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Old 7th September 2010, 05:48 AM   #181
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Originally Posted by The Space Egg Corp View Post
Are you a Transmission Line fan?
One of my favored kinds of bass loading

Early experience with Radford S90 left an impression on me.

dave
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Old 7th September 2010, 07:53 AM   #182
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Hi again Dave
The Transmission Lines use 8" Volt BM220.2 drivers with 3Kg magnets originaly designed as near field studio monitor units.
The top end is from Elac 25DT30 metal dome units.
The Elacs play two different tunes, one with the finely perforated (diffuser I guess is what you'd call it) cover on, and another with it off (you can remove it by carefully taking the quite large magnet off the front baffle). I prefer to listen without the diffuser in place, to my ears this widens things a bit also giving more depth, unlike some metal domes the Elac is very smooth.
The drivers cross at 3k, the bottom 2nd order 12dB/oct and the top 3rd order 18dB/oct.
The cross-overs were built on turret tag board with poly caps and air core inductors, the leads of which pass through the turret tags to the underside of the board, and were crimped and soldered to four partly striped lenghts of Van den Hul The Wind terminated at one end with a 4 pole Neutric Speakon socket soldered in parallel, and at the other two 4 pole Speakon plugs soldered in parallel. The cabinets have two 4 pole sockets each to enable bi-amping and the crossovers reside outside the speaker cabinet.
The cabinet and line are made from 3/4" MDF and further MDF was laminated onto the sides, top and back of the cabinet to 1 1/2" thick, the base is removable for stuffing and wireing.
I also have a pair of reflex speakers using the same Volt 8" and a soft dome tweeter, and by comparison the Lines are much more efficient.
I don't know what you think, but I feel they could be good candidates for a single ended class A amp like the BA-1.
Simon
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Old 8th September 2010, 01:53 AM   #183
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Default Compact High Dissipation Enclosure Cooling.

Hi BA-1ers

The Space Egg Corp. is considering doing a compact build of the BA-1 as a pair of mono-blocks with forced air cooling if needed.
The Corporation would like it's amps to be 6x12x12" in size.

I would like the transformers to be 225VA each (as I already have one in stock, and is the largest transformer available to me at 18+18v AC, and I can't do a series primary as I would like to make the amps dual UK/US voltage).

Nelson reckons each amp will kick out 7W of heat/PSU volt, so that means at 25.38v each mono-block will have to dissipate 177.66W of heat to an acceptable device temp of 65c. Also at an ambient temp of 20c I figure the transformers spec'ed at 60c temp rise for their 225VA rating will run at 67c (47c + 20c ambient) if their temp rise is linear that is.

Bearing in mind that the base line for centigrade/watt calculations is not the ambient temp in the listening room of say 20c, but the ambient temp inside the amps enclosure (if it has one that is), dealing with untamed heat sources inside the enclosure can pay big dividends. Allowing smaller, lighter and more economical cooling solutions for a high dissipation output stage where a compact build is desired (big chunks of black aly. aren't getting any cheaper these days).

A good way to cool hard working transformers and thus lower enclosure temp is to drill a perimeter of generously sized holes in the enclosure floor where they are usually mounted, around the periphery of the transformer to encourage natural convection.
Likewise, if the toroid isn't potted, generous holes can be made in the floor at it's centre around the mounting bolt, and similarly the steel mounting washer can also be drilled out with further holes (this has a fringe benefit of making the amp a few grams lighter as well !).
These holes can be protected from prying fingures and RFI, and I often use fine wire mesh like that used for condenser microphone grills epoxyed to the inside of the enclosure.
Some enclosures have louvred or perforated tops, others don't, for those that don't, consider making some, especially above the transformer which is a major unsinked heat source.
A cowling or chimney can also be used around a power transformer convecting radiated heat directly from the floor straight out of the top of the enclosure.

It is surprising the reduction in ambient enclosure temp that can easily be acheived just by channeling unwanted transformer heat quickly out of the amp by efficient convection.
I have a long darkroom thermometer that can be fed into enclosures with their covers on thru vacant switch holes and the like, to check temps with no danger of short circuits etc.

I guess rectifiers are the next hot topic for a compact heat free BA-1.
Whilst nowhere near as bad as transformers, rectifiers have been known to chuck out a bit of heat.
Why don't you ever see these little babys mounted to the underside of the top of an enclosure, where their heat could be conducted straight up and out of the enclosure?
Answer: cos no one wants a great big M6 machine screw carbuncle popping out of the top of their nice shinny new case!
Enter the space age and yet more epoxy.
For some reason, I think from when I was a kid, the Araldite only ever came out to fix broken things, not to make nice new things.
Never thought much about using it untill recently, now I get through it like jam. They make Formula 1 cars out of it and use it for glueing on aeroplane wings so it must be ok right?
How about a light coat of Arctic Silver on that rectifier, which is then clamped in position, and a fillet of epoxy (which just loves filling L shaped joins in materials all by it's self) between it's body and the enclosure top.
Bingo! job done, where's that broken cup handle? Epoxy rules!

In looking at the posts and views on the site for the BA-1 & 2 it is almost the case that the BA-1 has half the posts, views and interest that the BA-2 has received. Why? and does this also mean there are half as many BA-1's being born as BA-2's?

I started this post to talk about a forced air cooling system that I have not seen described or used before, but got on an ambient enclosure temp vibe as a bit of a preamble.
The system is a very light, compact and robust industrial system, that with the correct choice of fan and a low ambient enclosure temp promises quiet efficient output stage cooling.
I would like to get this working in a BA-1 build as I already have enough parts in stock left over from a previous project for one mono-block.

