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A DIY Tube Preamp/Line Driver by Passinwind

#22
lneal said:
Those are great numbers. How is that new Tung Sol compared to the older tubes? :cool:
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I was actually shocked by how good it is in this application. I bought an assortment of NOS 6SN and 6SL7s, and I already had a big stash of used 6SN7s from the 50s and 60s, which was what motivated me to do this build in the first place. I bought the EH to use as a surrogate for testing mods, and now I'll go back and sub in all the older ones I guess. But the Tung-Sol is likely to be a keeper due to the lack of microphonics and overall pleasant tone. I suppose the big question would be: how consistent are these new tubes?

I do also have room and power supply overhead left to add another gain stage or two, and a tone stack, if I feel like it. I have all the need parts on hand, so it wouldn't take very long to do that. But for the moment I'm really digging it with my simple SS preamp as the front end. :bassist:
 
#23
Passinwind said:
I do also have room and power supply overhead left to add another gain stage or two, and a tone stack, if I feel like it. I have all the need parts on hand, so it wouldn't take very long to do that. But for the moment I'm really digging it with my simple SS preamp as the front end. :bassist:
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You are going to post a link here to the SS preamp thread. <- Notice lack of question mark :p
 
#25
Bringing this thread back up to show how this piece is evolving. I spent a few weeks doing Spice models for an additional one tube preamp with tone controls, then finally got around to building it. I intend to do a new thread shortly, but in the meantime here's an in-progress look at how I crammed in the new sections:

Link Removed

Plenty of house cleaning left to do, but it sounded pretty sweet right off the bat. My modeling software (LTSpice) allows me to run sound clips through the model and audition virtual changes, but as with pretty much all modeling I've experienced, reality trumps the virtual. I learned a ton by trying so many things in modeling though.

I used one 6SL7 for the front end, currently it's a 50 year old Sylvania one. Bass and mids work in a local feedback loop, treble is in another stage by itself and is passive. I shot for subtle EQ, not necessarily "powerful."

Here's a quick and dirty sound clip, EUB-->preamp set flat-->soundcard. Clams are free, eat hearty!:bassist:

Link Removed
 
#26
Passinwind said:
Bringing this thread back up to show how this piece is evolving. I spent a few weeks doing Spice models for an additional one tube preamp with tone controls, then finally got around to building it. I intend to do a new thread shortly, but in the meantime here's an in-progress look at how I crammed in the new sections:

Link Removed

Plenty of house cleaning left to do, but it sounded pretty sweet right off the bat. My modeling software (LTSpice) allows me to run sound clips through the model and audition virtual changes, but as with pretty much all modeling I've experienced, reality trumps the virtual. I learned a ton by trying so many things in modeling though.

I used one 6SL7 for the front end, currently it's a 50 year old Sylvania one. Bass and mids work in a local feedback loop, treble is in another stage by itself and is passive. I shot for subtle EQ, not necessarily "powerful."

Here's a quick and dirty sound clip, EUB-->preamp set flat-->soundcard. Clams are free, eat hearty!:bassist:

Link Removed
Click to expand...


Don't know what it is, that nice pre, or if it's just in the fingers, nonetheless great tone.
As always, your DIY prowress leaves speachless. Great build !
For some more conventional reference points, could you post some clips with your Moon FL.

P.S. you need to explain that clam reference.... :p
 
#27
OldogNewTrick said:
Don't know what it is, that nice pre, or if it's just in the fingers, nonetheless great tone.
As always, your DIY prowress leaves speachless. Great build !
For some more conventional reference points, could you post some clips with your Moon FL.
Click to expand...

Heh, will do...understood, my EUB is quite a wild card. Maybe I'll even borrow a Fender from 4Mal. :cool:

But for now, my Crescent Moon fretless, with Q-Tuner pickups and T-I Jazz Flats: Link Removed

I'm still contemplating adding a Jensen DI and maybe eventually a few tone shaping switches. Compared to the stuff I usually build and work on, this one is crazy-easy to modify. The DC filament supply was a little tricky, but that's about it.
 
#30
I couldn't design anything like that Passinwind, just stopping by to say your skill, and just the neatness and professionalism of your work looks top notch, man. I'm sure it sounds it too. From the tiny bit I do understand, your noise numbers are at least as good, often better than what you see in top tier pro gear.
 
#31
lneal said:
Cool Charlie, very cool. 6SN7's and 6SL7's rule...........
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Hey Larry, somehow I knew you'd show up in this thread. :cool:

I still haven't gone off the deep end on Gucci boutique iron like your preamp uses yet, but the Jensen set I used is still pretty sweet. Should be no problem driving any amp I've ever heard of.
 
#32
will33 said:
I couldn't design anything like that Passinwind, just stopping by to say your skill, and just the neatness and professionalism of your work looks top notch, man. I'm sure it sounds it too. From the tiny bit I do understand, your noise numbers are at least as good, often better than what you see in top tier pro gear.
Click to expand...

Thanks Will. I can pretty much dime the treble control and still barely hear the hiss through my Thunderchild cab's tweeter. Close enough to pro gear for my hack playin' self!
 
#34
Well just great. You now have me wanting to do this. I'll have to look into it. Subscribed.

Waiting to see the face-plate. I suppose I could do some kind of snazzy trim with a build like this as I work at a Hi-tech machine shop. How about a stainless steel assembly, glass bead blasted and then plated in Gold. With my name CNCed across the front. And maybe a Lexan window for the tubes. Better check my piggy bank as I think it's empty right now.

So Passwind how much difference is there in tone/tubey character using the octals over a 12a?
 
#36
Red Planet said:
So Passwind how much difference is there in tone/tubey character using the octals over a 12a?
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Seems huge, but I've never tried 12A__ variants with this Jensen transformer set, or with this exact tone control topology for that matter. Through the rest of my rig this thing sounds more like an all-tube amp than just a tube preamp than any of my other DIY builds, if that makes any sense. I've only done one gig with it so far, but I have another one coming up next week.

I love your ideas on finishing panels. I'm going with blue powder coat with engraved graphics and light blue and gray infills on this one. Should have photos sometime next week, assuming I pull the trigger on my final design today.

This build could easily be condensed into two rack spaces if you used turret boards or did your own printed circuit boards.
 
#37
johnk_10 said:
i hadn't seen the updated version of it. man, that's a real beauty you made there Charlie! and the clip of it sounds sweet. super nice job, and thanks for the inspiration.
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Thanks John. I'm sure you know the feeling: "oh man, I have this killer NOS Sylvania JAN 6SL7 chrome dome halo-getter just sitting here collecting dust, what should I do with it..." ;)
 
#40
Red Planet said:
Can you expound upon why you like using your FET in conjunction with this as well?
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The solid state preamp has an aux input section, allowing me two independent channels, which is handy for a lot of what I do.

Beyond that, gain staging, mostly.
The line driver section in my SS preamp has a whole different flavor, and makes the whole system sound tighter and funky in a different way (I hate the term hi-fi, but...), but at the same time it also gives me another gain section which allows big wooliness at moderate volumes. It has a nice Jensen output transformer too.

I love the way the tube one sounds straight to power amp too though, and run it that way about half the time. I'm still acclimating, as this is a lot different feeling rig than my last few. Makes me want to play more BG and less EUB. :bassist:
 

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