The Steel Guitar Forum

Brad

How do you dial in the the variable impedance (Vari-Z) control. Just by what sounds best for a particular pickup? See ya in St Louie!


bob

How many tubes are in the input circuitry and do they run the EQ section also ?
What tube types are being used ? 12AX7, 12AU7, 12AY7, ECC83 ?

Kiyoshi, originally my eq curve analysis was merely a fascination with what made different amps sound the way they do. This tube preamp birthed itself out of necessity, and all that EQ analysis and understanding helped make it possible.

Bob, yea, you just turn the knob to taste. If you leave it in the middle which is about 500k, just like a pot pedal's load, it's pretty "normal" sounding. You can crank it to 1Meg and get a more clear and open and bright sound, more like an active volume pedal. If you drop it all the way down, it mellows out the pickup's tone. It's a very fun control that affects tone without being a "tone" control. It's not as simple as dark and bright. It sounds to me like it also affects the intensity of a pickup's resonant peaks, like the pickup's response curve actually changes. I'm not sure on that one, but that's what it sounds like. It serves sort of as a presence control. Also, if you turn the Vari-Z knob all the way down it clicks a switch that inserts a pad for real hot instruments. I don't think my specs say that yet.

Kerry, there are 3 tubes. The input tube is a 12AU7 like a Black Box. It's a buffer stage that drives both the tuner and the volume pedal separately. Then after the volume pedal returns, there's a 12AX7 to drive the tone/gain/FX section. Then there's another 12AU7 do drive the two stereo outputs.

Brad
www.steelguitarblackbox.com

Brad-

Will the gain saturate?

-dean-

Hi Brad .... please check your e-mail

Dean, the preamp will barely, just barely start to saturate. There is a pretty big range with the gain knob, but you won't really hear "dirt" or obvious overdrive. You will hear that low settings have a very clean sparkle and higher settings start to warm over with more of that "halo". In general it's a clean machine with subtle shades of drive. I kind of leave the overdrive factor up to using a stomp pedal of some sort in the volume pedal loop.

Dean, come by the table in St. Louis. I look forward to meeting you.

Thanks,
Brad

Dear Brad,

I read about your new preamp with relish, man. I have a few different tube preamps that I use with my racks, and have been considering having Tony Bruno build me some kind of rack version of the preamp section of one his amps, but why do that when you have yours ready to go? I wish I could make it to SL but I have some gigs. My question to you is, when will you have the preamp ready for delivery? If you mentioned this on your site and I missed it I beg your pardon.

Best,

Gerald
Williams D-10, Beard Dobro

Brad,
Are you using IC's in this? Burr Brown? It looks very nice.

------------------
God Bless,
Steve Stallings

Hi Brad ... I'm ready to order your new preamp, however I'll not be at the convention.

I've also sent you an e-mail. Please advise me of your earliest ship date. Thank-you.

kj

Gerald, Tony Bruno surely could build something fantastic. I love his amps. But you make a good point. I’ve already considered many of the steel player features and refined this design, so I fully support your interest in my preamp I hope to have them ready for delivery by the end of September or early October. I only have a couple ready for demo at the convention next week. After that I’ll be hard at work soldering my @$$ off to get them ready to go out the door. They’re quite labor intensive with lots of point to point hand wiring.

Steve, thanks. This unit is entirely tube with no solid state devices in the path at all. If I do ever have to incorporate some solid state circuits, Burr Brown is the first place I go. I’ve always liked their stuff for audio.

Kerry, I’m not quite ready for delivery, but soon. I’m not on my email computer right now, but when I do get back to it, I’ll respond to your email. Thanks so much for your interest. I think you’ll be quite pleased with what you hear.


Thanks,
Brad

Hey, Brad -- Congratulations and good luck with your new product! Just curious, what set-up have you been testing the pre-amp with: what power amp, effects unit, speakers? I assume one could use the pre-amp in mono with one speaker as well.

Again, congrats! Boo

Hey Boo. I've been testing the preamp mainly in mono because I typically play with a mono rig. I've been using a number of setups. One was a Hafler p3000 power amp into one or two JBL cabs. Another rig I've been using extensively is simply into the power amp in on my Nashville 112 like Randy Beavers does. That sounds great. I also modified channel 1 of my '68 Fender Deluxe Reverb to bypass the tone section basically using my Deluxe as a powered speaker (JBL D112). That's just amazing sounding. Tubes all the way thru. I've also messed around with it direct with the XLR outputs thru my small powered PA mixer that we use for small gigs. I must say it's the first time I've ever liked the direct sound.

As far as effects go, I've been mainly using my older TC Electronic M2000. Just verb and delay. I've also messed with the cheap Alesis Nanoverb and a couple of other standard FX units. Pretty much any modern line-level FX unit should work fine.

Brad

Brad - if you get sick of inhaling solder smoke - consider selling the PCB, Box, and parts, with a "solder-by-number" 'do it yourself' (DIY) kit for us underemployed electronics hacks. It could free up your time to move ahead on your other ideas while still making a buck or two for your ingenuity.

