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Discussion in 'Shock Brother's DIY Amps' started by JamesAM, Nov 4, 2020.
I have a nice stash of NOS/NIB 6V6's: JAN GTY's, GT's and GTA's.
Oh that's just cold, man!
Fair enough rant in many cases, maybe tonewood and PIO caps are better example than tubes...
My Dad was an amature TV and radio repair tech, and started his hobby back in the 50's until he passed away some years ago. I have many NOS tubes of all kinds and I use them, but only for fun in amps I don't play too much. To my ears the modern made tubes are just as good and I can hear no diff. So... I think in reality the only reason to use NOS is for fun and/or if you've got a vintage amp that you need to keep all original but basically never play it. Otherwise, I'd buy new tubes and save $$$ as well as convienience in finding them and also to help keep em in production . Just my 2 cents.
I bought a stock ‘77 Champ off Craigslist this year and all three tubes say Fender on them
I don’t know if they sound better than the JJs I have in many amps but they sure look cool.
They didn't sound all that good. It was just the best at the time.
Years ago, a guy I know that has been modding tube amps for years gave me a pair of 6EY6 tubes. They draw a little more heater current, but they have a 2500 volt rating because they're basically used in video applications.
OK, I've scanned through the posts up to now, and a lot of interesting and good advice. For one, the comment to the OP about having his amp 'checked' to make sure it's operating properly. The idea that some tubes red-plate and others don't rather concerns me, as the amp may be operating a bit outside of where it should be. On the other hand, if it's the same tubes doing the red plateing, it's probably the tube, which are probably shot! So, I wouldn't use.........PERIOD!! (Read the comment about the amp that red-plated during a gig and took out the output transformer!).
Here's something that has not yet been brought up, but may have some significance. Very few, if any (none that I know of) guitar amps have 'regulated' power supplies. As such, both plate voltage and screen voltage can vary significantly.......and this variable is often a function of the individual tube characteristics. SO..... what this translates to in 'listening' to the amp, is the simple fact that some tubes will sound different than others. Guitar amps are 'production' units. In many ways they're as much an 'instrument' as the guitar it self is. Like a guitar, every factor and function on a guitar amp can have a nuance affect on it's sonic signature. Changing tubes can be like changing strings or even pickups, depending on how far you're going. Things like 'bias' can make a subtle difference, depending on how far out of spec you are.....or a HUGE difference when things like blowing up your output transformer happen!
In reality, this is what makes buying a new amp such a beloved experience. It's like buying a new guitar. If guitar amps were like 'Hi Fi' amps, they'd all sound the same, as the goal of the Hi-Fi amp is to be a 're-production' unit....which the function of sonic 'accuracy' and zero-distortion being the goals of said am. It's really quite the opposite with the guitar amp. And, because of this, each amp is as much a 'personal' thing as the guitar itself is. Take 10 'new' Telecaster guitars off the shelf and try 'em all, and of the 10, maybe 1 or 2 will jump out at you as being the ones you like. If you did the same with 10 guitar amps, you'd probably find that the same thing would happen. If you dial it down to putting 10 different tubes in 1 guitar amp, it's like putting 10 different sets of strings on your favorite guitar. The bottom line is that what sounds good to you is what you should strive for. It's that which really motivates a person to play more and get better.
If you're looking for 'reliability' as you indicate, then you need to make sure the amp is 'proper'. Have the bias network checked, and then have it checked again each time you replace the tubes. The 'colder' you run them, the longer they'll last. BUT, you'll sacrefice some performance aspects which may be OK if you like that kind of sound. Likewise if the amp runs 'hot' (bias more at the upper limit), then you may get a sound you like, but you may be at risk for the dreaded red-plate monster to come gobble up your output transformer. In which case..........keep a back-up amp around!!!
I started on guitar amp repair and service about 35 years ago. About 10 years into it I migrated to Home Audio amps......and believe me when I tell you, there are significant differences between the two. I'm now back into guitar amps again at some level, and having some fun doing it, though I stick with the 'vintage' stuff and stay away from things much more complicated than your basic black face fender amp. But, I can honestly say that when it comes to tubes themselves, it's like the proverbial box of chocolates....... you just never really know what you're going to get......UNLESS someone else has gone through some extensive testing on that individual tube. Some vendors do this, others don't. I have come to prefer the Electro Harmonix brand for most 'output' purposes as they seem both consistent and rugged enough that I've not had problems with them, particularly in higher voltage circuits. The JJs on the other hand have given me some grief, with ocassional red-plateing of their 7591 tubes right out of the box. BUT, the 6V6 is generally not as critical, and from what I understand about this tube, many of the new ones being offered are actually a 6L6 in a slightly smaller bottle and re-labeled as a 6V6. So, they shouldn't necessarily be 'at risk' if being used in 6V6 circuits at lower voltages. If your amp is red-plating some Tung Sol 6V6s, I'd get that checked out. Those are a pretty good tube!
Well of course there's no accounting for taste, but overall the consensus is that today's guitar players want to make the guitar sounds they hear on old records.
And as far as the gear used on those old records, I've owned a lot of it and in my own experience, the best of that old gear really does make great great sounds if you operate it well enough.
Because like many of us here, including you I suppose if you played guitar back when the greatest now coveted gear was in every guitar shop; I can compare the gear from classic Rock, Blues & Country records to the gear in shops today.
What I find is that guitars are still great though no better, amps are in some cases still great if you're picky and can deal with the simpler circuits that IME require more player skills, and the pedals are way better.
Where it all goes wrong IMO is in two areas:
1) We can no longer play loud, so we trade whole amp dynamics for preamp distortion or SS pedal distortion.
