Stump

Welcome to the forum. I would start by getting a copy of the schematic and learning as much about the amp as possible. Electrolytics typically need replacement in old gear, so that's a good place to start, then start checking the resistors to see if they are still in spec, then touch up all solder joints. I do this stuff as a hobby, so I'm not really a tech, but I fix and build guitar amps pretty regularly. Make sure you know how to work on this stuff safely, Google is a great resource and YouTube has a ton of how to videos. Hopefully, one of the more experienced members will chime in here.

There's no tube worth $450, regardless of the hype surrounding it. The majority of mine are pulls from old equipment. I've purchased a few, but never more than $35.

I agree completely. V1 in the early, single channel Marshalls, JCM800 and earlier, models 1987, 1959, 2204, 2203 and JTM45, shapes the biggest part of the tone, output tubes the least, unless you're able to play them at high volume. My favorite tubes in my 50 watt Marshall 1987 model, is a Tungsram ECC83/12ax7 in V1, a Mullard CV4004 in V2 and a Brimar CV4004 in V3. The whole matched triodes thing, that some tube dealers recommend for the phase inverter(V3), is a bunch of baloney in my opinion. Most current production power tubes, of the EL34 family, sound and work just fine at considerably less cost. I have a pretty good collection of Old Stock tubes and have compared them directly against their modern counterparts with the only tube not comparing favorably being the KT77. There's just something about the original GEC Gold Lion that none of the modern versions have yet captured. My Dynaco PAS3 preamp uses the original Old Stock tubes, with Telefunken 12ax7's, which sound better than any modern tubes I've tried in it yet. In my ST70, I'm using Old Stock 7199's, the original Mullard GZ34, but current production JJ 6CA7 power tubes that sound nearly as good, but different than the Mullard XF2's that were in it. Some of my guitar amps use current production tubes in all positions and sound just fine, though I prefer to have a good Old Stock tube in the first position. The older, simpler design guitar amps seem to benefit the most from Old Stock tubes, the newer, more complex amps the least. This is just my experience, but in any case, tube rolling can be fun and yield some excellent tone, regardless of new or old manufactured tubes.

Thanks for the link. Do you happen to know the impedance of the slave speaker? I'll probably add a DIY slave to mine. I installed it in our living room last night and it sounds great, but I'd love to have more bass available, and I have a bunch of speakers that I might be able to use as long as the impedance is correct.

Speakers are generally rated at nominal impedance, so those numbers are fine. I don't recall ever having any speaker measure exactly what was on the label.

A neighbor gave me this sub about a week ago, I didn't know much about it, but free electronics are always worth what you pay for them, so I took it.:) I'm really surprised how good it sounds. So far I'm running the volume at the 9 o'clock position, 50hz low pass, and it really fills out the music nicely. I'm using it in our master bedroom 2 channel system, Onkyo TX-DS838 AVR and KLF20 speakers, I set it up here just for testing before moving it to our living room, where it will replace a Polk PSW10. The Polk has a tough time keeping up with my Chorus 2's and Heresy 1's, as well, the room is pretty big with high ceilings, movies really need more than the little sub can deliver. The PSW1 also has an output to add a passive slave sub, which I might do as soon as I figure out the correct impedance. I haven't found much info on either piece, but from what I've seen the amp puts out 150 watts alone and 200 with the slave, 25hz-200hz, 12" air suspension woofer. If anyone has more or better info please let me know. I'll post an update once I move it to the big room.

My early 70's Zenith Allegro Stereo Console sounds excellent through my Heresy 1's and KLF 20's, haven't tried the Chorus 2's yet. I was quite surprised at the low noise floor and overall quality through these speakers. I believe it's 30 watts rms, and was plenty loud. It was cool to listen to some old 8 Tracks at volume, though cassettes sound best, using my Fisher deck through the line input. Got the low end really thumping thanks to treble and bass eq.

Very cool. It's always great to see someone with great skill. Thanks for sharing this vid.

Just a thought regarding the power transformer getting hot. These amps were designed for 117 VAC, our power today is 120-127 VAC in most areas. Setting power tube bias around 1.2 volts or lower, instead of 1.56, seems to help and I've not noticed any negatives in the sound, I have an all stock ST-70 and Heresy 1's.

