I've never heard of a 7c7, but maybe? That sounds wrong! whithout even looking at a tube manual. I'm at work and have no reference material here. Take this approuch. Research your amp and find what tubes it should have in it! Before swapping to the "original tube". Make sure no one has modified it. Usually different wiring, resisters, capacitors and maybe the solder being shinnier are all clues someone has been in there. 7c7 Boy that doesn't sound right right!
OOpS I'm wrong. I just looked it up. I don't know if its any good for harp? Those are very old tubes!! Buy a couple NOS 7c7 and see if it that helps Thats a old amp if that was the preamp tube. There are two versions of this amp. The other has a 6SJ7. All the amps with 6SJ7 would be newer than the one you have. Thats why some of them may sound different. It could also be that yours just needs to be serviced! With a loctal preamp tube it is from the forties. Thats old! Probably needs a little work.
Last Edited by on Dec 01, 2011 8:28 AM
6SN7 is a drop in replacement & lower gain than the 6SL7, this would be a simpler & easier tube sub. To really explore options for the 7C7 means replacing the tube socket.
I hope you really mean that it has the original "spec" tubes, rather than "the original tubes". Good tubes and an overhaul of the electrolytic caps (if never done before) will be necesary before you can really evaluate the tone. ---------- www.myspace.com/markburness
I just got my amp back from a "repairman". I now its working.
He has put in all new tubes. 1:He switch'd the 6l6ga for a 6l6? what would you guys think? maybe buy some 6l6ga instead? or maby a 6v6? does that make any difference? 2: Can I swap the 7c7 for another "newer" tube? are there other tubes that I can put in this "tube slot" 3: can i swap a 6SL7 for 6SN7? so just buy a new 6sn7 and put it in? does this make a differences to the sound?
1 - All 6L6s made today are based on "6L6GC" spec, though all do not meet this spec, but all are satisfactory replacements for your amp. You may find 6L6GAs that you like the sound of but really the GAs are not capable of taking as much heat as GC/WGB/WGC. Mascos run pretty hot (hotter than 6L6GAs are rated for), I'd stick with the 6L6GC/5881 types. 6V6s will burn up if you just put them in without further modification. You might not like the 6L6GC that are in there now, but that does not mean ALL 6L6GC will sound bad in that amp.
2. You can only swap the 7C7 for other 7C7 tubes.
3. Yes, the 6SN7 will go straight in the 6SL7 socket (& this socket ONLY) & reduce gain and give you more sweep on the volume pot. It has a similar amplification factor to the 12AU7, Sonny Jr used a 12AU7 in the same part of the circuit, in his Masco inspired SJ1 & SJ2 amps.
---------- www.myspace.com/markburness
Last Edited by on Dec 01, 2011 11:24 AM
Keep in mind that as long as the amp isn't making funny noises and hissing. You might want to try a few different mics. I had a mic that I used for 16 years. Did some work on my main amp (that didn't really need it I was just bored) and bang the magic was gone. well also Hohner changed there harps in 2005 without asking me and it just messed me all up. I sold my mic, bought different amps, died my hair, took up yoga! Nothing worked. Oh yeah bought a dog. Nothing! Finally through the grace of God. A shure 450 came in the mail (with the help of Ebay, paypall and $45) and all is well once again. Moral of the story. It may be your mic not your amp. Uaually amps of that era (that are working correct) kick ass as harp amps!
Last Edited by on Dec 01, 2011 5:04 PM
Are there lower gain subs for either the 6SJ7 (preamp) or 6SC7 (PI) that are in my Masco ME-18? I've been researching ideas to lower gain but hven't had time to mess with it yet. (Already did the mechanical and big cap work - it works and sounds great, just feeds back too easily.) ---------- /Greg
I'm not aware of any "drop-in" replacements for either the 6SJ7 or the 6SC7. Jim Rossen has said in the past that he feels that the 6SJ7 is a contributing factor to the tone (in a good way), he knows more about Mascos than I do.
As far as the 6SC7 is concerned, it has a slightly different pin-out to the more common, lower gain, 6SN7 (6SL7 has a similar amplification factor to 6SC7, but same pin-out as 6SN7 ), so if you want to try alternatives you really need to rewire the tube socket, or rig up a socket adaptor.
@KOENJ "SO is it a good idea to buy a 6SN7 to replace it for the 6SJ7?"
NO! Absolutley not! You can only replace the 6SL7 with 6SN7. (I think that this is what you mean anyway, as your MA17 does NOT have a 6SJ7 according to your earlier post).
