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Old 22nd January 2011, 10:31 AM   #841
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Originally Posted by Vinylsavor View Post
This only means you can't use it with a 1:1 output transformer or with LC or RC coupled output. With a Lundahl 1660 4.5:1 it will easily drive your SS amp.

Thomas
Thanks Thomas, also can I use the same output LL1660 to drive my headphones Senns HD600 or but can do to use it?

Felipe
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Old 22nd January 2011, 10:58 AM   #842
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Hi Felipe,

this depends on what your headphones need. What is their impedance and the voltage they need? If they are 600 Ohm, a 9:1 transformer would be better, like LL1689 but then the linestage would have a gain of less than 1.
Porbably a separate headphone amp would be better in this case.

Thomas
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Old 22nd January 2011, 02:11 PM   #843
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Hi Thomas,

Sennheiser HD600
300ohm
12-39000Hz
97dB 1mW
THD 0,1%

Felipe
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Old 22nd January 2011, 03:04 PM   #844
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Hi!

That's quite low impedance.

That won't really fit for the 26. Either go for a different concept, or make a separate headphone driver

Thomas
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Old 22nd January 2011, 03:27 PM   #845
CFT is offline CFT  United States
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Originally Posted by andyjevans View Post
Here's mine - it has a separate power supply. Glow tubes on the left for the input tubes. I use a modular chassis with several interchangeable top plates, with rackmount parts as you can see. All my chassis are 2U and usual rack width. Lundahl transformers underneath.

Andy
Nice looking amp Andy!! And that's clever

Someday I would like to try out 10Y, heard a lot of good things about it...

Currently both this amp and the preamp are on cathode bias, battery bias is something I want next...
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Old 22nd January 2011, 03:43 PM   #846
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26 tube with 8:1 transformer; that means 2 VRMS in for about 2 VRMS out.
2 VRMS with a load of 300 ohms is about 13 mW.
Should be plenty enough to drive a HD600.
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Old 22nd January 2011, 04:32 PM   #847
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Currently both this amp and the preamp are on cathode bias, battery bias is something I want next...>>>

If you try filament bias, Rod's boards will be substantially the same as for cathode bias but you should check with him on that. The difference will be that you will need a higher voltage transformer, caps and maybe a larger heatsink. Worth thinking about!

Andy
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Old 22nd January 2011, 04:36 PM   #848
E.T. is offline E.T.  United States
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Originally Posted by Vinylsavor View Post
Hi Andy,

neglecting copper losses in the transformer this is calculated as follows:

rp of the tube divided by the square of the turns ratio.
That is 7000 Ohms / SQR(4.5) This is roughly 350 Ohms

Best regards

Thomas
350 ohms would agree reasoably well with hi-impedance headphones. Does a pair of 26's have enough grunt to run 600-ohm cans like the old style AKG k240's?

Thx!
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Old 22nd January 2011, 04:42 PM   #849
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Hi Pieter,

Quote:
Originally Posted by pieter t View Post
26 tube with 8:1 transformer; that means 2 VRMS in for about 2 VRMS out.
2 VRMS with a load of 300 ohms is about 13 mW.
Should be plenty enough to drive a HD600.
You would loose some gain since the output impedance would be somewhat above 100 Ohm. Loaded with 300 Ohm you will loose some signal. Also that would mean to load the tube with less than 3 times it's rp.

But the intention was to use it for both linestage with some gain and headphone amp.

What could be done is to provide some switching at the output between 9:1 for headphone and 4.5:1 for linestage

Best regards

Thomas
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Old 22nd January 2011, 04:44 PM   #850
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Hi!

Quote:
Originally Posted by E.T. View Post
Does a pair of 26's have enough grunt to run 600-ohm cans like the old style AKG k240's?
Not optimal. That would load the tube too much. The point of transformer coupling (among others) is to give the tube a high impedance load to achieve a load line close to horizontal. I like to load a tube with 5 times it's rp or more.

In your case that would be less than 2 times the rp

better would be a 9:1 output trans like Lundahl LL1689

Thomas
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