mike stehr Posted June 8, 2004 Share Posted June 8, 2004 I robbed this amp out of a RCA television/AM/FM phono console that I picked up free. Damn thing has some boogie factor on my Cornwalls for some odd reason.(Maybe it's the tone controls, I dunno.) It's a single-ended Pentode amp with what appears to be Ultralinear taps on the OPT's. However not near as clean sounding and quiet as my Magnavox SE 6BQ5 amp. But bone stock with orginal tubes, the RCA flat outcranks the Magnavox. Odd, I thought it was going to sound terrible. It sure looks homely, maybe another chassis would help. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 8, 2004 Author Share Posted June 8, 2004 Oops. Quote Link to comment Share on other sites More sharing options...
jazman Posted June 8, 2004 Share Posted June 8, 2004 Mike, It's beautiful! Klipsch out. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 8, 2004 Author Share Posted June 8, 2004 Thanks Edmond, and Mark. I guess if it's free, then it looks good to me. This thing has to be a UL circuit. Just has gobs of power. I'm not used to this with a SEP 6BQ5 amp. The amp sure doesn't seem like a 5 watt amp. Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted June 8, 2004 Share Posted June 8, 2004 The RCA may not win any beauty contests, but if it sounds good and has some umph, then it's a keeper! My brother Tom's Magnavox EL84-based SE console amp is no looker either, but it does sound great. It's 5 WPC (or less) does run out of steam when listening to large scale pipe organ CDs at 80 to 90dB levels, though...not so much with his Klipsch KG 3.2s, but with his 91dB Triangle Zephyrs...sigh! Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted June 8, 2004 Share Posted June 8, 2004 Bet this RCA has some balls... Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 8, 2004 Author Share Posted June 8, 2004 Yeah, those Zephyrs are starting to get down there on sensitivity. Keep your eye out for one of these RCA SE amps, this little amp jams rather well on my Cornwalls. My Magnavox SEP amp sounds somewhat like a SET amp, all clean and sweet. The little RCA SEP sounds like a 12, or 14 watt Push-Pull. It plays hard rock and metal pretty damn good. The RCA amp has some rather nice bass extension, it suprised me. The top end is typical of what these single-ended 6BQ5 OPT's have to offer in the old consoles. The little Magnavox SE amp of mine has a better extension in the higher frequencies. This is now my official headbanger amp, it drives the Cornwalls loud enough to keep me happy in my smaller room. For now..... Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 8, 2004 Author Share Posted June 8, 2004 "Bet this RCA has some balls" If it's Ultralinear, then it probably does. The drivers look like (6CG7?) the 6SN7 in a mini-bottle. The RCA SE amp outcranks my Magnavox 6BQ5 push-pull, but this amp has some input gain issues, so it's not really fair to say that. Quote Link to comment Share on other sites More sharing options...
sheltie dave Posted June 9, 2004 Share Posted June 9, 2004 Mike, I see the old dog has fleas, and is still scratching the itch! That 300B tube (or 2a3) was sneaking in thaT first photo. BTW, my littlest bro is overnighting in Germany, and will be flying home to Ft. Lewis this morning. He has made it out of Iraq safely, though not without finding some serious sheet there. Besides the two Scuds they found in the river bed, he also located a Capehart 2a3 PP in Mosul, and they got it repaired and hooked up to the battalion Heresys. Some of their quarters were lacking in sound isolation, so they would use either a Bogen 8417 based 50 watt mixer, or a H/K Model 18/19 to drive the Heresys. Most everyone liked the Capehart best of all, other than for when they wanted to crank after dindin. They kept losing CD players until they got fed up and built a custom case that they kept under negative pressure while in the field, which did the trick. Quote Link to comment Share on other sites More sharing options...
fini Posted June 9, 2004 Share Posted June 9, 2004 Mike, You ever tried doing anything with organ amps? Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted June 9, 2004 Share Posted June 9, 2004 Wow...battalion Heresys! When I was stationed in Germany in '85, we were considered very lucky that we had Wang word processors delivered to HQ! And to aquire a 2A3 PP power amp as spoils of war...well, that's better than what our boys found in The Eagle's Nest towards the close of WWII! The closest to an organ amp chops has is his Baldwin (Raytheon) 6SN7GTBs in his new Consonance M100SE integrated...bet all those Baldwin, Hammond, Conn, and Allen organ amps would be excellent to own as well. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 9, 2004 Author Share Posted June 9, 2004 Dave, Good to hear your brother is coming home. Did he bring the Capehart 2A3 PP with him? Fini, I've yet to mess with any organ amps. Though the ones with different OPT's for a two or three-way speaker would be interesting. My local audio bud has had a few pass through his place. The organ amps he had that I have listened to was a 2A3 parallel push-pull, and a pair of 90 watt Webster/Allen 6550 PP amps. (I loved those monsters, but I couldn't afford them at the time, and they are kinda overkill for my small place and needs.) Mark, The #'s on the chassis are RS193J, RVA27A. Another #'s is hid behind the 5Y3 rectifier, 62162. I bought a old RCA console a couple of years back, that had the very same amp as this. I shelved it when the PS cap was getting too noisy. I tried finding a schematic back then for the RCA SE amp, but never did. I can pretty much scope the circuit out and draw a schematic nowdays, being kinda used to these SE 6BQ5 circuits. The amp has a 35 mic section for the multicap, which is tied to the screens of the output tubes. Then off the 35 mic section, a couple of 39 ohm two watt CC resistors feed brown leads to the OPT's. The feedback has to be in the volume or tone controls. I know that ultralinear is usually common with PP amps, so it's strange(to me) to have a single-ended amp with screen (UL) taps on the OPT's. It's gotta be UL. it's the only explanation that I can come up with as to why this little amp seems to crank so. I ran the thing for 5 hours or so last night. The PS cap has seemed to settle in a bit, the line noise isn't as bad as it was. Grindcore SE! Quote Link to comment Share on other sites More sharing options...
