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King Tut

Increasing Clean Headroom on Old Valve Amp

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The recent purchase of a Peavey VB-2 has encouraged me to re-investigate the delights of my old Laney Supergroup 100 from 1969. When I bought this, my son renovated and revalved it using JJ power valves.

It’s an absolute delight tone wise and great for recording as I can get an overdriven tone at reasonable levels with no problem at all. Unfortunately this is also the amp’s Achilles heels. The couple of times I’ve taken it out to gig I’ve really struggled to get it to modest volume levels without the tone breaking up completely. Ideal for a Sabbath tribute I guess but not very practical.

I guess this is the nature of the beast and I need to learn to love it for what it is and how it sounds, but I was wondering if it could be modded for more clean headroom? Different valves maybe? Get someone to rebids it - would that help? Any ideas gratefully received!

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I don't know about mods, but I think that the circuit is similar to the Marshall 'plexi's. Assuming that is the case, how are you setting the EQ? Generally those old tone stacks only cut mids and only boost treble and bass. This makes max. mids and min. bass and treb the flattest response you'll get. Boosting lows in particular will overload things quickly, so using 0-2-0 tends to give the cleanest sound at volume and cuts through the mix better. Often when playing loud, turning up the bass doesn't increase audible low end much as it just increases saturation.

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15 minutes ago, Jus Lukin said:

I don't know about mods, but I think that the circuit is similar to the Marshall 'plexi's. Assuming that is the case, how are you setting the EQ? Generally those old tone stacks only cut mids and only boost treble and bass. This makes max. mids and min. bass and treb the flattest response you'll get. Boosting lows in particular will overload things quickly, so using 0-2-0 tends to give the cleanest sound at volume and cuts through the mix better. Often when playing loud, turning up the bass doesn't increase audible low end much as it just increases saturation.

Ok so that's similar to my old LH500. I'll have a play about with that. Thank you 

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Might be worth a call to Watford Valves, see if there are replacements that enable cleaner headroom. 

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It could well be the nature of the beast. 100w isn't a massive amount of power for bass, especially in a rock/metal band or similar. If you start experimenting with replacement valves, you may find the power supply can't keep up. 

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On 23/11/2020 at 18:03, Lozz196 said:

Might be worth a call to Watford Valves, see if there are replacements that enable cleaner headroom. 

This.

You need to look at the pre-amp gain valves. If these are 12XA7/ECC83, you could try an ECC81 in their place. Power amp valves will probably be fine.

If it's been a few years since you used it, I'd recommend getting someone to look it over, make sure it doesnt have any duff components etc.

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could you approach it a different way?  - you only have a certain amount of clean watts - so more higher efficiency speaker cabs will get more volume per clean watt... If you use a 1x12 cab, get another one etc

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1 hour ago, LukeFRC said:

could you approach it a different way?  - you only have a certain amount of clean watts - so more higher efficiency speaker cabs will get more volume per clean watt... If you use a 1x12 cab, get another one etc

Good call. I'm using a Big Baby II with it which is a pretty efficient cab!

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52 minutes ago, King Tut said:

Good call. I'm using a Big Baby II with it which is a pretty efficient cab!

I would think of two or the big twin then. 
Or a few of the 2x10 they make that won't be tuned as deep and are more efficient

 

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Back in the 60s you would have played one of these through 2 4x12 cabs, so that would have been plenty loud enough!

I asked a valve amp expert about this issue, and unsurprisingly, he had quite a lot to say. Long and short of it was these do not stay as clean as some similar power designs. I can post here or pm if you're interested?

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2 hours ago, MoonBassAlpha said:

Back in the 60s you would have played one of these through 2 4x12 cabs, so that would have been plenty loud enough!

I asked a valve amp expert about this issue, and unsurprisingly, he had quite a lot to say. Long and short of it was these do not stay as clean as some similar power designs. I can post here or pm if you're interested?

Please post. I'm obviously interested but others may be too. We think Stray's original baseman used one of these but apparently he had a slave amp as well and went through a stack.

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"Hi Jules,

Further thoughts:

 

Those Laney Supergroup 50’s and 100’s are indeed essentially based upon the old Fender Tweed 5F6A Bassman / Tweed 5F8A High Power Twin (see also Marshall JTM45/ Marshall Super Lead/ Plexi) circuits respectively, but lovingly made in Brum with heavy industrial steel chassis and Radiospares capacitors, resistors and other parts (like most British amps of that era). The key to them sounding distinctive despite this, in my opinion, is the use of a certain strain of Partridge Transfomers (different to those Partridge types used in say, Hiwatts) that have Primary windings with impedances that bias up in such a way that there's always some evident crossover distortion regardless of idle current, though not unmusical. 

