with a plate choke and a cap coupling to the output transformer... you might like that too.
_-_-bear
You might choose to use fixed grid bias with a battery - but that is a different circuit and a different idea and implementation.
Consider using an adjustable current source in the cathode - that's a jfet and a resistor... *way better* than any battery. Or you can buy a "current diode" which is merely a jfet in a two lead package selected for a particular current...
Tantalum caps are ng - unless you like that soupy tantalum sound. Use a film cap for bypassing
The 220R resistor's function is as a "grid stopper". The 417a is a VHF tube - designed to work into the 100s of Mhz. You don't want it oscillating, which it will do. So you want not one 220 ohm resistor, you want 3 (iirc) one on each pin that comes out for the grid - check the basing diagram - mounted as close as possible to the grid pin and all coming together with identical length leads, the body of the resistor as close as reasonable to the grid pins.
Set up the current in the 417a for the requisite high end of the tube's current range - they seem to sound better that way...
Consider running the output side with a plate choke and a cap coupling to the output transformer... you might like that too.
_-_-bear
Oh,
The resistor to ground from the 220 ohm (which should be modified as I suggested) is *required*. You can't count on the pot for providing the bias path for the tube.
Also, with DC coupling any current flowing through the grid circuit will also flow through the pot, making the pot noisy over time and making poping sounds in all probability as you adjust the pot.
Make that resistor a 1 meg or higher if you want to avoid loading the pot's curve... at least you'll have a sure path.
A better idea is to put an appropriate step attenuator or pot at the output side of the "line stage" avoid all DC through the level setting element, and keep the path to the tube free of these potential issues.
😀
_-_-bear
The resistor to ground from the 220 ohm (which should be modified as I suggested) is *required*. You can't count on the pot for providing the bias path for the tube.
Also, with DC coupling any current flowing through the grid circuit will also flow through the pot, making the pot noisy over time and making poping sounds in all probability as you adjust the pot.
Make that resistor a 1 meg or higher if you want to avoid loading the pot's curve... at least you'll have a sure path.
A better idea is to put an appropriate step attenuator or pot at the output side of the "line stage" avoid all DC through the level setting element, and keep the path to the tube free of these potential issues.
😀
_-_-bear
Bear, ok I do not like the idea of a battery either but fixed bias means a capacitor in the signal path and a FET means a transistor in the signal path ! Evil things..... I have had very good results with this preamp with bypassed cathode (carbon) resistor and maybe this is the best way ? I have used Kemet tantalums but I suggest anyone that is interested building this beatuful simple amp to try different types, personal preferences may be different.
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