212Mavguy Posted October 2, 2021 Posted October 2, 2021 It's been a while since posting here... I have had this 1965 Lectrolab R600C, 6ca4 tube rectified, 2xel84, 14-ish watts for a few years, courtesy of Fleabay. She has just the right amount of janky beat up chintziness to her stain spattered sides, chewed wood corners peeling out under the tattered dirty blonde cloth covering, and slightly sexy sagging grill cloth to have some decent visual mojo on stage. She came with a Censen C12R that was working fine but got immediately yanked. The clean tone was too mid scooped and the dirty tone of the amp as opened out of the packing box with the volumes cranked up reminded me of a jar of angry crickets, unique for sure not as musical as I thought that the circuit should do. There was something in the circuit that was making the speaker sound like that, and all of it had to GO. Yep, the late 50 year old dirty blonde sleaze bag somehow still out to do her hustle is the look fo sho Mojo. This was the second to last operation she'll have done, then I'll be finished with a long satisfying process. While I had the chassis out I noticed that one of the wood end mounting blocks had been broken loose from the cab side and had a staple leg preventing closing the gap back up. Either shipping or more likely the previous owner had a hard drop incident. Snipped of the staple and glued the block back. Then I swapped out the four remaining low quality tone caps for some really nice Russian mil spec ones at the same values. All of the originally (chosen for cheapness, screw the sound, just get the values within 20%) tone caps have now been replaced by some sort of foil and oil super top end Russky mil spec stuff, and yes, there is a huuuuuge difference in the sound going to the swapped in speaker, a 60's vintage all original University Diffusicone, which makes the original jensen of similar age sound like what it is, a cheap crappy speaker in comparison. Now I have an amp that looks crappy but sounds very, very, boutique-y expensive. There is a real warmth to the tones with great balance from a big bottom to the pixie dust on top (Diffusicone 12 has 35-10,000 freq response) now that was not there earlier. If you ever find one of these Lectrolab R600C's, snag it. Also if you can find a Harmony H-306A they can be tweaked to sound astonishing as well. The circuit is very close to the Lectrolab's but the Harmony runs 6v6's and a 5y3, or in mine, a Bendix Red Bank 6106. They are vintage cheese amps with what looks like spaghetti true point to point wiring but these run very quiet and their bias tremolo has that unique harmonic singing thang going on in the sustain that other tremolo topologies just can't do. Only one operation remains, I am going to go to my tech and determine the best place to break the circuit for a simple interrupt FX loop. For the first time I will drill holes in the chassis (gasp) but again, even though quite rare, this was only a cheesy amp to begin with. Not sacred. Right now the amp sounds great with the fx going into the front end but I have this Dumbulator style tube loop buffer waiting. There us a lot more out there online to make it easier to learn about how to work on and how these old simpler smaller tube amps work than just a few years ago. These two models of vintage cheese amps mentioned are very good rabbit holes to explore. The results for me in terms of quality of sound improvement has been flabbergasting, frankly. Grab and go greatness here.
212Mavguy Posted October 2, 2021 Author Posted October 2, 2021 Forgot to mention that on both of these the original output transformers were yanked for being cheap and unworthy of what the circuits deserved. The replacements in both cases were too large and heavy to mount on the chassis so they were through bolted into the bottom corner of the cabinet. The Harmony got a late 50's early 60's vintage Magnatone 6v6 PA amp unit that was several times the mass of the original, great iron, and the Lectrolab got a rooty tooty snooty japanese super iron super wire private small builder unit with an 8k primary and 35w rating. Big iron made a giant difference in these amps.
bolero Posted October 3, 2021 Posted October 3, 2021 Good to know! I have a Harmony 306A So you just changed the tone caps, & put a new output transformer + speaker in?
