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 Post subject: Re: 6EM7 power amp
PostPosted: 13 Jan 2012, 01:43 
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Location: Chilliwack, BC
mwhouston wrote:
What happens if you get it wrong?


It farts :D

LF oscillations.

Cheers!

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 Post subject: Re: 6EM7 power amp
PostPosted: 13 Jan 2012, 18:29 
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Location: Australia
mach1 wrote:
After you connect the bypass cap to the negative output of the secondary don't forget to connect the positive output of the secondary to earth. This is not shown in the diagram.

I wondered if you had to do that. This tweak is weeks away for me I haven't even started on the new amp. One more MC preamp to go first.

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 Post subject: Re: 6EM7 power amp
PostPosted: 10 Feb 2012, 19:31 
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Suncalc wrote:
I have been reviewing some of your and Qian's comments about this amp and I have two suggestions for the mono block builds. The first is to increase the coupling cap between the 6EM7 stages from 0.02µf to 0.047µf. This will push the lower knee down a little bit. I also suggest going with the Edcor GXSE 10-8-5k instead of the XSEs. (I hope you haven't purchased your OPTs yet.) I believe that these two changes should significantly help clean up the lower end between 30Hz and 100Hz while not affecting the mids that you like so much.

I'm about to start assembly of Paris - duo monoblocks. I will increase the inter-stage cap to 0.047uf. Unfortunately I had ordered the XSE OPTs - 10W.

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 Post subject: Re: 6EM7 power amp
PostPosted: 22 Feb 2012, 19:01 
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Location: Australia
I have finally got Paris back and now a chance to listen to the amp again. I had never screwed the base plate on. While it was off I took the opportunity to put my usual layer of bitumanised heavy Al foil up the center of the base plate. This adds weight and helps stop resonance and ringing in the big plate. I also screwed the base plate down. While the bottom was off I had a clean-up and tidy of the cct. Also taped over bare high voltage points. I also added teflon tube rings to the 6EM7s. The 12AU7 already had a tube ring. Now for a listen.

If you're not into subjective listening notes skip over the rest.

There is still some magic about Paris that can't be explained which draws you into it. Paris has a built in 4S Universal preamp using a 12AU7 so I plug direct from my Oppo 93SE and BHL phono stage directly into it. I'm playing a Naxos CD (Jana'cek) I picked up while recently away. I'm gobsmacked by the transparency of sound and a true sense of being at the performance (live orchestra of course). The Silver Dragon for all its cost and expensive tubes just does not measure up to the sheer realism of this giant killer. My $4.5K Osbourn 3 way towers can make most amps sound good with their Focal W cone mid-range drivers and inverted Focal tweeters but in this case Paris makes the Osborns sound good.

I'm about to lend Paris out again for a possible purchase. If it doesn't sell I may just put the Dragon up for sale. If you want a low power (2W) inexpensive amp which will punch far above its weight travel no further than Paris. Your ears will thank you.

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 Post subject: Re: 6EM7 power amp
PostPosted: 25 Feb 2012, 18:33 
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After lots of comparisons the Dragon will stay. BUT I took Paris to a friend's (Kuna's) house who has a pair of Music Fidelity 500Ks. We wired Paris into the MFs turbo input. The idea is any power amp connected to the MF will get a 4X boost and drive inefficient or difficult loads. The 2W Paris sounded OK into Kuna's ProAc slim towers with 2 X 6.5" woofer-mids and 0.75" soft done tweeter and down firing port.

I then suggested we connect direct to the ProAcs with some Cat6e speaker leads I made up for Kuna. The leads have the pairs and mates split off at the ends. Kuna likes his techno, house, electro etc.Paris played Progressive House at the same levels and with as much drive and bass as with the MFs. Kuna was surprised and so was I. I was asked to leave Paris for further listening.
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 Post subject: Re: 6EM7 power amp
PostPosted: 14 Mar 2012, 07:31 
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I have Paris back and have been spending some time listening to the amp. I had made the comment that I thought Paris maybe light on bass. Paris tests extremely well into a resistive load and even takes my 100lb each three way towers down to 40Hz but I felt there was little weight behind the lower mids to bass. Matt's suggested increasing the inter-stage cap from 0.022uf to 0.033uf. In Paris Duo this was done.

