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Old 13th July 2004, 04:46 AM   #21
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Well, I suppose I might just give the Lilliput a try. It seems simple enough... and the only expensive items will be the transformers.

So... the schematic calls for what looks like 160V at 100mA (a little hard to read) and 0V feeding a bridge rectifier. Well, of course Hammond doesn't have exactly that... But, they have something somewhat close. Angela Instruments has a Hammond 269EX that gives 190-0-190 volts at 65mA. If I used a full wave rectifier instead of the bridge, I would get about 269VDC at 130mA from the center tap, correct? Would this current be sufficient to drive both channels or should I look elsewhere for transformers? The 269EX just happens to be one of the cheapest ones there... hopefully it could work well. (I realize that the transformer doesn't have enough heater current available for two tubes... that is ok- I think I can scrounge up another transformer to feed the driver-- and I will be giving the 6AS7 DC voltage as well as the driver)

Also a note on output transformers... the only "affordable" ones they have that go near 1k load are the 125 series. The 125SE ones are supposed to be better, but only get down to 2.5k. What kind of wattage rating would I need on output trannies? The 125C can handle 8W, 60mA max bias... would two of these work?

I will try to find some other parts here in a few minutes... but these are my main concerns. (power supplies always confuse me most) Thanks all
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Old 13th July 2004, 04:52 AM   #22
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Default Re: Re: Glad you decided to stay!

Quote:
Originally posted by planet10


commonly called parafeed... a choke is often used instead of a current source.


Yes, I was thinking that compared to the classic parafeed the CCS version might be easier on the budget since there is one less bigh chunk of iron to buy. One would naturally have to consider whether the higher voltage requirement would be a problem. I suppose it would depend on the tubes used.

Quote:
I cannot emphasize enuff how dangerous this is... and if your insurance company ever finds out after your house burns down, you are likely out of luck.

dave
Understood and the reminder is appreciated. It would be wise to use a 1:1 isolation transformer in that design. My interest in the design centers around the output transformers though.
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Old 13th July 2004, 11:43 AM   #23
alk is offline alk  Europe
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Quote:
The 125C can handle 8W, 60mA max bias... would two of these work?
They would but not in ideal conditions. Those are designed for push pull applications. You need single ended output transformers with an air gap so you won't saturate the core. Why it saturates? I don't know the theory but it would be easy to find out if you are interested. IMO the Hammond 125 ESE would be a good choice. Saving in other areas is ok but don't save much in OT's.

Cheers!
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Old 13th July 2004, 06:00 PM   #24
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That makes sense... and the 125ESE's could be reused later for other projects. But, they only go down to 2.5k... would I need to parallel a resistor with the primary to lower the impedence?

There is a circuit on Angela Instruments here that I had not seen before, but looks fairly interesting... and I just happen to have some EL34's and 6550's laying around, too. So, I suppose I could save some on the output tubes by going with something like this... and it looks fairly simple, too. Would this be a better circuit to go with as far as simple SE goes?

EDIT: never mind... the power transformer alone costs $60. That is a little much....
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Old 13th July 2004, 08:12 PM   #25
alk is offline alk  Europe
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EL 34's?

http://www.megahertzaudio.it/IT-sche...20musicale.htm


Wanna go back to the original project?

http://www.megahertzaudio.it/IT-schema%20lilliput.htm


Quote:
But, they only go down to 2.5k... would I need to parallel a resistor with the primary to lower the impedence?
It's 1.4 k into a 6 ohm so if you got an 8 ohm speaker you could use the 2.5k tap but ...wait for better advice on this.


Cheers
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Old 13th July 2004, 08:32 PM   #26
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Konnichiwa,

Quote:
Originally posted by needtubes
That makes sense... and the 125ESE's could be reused later for other projects. But, they only go down to 2.5k... would I need to parallel a resistor with the primary to lower the impedence?
No, what you can do to lower the apparent primary impedance of the 125ESE is to is to connect an 4 ohm Speaker to the 8 ohm Tap. This way the primary impedance will appear as 1250 Ohm (nominal).

However, i would think the 125ESE would be quite marginal in performance in the Lilliput and many other Amplifiers. The Budget Tango (U-808) which has been described by Joe Roberts as not all that great in Sound Practices (I concur, it is worth than the entry level AN IMNSHO) was noted as notably better by Joseph Esmilla, especially at low frequencies, pretty mcuh a condemnation if you coinsider that the U-808 is far from a bass champ.

http://members.myactv.net/~je2a3/125ESE.htm

In the end please note that in the case of many Output Transformers you get what you pay for. And cheap (Audio) transformers means a compromise in a critical part.

