Tweeter Amp for OB or Horns
- IslandPink
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#46 Re: Tweeter Amp for OB or Horns
I was thinking the same. Black Gates have a pretty low Zout in any case.
I can get an OD3 in there to drop B+ from 300 to 150V for the choke-loaded ECC40's ( both ) for some 'bling' .
Found a few more bits this evening ( eg. UX4 sockets ), so layout can progress.
Will get an LT Spice model going soon, useful for showing the circuit if nothing else
I can get an OD3 in there to drop B+ from 300 to 150V for the choke-loaded ECC40's ( both ) for some 'bling' .
Found a few more bits this evening ( eg. UX4 sockets ), so layout can progress.
Will get an LT Spice model going soon, useful for showing the circuit if nothing else
"Once you find out ... the Circumstances ; then you can go out"
- IslandPink
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#47 Re: Tweeter Amp for OB or Horns
No, need more smoothing to drivers, so CCS from B+ to OA2 ( that should be enough shunt current ) to supply ECC40 sections at 150V minus drop through each choke ( 235R ) ie. 148V .
Maybe, looking at ECC40 curves, 200V or 210V is more linear, so that would be CCS to 2x OB2 ( is it ? ) at 210V, or 208.5V after chokes - valves at 5ma or 6ma.
Sorted !
Maybe, looking at ECC40 curves, 200V or 210V is more linear, so that would be CCS to 2x OB2 ( is it ? ) at 210V, or 208.5V after chokes - valves at 5ma or 6ma.
Sorted !
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- IslandPink
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#48 Re: Tweeter Amp for OB or Horns
Think I'll use a couple of damper diodes in PS anyway - slow start is good.
More or less finalised now, see pic below :
More or less finalised now, see pic below :
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- izzy wizzy
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#49 Re: Tweeter Amp for OB or Horns
Looks fine. The only thing I'd do different for starters is a resistor feeding the glow tubes and then sub in the CCS after. Just to see what happens rather than assuming the CCS is the go. I'm going to try similar on my line stage/headphone thingy.
cheers,
Stephen
cheers,
Stephen
- IslandPink
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#50 Re: Tweeter Amp for OB or Horns
Could do , yes , worth checking. I put DN2540 one in there, also have one of Gary Pimm's self-bias ones upstairs too.
I didn't draw the zobel around the OB2's , but that will be done, though I'd like to look into the values a bit more this time, after that article you linked.
I didn't draw the zobel around the OB2's , but that will be done, though I'd like to look into the values a bit more this time, after that article you linked.
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#51 Re: Tweeter Amp for OB or Horns
How about using all SS bridge with the 6AX4 in the earth rail between the negative side of the bridge and the negative of the first filter C? I have this built nearly (about 5 months ago!) but haven't finished it off yet.
Benefit of only one 6AX4 and half the heater current. But I've seen jc morrison do this - supposedly has the benefit of the stiffer SS supply but still has the soft start.
Benefit of only one 6AX4 and half the heater current. But I've seen jc morrison do this - supposedly has the benefit of the stiffer SS supply but still has the soft start.
- izzy wizzy
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#52 Re: Tweeter Amp for OB or Horns
All glow tubes have different impedance so you might have to measure them as Bjorn did to get the right values.IslandPink wrote: ↑Wed May 30, 2018 7:07 pm Could do , yes , worth checking. I put DN2540 one in there, also have one of Gary Pimm's self-bias ones upstairs too.
I didn't draw the zobel around the OB2's , but that will be done, though I'd like to look into the values a bit more this time, after that article you linked.
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#53 Re: Tweeter Amp for OB or Horns
Interesting idea - but whether I'd notice the difference given this is working typically only in the kHz, I doubt it. I'm likely to have a few volts to 'waste' with this transformer and full bridge, so it's not an issue to lose 15 or 20V through the damper diodes.simon wrote: ↑Wed May 30, 2018 7:45 pm How about using all SS bridge with the 6AX4 in the earth rail between the negative side of the bridge and the negative of the first filter C? I have this built nearly (about 5 months ago!) but haven't finished it off yet.
Benefit of only one 6AX4 and half the heater current. But I've seen jc morrison do this - supposedly has the benefit of the stiffer SS supply but still has the soft start.
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- IslandPink
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#54 Re: Tweeter Amp for OB or Horns
Bit of buying today. Spoke to Gerry at Crowthorne and managed to get some 7-pin sockets and a couple more ECC40's.
Ordered some MIlls resistors and Nichinon ES caps and some other sockets from HiFi Collective.
Checked upstairs and found an unused 15VA 2x15V toroid and so I bought 4-off 17AX7 damper diodes from the states.
Ordered some MIlls resistors and Nichinon ES caps and some other sockets from HiFi Collective.
Checked upstairs and found an unused 15VA 2x15V toroid and so I bought 4-off 17AX7 damper diodes from the states.
"Once you find out ... the Circumstances ; then you can go out"
- IslandPink
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#55 Re: Tweeter Amp for OB or Horns
RS order in, for Crees and IEC panel socket.
Ordered HV toroid and a 10H/125ma choke from Bluebell.
Ordered HV toroid and a 10H/125ma choke from Bluebell.
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- IslandPink
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#56 Re: Tweeter Amp for OB or Horns
Ladies and Gentlemen... the starting gun has been fired . I soldered 3 components into one of the filament supply boards this evening
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- IslandPink
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#57 Re: Tweeter Amp for OB or Horns
Just bought some of these. Looked quite fancy for an OD3. Better than the taped-up ones I have to hand at the moment.
Ok, they are probably not going in the tweeter amp...
Ok, they are probably not going in the tweeter amp...
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- IslandPink
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#58 Re: Tweeter Amp for OB or Horns
Three of those were from Langrex ; 'See seller's other items' ....
No, please, don't tempt me :
https://www.ebay.co.uk/itm/DA100-CV1219 ... 48a73d5ee3
No, please, don't tempt me :
https://www.ebay.co.uk/itm/DA100-CV1219 ... 48a73d5ee3
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- pre65
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#59 Re: Tweeter Amp for OB or Horns
Can I tempt you with 833c ?
Carbon anode version.
Carbon anode version.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- IslandPink
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#60 Re: Tweeter Amp for OB or Horns
Thankfully no !
It amazes me how much 'stuff' goes into a simple amp. This doesn't even show everything.
( Two DHT supply boards done, a start has been made )
It amazes me how much 'stuff' goes into a simple amp. This doesn't even show everything.
( Two DHT supply boards done, a start has been made )
"Once you find out ... the Circumstances ; then you can go out"