Gitfiddler Posted October 4, 2021 Posted October 4, 2021 Another great "cheese amp" review by 212Mavguy. 6ca4 are skinny-Minnie's of the rectifier tube world. Never played an amp with them. Now I'd like to check one out.
rockabilly69 Posted October 5, 2021 Posted October 5, 2021 Come on Wheaties let's see a pic of this hussy!
yoslate Posted October 5, 2021 Posted October 5, 2021 If the tone of the amp is as good as the tone of the post, that amp's a good 'un, no doubt. Swell post Mav! Good to have you back!
bolero Posted October 7, 2021 Posted October 7, 2021 Hmm where's mavguy? I hope he's not convulsing doing the 120v boogie, with his fingers jammed inside an amp chassis, unable to post any updates...
rockabilly69 Posted October 7, 2021 Posted October 7, 2021 3 hours ago, bolero said: Hmm where's mavguy? I hope he's not convulsing doing the 120v boogie, with his fingers jammed inside an amp chassis, unable to post any updates... I don't know if you know this C, but Mav and I are friends. He's a ski instructor in Deer Valley Park City Utah, and he teaches at a few of the resorts I play. And my steady wintertime Saturday gig (the Corner Store) is a place where Mav will come and get a beer when he's done with his work day. And the last time I saw him, he told me that he was gearing up to do a lot of fishing (he just got a new fish finder for his boat). So most likely he's out there slaying fish while the weather's good, which it has been here in Utah. Skiing, fishing, and playing music, Mav is living the bachelor good life
bolero Posted October 7, 2021 Posted October 7, 2021 Ah!! So he's gone fishin' I was trying to get a rise/laugh out of him :)
212Mavguy Posted October 21, 2021 Author Posted October 21, 2021 @Bolero... Yes, exactly. Russky k40 y-9-s in .01 and .015, .033's were Russky k42 greenies, think everything either 400 or 630v rating for these tone caps. Also yank the original coupling caps and put some of those Russky PIO's there, nice sweetening in tone just from that. I strongly prefer to revoice an amp from the speaker forward. Get the speaker, then the new OT, those two are bigger than anything else to get right first. Then you get to start messing with filter and tone caps, Get the tone caps a dozen at a time from eBay. Takes a bit of time to arrive but the Russian sellers have been great. Way cheaper in lots of 10-15. Did forget one thing...I did a no-no and soldered some radial filter caps on top of the original can cap, pretty much doubling all the stock values with 400-450 -ish volt rating piggybacked on top. A real amp fab repair badass would have fabricated something more sanitary looking but dang, it works and sounds great. I notice better dynamics at attack now, and improved bottom end. When that old can cap finally swells and lets go a JJ can cap should work there. I'm not replacing that old original can cap, the amp runs dead quiet now. Over and over again I have increased filter cap values to double in what comes in tube rectified old guitar amp circuits with only great results. With that said, I did not increase by giant amounts, not trying to see how much I can pack in there, there is a sweet spot with how much filtering goes to different parts of the circuit. The single note work is more dynamic now, and the chords are still limited by the rec tube output anyway, they will distort and sag, while the single note work just freakin' soars...double stops split into chords during multi whole note length sustain on these circuits, with that bloom enhanced even more when the tremolo is going. The bias wiggler style tremolo starves the output tubes, they squeal sweetly in protest at the low point, and that added harmonic output is sustained when the rising current hits the plates hard again. Speaking of sustain, both of these circuits provide unusual, long sustain if the player is patient enough to utilize it, and both of these can run at bedroom volumes sounding fantastic. I always jumper two of the four inputs so that the preamp has one pair of inputs' signal going through a triode in V1, while the other pair of inputs utilize a triode in V2. The parallel inputs richen the tone, and in Rhonda Jean, her four glory holes are arranged a la Marshall, a pair in a darker, normal channel and a pair of inputs are set up as the bright channel. The Harmony H306-A (AKA Cinderella) has four similarly voiced inputs, both input channels similar, unlike her younger cousin Rhonda Jean.
bolero Posted October 30, 2021 Posted October 30, 2021 Haha, great to hear from you, I was worried when you disappeared
Recommended Posts
Archived
This topic is now archived and is closed to further replies.