I read that one too in Morgans book...one-and-a-half-envelopes distance...but we see often times in someones build, that rule is tossed out the window...
--------------------------------------------------------------Rick........
Typical chinese.
Sorry when I see the standard of wiring, the capacitors and the general horrible presentation I can understand why most "hi end" stuff is awful crap and is based on marketing, BS, and a combination of asian dumping, fancy web sites and convincing the press to make superlatives until they come out of our ears.
I've now seen so much of this stuff, "underwhelmed" will be the flavour of the next decade and more... or maybe people like stuff which sounds & looks horrible?
Who knows?.
You seem to hold all answers so it'll come from you probably 😉
Gerrit, do some testing with your rig on forehand and take some IR shots to be sure tubs stay onder 250 celcius. When arguments for opposed views cancel out let the facts speak...
In the last months I've noticed the departure from MJ books too, and not by the least studied persons. Not all's true when black on white 🙂
Gerrit, do some testing with your rig on forehand and take some IR shots to be sure tubs stay onder 250 celcius. When arguments for opposed views cancel out let the facts speak...
In the last months I've noticed the departure from MJ books too, and not by the least studied persons. Not all's true when black on white 🙂
"I've used some SilenX low noise fans to fix some noisy Hoefer HV supplies, and you can hardly hear them without any audio" Thanks for the heads up smoking-amp. I looked on Digikey, Farnell etc but was a bit bamboozled by the specs and gobsmacked by some of the prices.
Cheers, Andy.
Cheers, Andy.
I've also read Morgan Jones's rule on tube spacing, and it's generally a good guideline, if not always a practical one. On the other hand, gobs of commercial amps flout that rule, among them:
From a DIY standpoint the arrangement and spacing of tubes is important, but so are all the other little things like lead dress, shielding, mechanical integrity and the like. It makes little sense to worry about inter-tube spacing if the resulting arrangement places them too close to heat-sensitive components like OPTs (bad) or capacitors (worse).
I'll throw some gas on the fire and say my normal minimum separation is one tube diameter on my builds, with an absolute minimum of 90% under special circumstances. This generally provides a good compromise between sound electrical/mechanical performance, material considerations and aesthetics (aka WAF). For example, I might do 90% spacing in a 6V6-oid PP amp if I'm absolutely crushed for space, since the tubes themselves are small and dissipate only 17 W each at most (14 W plate plus ~3 W for the heater). I've never had the need to space 6AQ5s or EL84s that closely since their diameters are so small to begin with. Larger tubes at higher dissipations do call for greater spacing, but it's usually not necessary to go overboard. Of course, all of this assumes tubes mounted out in the open; enclose the whole deal and you're holding an entirely different bag of cats.
Experience and judgment are key, but here's not a whole lot of tribal knowledge surrounding the KT-150. My suggestion is that you breadboard one channel and experiment. And of course, if you do so please let us know what you find out. 🙂
- Dynaco ST-70 and Mark III
- Leak TL/12 (and how!)
- Marantz 8B
- McIntosh 275, MC60, etc.
From a DIY standpoint the arrangement and spacing of tubes is important, but so are all the other little things like lead dress, shielding, mechanical integrity and the like. It makes little sense to worry about inter-tube spacing if the resulting arrangement places them too close to heat-sensitive components like OPTs (bad) or capacitors (worse).
I'll throw some gas on the fire and say my normal minimum separation is one tube diameter on my builds, with an absolute minimum of 90% under special circumstances. This generally provides a good compromise between sound electrical/mechanical performance, material considerations and aesthetics (aka WAF). For example, I might do 90% spacing in a 6V6-oid PP amp if I'm absolutely crushed for space, since the tubes themselves are small and dissipate only 17 W each at most (14 W plate plus ~3 W for the heater). I've never had the need to space 6AQ5s or EL84s that closely since their diameters are so small to begin with. Larger tubes at higher dissipations do call for greater spacing, but it's usually not necessary to go overboard. Of course, all of this assumes tubes mounted out in the open; enclose the whole deal and you're holding an entirely different bag of cats.
Experience and judgment are key, but here's not a whole lot of tribal knowledge surrounding the KT-150. My suggestion is that you breadboard one channel and experiment. And of course, if you do so please let us know what you find out. 🙂
Last edited:
Only post #7 has hinted at valve orientation.
Sadly it seems that the 'KT150' label is printed in front of the small rectangular openings in the anode structure, and most amps orient the 'KT150' to show from the front of the amp.
When an anode structure red-plates, then that clearly shows where the hottest part of the plate is, and so the 'typical' orientation points the hottest part to the next KT150's hottest part.
I would highly recommend orienting the valves so that the anode structure side wall openings face the next valve. Those small rectangular openings are on the coolest face of the anode, as they are internally shielded by the beam plates.
Does it matter? Not initially, but as the valve ages, the getter will approach a state where it cannot neutralise outgassing from the various hot parts in the valve - and keeping the anode and the glass as cool as practical may well show up a longer service life.
Sadly it seems that the 'KT150' label is printed in front of the small rectangular openings in the anode structure, and most amps orient the 'KT150' to show from the front of the amp.
When an anode structure red-plates, then that clearly shows where the hottest part of the plate is, and so the 'typical' orientation points the hottest part to the next KT150's hottest part.
I would highly recommend orienting the valves so that the anode structure side wall openings face the next valve. Those small rectangular openings are on the coolest face of the anode, as they are internally shielded by the beam plates.
Does it matter? Not initially, but as the valve ages, the getter will approach a state where it cannot neutralise outgassing from the various hot parts in the valve - and keeping the anode and the glass as cool as practical may well show up a longer service life.
I think it really depends on the tubes. As an example, if we follow the 1.5 tube diameters rule, with 807s, then it is not possible to fit four of them all in a row on a standard-width rackmount chassis. At some point you need to draw the line of what's reasonable.
At the same time, with more slender tubes like the EL34 and 6BQ5, a little more spacing might help keep them from getting too excessively hot since there is so little space between the anode and the glass. The Heathkit AA-121 packs the tubes pretty close together (and pretty close to the transformers too), and it runs screaming hot. They're also running those tubes at the bleeding edge of their dissipation rating (I think 24.5W idle on the EL34 plates).
So long as you aren't pushing the tubes too hard, I wouldn't worry too much about spacing. If you want to abuse them and squeeze every last watt out, a little spacing might be beneficial.
At the same time, with more slender tubes like the EL34 and 6BQ5, a little more spacing might help keep them from getting too excessively hot since there is so little space between the anode and the glass. The Heathkit AA-121 packs the tubes pretty close together (and pretty close to the transformers too), and it runs screaming hot. They're also running those tubes at the bleeding edge of their dissipation rating (I think 24.5W idle on the EL34 plates).
So long as you aren't pushing the tubes too hard, I wouldn't worry too much about spacing. If you want to abuse them and squeeze every last watt out, a little spacing might be beneficial.
Last edited:
The 'little space' results in a small glass 'area' from which to cool the glass. Sort of like a typical metal heatsink - the larger the heatsink surface area the more easily the heat can transfer to the air. Inside the heatsink, the metal transfers the heat, so it is the type of metal and its thickness that influences performance. With a valve it doesn't matter how far apart the anode is from the glass, as heat transfers by radiation, but it helps if a certain amount of heat is absorbed by a larger surface area of glass (ie. a larger valve bulb, as per how a KT88 bulb expands out adjacent to the anode structure).