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 Post subject: Re: GU29 Amplifier
PostPosted: 29 Jul 2013, 00:14 
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Joined: 27 May 2012, 07:21
Posts: 26
Location: Romania
Hi, Les, thanks for your impressions.

The amp's not finished yet, for know I'll keep it in tests, but soon I'm gonna finish it.
For the anode I'll use some anode caps, still don't have them.
I'll come back with more pictures and measuring parameters.

Have a nice day and good music!

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 Post subject: Re: GU29 Amplifier
PostPosted: 29 Jul 2013, 21:17 
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Joined: 06 Jun 2008, 18:23
Posts: 5143
Location: Australia
I'm with Les, get the HT covered. I like the amp though.

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 Post subject: Re: GU29 Amplifier
PostPosted: 31 Jul 2013, 20:01 
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Joined: 02 Mar 2009, 12:41
Posts: 1110
Location: Vänersborg, Sweden
There are anodecaps to buy for the 829, 832 and similar tubes, but often they are more expensive than the tube.
Here's one shop on Aliexpress that sells that kind of caps: http://www.aliexpress.com/item/bakelite-tube-caps-for-fu29-829-829b-fu32-832/462183397.html

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 Post subject: Re: GU29 Amplifier
PostPosted: 31 Jul 2013, 20:47 
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Location: Australia
Soundbrigade wrote:
There are anodecaps to buy for the 829, 832 and similar tubes, but often they are more expensive than the tube.
Here's one shop on Aliexpress that sells that kind of caps: http://www.aliexpress.com/item/bakelite-tube-caps-for-fu29-829-829b-fu32-832/462183397.html

I think for $5 or $6 a cap they are well worth it. I think from a visual point of view they could enhance the look of the amp. My 807 amp has $7 second-hand tubes and ceramic top caps. I think the caps cost more than the tubes but look good and are very functional.

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 Post subject: Re: GU29 Amplifier
PostPosted: 31 Jul 2013, 21:08 
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Joined: 02 Mar 2009, 12:41
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Location: Vänersborg, Sweden
If you want some I can ship a few to you, but we are in St Andrews, NB, Canada right now.

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 Post subject: Re: GU29 Amplifier
PostPosted: 31 Jul 2013, 23:13 
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Joined: 27 May 2012, 07:21
Posts: 26
Location: Romania
Hi everybody!

Soundbrigade, thanks for your anode caps offer, but I think I'll find them on a local store or mabe, I'll make them myself.
Anyway, the anode caps are the last thing missed from my amplifier.
The amp is a Push-Pull, GU29 are the final stage, for the driver I used an dual j-fet opamp, LF353.
That's why my amp is a hybrid amplifier, but it sounds great with deep bass and kick trebble.
I want to thanks to Mr. Lazaroiu for the schematic and OTPs and I'l give you some pictures with different construction stages and the finished amp, exccept the anode caps.

Sorry for my poor english and enjoy the music.

Best wishes from Romania!
Peter.


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 Post subject: Re: GU29 Amplifier
PostPosted: 01 Aug 2013, 03:02 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Piotr67: there is a lot of things I like about your amp. The timber panelling looks good. Tubes are crazy. How does the amp sound?

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 Post subject: Re: GU29 Amplifier
PostPosted: 01 Aug 2013, 04:40 
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Joined: 27 May 2012, 07:21
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Location: Romania
I can say the amp sound over my expectations!
I thought if the GU29 tubes are beam power double tetrodes and they are made for the radiofrequency range, to use these tubes in audio could deliver a SS sound. But the sound is warm and full of bass and treble, like dedicate audio tubes, without any tone control, equlizer, etc.

I'm pretty proud that I builded it!

Cheers!

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 Post subject: Re: GU29 Amplifier
PostPosted: 01 Aug 2013, 05:59 
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I'll take a better look at the schematic. How many watts do you think?

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 Post subject: Re: GU29 Amplifier
PostPosted: 01 Aug 2013, 06:34 
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Joined: 27 May 2012, 07:21
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Location: Romania
I estimate arround 10 or mabe 12 Watt.

In the original schematic, the Ua is 350V and the power is 20 Watts, but my power transformer deliver only 295V, after the bridge and 2x330uF/400V caps. So, I feed the anods with only 295 V and that's give to me enough power and, like a plus, the tubes are working easy, I estimate a long GU29's life. :headphones:
For the opamp driver, I have a small regulated dual supply, +/-15V with LM7815 and LM7915 regulators with 2x4700uF/40V caps and a small resin encapsulated transformer with 18v-0-18v.

There is no hum, hiss or anything else. The amp is completlly silent. Mabe because I used a star grounding? :)
Because the schematic is Lazaroiu's concept and simulation, if I'll have Mr. Lazaroiu accept, I will post the schematic here.

Thanks for understanding.

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