Advice for a newbie needed

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shane
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#1 Advice for a newbie needed

Post by shane »

My daughter's partner inherited my old Heybrook HB3s some years ago and has been driving them with a rather nondescript Wharfedale amp from the mid 90s, which was a cheap way to get them running but leaves a lot to be desired. He's recently decided that they deserve better and wants to get into building valve amps. The HB3s needs fair bit of oomph to make them sing, but as usual there are budget limitations, so blowing a grand on a WD88VA isn't on his horizon. I have a quartet of 6550s and a pair of op txs from a Maplin Millennium which can be donated to the cause, but I'm trying to find a suitable circuit for him to look at, and a build thread where he can see a typical case study. Can anyone point me st something suitable?
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Mike H
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#2 Re: Advice for a newbie needed

Post by Mike H »

Did a quick Google, most attractive I found (IMO) is this -

http://www.sarris.info/main/files/Push- ... atic-1.png

NB: Millenium OPT is 6.6k for 20 Watts, so I would think the 6550's could have anode current reduced a bit.

PSU HT = 400VDC, plus RC filters to drop down for the 300V rails.

.
 
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#3 Re: Advice for a newbie needed

Post by Mike H »

Usual caveats, carbon comp resistors, or wirewound, audio grade caps etc. etc.
 
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shane
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#4 Re: Advice for a newbie needed

Post by shane »

Thanks Mike, that's exactly what I was looking for. I've told him to join the forum, so we' probably have more questions about the power supply.

Have Danbury shut down completely now, or might there be a suitable mains tx left somewhere?
The world looks so different after learning science. For example, trees are made of air, primarily. When they are burned, they go back to air, and in their flaming heat is released the flaming heat of the Sun which was bound in to convert air into tree.
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#5 Re: Advice for a newbie needed

Post by Mike H »

Yep he's gone, totally lost contact now as I never had his home details, which is fair enough don't suppose he wanted people trying to phone him at home and that sort of thing, but not answering emails either, but again I suspect he only ever used Internet for work.

By the looks of it will need something with 350V AC, next question is monoblocks or one unit? Cos if one unit the mains TX will have to power both amps. So monoblocks probably easier and likely the mains TX's should run cooler like that.
 
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#6 Re: Advice for a newbie needed

Post by Mike H »

Afterthought - I gave a bunch of stuff to Dave the Bass, should be a couple of 350 or 375 V mains traffos in that lot if memory is correct. These were "improved" versions of the Millennium mains. (Bigger stack.)
 
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simon
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#7 Re: Advice for a newbie needed

Post by simon »

http://www.jmsonline.co.uk/product-cate ... nel-trans/

Good quality and decent prices if you need to buy Shane
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shane
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#8 Re: Advice for a newbie needed

Post by shane »

Thanks Simon. Looks good!
The world looks so different after learning science. For example, trees are made of air, primarily. When they are burned, they go back to air, and in their flaming heat is released the flaming heat of the Sun which was bound in to convert air into tree.
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andrew Ivimey
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#9 Re: Advice for a newbie needed

Post by andrew Ivimey »

If you are looking for extremely good value transformers for valve amps (and lots of other types) I can heartily recommend The Majestic Transformer company, Poole Dorset. They are a co.uk so on the Web. On the telephone they will discuss any of your vital needs and for what they produce they are a super choice. They will wind anything for you personally but have a stock of designs of almost anything valve oriented.

My 45PP amps have Majestics for the PSUs. My RGi-250 4 volt heater mercury rectifiers use centre tapped majestics. I have seen them in use with six kt66s in parallel per channel output transformers producing an enormous PP amp.

And so on.
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shane
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#10 Re: Advice for a newbie needed

Post by shane »

I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers
I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers.
I must not think about mercury arc rectifiers.

Thanks Andrew.
The world looks so different after learning science. For example, trees are made of air, primarily. When they are burned, they go back to air, and in their flaming heat is released the flaming heat of the Sun which was bound in to convert air into tree.
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#11 Re: Advice for a newbie needed

Post by Dave the bass »

I can do a an ex-MikeH DB424 Issue 2 (it says on the hand written label, 350V (not CT'd) @ 200mA w/6.3V CT at unknown current.

Is that in the right ball park for our-Shane's project?

DIET, possibly 2 of them. I need to check the 2nd one to make sure it's OK before boxing up and sending them if these are the daddy-o's.
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#12 Re: Advice for a newbie needed

Post by Mike H »

Heater winding will be 6 - 7 Amps. HT winding is single 0- 350 so will need a bridge rectifier. Note two req.d, as the DB424 was down graded to 200 mA so trying to power two amps with it will cause the winding to melt. The original could fry eggs at 10 paces in 'stereo mode', it's still going to be quite hot in monoblock use.

HTH
 
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#13 Re: Advice for a newbie needed

Post by Dave the bass »

2 it is, whahey!

I've just powered up the other one, AOK.

Image

They OK for his project Mike?
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#14 Re: Advice for a newbie needed

Post by Mike H »

Look like prototypes, how can I tell, numbers written in biro. :D

The one on the right at any rate looks like a prototype for the newer 200 mA version.

Run strictly as monoblocks only. No more made if you blow them up!

.
 
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#15 Re: Advice for a newbie needed

Post by Mike H »

Dave the bass wrote: Mon Apr 10, 2017 7:37 pm They OK for his project Mike?
Oh sorry yes can't see why not, provided standing HT current is modest, I think Millennium is like 120 mA or something.

Off load, the 350VAC will produce somewhat over 500VDC, so choose supply capacitors accordingly. Ditto rectifier diodes, e.g. 1N4005 minimum, tho I would prefer 4006 or 4007.

HTH
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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