sheltie dave Posted June 9, 2004 Share Posted June 9, 2004 Mike, the Capehart and all the other gear is staying behind. When they first got there, everyone in a couple spuads chipped in $20 so if the Heresys got mauled, Mike wouldn't be out anything. He got his hide tanned a couple times early on for being a maverick, but they retroengineered the one Heresy into the stryker, and were driving it off a backup computer soundcard. The other would stay behind at HQ for the staff officers. Looks like he might end up with a commendation for improving morale throughout the battalion, though he dashed my hopes when word made it here he could only send his ditty bag home We are overjoyed he is coming home with all ten and ten still intact, and we hope they have a brighter future ahead for the country. The 6bq5 stereo Fisher, and the Pilot 232 both sound nice, with lots of midrange presence and not as much bass as your Corns throw out. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 9, 2004 Author Share Posted June 9, 2004 I assume you found some 6BQ5's for that Pilot amp. Time to unhook the Cornwalls, hook up my homebrew cabinets with the Criterion 10's, and noodle with these. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 9, 2004 Author Share Posted June 9, 2004 Red primary B+, Blue primary plate, and a third brown primary. Must be UL. Quote Link to comment Share on other sites More sharing options...
sheltie dave Posted June 10, 2004 Share Posted June 10, 2004 Mike, I'm finally going to see the good School Sisters of Notre Dame today. I ran into one of the sisters yesterday at the hospital, and she said they have twelve various Altec horns that can be had for a donation. She mentioned they are looking to have a "Fighting Irish" mascot painted on the wall in the new gym. A good double tape job, two hours of painting, and hopefully I will be heading home with some heavy metal if things work out Quote Link to comment Share on other sites More sharing options...
fini Posted June 10, 2004 Share Posted June 10, 2004 Bless your heart! Quote Link to comment Share on other sites More sharing options...
Klipsch Employees Trey Cannon Posted June 10, 2004 Klipsch Employees Share Posted June 10, 2004 Hey Guys, I have a pr of thoes JBL tweeters like whats in the pic above...They need a home...they both work and sound "ok" . I am not a big fan of that tweeter. Make me a "real" offer. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 10, 2004 Author Share Posted June 10, 2004 On 6/10/2004 1:13:38 AM Ryan C. Inman wrote: Yep. Is the brown wire connected directly to the screen, or is there a limiter resistor in series (like 10 Ohms)? Either way it's still UL, and is unique for a console amplifier. I bet it does seem powerful. ***Each OPT has a 39 ohm resistor in series on the screen taps. If there's a resistor, try bypassing it and see if it sounds better. Often times, a resistor will be there to drop the screen supply voltage a bit, so that the more positively charged plate conducts harder and gives more power output. You'll lose a bit of power, but it will probably sound better. ***I guess I could try bypassing them. Since this amp is relatively low current, you could hang 50 uF off of the 5Y3 cathode and improve the bass response a bit. ***The amp has a 80 mic hanging off the cathode of 5Y3, or filament being a 5Y3 is a directly heated tube. Also, if it still has the paper/wax coupling capacitors intact, you can get more high end detail by replacing them with something like Orange Drops. ***I'm sure I would, but I'd rather use oils, or polyprops. I was never much of a fan of the 716p's. Don't ask me why. I do have some, and should just swap them out just to be safe. Don't forget about replacing the ceramic caps with silver micas. That's something I do notice. I can always hear those sibby ceramics, and I can hear the few of them in the RCA SE amp. And I also think that building another PS with a CLC, would make the amp way more quiet. Something that should be pretty much standard with these little 6BQ5 SE pentode amps.(A choke.) Cool, Dave! I wish I was there, I'd help you paint the Mascot. I didn't get straight 'A's in art for nuthin'. Then again...... Get in touch if you do hook up with Atec horns, we could work something out. Trey, Depending on vintage or how cherry those JBL 075's are, you can get upwards to 500 bucks a pair on Ebay. Flog them. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted June 15, 2004 Author Share Posted June 15, 2004 Update: I don't know what theh hell this little RCA amp is circuit-wise. I know it has air-gapped OPT's, with screen taps. I think it is just pentode connected, with the screen taps, (3.9K) resistors, and the 35 mic cap used for filtering and voltage drop in the screens of the 6BQ5's. We tried actually hooking it up in UL. By swapping the screen taps to B+ and the B+ to the screens. It more or less required more filtering, and it's already got 80 mics hanging off the 5Y3. A CLC PS would help quite a bit. Filtering helped quite a bit on the cathode bypass for the output tubes. The tubes were biased up in la la land(75,80 mils?), the 68 ohm resistor was swapped for a 150 ohm. The OPT's barely make it to 50 Hz on a scope, if that... The Tone controls are some make or break kind of setup. I still need to follow through with the UL connection, it did sound a bit more refined. Typical 45 year old amp made in the days when a 5Y3 was a quarter. Something about a sloppy ol' amp on the rough ol' Cornwalls with headbangin' music is kinda cool, JMHO. The ultimate distortion box. Quote Link to comment Share on other sites More sharing options...
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