Tube rolling with Quicksilver Mono 60s -- from KT77 to KT88? KT 120? etc.

Tighter Bass?. That’s not going to be an EL34. The KT88 is one of the best BASS valves. They are known for just that. I think the brand you were using and the signal valves, are the least expensive, and the better combos. KT88s in Solvex, GL (expensive), but JJ (yuk) in a KT88 not my first pick. That being said. The signal valves are the key to really making a KT88 sound BETTER.

I would put the JJs back in and roll the signal valves. Tellies, GOOD Black Plate RCAs, Amperex. STAY away from Sylvania, PSVANE, GEs (can be all over the map, but there are good valves)

You selected a good valve (KT77) for MidBass, great mids, and wonderful highs they just don’t do BASS duty well without some serious consideration in the speaker department.

KT90s are a consideration, again the key for me with a KT90 was the signal valve. My units that use KT90 ALL do better with GREAT signal valves. Put some so so signal valve in front of them, they sound harsh, sharp, bloated mids, boiling highs. The right signal, valves.. Night and day.. BUT I still think a good KT88 for the money. You can’t beat it.

120, 150s. Never used the valves, of the two the 150 is getting the better reviews, would I try them, yes.. Would I pay for them NO...

I’ve used 450, 750, and 1200 watt valve amps..ALL KT88/90 base.
FOR the $$$$$ you can’t beat them..

 AND a Happy Turkey Day to you and yours. Now turkey sandwich day for me.. My favorite!

Regards

Thank you, folks. And special thanks to you oldhvymec for the time you took with your post. I'm tempted to get the GL KT88s but may I ask a question? When you say "signal valve" what do you mean? I'm a bit new to this stuff. 

In my rig I have two tubes in my line stage -- are those the signal valve?

Otherwise, in my mono amps, I have (starting from the rca input plug) (a) an input and (b) a driver tube before I get to (c) two output tubes.

So which is the "signal" tube you're suggesting I play with?

Thanks again and hope your holiday was festive! 

@tablejockey Those are honkin' tubes. Would they work in my amp? I don't know. They're not on the list the amp came with.

The small valves.. Roll a couple sets.. Go to someone with a good rep. for your valves IF you don’t check you own.. The guys will chime in..
I have my own gear to check valves... I’m not one to trust to many, it is always trust and VERIFY!!

12AX7
12BH7

The 12AX7 that’s your best friend. ;-)
12BH7 can add a LOT of harshness too. You have to be careful with that valve.. DON’T spend a lot of money, BUT make sure they are balanced and matched.. ASK the seller (of the valves) to help you. LOW noise, and tell them what you want and what you’ve heard... WORK with the tube seller, if he won’t help.. WRONG guy.

Small valves FIRST.. 50 - 100 for a pair. NO MORE...
Tellies, or GOOD RCAs, GE, Volvo, Mazda, Mullard, Solvex, night and day...

PSVANE, Sylvania, be careful, BRIGHT, comes to mind..

JJs nothing come to mind. C- on the ol sound scale at best.. it’s right in there with most RCAs sold as NOS, LOL rare indeed to find GOOD, stock.. you have to test EVERY one...

Have fun save your money, just a bit.. YES the GLs, though expensive are a good valve. My problem, I’ve had higher failure rates than Solvex, at 1/2 the price, and as good if not better in some ways, sonicly.. I don’t care for the 10% matching either. The solvex I use are within 5% (closer to 2% for me) GL is a good choose though. Kinda.. LOL

GE 6550s are a wonder to behold too. really one of the great tubes..of old if you can find a good old set... Push Pull units, love that valve.. Macs sure do...

When the ol hand feel good, I type away.. Friggin blabber mouth.. LOL. It's ok, I know...

Regards

Thanks, oldhvy. Here's what I currently have (all closely matched) in addition to the outputs:

12AT7/6201 Valvo made for Amperex/Philips, gold pin selected tubes, (1962/1968)
12AX7 Amperex Holland Bugle Boy (1960/1962)
12BH7A RCA (Greyplate)