KT88 power valves with low end grip?

[Gazjam]

Mulling over improving the sound of my valve amp until such time I can afford to replace it with something another level up from what I have.

Cant fault the mid and top end, but after a recent get together at mine and plumbing in a very good solid state amp to my system showed that a bit of extra grip on the lower end will work wonders with my speakers.
Currently using Gold Lion KT88 Reissues which I like a lot, but as I say...if I could get a bit more grip on the bass it owuld be better.

Would I get more grip rolling the preamp valves, which are 12AX7 and 12AU7?
Tried a few different ones which made subtle differences, more in the top end than down below.
This made me think swapping out the power valves would change the grunt a bit more...

My speakers are a very efficient 94dB and all cabling is fine.

Any thoughts guys?
Thanks.

[DSJR]

Please forgive this, but valves coupled via transformers and passively driven speakers isn't a recipe for TAUT bass. Musical and involving certainly, but not taut at very low frequencies - that's an artefact of the output transformer.

This really shows my ignorance, but can KT120's be substituted? probably not, but I'll chuck it in anyway...

[M6NTL]

It is a function of the way transformers work, the voltage through the primary winding saturates the magnetic core, which induces voltage into the output winding. Unfortunately this process is not instantaneous, you get something called a hysteresis loop - it is this that makes the low frequencies wooly (the amount of wooliness depending on the density of the core). I replaced the output transformers in my Grant G50 with some comparitively MASSIVE items, and it tightened up the bass loads...

[Ali Tait]

Aye, as we discussed Gaz, you'd need better output trannies, but by the time you've paid for them you'd be as well going for a new amp...

[Ali Tait]

If you want to nip over, you can borrow the KEL84 if you like?

Something different to listen to.

[struth]

not using my valve amp combo either if u want to try it.

[Marco]

Please forgive this, but valves coupled via transformers and passively driven speakers isn't a recipe for TAUT bass. Musical and involving certainly, but not taut at very low frequencies - that's an artefact of the output transformer.

<Cough> Not here it ain’t, muchacho, where bass is as taught and grippy as a very taught and grippy thing! Sometimes you have a habit of talking in absolutes

This really shows my ignorance, but can KT120's be substituted? probably not, but I'll chuck it in anyway...

They can if Gary’s amp can safely take them - and if so, they’ll likely provide much more grip than any KT88s.

Marco.

[Reffc]

Please forgive this, but valves coupled via transformers and passively driven speakers isn't a recipe for TAUT bass. Musical and involving certainly, but not taut at very low frequencies - that's an artefact of the output transformer.

This really shows my ignorance, but can KT120's be substituted? probably not, but I'll chuck it in anyway...

How did you work that one out? Someone more direct might have responded with "Complete and utter cobblers!"

Providing that the amp has low output impedance and is well matched to the speakers, plus the bandwidth (ie decent transformers) is good and distortion low, there's NO reason why bass from a valve amp shouldn't be taught and punchy. It's high output impedance resulting in low damping factor combined with low or no negative feedback (which makes the amp less stable into difficult loads) which is a recipe for poor bass control, NOT the fact it's transformer coupled. Substituting one make of KT88 for another WON'T make bass significantly better or worse. The circuit, whether feedback is used, available current, bandwidth and output impedance are far more significant than what brand of valve is used.

Sustituting KT120s into a poorly designed valve amp wont make the bass any better. I use KT77s in mine and have no shortage of deep, taught bass, even into difficult speaker loads.

[DSJR]

Valve amps DO NOT usually have low output impedances and this is why (I understand) 1960's and early 1070's speakers were nominally 15 ohms with an absolute minimum of 8 ohms, hence Marco's good perceived results as his Tannoys should be average 11 ohms I think and his amp having very expensive and carefully selected transformers (why else would TD custom amps cost so much - I bet the ironwear accounts for a substantial amount of the cost). VERY few could accommodate humungous old Tannoys in any shape or form though Marco, and I have no idea how the Eddingdales fare in comparison in the bass.

Paul - not sure you're totally right here, since the quality of the transformer seems to almost totally dominates the sonic and technical performance of the valve amp using them. Sure, you can tinker around with the other things, but people who've done this usually ruin the whole thing by trying to shut the stable door after the (transformer) horse has bolted. best get the iron sorted first and then the rest can fall into place. I await your own valve amp with interest

Of course, this is a polite thread where the OP was proposing a few things to do. I gave an opinion, which is subject to change and much correction if I'm wrong. I think enough here both now and in the past have commented on how important the output transformer really is and it was talented design that made the 1960's Radfords so advanced for their era, bass distortion and damping factor (what little there is) being ahead of a lot at the time I remember.

[Marco]

Valve amps DO NOT usually have low output impedances and this is why (I understand) 1960's and early 1070's speakers were nominally 15 ohms with an absolute minimum of 8 ohms, hence Marco's good perceived results as his Tannoys should be average 11 ohms I think and his amp having very expensive and carefully selected transformers (why else would TD custom amps cost so much - I bet the ironwear accounts for a substantial amount of the cost). VERY few could accommodate humungous old Tannoys in any shape or form though Marco, and I have no idea how the Eddingdales fare in comparison in the bass.

Indeed, Dave, but the point is that not all valve amps have wooly bass and poor grip (in comparison with SS amps), which is the way your original comment came across and the picture you were painting, as if it was a ‘universal fact’.

Yes, with valve amps ‘it’s all in the iron’, but if you afford to buy a valve amp with suitably good/large transformers, and most importantly, partner it with the right speakers, then wooly bass is a non-issue. Again, it doesn’t matter that not many can accommodate humungous old Tannoys (or whatever else is chosen to get the job done) - the point is that the technology itself is capable of it!



In 30-odd years of using hi-fi equipment, and mostly solid-state amps (some huge behemoths amongst them), I’ve never had such deep, tight, tuneful and extended bass in my system, as I have now - and that’s with a valve amp in the equation.

Marco.