I will describe the system in my next post, provide a PDF from the manufacturer and see about some actual figures for it's use as a BA-1 cooler.

Cheers for now Simon
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Old 8th September 2010, 10:51 PM   #184
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Quote:
Originally Posted by The Space Egg Corp View Post
How about a light coat of Arctic Silver on that rectifier, which is then clamped in position, and a fillet of epoxy (which just loves filling L shaped joins in materials all by it's self) between it's body and the enclosure top.Cheers for now Simon
Arctic Silver makes a thermally conductive epoxy
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Old 9th September 2010, 01:05 AM   #185
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Default Don't Come Un-stuck

Quote:
Originally Posted by flg View Post
Arctic Silver makes a thermally conductive epoxy


Hi flg

All is well & I'm doing just fine today.
Shame the same can't be said of the darn weather.
It ought to be summer here but has rained for the last two weeks.

So I stayed in today and cooked a big hot chilli lunch & did my own global warming experiment on the miniature replica of the antarctic tundra that was taking over my ice-box, with a hair drier !

Didn't find any polar bears or penguins flaping around in there on the 'berg's, but did spot thru my snow goggles a very soggy squirrel playing football on the sun deck with a large walnut fallen from it's tree.

I wondered where all my walnuts were disappearing to.

If I catch that furry rodent robber red handed, feloniously plundering my provisions, I may just have to call the cops to slap the cuffs on the cheeky chomper.
See how he likes hard time crushing walnuts in the prison cereal factory !

Rain, rain, rain, rain, rain, chilli lunch, yum, yum, yum, yum, yum, rain, rain, rain, rain, rain, dark, bit of TV, even darker, bit more TV, bed, sleep, nothingness....
( Is that too many lines or syllables for a Haiku ? )

Cheers for now, Later... Simon
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Old 26th October 2010, 06:51 PM   #186
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Request for help,

Which amplifier (pass design) would be the best choice. Having the following components already available:

4 separate transformers. each of them rated 2x18v 500va. (so these would amount to for example two mono channels drawing 2x 36v 500VA or 2x18v 1000VA etc).

32 elna capacitors each good for 15000 mf 35 volt. So thats at least 240.000 mf per mono channel and if more capacity is needed it can easely be added.

4 heathsinks each being. 42cm x 17cm x 4 cm (43 fins each)

The amps need to drive 2 (old style ) b&w 801 with 85 db sensitivity and as the sales brochure states nearly flat impedance characteristics at 8 ohms
(At this moment driven bij wadia 830 in combination with Beard P100 tube amplifier (2x kt88 on, if I remember well 560 volts or was it 680v ...)
Which I believe sounds very well. This combination surprisingly made many people with modern expensive (exotic) loudspeakers and very expensive tube and solid state amps turn pale after hearing it.
But still (as a semiproffessional musician) I also hear a lot of shortcommings in this system.

- Next to that becaus of the high voltage and high biassing of the Beard amp there are (to my taste) to often (tube) faillures in this amp
- I want to enjoy building again something myself
- can't wait to see If solid state (Pass designs) can improve on the current soundquality. (combined with the reliability of solid state)

I believe from reading here for a long time that to get the best possible soundquality from solid state the way to go is; single ended class A

Some time ago I ordered the aleph JX boards from Peter Daniel. But are a little worried about the available output.
Why put my question in this thread? I don't know to much about electronics but my feeling tells me the BA-1 (or BA-1 X if that is possible) might be just a little better sounding amp than the Aleph-J(-x). But then again will it have enough power?

Or would perhaps the high power aleph-x with Jfet gainstage or, the Chef de Gaar (ugs power )design combined with aleph outputstage be fitting better...........(and for this last option how to realise this?)


On the other hand I also believe that sometimes to much emphasis is put on output power.
85 db sensitivity combinined with 62 watt amp will be good for 103 DB wich I understood is good enough for high end indoor listening or could i do with lesser when there is enough current available.
Had these loudspeakers also hooked up with a 35 watt tube amp (6x el84 per mono channel) could also be very loud but with less dynamics....


Your comments or advice are very much appreciated
Thanks in advance
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Old 26th October 2010, 07:00 PM   #187
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biamping is possible solution ?
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Old 26th October 2010, 08:31 PM   #188
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Zed mod,
Thanks for the quick reply (if that was for my post)

What exactly do you mean when you mention bi amping? Bridging? Or separate amps for bass and mid high...? I believe this last one will confront me with a lot more complexity in order to get it tuned and sounding right. want to keep it simple at first.

Im not sure but when I go for single ended class a with the 18v transformormers I will get about 22,5 v effectively at rail. Does this mean I will have about 2,8 amp (22,5/8) available at the output? And does this mean that this will amount to 2,8x22,5= 63 watt output at 8 ohm? Hmm or do I not remember ohms law to well...?
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Old 26th October 2010, 10:09 PM   #189
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just forget numbers for a while ........ and continue thinking in watts ( as they aren't numbers )

having speakers as your's , and number & type of xformers as you already have ....... I would go for Papa/Thagaard A75 ;

heavy loaded (biased) PSU - you'll be in ballpark of 36Vacx1,25(1,3) , so somewhere around +/- 45Vdc ......

plenty of amp(ere)s , plenty of watts for your lazy spks

tip : even if , by the book of greedy & spoiled Papa's kids , A75 is oldie - do not underestimate how's sounding
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Old 26th October 2010, 10:59 PM   #190
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On the other Mainu, El Jefe de la Estacion's UPie is perfect for his transformers, with the option to force it single-ended.
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