Greetings everyone, first time posting here, tried to find an answer to my question in an existing thread but its a bit specific so here we go!
I'm currently playing in a Doom-ish Stoner Metal band, lots of headroom and a huge variety of tone (from clean to high gain with some fuzz and low/mid-gain here and there) so I'm looking for something balanced to cover as much sonic spectrum as possible. Right now my rig is as follow:
Amp: Ceriatone Overtone HRM100 MKII (Dumble Overdrive Special clone) w/ 4x 6CA7EH tubes (homemade with external HRM tone stack)
Cab #1: Peavey Triple XXX 4x12" w/ 2x Sheffield Triple XXX (basically V30s) and 2x Sheffield 6505 (which sucks)
Cab #2: Homemade oversized 4x12" w/ 4x WGS HM75
So my plan right now is to split the HM75 between the two cabs, one of them will have the Triple XXX and the other one will have two new speakers as I want to get rid of the 6505s. Since I got the HM75/V30 combo covered already, I was thinking about pairing the other pair of HM75 with something similar, maybe a bit darker as they'd go in the bottom cab. Right now I'm looking at either a pair of ET65 or ET90, unless someone has a better suggestion to make, I'm open to try anything but I really want something that will shake the basement.
Cheers to all!
Not sure what speaker to recommend, but be aware that the EH 6CA7 does not have an internal pin 1 grid connection like an EL34. That can cause overheating in some EL34 amps. It also has a relatively low grid limit of 425V. Unless you know for sure the grid supply is well below the amp's 450V plate supply and the internal wiring is not an issue, I would stop using those tubes in that amp immediately.
Fortunately, the JJ 6CA7 is internally-wired just like an EL34, and has a grid limit of 500V. They sound best biased just above 40mA and take a bit of playing to warm up for the full dynamics. Maybe not as much high harmonics as the EH, but you can order a low grade set, or just bias them a bit higher, if you want more distortion. The JJ EL34L is actually an ideal Doom Metal tube with a fat aggressive midrange, deep tight bass and a bit more headroom than an EL34, and a 450V grid limit. It may also sound more articulate in half power mode, due to the lower internal resistance. Mixing a pair would be cool, but the resistance difference would be a problem without separate pair biasing. Maybe try just a pair of each first to see which you prefer. I'd order JJ tubes from Eurotubes to be sure of full testing, and you can specify a tube grade. A tube's transconductance is good down to ~40% of its current rating, but lower grade tubes tend to sound more saggy/muddy. They might recommend something just right for the amp and your target sound. I don't know the grading scale, but ~7/10 should be a safe bet for some more crunch without mud.
My guess on the speakers is the ET90 or Retro 30 are more likely than the ET65 to match the bass strength of the HM75. The increased presence of the ET90 probably won't be noticed on the bottom, but you might like an X pattern. I assume the Retro 30 would fill in the mid-bass more, which might compromise the scooped sound a bit, but I dunno.
...and I should have mentioned that if the amp came with all short plate JJ ECC83S preamp tubes, replacing at least one with a medium plate 83MG and an 803S in the PI slot will give the amp a more balanced sound with better touch dynamics, a deeper punch and less grainy highs. If you like the 83S in V1, try the 83MG in V2. Maybe get two of them to experiment with in V1 or the PI as well. I'd also get some Eurotubes Tube Damper Rings: One for the 803S and two for the power tubes to minimize microphonics and possibly extend tube life. The PI tube noise sheild cover is not really needed in the PI slot. The JJ 6CA7 in particular should last years anyway -- probably the most sturdy power tube made.
Hey man, thanks for the reply, didn't thought that we'd end up talking about tubes. different topic but I'm game for this subject!
Wasn't aware that it would be such an issue to be honest, for the record I've put a couple of amps together but can't say I'm a huge expert on the subject. I've read a good bit on amp electronic theory though so I know what you are talking about so I'll measure that voltage before using it again and worst case scenario, I have a quad of Tung Sol EL34 that I can use. Can't really mix as the amp has a single bias control for all 4 power tubes, I did some mixing in one of my other amp (4 stage gain JCM800 2203 clone) and found out that a pair of JJ KT77 along with a pair of Tung Sol EL34 really sounds awesome, well balanced bass along with the grit of the EL34. Wanted to try something different with this amp and the 6CA7 was one of those I haven't seen too ofen.
