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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 20 Jun 2013, 19:26 
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Start with that 100K resistor you added to stop the ringing. Remove it and see if your end to end gain is restored. If so, I can give you other options which can suppress the resonant peak at 10kHz without costing you mid-band gain. (I think :blush: )

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PostPosted: 21 Jun 2013, 03:51 
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Suncalc: no the issues was there prior to the 100K resistor.

The problem is some how related to the earthing. I thought amp earth to the input RCAs may have been the cause but removing it did nothing. Can you see any reason why the amp shouldn't have gain? If I look at the input signal and what is going to the grid with respect to ground there is a gain from the input tranni. But the tube appears crippled.

I re-checked all voltages and even tried different tubes . I am sure the amp played louder in the past but as to time has rolled on did I have input and output on the CRO around the wrong way.

Even tonight when I opened up the amp and tested it had gain. But back in the system none. So at pulled it apart at the system and now no gain. Maybe the amp never had gain but my notes show it did have gain.

Without pulling all the earths off and starting again it maybe hard to fix. Quietly played the amp sounds excellent with the right material. But the bugger should have gain!!!

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PostPosted: 21 Jun 2013, 15:42 
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Hi Mark, Very strange. Can you post a current schematic and possibly some photos of the insides. Sometimes another pair of eyes can see something that is not right.

Good Listening
Bruce

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PostPosted: 22 Jun 2013, 03:54 
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Fostex FE206 with Paris - 6EM7 amp and Oppo BDP-95
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PostPosted: 08 Jul 2013, 20:53 
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I'm a Stereophile nut, love the mag. and always lookout for gems of info, suggestions or comments from the reviewers. I think quite often remarks and comments they make are on the money and I try to use or incorporate the snippets I think I can use. One comment which was made in a recent Stereophile is one reviewer found that a system always sounded better when preamp was used.

A lot of amps have sufficient gain to allow direct connection to a CD player or phono preamp etc. So why use a preamp? The reviewer found that regardless of what combination of SS or tube preamp and power amp were strung together (I am embellishing a little here) the final sound was always better with preamp in place. Even there reviewer didn't know why but felt he should state his observation.

I have to agree. I have always felt that any one of my systems sounded better with a preamp. When every component, active or passive, buggers the sound it seems strange that a preamp can magically improve the sound? For me, with very low gain power amps, preamps are essential but there have been times when I have connected my CD player direct to one of my higher gain power amps. Then with a preamp. And I have to agree (once more) that a preamp appears to improve the sound.

Any comments?

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PostPosted: 09 Jul 2013, 16:55 
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Hi Mark, This is bound to cause consternation in the ranks. I find just the opposite. I find the level of clarity and detail better without a preamp. I normally use a passive volume control between my sources and amps. I wonder if the issue relates to impedance matching or perhaps long cable runs. Most curious.

Good listening
Bruce

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PostPosted: 09 Jul 2013, 18:17 
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I have read on a few occasions where the back-end of CD payer generally does not have drive capabilities. This is where the preamp takes this delicate signal and buffers and amplifies.

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PostPosted: 03 Jan 2014, 01:07 
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With the wife and daughter home I setup one of my headphone systems. A PD C400 Teac multi-disc player, "Woody Pro" headphone driver\preamp and AT Air headphone. Also I hooked up the second of my DC blocker\power filters.

Listening to classical and opera provided me with two days of outstanding listening pleasure. I had forgotten just how good music can sound through a good HP system. I add a 6.5mm phone output jack to Woody Pro and thought it has two selectable RCA inputs I will parallel up a 6.5mm jack to one of the inputs. This means you can use any combo of RCA or phone jack for input and output.
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PostPosted: 13 Mar 2014, 00:24 
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Intermezzo, my UX-171A power amp, use to play tricks on me and go from not delivering full power (an ear bleeding 0.5W) to a tenth of this. But I did find a problem. As the wife would say "is it a lose wire or something". Well it was. I very rarely use screw connector and this time I did and one refuse to bid-down properly. But since the heavy-handed adjustment, full power.

While I have gone to the trouble of pulling this very retro amp out with its 1920s UX-171A and 80 rec. tube I thought I may have a listen down listen lounge #3 (which my wife foolishly calls the "family room"). I have some Fostex FE206En based speakers here and with my 4S based preamp (with 12AU7) and using the iPad playing itunes radio (classical) I should be in for a good time. With the iPad I take the output from the charging\access port at the side with a lead which has the iPad connector and RCAs. This way you get direct access to the 24B\96K DAC inside without all the headphone drivers and volume controls getting in the way. Much, much better. itunes radio is 256K variable bit rate so possibly the highest resolution internet radio around. Definitely the very best classical content of everything I have listened to so far.

Take a look at the setup. Behind is my Oppo-93 SE and High Sense 47" LED TV. "Number 9" (80W tube and chip amp) usually drivers these speakers. Intermezzo has such a detailed and gentle touch.
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IntermezzoSystem.jpg


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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 12 Apr 2014, 22:33 
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Hi Mark, I had a TV stand just like the one in the photo. Now there is no TV in the listening room. Partly because I almost never used it (I have one in my shop next to the PC) and also so no one else would want to take over my room. I already lost one that way and we don't have any spares to go around if it would happen again. ;) The speakers are rather nice looking and no doubt perform as well. They look like Fostex 206s. Do you use subs with them?

Good listening
Bruce

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