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Post by Mr Trev on Jan 25, 2018 20:08:32 GMT
So I ended up getting the 2 adapters I mentioned a few posts above. It does work great other than being a funky looking totem pole of "brass n glass"™
Now I'm thinking about making (or just buying) a new top plate and drilling the tube opening bigger so I won't need to use a socket saver (or in my case the 12au7 to 6922 adapter). If I do this I would need to change my 6SN7 adapter from 12au7 to 6922 operation. What's the best way to do this? (I haven't tried cracking the adapter open to see how its wired yet)
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Post by lobalwarming on Jan 25, 2018 22:02:48 GMT
Brass 'n Glass sounds like an 80s fashion horn band.
Do you have to rewire anything? From the amazingly detailed description at ebay they say:
Don't see any 12V specs there. Says to my little low voltage mind that the adapter only works in 6V sockets - like the Vali 2. You're good to drill.
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Post by Mr Trev on Jan 25, 2018 23:06:24 GMT
Since I'm currently going 6SN7->12AU7->6DJ8 I'm not sure if there'll be any rewiring required if I try to remove the 12AU7 part of the equation. Its possible the 6SN7 adapter will work as is. In theory nothing will explode in my face leaving me looking like one of those politically incorrect black-faced cartoon characters from the past if I do try?
Schiit doesn't sell parts so it looks like I'm going to have to dust off my metal working chops and make my own top plate
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Post by lobalwarming on Jan 26, 2018 0:00:58 GMT
In theory all explosions are harmless entertainment. If there's a brilliant billion lumens flash of light, then you can patent desktop tube amp fusion and maybe we'll finally get low cost, decent sounding tubes from startup tube manufacturers as a side benefit.
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Post by Mr Trev on Feb 11, 2018 4:15:24 GMT
Hi Frans. Wondering if you could do a quick confirmation for me…
I'm using a 12au7 tube in my Vali2 with the "proper" adapter. Everything is working, sounds great, but the one thing I noticed is the filaments are very dim compared to when I'm using the same tube in my P1. I decided to crack the adapter to wrap my brain around how the rewiring is happening.
I hope this makes sense… When it gets down to the heaters I have pin 4 of the 6dj8 side connected to pins 4&5 on the 12au7 side. Pin 5 of the 6dj8 is connected to pin 9 of the 12au7. Is this correct? (don't know why this is confusing me so much - I guess I'll just blame it on years of mtn. biking without a helmet)
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solderdude
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Post by solderdude on Feb 11, 2018 10:57:21 GMT
That configuration seems correct. You could lift the 12AU7 tube somewhat so it still makes contact and then measure the voltage between pin 4 (or5) and pin 9. There should be approx 6V on it (AC or DC, don't know in this case).
A 6V tube has its 2 x 6V filaments in parallel and connected between 4 and 5. In this case pin 9 is open or connected to a shield between the tube halves when present. In that case pin 9 is usually connected to ground.
In a 6V tube the 2 x 6V heaters are in series and connected between pin 4 and 5 just like the 6V versions. The tube will thus work when 12V is connected between pin 4 and 5. Smart designers in that era used the (mostly unused) pin and connected the middle point of these filaments to pin 9.
When 6V is connected between the centertap and pin 4 one tube half filament lights up. When 6V is connected between the centertap and pin 5 the other tube half filament lights up. So when pin 4 and 5 are connected and 6V is applied between 4&5 and pin 9 both tube halves will light up on 6V.
This way a 12V tube can work on 6V after all. but when connected between pin 4 and 5 and 9 is open (or even when connected to ground) but with the 6V winding 'floating' the 12V tube will work on 12V as well. A 6V tube can only work on 6V BUT a screen can be present between 2 tube halves which may come in handy in certain radio frequency applications.
Some heaters of 12V tubes can heat the cathodes just enough to have some emission and 'work' just barely when low currents are used (hybrid design for example) but don't glow as bright and may be more noisy or pick up hum more easily.
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Post by Mr Trev on Feb 11, 2018 17:17:32 GMT
Thanks again.
For some reason I was thinking that pins 4&5 on the 12au7 also had to be connected to pin 9. So I gather if a 12au7 is being used in a Solstice then it'd be preferable to use the OHV option?
On this point, looking at my 6sn7 to 12au7 adapter, would it be correct that the 6sn7 heaters are connected to pins 4/5 and pin 9? I tried using the adapter directly in the Vali2 without the additional 12au7 to 6dj8 (top removed on the Vali) and nothing worked. No sound, and it didn't even look like the heaters lit (hard to tell with the Raytheon tube I have since the flashing is everywhere). I'm still pondering rewiring the 6sn7 adapter and modding the case (making a new one) so I don't need to stack adapters. I'll still need to find a way into the adapter - I think its been glued somehow, but can't figure out how.
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solderdude
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Post by solderdude on Feb 11, 2018 21:02:34 GMT
I would use rge 12AU7 in the 12V setting and not in OHV option. Reason for this is that when swapping tubes and pushing in a 6V tube while still in OHV setting the 6V heaters may have a very short lifespan left.
Most likely Yes.
Maybe the adapter is potted (filled with a fast hardening material) ? The 6DJ8 socket has its heater voltage between pin 4 and 5. When pushing a 12AU7 socket in there the 4-5 pins are shorted. No heater and also the power supply in the amp for the heater is shorted.
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Post by Mr Trev on Feb 12, 2018 2:39:04 GMT
I would imagine you could have a pretty light show running a 6v tube at the full 12v
The adapter isn't potted. I can look down the centre of the 6sn7 socket and see the wiring. I just can't tell what the screw on the bottom is screwed into. I think it might be one of those threaded rods they typically use in adapters - or possibly just a nut - but with epoxy on/in it. I can't see clearly, but poking a small eyeglass screwdriver, it feels like something epoxied. I won't worry much about it now, no point until I can get the tube to physically fit in the amp first.
Forgot to mention, the 12au7 tube (EI Yugo) flashes properly in the Vali. Didn't do that in the P1. I know it really doesn't mean anything sound wise, but its a nice embellishment (I amuse easily)
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solderdude
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Post by solderdude on Feb 12, 2018 7:45:43 GMT
There is an explanation for this.
There are 2 kinds of heaters. One type is a 'slow' one that lights up slowly and the other type is a fast one. The fast one lights up really bright and then goes down to normal temperature. The last version draws a lot of current when a voltage is applied and them lowers the current. The first version has a more constant current draw.
The Vali2 has a heater power supply that feeds it a voltage. Thus fast heater tubes 'flash' and slow ones go slow. The same is true for G1217 amps. P1, however, has a current source for the heater supply as the heater is part of the amplifier itself. Normal tubes will start normal but the fast tubes are current limited so won't 'flash' but turn on like a normal tube.
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