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Old 31st March 2008, 10:44 AM   #1971
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How do you fix the thumbnails? Gotta a lotta photos but they are too big, and a simple text-link is boring.
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Old 31st March 2008, 11:23 AM   #1972
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Quote:
How do you fix the thumbnails? Gotta a lotta photos but they are too big, and a simple text-link is boring.
Make sure the photo's are below 100kb. Best done by altering the image size to something like 640*480 and save as jpg with some compression.
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Old 31st March 2008, 04:31 PM   #1973
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zzf, very nicely laid out inside. Nice and clean. When your done, you can start on mine.
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Old 31st March 2008, 04:54 PM   #1974
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richwalters

Did you have to wire your box in layers?

"Using KT88’s and 575VB+ the design goal is achieved with outputs exceeding 250W per channel extracted. (Strangely I got 650W in bridge mode, this seems high)"

What load impedance did you use in bridge mode vs. stereo?

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Old 31st March 2008, 10:05 PM   #1975
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Quote:
Originally posted by Michael Koster
richwalters

Did you have to wire your box in layers?

"Using KT88’s and 575VB+ the design goal is achieved with outputs exceeding 250W per channel extracted. (Strangely I got 650W in bridge mode, this seems high)"

What load impedance did you use in bridge mode vs. stereo?

Cheers

Nup, the first was the thick twisted heater wiring and to avoid volts drop interconnected each quad to another, then buss all sockets at transformer end. Cumbersome but although I get darned good performance out of 6550's they are sensitive to heater/emission variations. Compared to some brand 88's, 6550's can take a good 15mins to get fully settled down.

As for bridge mode, I'm going to recheck this more seriously.- I used 8 ohm o/ps on amp into a 4 ohm load, and I knew the transfer match wasn't optimal. 8 Ohms on many tube amp output transformers is codged up using a parallel winding and two series and this poses a lossy problem. Far better to use 4 ohm o/ps i.e double parallel windings in series and use a 2 ohm load. This is what alot of studios use.
Changing tube amp secondaries from designated isn't the done thing as different winding configurations can lead to phase and square wave problems.
I use balanced 600 ohm and best way is to use reed relays and two identical input transformers and change input on one channel.
more anon.


richj
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Old 1st April 2008, 02:59 PM   #1976
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My first attempt to build something out of my own head and thinking and by the way learning to calculate implementation of every singel component. Make every singel valve work at its best centerpoint. Some 15 years ago. At that time there where no help at internet, so I had to shoop many books and read a lot.

Once ready it workt at once, just some corrections of the stabdiodes for the smalltriodes and little correction of the NFB.
Messured very nice at the oscilloscope, driven with different monstertraps at the outputterminals.
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Dynaco mk3 outputtransformators driven by Svetlana 6550s in ULPP low voltage klassA. The sound is like a very good transistoramp (nothing), I mean there is very little cooloration of the sound.

(Second from left, is an old GE, they never die)
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Old 1st April 2008, 04:09 PM   #1977
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Quote:
Originally posted by Ragnwald

Dynaco mk3 outputtransformators driven by Svetlana 6550s in ULPP low voltage klassA. The sound is like a very good transistoramp (nothing), I mean there is very little cooloration of the sound.

(Second from left, is an old GE, they never die)

The only transistor or mosfet amp that has come anywhere near the < tube sound> is the simplest Maplin amp, an early mos Jap design from 1978 which I mentioned in another thread. The rest are basically all the same complementary pairs poorly designed overheated class A drivers which eventually fail. The number of SS amps I've repaired is countess and nearly have all the same problems.

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Old 6th April 2008, 08:00 PM   #1978
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Default 6V6 SE

Hi there,
My first post.
My first amp.
It's a 6V6 Single Ended with a ECC83.
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Old 7th April 2008, 08:23 PM   #1979
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How does it sound?
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Old 7th April 2008, 09:42 PM   #1980
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It's not the worlds greatest sound, but I like it. It kind of grows on you....
It sound relaxed, it does not wear you out. Whit my Fostex FE107E single driver QWTP it is just right.
I like simple music, singer/songwriter-stuff; small jazz-fusion combo's; folk/folkrock. All this sounds great. I'm a happy man.........

Although I like to build stuff; so I'm already thinking up new plans.....
An 807 PP is on its way; combined with an Fostex FE208 hornsystem.

I'm a busy man....

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