Tweeter Amp for OB or Horns

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simon
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Re: Tweeter Amp for OB or Horns

Post by simon » Tue Jun 26, 2018 8:38 pm

How about this monster?

https://www.cromwell.co.uk/shop/hand-to ... MX0451129G

Not sure what I'd use it for, but someone obviously does.

Anyway, I've just realised that Owston is THIS weekend (my life is too busy!) - if you're coming on Saturday you can borrow mine?

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IslandPink
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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Tue Jun 26, 2018 10:13 pm

Well I must say this is a jolly fine idea. I will be there and welcome it with open arms.
Life just gets better and better ( see 'what are you listening to ...' thread ) .
"It's so easy to decide on a name
It's a name caller's game
It's so easy to look down from above " (Wyatt)

simon
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Re: Tweeter Amp for OB or Horns

Post by simon » Tue Jun 26, 2018 10:30 pm

Just need to remember to bring it now :-)

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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Tue Jun 26, 2018 10:41 pm

simon wrote:
Tue Jun 26, 2018 8:38 pm
How about this monster?
https://www.cromwell.co.uk/shop/hand-to ... MX0451129G
Not sure what I'd use it for, but someone obviously does.
Only weightlifters need apply.
"It's so easy to decide on a name
It's a name caller's game
It's so easy to look down from above " (Wyatt)

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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Thu Jun 28, 2018 9:51 pm

I powered up the filament toroid from a Variac today , with the DHT supplies on there. The voltages checked-out well. With 10R and 5.1k on the board, I got 2.45 and 2.47V out to the 45's.
I had the oscilloscope down ( thanks, Neal ! ) and did some playing around to check limits.
The supply 'out' becomes clean at 5.62V AC into the boards. Obviously some margin is required then.
Even at that input voltage and the 63mm heatsinks they are getting slightly too hot to touch for more than a couple of seconds, after 15mins.
This only takes 198V AC into the toroid primary.
So , I will have to burn off a few volts/watts going into the primary, and probably will attach the heatsink to the top plate.
"It's so easy to decide on a name
It's a name caller's game
It's so easy to look down from above " (Wyatt)

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IslandPink
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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Sat Jul 21, 2018 3:07 pm

Slow going at the moment, but not stalled entirely !
Top plate has progressed a bit.
When I went to Owston, Simon very kindly got out his tool...kit in the pub beer garden and we went to work cutting two 37mm holes for the UX4 sockets. Since then I've drilled a few holes for those and the output transformers.
In the meantime I've realised I lost another thing on the Farnell order - didn't get the SiC rectifiers , something happened with that 'shopping basket' never got to the bottom of that. Anyway...
Tweeter_top_plate.JPG
"It's so easy to decide on a name
It's a name caller's game
It's so easy to look down from above " (Wyatt)

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Re: Tweeter Amp for OB or Horns

Post by simon » Sat Jul 21, 2018 4:50 pm

For you Mark, it was a pleasure :D

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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Mon Sep 24, 2018 11:46 am

Just about to re-start after electrics review and re-fitting of kitchen, which seemed to take most of the summer :!:
Decided pentode driver has least risk, easy to get going and is proven in the HF . I have a pair of nice E83F gold-pins saved for future phono, but plan has changed on that circuit so these are free. I will try & do a diagram later, but here is the gist of the driver –
  • E83F running at around 6ma
    Anode 210V , G2 150V, cathode about 3.4V
    Anode load ~15k , cathode R ~430R if no additional current from G2-setting.
    No cathode by-pass required as gain is around 90 with it decoupled, estimate ~60x with no cap.
    Now G2 setting is an area worth discussion. My starting position would be a resistor from B+(310? ) of about 66k , and a 100uF cap from there to cathode. I don’t think the extra stability afforded by a VR tube from k to G2 is necessary from midrange upwards. Comments welcome.
In terms of holes on the top-plate, starting with just the noval drivers does provide flexibility for future ideas that need more/bigger holes - eg. with Loctals or VR tubes.
"It's so easy to decide on a name
It's a name caller's game
It's so easy to look down from above " (Wyatt)

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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Sun Oct 28, 2018 4:53 pm

What's that coming over the hill, is it some progress ?
Tweeter_moreholes.JPG
"It's so easy to decide on a name
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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Sun Nov 04, 2018 6:24 pm

More holes done this week, but the more I look at the 'stuff' that needs to go into this, the more it's going to be a bit of a shoehorn job - I need to sit down carefully and think carefully about where things are going !
"It's so easy to decide on a name
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It's so easy to look down from above " (Wyatt)

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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Mon Nov 12, 2018 10:28 pm

What kind of dunce would design something with a mains transformer and three filament transformers ! :roll:
"It's so easy to decide on a name
It's a name caller's game
It's so easy to look down from above " (Wyatt)

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Re: Tweeter Amp for OB or Horns

Post by izzy wizzy » Mon Nov 12, 2018 10:53 pm

IslandPink wrote:
Mon Nov 12, 2018 10:28 pm
What kind of dunce would design something with a mains transformer and three filament transformers ! :roll:
Hey I resemble that remark. My amp has a mains tx and 3 fil transformers :P

Cheers,
Stephen

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Re: Tweeter Amp for OB or Horns

Post by pre65 » Mon Nov 12, 2018 11:07 pm

IslandPink wrote:
Mon Nov 12, 2018 10:28 pm
What kind of dunce would design something with a mains transformer and three filament transformers ! :roll:
I could be that person when I finally get round to the 833a rebuild. :lol:
Life is what happens to you while you're busy making other plans. John Lennon

G-Popz THE easy listening connoisseur. (Philip)

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IslandPink
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Re: Tweeter Amp for OB or Horns

Post by IslandPink » Sun Jan 13, 2019 10:36 pm

Some progress. Still pondering the placement of two filament transformers, the volume control and the input sockets !
Tweeter_internal2.JPG
"It's so easy to decide on a name
It's a name caller's game
It's so easy to look down from above " (Wyatt)

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Re: Tweeter Amp for OB or Horns

Post by RhythMick » Sun Jan 13, 2019 10:41 pm

izzy wizzy wrote:
Mon Nov 12, 2018 10:53 pm
IslandPink wrote:
Mon Nov 12, 2018 10:28 pm
What kind of dunce would design something with a mains transformer and three filament transformers ! :roll:
Hey I resemble that remark. My amp has a mains tx and 3 fil transformers :P

Cheers,
Stephen
If we're counting mains transformers, I'm up to 4 HV mains (6 secondary windings in use) plus 6 toroidal (12 X 7v secondary).

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