And 2) Players become so dependent on numerous electronic devices to change the sound and imbue our playing with nuance, that something is lost in the shift to pushing buttons for expressive range.
Again though, no accounting for taste!
I love what Tom Morello does or did with lots of pedal control, and a few other players have outstanding sounds.
Funny though how huge boards seldom result in memorably great sound.
It's a fact that many players today spend more money on just their pedal board than the adjusted cost of the whole amplification rig used on great sounding classic recordings.
When I bought old Plexi and metal panel Marshalls they ran between 1 & 2 weeks pay, Fender amps ran cheaper, maybe one weeks pay bought a BF Super Reverb. Hell I bought a BF Deluxe Reverb for half a weeks pay.
Pretty sure I'm not alone here in the get off my lawn crew in feeling that there was a high incidence of truly great sound in classic recordings, compared to today's over processed fizzy distortion, copycat compressed chicken pickin or Blooze pedal Blooze tone.
The classic great amps I've owned were in many but not all cases capable of better sound than most of the modern and RI amps I see today.
But I think players generally moving to convenience based gear, and to getting an expressive range on the instrument via electronics rather than via technique; has really lost a lot of what artists did with the simpler tools.
As far as specifically power tubes, many tube amps now sold are designed so you really don't hear much from the power tubes IMO.
Amps like the 20w Marshall Origin running 2xel34?
I doubt those loafing power tubes contribute much of a sonic signature? Not certain though, never tried one.
My point on that is to choose better tubes in places you can actually hear them.
Any tube amp is influenced by V1 but it's possible that running preamp distortion amps turned way down, you only hear the preamp tubes clipping, and the power tubes just have to make the preamp simulated cranked toob amp sound louder.
Not always, could be the power scaling designs allow the power tubes to contribute some signature.
AFAIK when great 6L6 stopped being produced, Mesa redesigned the amps to sound effectively the same with the weaker power tubes they were forced to work with.
But those great Sylvania STR415 tubes used by Mesa, Fender, Peavey and others had almost no personality aside from massive headroom and fidelity. Run your old Boogie with cranked preamp dirt into a less awesome power section and you'll likely hear the cheaper weaker power tubes contributing mush where they should deliver punishing fidelity at massive volume.
But who runs a classic Boogie at anywhere near loud enough volume to stress cheap Chinese 6L6 duets or quads?
Modern amp designers adapted circuits to sound right with cheaper new production tubes.
That alone confirms that new production tubes don't perform the same.
RI amps like the Fender and Marshall reissues maybe not so much.
thanks for this- appreciate it! As for the tung sols, I don’t think I’m the only one who has seen redplating from “normalish” voltages- I’ll concede that 369 plate to cathode is certainly on the higher side of OK for a tweed deluxe, but I do have two other sets of power tubes that work fine with the amps b+ levels.
I do remember a few threads here about the hardiness of modern production tung sols. According to their own data sheet, it looks like they only rate their 6v6GTs for 315v at the plates. I would hate to use these in a Princeton reverb, which routinely get plate voltages of over 400v as far as I’m aware. As always, ymmv on this big time.
I never did consider a 6V6 to be a 'robust' tube. On the contrary, I've always considered them rather fragile. I believe them to be GREAT tubes for audio purposes, but I think their use in Guitar Amplifiers was more a function of availability and cost than actually being the 'design' preferance. Later amps either used 6BQ5s, which are perhaps a bit more resilient, or moved up into the 6L6 category. I know Ampeg and a few others used 7868/7591 tubes, and of course for high power the venerable 6550. Most 'audio' guys consider the 6V6 to be a 'sweeter' sounding tube than the 6BQ5, and also work around it's lessor capability of power production. Magnavox, Motorola, Zenith, RCA, and a bunch of other home audio companies used the 6V6 a lot back in the '50s and '60s, but moved to the 6BQ5 as they became more popular and available. I know this is not clearly relative to your original commentary/question. But, when guitar amp companies really started ramping up production of electric guitar amps in the late '50s and early '60s, the quest for more power was also accompanied by the fact that these companies were still on a growth curve that did, in fact, limit some of their production capability. So, using cheap and available 6V6 tubes wasn't a big deal. And, pushing them in terms of voltage ceilings was a way to get more power from their amps.....which led to advertising claims and 'marketing advantages'. The games people (and companies) play! Anyway, remember that the specs on these tubes are for designers to work around 'optimum' performance....which means as close to 'zero' distortion as possible. That what the productions specs were intended to be used for. When guitar amp builders got ahold of them, all that went out the window, particularly as 'distortion' became a desireable characteristic. If you want 'clean' power, buy an old Twin or Twin Reverb amp. But, if you want the break-up that most guitar player strive to get, you 'push' the amp beyond the design limits. No wonder tubes red-plate!!
I'd still check your bias. Just because you have measured plate to cathode voltage, you only know part of the equation. You need to measure the voltage across the bias resistor, and do the math. Prior to that, you should measure the actual value of the bias resistor itself. Many of these are surprisingly out of spec! But, do you math based on actual measured values. This can be quite revealing......
Thanks for this great advice! Last time I checked:
Bias resistor is 326r
VK is -22.4
V=IR with 5% grid drop means about 68ma or 34ma/tube for 105% dissipation.
All (pretty) good on the amp. It’s on the high side but should not be red plating a 12w 6v6 imo.
FYI: I had one Russian Tung Sol redplate in my cathode biased '59 Ampeg Mercury. It wasn't pulling higher current than it's "partner" and did not exhibit this problem in my fixed biased '61 brown Deluxe. That one tube just wasn't happy in a cathode bias format. Go figure.