I suppose thats the optimistic side of the idea...seller's liability and endless phone calls to troubleshoot mistakes might be the downside.

Just a thought for ya !

Brad,
Congrat's !!....I'm glad that this preamp has become a reality !!.....Couple of questions...

1) What are the frequencies of the EQ section ?

2) What is the cut or boost frequencies using the brite or dark switch ?

BTW ....The Vari Z is a GREAT feature..It's also no small feat to out do a Boogie Studio and an Alembic pre ( 2 of my favorite pre's for steel ) .....Thanks again for a much needed product .....Sincerely, Jim

Tom, I love kits, but you make great points as far as getting someone thru any debugging that they may need. That could become a real headache. I like being able to be the one to have final quality control over what goes out. Then I can be the one to take the heat

Jim, the EQ section is very similar to an older amp that uses the classic tonestack like an old Bassman, Twin, Marshall, Sho-Bud, etc. The midrange control is broad, but the midrange dip is more narrow and is interactive with the treble control. More treble makes the dip go into the lower mids. Low treble settings makes the mid dip rise up toward 1kHz. My added color knob gives extra control over that frequency so it's quite tweakable. The bass is a bass shelf that kind of starts up around 300Hz or so an extends on down to around 30Hz. The bright switch is just like what you're familiar with. At low gain settings it's dramatic. At full gain, it does nothing. It generally boosts the frequencies above 5kHz. The dark switch is a gentle shelf that starts around 4kHz and at around 12kHz it's about 9dB down. The Vari-Z is very effective too.

We had the preamp in the Zum room yesterday (9/3/05 ISGC) and Larry Sasser, Randy Beavers, and Doug Jernigan played thru it. We were thrilled to say the least with what we were hearing. Later yesterday Larry Sasser and Russ Hicks used it on the big stage and it sounded great too. They used the rack rig and plugged into the power-in of the Nashville 1000's.

Brad

Brad,
Thanks for the reply .....I like the fact that you have the Vari Z setup on this amp...It gives another option to change the EQ without adding or subtracting EQ via tone knobs .....This is a feature that is included in some mic pre's that is overlooked in guitar and pedal steel pre's ..Brite and Dark is nice too ....You can lay back for rhythm work with the Dark setting, then flip the switch for lead work ... I''m also assuming that with the quality parts that you are using that this is a very quiet running pre .....Thanks again..Sincerely, Jim

You guys should have heard this at the show. Randy Beavers in the Zum room and Larry Sasser and Russ Hicks live on stage. This things a real winner!


bob

I played through Brads pre-amp and I LOVED it. It's that sweet sound we've all been looking for. My Zum with Bruce's singles in it was a GREAT fit. Good job Brad!!! And Bruce!!!
Larry

I agree with Bob Snelgrove. It sounded great. Looks cool too!

Tony Rankin

Brad
It looks like the signal should go from the pickup thru a short Lo-Z cable directly into the pre-amp. How did you guys mount it on your guitar?

Doug,

The rack was standing on the floor, face up. I don't see where a short cable coul have made it sound any better Besides, Brad has that pickup balancer, impedance thingie


bob

With some pickups, a 4 inch cable to the buffer amp sounds different from (better than) a 24 inch cable. I had a hard time believeing this before I experimented. The difference is most obvious to me with the Lawrence 712 pickup (710 for the unenlightened).

Earnest, you make a good point and I do exactly what you describe. Since the rack can sit immediately to the right of the guitar, I run a real short cable from the guitar output right to the first input of the preamp. It could be as short as a foot or so. Mine is actually about a foot and a half long. Using George L's cable makes it pretty much a non issue. George L's cable has such low capacitance that it takes a pretty good length to start to hear any loss of highs at all. On my preamp I have a bundled (braided) group of 3 cords. The first one is the real short one to go from the pickup to the first input of the preamp. I use the fat George L's for that. Then I have a matched pair of the thinner George L's cable to go down to the volume pedal and back. It's a real short and neat hookup system. But really with no volume pedal between the pickup and first tube stage, whether that first cord is 5" or 50", I really think it's quite negligible, as long as it's good, low-capacitance cable.

Brad

Earnest. I re-read your text. You said a "low-z cable". I'm not clear on what you mean by that in this situation.

Brad

"On my preamp I have a bundled (braided) group of 3 cords. The first one is the real short one to go from the pickup to the first input of the preamp. I use the fat George L's for that. Then I have a matched pair of the thinner George L's cable to go down to the volume pedal and back. It's a real short and neat hookup system. But really with no volume pedal between the pickup and first tube stage, whether that first cord is 5" or 50", I really think it's quite negligible, as long as it's good, low-capacitance cable."

Brad,

I'm still a little spun from the trip home. (Plane had electrical problems out of O'hare and and made an emergency landing, firetrucks, ambulances and all! (All is fine)

Can you explain the " no cable from pickup to preamp input"? I know some Peaveys have a volume pedal loop. is that it?

thx

bob

ps: did you get my voicemail?