Regarding the preamp tubes, funny you talk about the 803s in the PI, been doing it for quite a while. Right now the preamp is as follow:
V1: Preferred Series 7025
V2: Gold Lion B759 Premium
V3: Tungsol ECC803s
Never tried the JJ MG model, since this particular amp ain't got a cathode follower and that V2 is basically the two stages of the Overdrive channel, I've naturally went with something with a good bit of gain to it but with a warmer sound than the JJ ECC83S. I've switched the 7025 with the B759 recently but I'm still not sure which I prefer the most.
Back on the speakers, I'll check a couple of youtube videos on the Retro 30, haven't put too much if any attention to that particular model.
Sounds like you have the tube situation well in hand. I trust CP tube sources in this order: Slovakian, Chinese, Russian. They are all getting better for the most part, but JJ has really gotten reliable since the move to the new plant. The lineage starts with the coveted Tesla brand, and I don't think there was ever a loss of methodology as there was with the Russian and Chinese plants and personnel. The purpose of JJ may have been conceived as a budget line, but the Tesla factory was just too cramped and disorganized for proper QC. Check out the YT Tesla factory tour to see the old masters in action. It's a wonder to behold.
New JJ tubes may have extra stabilizing points and soldered joints not found in the best NOS tubes. The JJ 6CA7 is the newest JJ power tube (with the EL34L not far behind). They may sound more like NOS than we think. Tubes loose vacuum over time, and old tubes may not have had as tight a vacuum to begin with compared to what modern tech can offer. A looser vacuum generally causes a tube to get hotter; hence, distort/compress sooner. The effect is a softer/harrier sound with less punch and clarity. Lower temp means the tube can be biased higher, so the same level of distortion can be achieved as with a weak vacuum, but with a higher ratio of even harmonics and with less compression and low end mud. Beam power tubes, like the 6CA7 generate ~1/3 less 3rd harmonics than Pentodes, so getting a richer/sweeter harmonic balance is possible without as hot a bias point. Again, just above 40mA at ~450V plate is a good target point for the JJ 6CA7, and hardly a strain.
You might consider rewiring the power tube pin 1 to neg bias mod, so the grid suppressors can keep the current more stable at higher volumes to prevent red-plating and other related disasters that have plague EL34-type amps. However, true beam tetrode tubes, like the EH 6CA7 or JJ KT77, KT88, 6550, can not then be used, so a warning sticker is advisable.
Finally, an adjustable sag resistor, or a London Power 'SUS-...' kit mod can be used to even out the attack/sustain sound per your taste at a given volume and distortion level. Just the right amount of sag can make an amp sound massive via the sense of "weight" it imparts. GMX multiplication can make it sound even bigger, but you probably don't need or want that with a four tube 100 watt amp. I suppose there is such a thing as too big a sound...or is there? I know Nik at Ceriatone has done sag mod, and he may know about the pin 1 to neg bias rewiring. He may advise you on how to do an adjustable sag mod yourself, so you can use tighter/higher grade tubes and tune the distortion via biasing and sag. Otherwise, look to the appropriate London Power SUS kit.
Just side note, long, long time tube lover... use all Marshall amps...old and newer school ones. When it comes to power tubes..man, Shuguang is making imo, the best sounding, most durable tubes now, even their cheap preamp tubes (especially the long plated ones) go toe to toe with my American made Raytheons, GEs, Sylvania, etc.... They make power tubes for TAD, Ruby, GT and under their own name. Use to be a big JJ guy...still like their tubes, but if you want that old school guitar tone as a keystone...sounds that emanated from the mid and late 20th century, Shuguang is where it's at!
Yeah, Chinese tubes have been getting very good since they acquired the GE equipment and practices, but make sure you get tested tubes just to save a hassle. The TAD and Preferred Series are highly rated. Good feedback about the Chinese preamp tubes as well. Long plates tend to sound fuller and more dynamic, but they can be noisy in the V1 slot. Mixing different plate sizes can be a good way to fine-tune the sound.
My impression is that Shuguang tubes have more compression and resonance than JJ, lending a velevety quality to the more pronounced harmonic presence. It's a nice sound, but may get too mushy in some cases.
Marshalls were generally loaded with Mullards in the 60's. The JJ EL34 is claimed to be like them with the EL34L possibly like the tighter, cleaner Mullard EL34 XF2. Who knows at this point, but it's good to understand how different tubes affect the sound. The Mullard (Sovtek) RI's are apparently somewhat dull sounding -- might be good with certain bright speakers.
Just saying I love this combo JJ 83mg (v1), JJ 83s (v2), and TAD EL34 preferred series, H@K Switchblade going into WGS ET90 Port City OS 2x12.
It's a keeper. It's not super doom like the fella is looking for but the MG does really give rounds the tone off the high end where the TADs and are propping the high end frequencies.