The (ab)use of certain brands of mains torroid transformers as Push-Pull output transformer is a "lucky coincidence", usually you do need to pay for quality.

You need to decide what is most important to you.

A SE Amplifier made with exceedingly cheap and inapropriate components will invariably make simply a bad amplifier, objectively and subjectively. A Push-Pull Amplifier made with the same budget is likely to be made to a higher standard of quality and will then make a better amplifier. I suspect that the Lilliput relies heavily on (quite legendary quality) Megahertz Transformers and will sound quite ordinary to awful using the "cheap out" option.

If you want an SE Amplifier I'd suggest go for a real 2A3 SE, use a suitable mains and output transformer (Audio Note Trans-144 is a quite reasonable Transformer, not exceptional but solid and fairly cheap) and you can still get away with a reasonable parts bill, without having to compromise.

If you shop around the Sun SV-2A3 Amp Kit can be had at fairly sensible prices (buy directly in Japan) and Audio Professor has some nice (and affordable) Kit's as well.

If you want a CHEAP Amp with a 6AS7 consider making it push-pull based on the maurits.

Get two large wattage (say 230VA+) 115V+115V:12V+12V mains transformers. Connect them back to back to get 230V HT (at around 0.6A) and use the 12V for the heaters (6AS7 in series with 12V/2.5A, drivers as needed) as well.

There you have the HT for a Maurits, looking at Surplus transformers can make the cost VERY LOW. The Maurits has no choke, so no (cost) problems there. The torriodal Transformers used (among others) by Richard Sears should be available for no more than around 30 Bucks each. The Supply Capacitors can be 350V Electrolytic Capacitors, which should open the door to extensive "salavging" (Photo Flash Capacitors?).

Depending on what you pay for the valves (russian 6922 and 6AS7 are dirt cheap, NOS 6AS7 are very affordable and many NOS ECC88/6922 are also not breaking the bank) you should manage a VERY inexpensive "Toob Amp".

It will give you experience and background. Then you might be interested in modifying the Amp and you slowly aquire experience first hand. I agree, it will not be an SE Amp, but "just SE" is no magic formula. In many ways it is harder to make a great SE Amp than it is to make a great PP Amplifier, but yes, WHEN they are great, then they do something nothing else does. But expect to invest a few grand in parts for that kind of level of performance, not just a few bucks.

Sayonaray
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Old 13th July 2004, 11:33 PM   #27
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Hi,

90 Euro (17% VAT included) for an OPT of this quality is dirt cheap IMO.
USD 400 for the kit minus the chassis? Now that's what I call the steal of the century.

Why waste time and money on something mediocre when you can have some worldclass quality amp for such a small outlay?
If I had some 96db/m speakers this would be the amp I'd use to go with it.
No doubt in my mind about that, it's THAT good, it uses readily available tubes and the one that's going to burn up the fastest (6AS7G, 6080) is sooo cheap it's hard to believe...

Is my comparison with the AN Baransu costing upwards of USD 15.000 upsetting someone's wallet perhaps?

Cheers,
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Old 13th July 2004, 11:38 PM   #28
alk is offline alk  Europe
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Hi,

Quote:
The Budget Tango (U-808) which has been described by Joe Roberts as not all that great in Sound Practices (I concur, it is worth than the entry level AN IMNSHO) was noted as notably better by Joseph Esmilla, especially at low frequencies, pretty mcuh a condemnation if you coinsider that the U-808 is far from a bass champ.
Now my 125ESE's are eternally damned.


Quote:
A SE Amplifier made with exceedingly cheap and inapropriate components will invariably make simply a bad amplifier, objectively and subjectively
I don't agree on the subjective side. I had only heard SS before my first cheapo SE. Well it is a good amp in comparison...i haven't heard your favourites amp so i'm content for the moment.. A few grand? I thought about buying some nice Lundalh's transformers and some nice 300 B's or 2A3's and that was all...less than a grand. Isn't that good enough for a great sound? If is not then maybe i would never get it.
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Old 13th July 2004, 11:45 PM   #29
alk is offline alk  Europe
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Well i read fdegrove post and my morale went up i am going to order the Lilliput i live close(Spain).

Cheers and thanks...i knew it was a good amp
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Old 14th July 2004, 01:23 AM   #30
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Konnichiwa,

Quote:
Originally posted by fdegrove
Is my comparison with the AN Baransu costing upwards of USD 15.000 upsetting someone's wallet perhaps?
Nah, I'm still trying to work out what "horn loaded Sowthers" are.

BTW, given that needtubes already linked in the details from audiokit's website I had figured that he did consider the 400 or so Euro for the parts Kit past his budget, otherwise why argue about 125ESE and the like?

Sayonara
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