Today I added an additional 0.01uf cap to the current 0.022uf cap to bring the inter-stage cap closer to 0.033uf. I like adding a smaller cap to larger caps and feel it is a better way to reach the desired capacitance. After listening to the result for a while I think it has made a significant improvement to the overall sound and particularly the bass end. There appears to be greater weight and more dynamics in the music right across the frequency range and the bottom end is more dominant.

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 Post subject: Re: 6EM7 power amp
PostPosted: 07 Sep 2012, 02:13 
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Paris has a new home driving a freshly made pair of Fostex FE206En speakers. The setup is around the TV end of the house and gear comprises: 46" LED Hisense TV, Oppo BDP-93 SE Blue Ray/CD player, Paris and a Pair of Fostex FE206En drivers in the bass reflex box plus a 125W 12" sub-woofer in 80L ported box. The LFE output of the Oppo supplies the signal to the sub amp (SS). Interconnect and speaker wire is single strand wire wrap wire.

The drivers are 96db efficient and with no Xover or BSC you get the full sensitivity so the 2.5W 6EM7 Paris amp delivers full volume. Usually with high sensitivity speakers any back ground noise in the amp will be heard. I stuck my ear right inside the drive with the the Oppo paused and heard - NOTHING. No buzz, no hum and no hiss. Dead quiet amp and dead quiet system. Very pleased. From early impressions Paris and the new Fostex boxes (retro-F206) are getting along really well. The speakers are tight though so improvements on the way.

http://www.diyaudioprojects.com/Forum/viewtopic.php?f=11&t=4006
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 Post subject: Re: 6EM7 power amp
PostPosted: 29 Jul 2013, 20:15 
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I've just started another 6EM7 power amp inspired by an Acacia chopping brd. The brd. is attractive and quite heavy. Big holes are drilled but a long, long way to go. I have been waiting parts which only just arrived. The amp will sit on gold cones with a back Al skirt behind them hiding small parts and wiring. The metal box at the back will hold the larger PS caps and have the terminals mounted on them. Bit of a crush but I think I can do it. Tube rec of course. Tubes are NOS Silvania's. Power tranni and 10H choke and Hammond and OPTs EDCOR.

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 Post subject: Re: 6EM7 power amp
PostPosted: 30 Jul 2013, 19:58 
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Paris has been sold but the amp use to power my Fostex FE206 double bass chamber speakers either side of my TV. My Oppo 95 provides two channel listing from Blue Ray discs. I have had to put the only spare tube amp I have in Paris's place which is a K12. To my absolute amazement it actually sounds better. I think the K12 has a little less detail and it is mellowing the Fostex a bit.

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 Post subject: Re: 6EM7 power amp
PostPosted: 01 Aug 2013, 19:21 
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The new Paris owner is pleased with the amp and says it well outperformed his Audio Space AS2i. The speakers Paris is driving is a pair of Usher 520s. These are very compact bookshelf speakers. When connected to the Audio Space I thought them to forward in the upper mids. After making that comment to Allen (the owner) he said though the Ushers got excellent reviews others had said the same.

The Audio Space is a PP amp where Paris is an SE amp. I feel Paris' better bass extension and smoother sound 'tended to balance the Ushers better. Allen agreed. Paris also appears to have better soundstage, possibly due to the dual mono construction, tube rectification and choke filtering. End result is I'm happy Paris is getting more use as a main amp and not an occasional TV\movies amp and Allen is happy due to the Ushers sounding a lot more balance.

The Ushers are are only 86db efficient and with Paris only delivering 2.5W I was worried about volume level and dynamics. After two hours of listening to a wide variety of music, at good listening levels, I could hear no strain or distortion.

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