 

There's also a unbypassed shared common 10 Ohm cathode resistor between the cathodes and the chassis for reading the overall bias current as a voltage (by Ohms law: 1V = 100mA) which might just cause some tangible cross-coupling or back-biasing. In my experience anyway they've never sounded especially clean, perhaps this was somewht deliberate, as the late 60’s timeline fits the advent of then-fashionable heavy rock, who knows? ! I only had one 100 in for a service (I’ve done several 50’s) and noted that it used a big Wirewound resistor rather than a choke in the HT supply (some do, some don’t, but all the 50’s I’ve seen had chokes fitted). 

 

One amp guru I know detracts from Laney’s by saying they sound "like a Marshall with a cold” However, I still really like them for guitar (adopts Brummie accent “yeah roight….wouldn’t mind one meself, loike") as they sound very ‘electric’ and scary, in a good way and don't need cranking quite as loud as a Marshall to achieve that ‘smear' from saturation! 'Hear me Calling’ on the 'Slade Alive!’ from 1971 is testament to that Laney sound: there are Supergroups visible in the ‘live’ session photos. More obvious than Sabbath as far as i’m concerned. But I guess Geezer Butler also had quite a fruity tone when he used them. The Paranoid recording session photos from 1970 show a 100W Laney Supergroup head and cab for Geezers bass, but also a Vox AC30 with Rangemaster treble booster(s) behind Tony Iommi, which I suspect he used (as did Ritchie Blackmore similarly when in the studio e.g. on 'Machine Head’). 

 

I’ve been listening to late-era Move and early ELO today….guess I’m a ‘Brumbeat enthusiast'!

 

Hope this helps."

 

Reproduced from an email, with permission, from my acquaintance Dan Coggins, designer of Lovetone pedals, and more recently, Dinosaural and Thorpy FX

I hope you find this useful, there was another email about amps he considers louder, but that's slightly outside the scope of this thread!

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1 hour ago, MoonBassAlpha said:

"Hi Jules,

Further thoughts:

 

Those Laney Supergroup 50’s and 100’s are indeed essentially based upon the old Fender Tweed 5F6A Bassman / Tweed 5F8A High Power Twin (see also Marshall JTM45/ Marshall Super Lead/ Plexi) circuits respectively, but lovingly made in Brum with heavy industrial steel chassis and Radiospares capacitors, resistors and other parts (like most British amps of that era). The key to them sounding distinctive despite this, in my opinion, is the use of a certain strain of Partridge Transfomers (different to those Partridge types used in say, Hiwatts) that have Primary windings with impedances that bias up in such a way that there's always some evident crossover distortion regardless of idle current, though not unmusical. 

 

There's also a unbypassed shared common 10 Ohm cathode resistor between the cathodes and the chassis for reading the overall bias current as a voltage (by Ohms law: 1V = 100mA) which might just cause some tangible cross-coupling or back-biasing. In my experience anyway they've never sounded especially clean, perhaps this was somewht deliberate, as the late 60’s timeline fits the advent of then-fashionable heavy rock, who knows? ! I only had one 100 in for a service (I’ve done several 50’s) and noted that it used a big Wirewound resistor rather than a choke in the HT supply (some do, some don’t, but all the 50’s I’ve seen had chokes fitted). 

 

One amp guru I know detracts from Laney’s by saying they sound "like a Marshall with a cold” However, I still really like them for guitar (adopts Brummie accent “yeah roight….wouldn’t mind one meself, loike") as they sound very ‘electric’ and scary, in a good way and don't need cranking quite as loud as a Marshall to achieve that ‘smear' from saturation! 'Hear me Calling’ on the 'Slade Alive!’ from 1971 is testament to that Laney sound: there are Supergroups visible in the ‘live’ session photos. More obvious than Sabbath as far as i’m concerned. But I guess Geezer Butler also had quite a fruity tone when he used them. The Paranoid recording session photos from 1970 show a 100W Laney Supergroup head and cab for Geezers bass, but also a Vox AC30 with Rangemaster treble booster(s) behind Tony Iommi, which I suspect he used (as did Ritchie Blackmore similarly when in the studio e.g. on 'Machine Head’). 

 

I’ve been listening to late-era Move and early ELO today….guess I’m a ‘Brumbeat enthusiast'!

 

Hope this helps."

 

Reproduced from an email, with permission, from my acquaintance Dan Coggins, designer of Lovetone pedals, and more recently, Dinosaural and Thorpy FX

I hope you find this useful, there was another email about amps he considers louder, but that's slightly outside the scope of this thread!

That's brilliant stuff - thank you. D'you know what? I'm gonna keep the fecker as it is and use it for recording and maybe the odd small venue gig and embrace the 'drive'!!

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