Another thought, as I experienced this recently with a friend's 4x12 guitar cabinet. Check and tighten the push on connectors that go to each speaker, as well as the connectors to each binding post. The guitar cab started sounding thin and lost some thump, seemingly overnight, for no apparent reason. I opened it up and found that one speaker's positive connection was very loose, the rest weren't much better, so I cleaned all speaker tabs with DeOxit, tightened the connectors and all is well. I solder all of my internal speaker connections for this reason.

Not mine, but a good deal in Andover, Massachusetts. http://boston.craigslist.org/nwb/ele/5628292137.html

I run my Heresy 1's with a Dynaco ST70 and Dynaco PAS 3 preamp, and find it to be awesome. I've also heard Heresy's powered by McIntosh MC60's, Peachtree Audio, Will Vincent ST70& Mk3's, they have sounded great with all of these tube amps. Maybe building one of the new ST70 kits would be a good option for you, http://www.tubes4hifi.com/bob.htm

Radial Electronics in Canada owns both Hafler and Dynaco. I own a few of their guitar products, they are excellent. Hopefully their Dynaco gear is just as good. They have released a number of products under the Hafler name, tube and solid state headphone amps, phone preamps for mm/mc, and a couple of other things.

Actually, I just ordered an Apex matched, burned in quad for $63.60, JJ 6CA7. This has become one of my favorite tubes for Hi Fi and guitar amps. This is the third set I've put in my Dynaco over the past year, not because they fail or have any issues, I end up pulling them for customer guitar amps, as in emergency, have a gig tonight type scenarios. Excellent tubes.

A single speaker sounded much better when I tried it, probably for all the reasons that were mentioned previously.

I've run the Mullard reissues in my Dynaco ST70 and they sound good, not sure about longevity because I pulled them after about 10 hours to use in a guitar amp. The amp they were put in is still going strong after at least 100 hours. The original Winged C tubes were my favorite new production EL34, but the prices have gone through the roof. I've had good luck with JJ EL34's and 6CA7's, EH 6CA7's in the ST70 as well. I currently have the JJ 6CA7's in it, they sound excellent, the bias has not drifted at all and they are about $70 for a matched, burned in quad, depending on where you purchase them.

Congrats, beautiful speakers.

That explanation is perfectly fine, just the fact that you prefer the phenolic is enough. The more I listen to these speakers, the more I like them.

Why did you go back to phenolic mid? The tweeter is a solid improvement and I really like the way they sound now, I don't want to "ruin" it and spend money for nothing.

I finally got around to installing Titanium tweeter diaphragms in my KLF 20's and notice a huge difference in the overall sound of the speakers, not just the highs. The highs are so much smoother, but I also notice that the mids sound clearer and the low end seems more pronounced. I'm curious about what causes this, is it just perception or something electronic that changes? In any case, this upgrade alone is well worth the cost. I might, when finances permit, upgrade the midrange diaphragms, as this is another upgrade that is recommended for these speakers. I'll try the mids from my Chorus 2's first though, to make sure I like it. Many thanks to Moray James, and others, for the information about the upgrades.

Outstanding, I look forward to your review in the near future. My brother in law has a pair of MC 60's that were used to drive KLF 20's, incredibly beautiful sound!

have you tried dropping those Crites tweeter diaphragms and phenolic mid diaphragms into the K79 and mid horns in your KLF20 yet? Its a tasty mix.I finally got around to installing the Titanium tweeter diaphragms in the KLF's and love how they sound now, much smoother. When finances permit, I plan on doing the Titanium mid diaphragms and possibly new Crites crossovers, but for now I'm really digging them the way they are.

Congratulations and welcome to the club. You can't beat free, working Klipsch speakers. I have the same speakers, but modified with Crites crossovers, Crites Titanium tweeter diaphragms and Crites Phenolic midrange diaphragms. Even in stock configuration, these are awesome speakers, the mods take them up a notch and with tube amplification I can't fathom anything sounding better, though they sound just fine with a decent solid state amp or AVR. Enjoy!

I'd gladly get K Horns, if I had room for them. For now I'll just "suffer" with what I have.

Roger, I'd love to hear some Jubilees, I heard K Horns a very long time ago and remember how huge they sounded. Matt, thanks, I really enjoy the KLF's. They really thump when pushed, the dual 10's Rock. Ceptorman, it's very refreshing to hear everything clearly, sometimes it's like hearing a song for the first time, even though I've listened to it forever.