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Old 19th January 2009, 03:16 AM   #1
RMS is offline RMS  United States
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Default Looking for a 45 SE Schematic

Where can I find a simple 45 SE schematic? Eventually I will build all three, 2A3, and 300B I have been wanting to do this for a long time and I am ready! I am looking to keep it very simple, so if you can recommend me a schematic that would be great!

Thanks
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Old 19th January 2009, 06:22 AM   #2
kmaier is offline kmaier  United States
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I did this as a small project for my son last year, then offered it up as a DIY project on AC. Also have a 2A3 version, but would use something different for a 300B. I can send anyone interested the PDFs and RTFs for cleaner schematics and BOM lists. They sound very nice using good parts and a clean layout, specs are excellent (within 1dB past 30KHz with good OPTs) if you get some good (read NOS) tubes and match them up well.

Click the image to open in full size.

Regards, KM

PS - larger direct jpeg image here... hope it's viewable.

http://image66.webshots.com/566/4/45...7ZaJGuO_fs.jpg
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Old 19th January 2009, 04:39 PM   #3
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The Bugle might be a good choice if built with good iron...


http://www.hificollective.co.uk/a/article4.html
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Old 19th January 2009, 04:56 PM   #4
kmaier is offline kmaier  United States
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Yes, the Bugle article has some design choices explained and some good formulas for calculation of certain circuit parameters and values. You can get the entire article in PDF and a good recommended read here:

www.wavelengthaudio.com/bugle.pdf

Personally I just don't care for SRPP stages, but at least Gordon chose a great tube, the 12AY7. I would still recommend the split balance from my design. With a good 45 you can get hum levels balanced out much lower than using a combined balance.

Regards, KM
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Old 20th January 2009, 01:18 AM   #5
RMS is offline RMS  United States
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Quote:
Originally posted by kmaier
...I can send anyone interested the PDFs and RTFs for cleaner schematics and BOM lists.
Yeah that would be great!
dreamtoneamps-at-gmail-dot-com

Quote:
Originally posted by RockysDad
The Bugle might be a good choice if built with good iron...
Thats an interesting design too, would have to look into SRPP ... not up to speed with the hi-fi circuits.

So basically we have one using a 12AY7 and the other a 12AT7, why these vs. say a 12AX7 or a 12AU7? What other preamp tubes are normally used on a 45 design?

What Iron would you guys recommend?

Thanks for the data!
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Old 20th January 2009, 07:15 AM   #6
johnYks is offline johnYks  Australia
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Hello Kmaier

'I can send anyone interested the PDFs and RTFs'

Yes please my email address is jyiannak@hotmail.com

Yours Sincerely
John
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Old 20th January 2009, 08:21 AM   #7
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Quote:
Originally posted by RMS
So basically we have one using a 12AY7 and the other a 12AT7, why these vs. say a 12AX7 or a 12AU7?
12AX7s don't really have the drive capability due to the low currents these typically run. The 12AU7 may not have enough gain (u= 20) and this is more of an RF type than a good audio type.
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Old 20th January 2009, 08:23 AM   #8
kmaier is offline kmaier  United States
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RMS,

Tried to send you PDFs and RTFs to your requested email account, the mail server prevented it, possibly due to attachments. They are certainly clean and free of any bad code. Maybe something specific with the gmail servers. if you have another mail account you'd like me to try let me know.

Anyway, there are all kinds of input/driver tubes used for SE amplifiers... to each his own actually. I've used all of the ones you've listed plus several others. It gets down to the actual application and circuit requirements, which are basic design choices. The 12AX7 has a lot of gain but not a lot of current capability, the 12AU7 is inverse, i.e., low gain and much higher current capability while the others are in between. I selected the 12AT7 as it fit the circuit topology best. It yielded enough gain and had the ability to sink enough current for the cathode follower. Neither of the others fit this application as well.

Regards, KM
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Old 20th January 2009, 08:30 AM   #9
kmaier is offline kmaier  United States
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RMS, John,

PDFs sent... for some odd reason neither hotmail or gmail servers will accept the RTF docs... probably a default on their configuration. Will try and convert to something else and re-send.

Regards, KM
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Old 20th January 2009, 08:38 AM   #10
kmaier is offline kmaier  United States
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RMS, John,

Just made a PDF for the BOM... sent.

Regards, KM
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