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Olson SE 6BQ5, pt.2: How can it be this good?!

Redboy

Redboy

a few good watts
I've already posted about the work I did on my little Olson amp, so this is part two...

I've been listening to Bjork's Vespertine album today, which is one of those great CDs with gems of sound all over the musical spectrum, and it floors me that this 45 year-old piece of industrial metal and glass can sound as good as it does! It also happens to be the very simplest thing in my entire system, if you don't count speaker wires. Maybe that's part of the explanation.

I'm really enamored of this thing lately, and I don't think it's just my "thrifty deal" (about $15 invested so far) high talking! There's some real magic here!

Anyway... thought I'd share.

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I'm with you . . .

I'm coming to the same conclusion . . . . I'm using a little PP 6bq5 manavox amp with an $8.00 70's Fisher receiver with pre-outs :music:

simple is better !
 
Hey !

thats a good idea . . . using the cheapest and ugliest parts available (scavanged from consoles of course) try and make a bad sounding Frankenamp using 6bq5's . . .

I think I have a new project :D
 
try about 30V B+ and run the grid positive...

EDIT: Actually the transconductance of an EL84 is high enough that it is (reportedly) possible to make a true spud (one tuber) amp with one, driving it directly from a line level input (e.g.,a CDP). There's a site somewhere on the interweb...
 
that would be funny . . . I do have some ultralinear OPT's from a 6bq5 RCA console, and a power transformer from a 6V6 mono integrated amp . . . throw in some radio shack resistors, orange drops, and cheap PS caps, and I'd be in business :D

EDIT: Redboy: I love that jewel light : ) now you just need an old chicken head knob from a PA amp for the volume control
 
markus said:
Redboy: I love that jewel light : ) now you just need an old chicken head knob from a PA amp for the volume control
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The jewel light lens was "borrowed" from another little console amp that came to me in non-working condition. The fuse assembly also came from the same amp. The switch came from a garage sale parts box, and the "new" cord came from a humidifier that bit the dust the other night.

I don't know about the chicken head knob... I'm kinda diggin' the naked shaft at the moment.
 
I heard Nate"s amp over the weekend and must say that I was very impressed. Sweet as peaches driving a pair of AR 4X speakers.

Nice job on the reconfigure Nate!

RC
 
6bq5s are a fairly versatile little tube. I have some old CB equipment using a 6bq5 for both an audio amp and the final RF amp (not the same physical tube obviously) as well as an extra booster amp with a single 6bq5. Not a super powerful thing but its very clean and works well. Somewhere around here (I hope I still have them) I have about a half dozen 6bq5s I salvaged from an old electric organ that was well beyond it's prime. I wanted to save the amp but time was a factor, and the poor old thing got heaved before I had a chance to go save more from it.
 
Yep, great little amp.

Just goes to show you and get into tubes on the cheap if you keep your eyes open.
 
I have a really ugly SE EL84 amp that came out of a Silvertone console that amazes me every time I play it (on a set of tired bone stock Heresys). I tend to agree that I've never heard one I didn't like. Makes me wonder how it would sound with some decent looking output iron.:scratch2:
 
mhardy6647 said:
Actually the transconductance of an EL84 is high enough that it is (reportedly) possible to make a true spud (one tuber) amp with one, driving it directly from a line level input (e.g.,a CDP). There's a site somewhere on the interweb...
Click to expand...
I like the idea! I spent a couple of minutes trying to find a schematic, came up emptyhanded. Any chance you could find one... :scratch2: Not like I need another project! :no:
 
"thats a good idea . . . using the cheapest and ugliest parts available (scavanged from consoles of course) try and make a bad sounding Frankenamp using 6bq5's . . ."

Been there and done that, a couple times. You can make a bad sounding SE 6BQ5 amp if you try hard enough, trust me.....

I played with couple SE 6BQ5 RCA console amplifiers, I thought they had a UL winding in the OPTs, but it's just a screen winding for noise.
They always seemed ratty would come unglued easy in stock form, the tone pots were strange.
I gutted them and made a homebrew triode strapped SE 6BQ5 amp with no feedback, 6EU7 driver and 5Y3, and some Ampex SE 6BQ5 OPT's. Had good damping, and the bass was good, but it was a screamer in the midrange.

I rebuilt a Motorola SE 6BQ5 console amp for a buddy. I put in a 100K pot and did some things different, but stuck with the plate to plate feedback they used. That little amp could crank on my Cornwalls, bass was strong.
That was a good sounding little amp, just a wee bit shouty in the midrange was my only objection.

I going for a pimped-out Magnavox clone next, mostly for aesthetics.
Then there is the mighty maggotbox.

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...gutted them and made a homebrew triode strapped SE 6BQ5 amp with no feedback, 6EU7 driver and 5Y3, and some Ampex SE 6BQ5 OPT's. Had good damping, and the bass was good, but it was a screamer in the midrange.
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Strange... that's dang close to the receipe for Steve Deckert's Decware Zen SE-84's. They don't have much bass, but don't scream in the MR either.
 
mhardy6647 said:
Strange... that's dang close to the receipe for Steve Deckert's Decware Zen SE-84's. They don't have much bass, but don't scream in the MR either.
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I dunno...I just threw it together to find out what triode strapped 6BQ5 was all about. I didn't pay any attention to Deckert's designs.

Is there even published schematics online of the Zen SE amp?

I used a 5Y3 because it was the rectifier for the RCA PS transformer that was used for that little amp.
It sort of started as a stock RCA SE 6BQ5 amplifier, with the tone pots, and screen supply and then progressed to a triode strapped amp with the Ampex OPTs. With no tone pots.

That chassis was small and thin, everything was really cramped, it was kinda noisy, and was accentuated in the midrange. Some big ol' russian .047 uf teflons did kinda help the midrange shout, but it didn't stop it.

The little amp turned out cool, but it only exists in that picture now.

I wonder if a guy can triode strap a 6BQ5, then use plate to plate feedback to the driver tube?
The Motorola SE 6BQ5 amp had a capacitor and resistor in series from the 6BQ5 plate to the 12AX7 driver plate. It would seem a guy could use a scope and play with those values for best response?
The Motorola had a screen supply, and was pentode connected.

Sorry to rip-off your thread redboy......I like the single-ended 6BQ5 amps. They seem to work well with high efficiency speakers. Your amp has a cool look. The shaft on the pot is long enough to mount a knob after a wood face is mounted. Scrounge up a fancy piece of burled and marbled stuff.
It won't cost a arm and a leg to roll tubes either.

Hard to beat that kind of sound for 15 bucks.

The Motorola amp has that oil tanker look.....

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Yes, Steve's schematic is on his website; you have to dig around a little. It was lifted almost verbatim from a SE Zenith console amp design :-)
 
Mike Stehr said:
Sorry to rip-off your thread redboy......I like the single-ended 6BQ5 amps. They seem to work well with high efficiency speakers. Your amp has a cool look. The shaft on the pot is long enough to mount a knob after a wood face is mounted. Scrounge up a fancy piece of burled and marbled stuff.
It won't cost a arm and a leg to roll tubes either.

Hard to beat that kind of sound for 15 bucks.
Click to expand...
No worries. I learn by osmosis - just swim in the stuff long enough, and eventually it will sink in... Most of what you guys are saying is mumbojumbo to me right now, but someday I'll get it.

I'm diggin' the industrial look right now, but someday might beautify the thing a little. And I do have some tubes to play with.
 
FWIW, here's the SE-84C schematic from Decware's site. The amp comes with Russian SV83 outputs, but will also run EL84's (at least the SE-84B I have will).
 

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