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Hey guys Iam back in black, this computer tube I tried driving in parallel a 10y once when I didn't know better. I liked them very much. I want to make a simple line stage Iam open to suggestions if you suggest another tube I probably have them A 5755 in parallel driving a trans LL1630 5ma with a little fb might work. 2C51 another option. Should be sensible go for the 2c51.I have to find them got 5 5755 in front of me here. Another option double up the winding on the lundahl 1630 and use a 12 b4. what should I do want to drive my f7 with this.I got 2c22 I could drill them out or 6cm5.
Edits: 02/21/25 02/21/25 02/21/25 02/21/25Follow Ups:
The 5755 is essentially a zero bias triode. Look at the 0V grid line and it's obvious. This tube is not only unsuited to line-level signals, it has too much gain.
So Tk what do think go for the e1148 the hyton topcat 6j5? That or 12au7. the 6j5 will like 250. 5ma is the problem. I got 9pins in though.edit can't find my 6cm7 found a lot of 6dj8 and au7.only other option is double up the primary and run 12b4 at 10ma not sure if that will work I only fluke stuff without help. Iam only guessing the plate resistance is low enough to drive the trans in parallel. How I will test this is with phone and iem on the bench dont have a scope so the fb is unrealistic too until I get one.
Edits: 02/22/25 02/22/25 02/22/25 02/22/25
Forget about it. With an Rp as high as these of the 12Axx you will get MASSIVE frequency response problems with an output transformer. You will need an ungodly inductance for an acceptable LF rolloff and that many windings will give you a hell lot of interwinding capacitance screwing your HF response. so au7 is out 6j5 types leftedit should I start drilling?: ^)ah 12b4 across parallel winding 12 has low rp low enough? Ilike 12b4 my epay name. Holding back on the step drill until somebody help me do the math i'm a fitter turner done 1st year radio and tv 20 years ago. I just bias and listen. Need to get a scope. learn more.
Ok found 6 6cm7. According to data I can run 200v 5ma on plate hows that?
Edits: 02/22/25 02/22/25 02/22/25
I agree the 6CM7 looks good for this. It seems well suited for the 5 DCmA limit of the LL1630. Many tubes would work well here, including the 6SN7.
Edits: 02/23/25
Iam going with 6cm7 then. I have a dumb question TK I can't remember for sure the trans phase. Does the asterisk indicate positive phase? Its been ten years.
Edits: 02/24/25
Phase in this case isn't positive or negative, it's simply the direction of the primary and secondary windings relative to each other. The diagram of this transformer at Lundahl's site shows suggested hookups. Note that their use of 10K terminating resistors in the SE example means the tube must be suited to a 40K plate load (in parallel with whatever is reflected back from the load).
I just realized the 6CM7 is two dissimilar triodes. Is that what you intended, to use each section for a different purpose? If this is a straight line amp with a level control at the input, I think you'll be better served with a 6SN7 or similar.
I added 32 ohm carbon to the grid maybe a little more air but less dynamic. Iam going to try find a cadock or vishay pair for the grids. I dont know about the load still have 875 vishay across it still not sure if Iam ib phase with the astrix as ground. It could explain the poor sound.
Edits: 03/01/25
Tk Iam mixing them up they are twin n7 types and shockingly ;[ its driving my ab workshop amp. Iam biasing the tubes through a motor blue alps 5k I never think thats a good idea. Iam not sure if I have the phase right if the astrix is positive iam inverting phase.
Edits: 02/27/25
Little thing built on an old chassis every hole is crooked and covered with copper sheet its quiet!. I love using old chassis Rat preamp build. It's not even folded strait.
I love to copper out everything and use as a ground plane occasionally. 2.1 Earth bus on amps I use sakuma's method. I got lazy here and used only one bus not separate signal and ps. But I am still careful where I place bipases and signal. Not a fan of blue alps I usually use the cheaper black or a alps carbon. with the circuit board what I might do if I can't get the warmth Iam looking for. I will use a 6ak5 triode if I have too I have better 7 pins basses I trust also. I'll keep working on it trying different valves. Or start a new dht or p. I really think globe 47 triode would make a great preamp. It's a rat but quiet I enjoying it now. Tidy it up.
image
Edits: 02/28/25
Its built Iam testing it with my penon serial iem Sounds kind of sterile but super quiet but Iam sorry I stripped caps and trans out of my 26 project now it had the warmth this one does not. Since its so quiet I will start afresh on a dht preamp 26 71a or 47 triode and try to sweeten this one up. Maybe I need to put a cap in front of the triode rather than bias through the blue alps. It's just not sweet maybe the bases I never used them before. Too much untested parts. Iam not sure where to start more oil caps I used polly bipas on the power supply and an echoke. I might try the tube power supply. Maybe just break it in more. I compromised for a safe build and it's quiet and dynamic it's sure quiet max volume its silent. Iam sus on biasing through the alps maybe try a gridstop.
R =
V
I
=
7 volt
.05 ampere
= 140 ohm (Ω)
P = V × I
= 7 volt × .05 ampere
= 0.35 watt (W)
140 ohm cathode resistor seems off 5 milliamps 200 plate .35 watts. 6cm5 very tired but keen to wire in something tomorrow I have a plethora of 8 pin 6c6 and all the top cap pentodes and dual triodes and loctals but 9pins are easy and installed and 6 is enough I haven't tried them in decades because I didn't have nos but these look fine, wire them alternate triode two swap triodes left to right to get ballance.. 005 maybe 1400ohm more likely
Edits: 02/23/25
140ohm seems so low.
I got a series tube reg ps thats two high 250volt. I've got 12at7 au7 ax7 I got 6gk5 6ak5 417a which I've never tried d3a e180f two much gain and current. I got nice octal and loctals. If I fudged up a separate filament supply I could try cm3.I got lots of pentodes even el84 triode with the ll1630 winding parallel I bit much gain. I want good band width so I want to run loop fb just a little. maybe 12b4 is the go if I parallel. Anyone, I need some encouragement. prefer to stay with 9pin less chassis work. The 7pin would be a bit messy too. Never tried at7 because there not linear but maybe thick tubby but tight sound is what Iam after.. I got ss E choke 250volt supply too Iam running remote blue alps motor winder and one of those shiney china selectors that take the circuit board untested. Hope their ok. Just want to try a tube I haven't used for most fun. I chose idh because I want it supper quiet compact and reliable. I want good phase come to like good phase of the f7 driving fullrange. Something I might miss might only full range currently. au7 would be novelty for me. I haven't tried those in 20 years like all the common ones.edit Iam thinking going back to my old favorite a 2c22 type because the gold octal bases would look great well there the laid over hyron version. 6j5 triode inside I think in spec I just found a pair. a bit of a safe choice. Right voltage. I Don't know about running them at five ma. The fun part dreaming about tube choices to sleep with so many. the 5755 made a nice driver. I searched, nothing for line use. .
Edits: 02/21/25 02/21/25 02/21/25
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