So to recap..
6SN7 & 6SL7 are interchangeable, they are both really 2 tubes in one, like a 12A#7 (AKA "dual triodes"). Triode means 3 components to each tube.
6SC7 is a dual triode but a different pin-out to 6SN/L7. Where the 2 halves of a 6SN/L7 are self contained (each half has it's own grid, plate & cathode), the 6SC7 shares one cathode between both halves & they only have their own grid & plate.
6SJ7 is a "pentode" (5 components to each tube), totally different ball game to those mentioned previously - all the above look like they will "fit" in the same socket BUT THEY WON'T WORK if you try it & you may cause damage to the amp!
7C7 has a "loctal" socket, no options in alternatives without replacing the tube socket.
KoenJ - Different power tubes will change the tone some, so feel free to experiment, but if the amp is less than "90-95% there" you might be looking to make (or have your repairman make them for you) some circuit/tube socket mods. It might be useful for you to describe what is not to your liking about the amp, maybe post an audio clip? Keep in mind that despite the 2x6L6, this is a low powered amp & the design does make it feedback prone. If this is your first amp, you have jumped right in at the "deep end". ;-)
lol thats what i mean replace the 6SL7 with a 6SN7. Maybe this will work with my amp.
I will post a sound clip next week, and let you know what i want different. Maybe its a idea to buy the lonewolf tone+ and experiment with this pedal. to get more bass out of the amp.
but first i will post the soundclip, maybe you guy know what to change.
If you want more bass, use a lower setting on the tone pot, the more you turn the tone pot up the more high end you get.
Mascos can have a sweet, singing fundamental note & rich harmonics but they are not known for lots of "bass". Different 6L6s aren't going to make a great deal of difference, 6V6 should not be fitted to this amp without voltages & idle bias current being checked (they will not increase bass anyway).
Compare to these clips, are you sure that your Masco lacks low end?
I'm tempted to suggest that you stop stabbing in the dark & contact Skip Simmons, he will make sure the amp sounds as good as it can for harp.
Last Edited by on Dec 06, 2011 3:12 PM
I wouldn't make any tube changes! That should be a great amp for harp. Setting it a 6 is pretty high. Try it at 3 or 4. Its an old amp and the values of resisters change, tubes wear out and capacitors dry up and don't work as well. With a good shure element and that thing working right that should sound sweet! Don't change tubes! Have someone that knows what to look for and knows what it should sound like when its right. Your setup should sound similiar to the first video. The second and third video is crisper/brighter than yours should sound.
I've watched your video and don't think that your amp is "missing" significant amounts of bass for an amp of its type. Could it be improved? Probably, but you need to identify in what way you want to improve it. If you want "lots of bass", this may not be the amp for you. Can you perhaps post a clip of someone achieving the sound you expected to hear from your Masco?
As MP says, speakers have a bearing on the sound, if your Jensens are the modern Italian SICA reissues, then they lack low mids that beef up the sound. You could also try some darker 6L6 types, maybe some TAD 6L6WGC (they have a dark, rolled off high end)?
Decide if the amp needs modification, rather than fine tuning/servicing? If, in your opinion, it needs modifying Skip Simmons has modified Mascos for very well known harp players. Or, be prepared to do some development work with a local tech, preferably with experience with harp amps. As mentioned in a previous thread, replacing the preamp socket and rewiring for a 6SJ7 tube has been suggested.
Tube swaps are limited in choice, in your case, & are unlikely to significantly revoice the amp. To make significant changes will require some soldering & experience with amp circuits.
It would seem a shame to extensively modify an amp that some may like well just as it is with a service/minor tweaks?
---------- www.myspace.com/markburness
Last Edited by on Dec 07, 2011 6:23 AM
I just swamp'd my 6sl7 for a "sovtek 6sn7gt" and WOW! The sound is so much better! Its warmer and got more bass! Its drops the volume a little bit, but no problem.
Iám now searching for some 6l6 tubes. anyone got some experience with good 6l6 tubes? Maybe the *6LGC/WGB/WGC ore 7581 ore 5881 ore the 6l6 GE
If you have RCA 6l6's I would keep those and try some NOS (New Old Stock) 6sn7's. Try buying 4, but different brands. Nothing newer than the 60's. I don't remember what WW2 military equivelant for 6sn7 is (VT-?), but I would get a couple of those and a RCA from the 50's and maybe a Tung-Sol from the 50's. These tubes will drastic tone changes!
