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Old 9th March 2007, 01:31 PM   #1
WE91 is offline WE91  Norway
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Default HELP; DIY PP amp - it's phase splitter, or buy Chineese.

Hello...

I'm contemplating building my own KT88 or 6L6 push pull amplifier to be used in a bi-amplified system in the bass region (as a "different" but potent alternative to my Lectron JH50). In the mid/highs I will be using a WE-91 type SE amp.

I would really like your comments on this:
I have have done a bit research and found that this DIY project by Pete Millet may seem "promising":
http://www.pmillett.com/push-pull_kt...driver_pcb.htm
I can swap tubes in this one between KT88 or 6L6, - BUT is it any good? What about input trafo for phase splitting instead of any tubed solution? What is your opinion and recommendation?

Should I just give up on making my own, because amps like these exists, and a pair can be mine for 1700 USD in total: http://www.melodyhifi.com/S88.html

And finally, - another question. Do anybody have any experience with such OPT's as these: http://www.tubebuilder.com/mdcorexfmrs.html

Looking very much forward to your answers and input.

Best Regards
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Old 9th March 2007, 01:41 PM   #2
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hi we91,

I was testing full line of this tube amp from japan.

they work good. sound great.

But still had some space can improve.

If change to nnao amorphous OPT can improve the sound. I will do. Since the phase spitting tubes such as ECC84 was cheap in market U will have many choice such as telefunken, valvo & mullard & reasonable price.

thx

thomas


this is circuit.


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Old 9th March 2007, 04:33 PM   #3
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Default Re: HELP; DIY PP amp - it's phase splitter, or buy Chineese.

Quote:
Originally posted by WE91


I would really like your comments on this:
I have have done a bit research and found that this DIY project by Pete Millet may seem "promising":
http://www.pmillett.com/push-pull_kt...driver_pcb.htm
I can swap tubes in this one between KT88 or 6L6, - BUT is it any good? What about input trafo for phase splitting instead of any tubed solution? What is your opinion and recommendation?

Should I just give up on making my own, because amps like these exists, and a pair can be mine for 1700 USD in total: http://www.melodyhifi.com/S88.html

And finally, - another question. Do anybody have any experience with such OPT's as these: http://www.tubebuilder.com/mdcorexfmrs.html

Looking very much forward to your answers and input.

Best Regards

1. IMHO the "universal driver" is a solid, working solution. Nothing about it strikes as being particularly smart or original; i guess that's the price for being universal.

Otoh, it's not that universal either. I have doubts about its ability to drive convincingly 300B and it seems inappropriate for any kind of nfb i.e. pentodes.

So, you have to live with trioded KT88/6L6 etc as the UL mode is likely to result too high output impedance.

I'll take a pentode KT88 any day, especially in a multi-amped system.


2. The Melody amp is probably quite nice, especially second hand as it's is not likely to keep it's value too well. A valid choice, but think about all the nice iron you can buy for the price - entry level Tango/Tamura/James is quite possible.


3. Never heard of MD cores. Building a nice tube amp is expensive and time consuming. Only the best iron is worth using - see 2.
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Old 11th March 2007, 08:18 PM   #4
WE91 is offline WE91  Norway
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Thank you very much for your answers, Tube-Lover and analog-sa!

I will choose a KT88 amp for the bass in my multi-amp (bi amp) system. I have plenty of time in finding a good solution, though. I do have the 50W PP EL34 Lectron. I will be on the look out for good used PP KT88 amps. If none shows up, I'll just "roll my own" using good iron and a tube rectified psu. Good DIY and kit PP KT88 amp-designs wanted!

Best Regards
Aril
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Old 13th March 2007, 09:04 PM   #5
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if u really like the PP amp. will U considerate 12E1.

this was a good tube & very good sound.

thx

thomas


this circuit from japan test very good sound.

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Old 14th March 2007, 09:50 AM   #6
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Hi Thomas,

this is an analog the Q.U.A.D. II schematic; the grids of the input pentode an the phase inverter pentode have different potential to ground!
In the QUAD-amplifiers (EF86, KT66) this works fine, may be feedback helps?

Regards
Andreas
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Old 14th March 2007, 12:57 PM   #7
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Yes, that last circuit is indeed copied from the Quad II.
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Old 14th March 2007, 03:25 PM   #8
WE91 is offline WE91  Norway
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... Since I posted this thread, I've found that I'm not going for a Chineese ready-made amp, even if the Melody amps seems a really good choice (some of the best from China?).
I'm going to build it my-self! Thank you, Thomas/Tube Lover for your schematics. I've yet to see them properly, though. I do not know how to amplify the pictures. I've put them in Word, and tried to make them bigger, but they're not sharp enough to see. I need help
Thank's AndreasS and EC8010 for your comments on the last schematic!
What I "need" is a PP amp thats renown for its rich tone and clarity in the midrange, together with a realy superior, tight and extended bass. My thought has been KT88 or 6L6, - but a really well executed PP DHT amp is also of interest. Although, please do not recommend any 211, 845 or the likes, as I do not like to push the envelope too far on electricution

Best Regards
Aril
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Old 14th March 2007, 04:28 PM   #9
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the schematics you can find here:

http://www.audiopro.co.jp/kitkakaku.html

Andreas
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Old 14th March 2007, 05:38 PM   #10
EC8010 is offline EC8010  United Kingdom
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Superior bass tends to mean PP simply because it's so difficult to do the output transformer for SE bass and still have some treble.
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