Re: a single output transformerstereo tube amp ??

Since the output depends on changing flux in the transformer, unless the transformer has some sort of a split core, the output from each of the secondary windings on the transformer will be identical. Let's see the schematic if you have one.

H. R. (Bob) Hofmann

I can get binaries, but I don't see a link.

I really would like to see the print for this contraption.

JURB

snipped-for-privacy@aol.com spake thus:

What's up with this? There's no link; look at the OP's 3rd post here. It has a JPG of the schematic attached.

-- Just as McDonald's is where you go when you're hungry but don't really care about the quality of your food, Wikipedia is where you go when you're curious but don't really care about the quality of your knowledge.

- Matthew White's WikiWatch

Many ISPs (including mine) strip attachments off text only newsgroup posts. Otherwise their servers would be jammed with HTML files...

--
*We are born naked, wet, and hungry.  Then things get worse. 

    Dave Plowman        dave@davenoise.co.uk           London SW 
                  To e-mail, change noise into sound.

Could someone email me the schematic? I'd like to have a look at it.

Try

Don't whine about the server.

cant get anything from it. Is it up at specific times only?

NT

No. You have to step through its annoying process but it's only 30 seconds.

Well, I'm getting webpage data now, and went through their bizarre routine twice, but each time it suddenly decides I want to upload instea of download, no dlwnload to be found anywhere. What a waste of time. What kind of bizarre mind created that site.

NT

Hi,

I was able to download it, I'll email it to you.

-Landon

thank you, I'll retrieve it from the spam dump later on, and see if I can get any clues from it.

NT

The cct diag of this bizarre amp is on this horrid server:

Unfortunately the image quality is so poor that some relevant details are not legible, eg switch & input markings etc. A first look at the speaker wiring suggests this is one of those units where one speaker was in the amp case, and the other was in its own separate box. So at least one can rule out the speakers themselves being wired in mono - unless I've misread something.

I'm now wondering why 2 tweeters per cabinet.

OK, I've found a phase splitter. Where the input is, it goes to a double valve, and below that valve on the diag is a switch. In its upper position, ie not as shown on diag, the switch decouples the cathodes, making the double valve a conventional pair of amplifiers. But in the position the switch is shown, there is no cathode decoupling, and the double valve acts as a long tailed pair. Note also in this posn the grid feed to one is shorted out. So in this position we get traditional push pull operation on the output, ie a mono high power class B amp using the bigger transformer. I havent looked at the smaller output tf yet.

6L6 = KT66, a fairly high power high quality high price valve. So this doesnt look much like a cut price unit. And it still has 2 output transformers, which is no cheaper than having 2 as usual.

OK I see the smaller output tf sees the total B+ current of both output valves, and unbalances the speakers by an amount proportional to this. What I dont know is what the tf ratios are, so dont know if theyre the same or out by a ratio of 10:1.

Lets guess theyre the same ratio, as its the most likely and it makes analysis relatively easy. Where B1, B2 are the anode current in valves 1 and 2:

top speaker output is then B1-B2 + B1+B2 = 2x B1 btm speaker output is then B2-B1 - (B1+B2) = -2x B1

but driving both speakers off one valve's anode current, thus having to run it class A, makes as much sense as stuffing mushrooms. As does running the speakers in antiphase!

And the above equation holds regardless of what the early stages do. I must have made a mistake, as it doesnt make any sense to run an amp that way - but I'm not seeing where.

NT

2 @ 4 ohm = 1 @ 8 ohm.

obviously, but that isnt a reason to use 2x 4 ohm tweeters instead of

1x 8 ohm.

NT

You've never worked in industry? Generally the 'reason' comes down to $$$$.

Surface area vs. inertia is.

Cheers! RIch