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Hello all,

currently using Groove Tube 6550's(sovteks) in my 1977 DR201 6xEl34. im not happy. I use a 70's fender pbass and marshall VBC412 bass cab. can anyone out there suggest what they think would be a good tube for this use. the current tubes sound harsh in the higher frequencies and are not smooth in the lows and mids. they were expensive tubes and they are causing me to hate my hiwatt!!! should i switch back to EL34's as thats what the amp was designed for? help.

thanks chris

I might try 4 x KT88. I changed the Sovtek 6550s in my Fender PS300 to JJ KT88s, and it made a big improvement. I'm generally not a fan of Sovtek power tubes.

--mark

I've been tempted to try the EHX 6CA7 in mine for bass use. I don't hate the Winged C EL34s I have in there now, but I am curious. They are described to be sturdy and have big sound with more headroom than EL34s.
They are not too expensive either.

mhuss wrote:I'm generally not a fan of Sovtek power tubes.

With the exception of their 5881 replicas, neither am I.

I also don't feel 6550's are the best match for Hiwatts.

@elkbass: If vintage Mullard XF2's are out of the question, guess I'd just stick JJ E34L's into it for the moment.

Dave

I usually don't jump on the bandwagon, but I tried a quad of these

http://www.ebay.com/itm/EL34-Vacuum-Tub ... 19cadd229a

in a DR103 and was very pleasantly surprised.
The construction is far better than the ehx/sovtek stuff. The glass is heavy and thick, plates are welded, everything about the tubes just give the appearance of "beefy" and well built.

Tonally they seem pretty neutral, big and bold. Not Sterile sounding like some tubes can be, just neutral. Not too bassy, not to thin.

I will probably buy them again.

Dr.HIWATT wrote: I will probably buy them again.

They look nice. Do they appear tolerant of high plate voltages?

Dave

I put them in a new HI-TONE a couple months back. Since we have adjustable bias, I don't know for certain.

But they sound good and took some abuse up at the Drum Farm in a two week recording session. it was dimed for hours.

My HIWATTs are stacked on shelves presently and I haven't had much chance to find a hot one and take it to HIWATT Valley to try them.

I am liking the current crop of Chinese EL34s too, they sound good, are well built, and don't cost a lot.

--mark

I was wondering if 4 kt88's wouldn't work in place of 6 el34's.

They certainly would, but I would use the end sockets:

O x O O x O

A proper KT88 installation has those long thin ventilation slots on either side of the tube sockets.

--mark

mhuss wrote:They certainly would, but I would use the end sockets:

O x O O x O

A proper KT88 installation has those long thin ventilation slots on either side of the tube sockets.

--mark

Really, wow that opens up the opportunities. Mark, what does this do to the output impedance? Would you have to compensate?

No, the impedances are roughly the same, so (except for a major bias tweak) no other adjustments are needed.

--mark

Hey I bought this amp and I'm very happy with it!

I do see what Chris was saying about the harshness in the highs so I've decided to go ahead and start re-tubing the beast. As mentioned before by the previous owner the amp has Sovtek Groovetube 6550s in the power section (which admittedly is a brand I haven't been fond of in the past). For the pre-amp section there are 3x JJ ECC83s + a JJ ECC81 in the Phase Inverter slot (another brand I haven't had great luck with). I've gone ahead and ordered a Mullard 12AT7WA to put in the PI, however I was wondering what you all would recommend for the other slots? I've had my eye on the JAN-GE 12AX7WA for the 12AX7s and probably Winged C 6550s for the power section. However I am looking for the opinions of others, I've heard Hiwatt amps are sort of picky with tubes.

For informations sake I'll add that for a cab I use either a Emperor 4x12 or a Ampeg 810, I play with a Rickenbacker 4003 and a Fender Precision.

for new valves the JJ12 ax7 is the most mullard like in a HIWATT. But I do not care for the JJ 12at7, it is very harsh and brittle sounding.
a real Mullard in the PI is a definite upgrade.

I am not a fan of GE 12ax7's in HIWATTs, its real mullards, or brimars if its old glass.

IMO the four JJKT88's or almost any el34 will sound better than a 6550

Dr.HIWATT wrote:for new valves the JJ12 ax7 is the most mullard like in a HIWATT. But I do not care for the JJ 12at7, it is very harsh and brittle sounding.
a real Mullard in the PI is a definite upgrade.

I am not a fan of GE 12ax7's in HIWATTs, its real mullards, or brimars if its old glass.

IMO the four JJKT88's or almost any el34 will sound better than a 6550

Thanks for the quick reply, I certainly appreciate it.

I'm gonna wait and see what the change in the PI does before I start buying anything else. Do you think changing this single tube will "smooth" things up a bit? Harsh and brittle sounding sounds exactly what's going on for me, and I can combat it with the treble and middle controls (I have them before noon) but I know this amp just needs a little tweaking to get it performing the best. Would switching the 6x 6550s for 4x KT88s deliver the same power without hurting anything in the amp? I've been considering switching the amp back to EL34s but probably not in the near future.