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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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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 02 Nov 2018, 20:23 
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Joined: 04 Jun 2008, 20:59
Posts: 4031
Location: Arizona, USA
Hi, I have used the JJ 6L6GCs and they are quite nice. I also tried some Sovtek 6L6WXT+ A slightly beefier version of the tube. (guitar folks like the way the overdrive BTW) They also are good in SE U/L use. If you have enough heater power you might give a try to KT120s. No other changes. I recently stuffed some in my KT77/EL34 Oddblocks and was really impressed with the sound. I have heard that "big bottle" tubes sound better than their skinnier mates. I am becoming a believer. All my personal mono blocks are running with KT120s. B+ of 450 and cathode current per tube is 62 ma. They just loaf along. I would expect some vintage large bottle tubes to be nice as well. Older 6V6G, 6L6G, KT66 and so on.

I agree with Mark your stuff looks great.....makes mine look like garage builds.

Good listening
Bruce

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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 09 Nov 2018, 23:02 
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Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
Matt having built a 6V6 and a 6L6 power amp you may like to highlight your preference. To you, which amp sounds the best and why.

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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 09 Nov 2018, 23:07 
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Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
gofar99 wrote:
Hi, I have used the JJ 6L6GCs and they are quite nice. I also tried some Sovtek 6L6WXT+ A slightly beefier version of the tube. (guitar folks like the way the overdrive BTW) They also are good in SE U/L use. If you have enough heater power you might give a try to KT120s. No other changes. I recently stuffed some in my KT77/EL34 Oddblocks and was really impressed with the sound. I have heard that "big bottle" tubes sound better than their skinnier mates. I am becoming a believer. All my personal mono blocks are running with KT120s. B+ of 450 and cathode current per tube is 62 ma. They just loaf along. I would expect some vintage large bottle tubes to be nice as well. Older 6V6G, 6L6G, KT66 and so on.

I agree with Mark your stuff looks great.....makes mine look like garage builds.

Good listening
Bruce

I too have the JJ 6L6GC in one wine box amp. They are a big impressive tube. Really like them in my wine box amp but when searching for more bass the Class D T3s provide it. I've been off tube power amps in my main system for some time now and are missing the sound. Bass or not I may have to swap in the wine box or two just for fun. I do like the mids of tubes.

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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 28 Jan 2019, 19:52 
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Joined: 22 Aug 2017, 21:57
Posts: 11
Location: Layton, Utah, USA
I built Matt's excellent marblewood amp a few months ago, and I like it a lot. I made PCBs, one for the 12AU7 and one for the 6V6s. The power supply is point to point wired. The chassis and bottom plate are plasma cut steel, painted with black Rustoleum. The wood is marblewood like the original, very beautiful wood, but kind of expensive. I completed the testing today using ARTA Steps software and my Steinburg UR22 MKII USB audio interface, so I thought I'd post the results here. There are 3 separate graphs of the frequency response and THD at low drive (abt 250mv RMS), moderate drive (abt 500mv RMS) and high drive (abt 800mv RMS). The 3dB bandwidth is from about 42Hz to 20KHz+, gain of about 45dB. Distortion at 1KHz ranges from less than 1% at low drive to about 3% at high drive. Distortion is primarily 2nd harmonic as expected. I have only tried the 12AU7 and 6V6s (all JJ Elect.) and haven't had a chance to do any tube rolling yet.


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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 28 Jan 2019, 19:55 
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Joined: 22 Aug 2017, 21:57
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Location: Layton, Utah, USA
Here's the distortion graphs.


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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 28 Jan 2019, 20:31 
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Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
Gorgeous build.

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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 30 Jan 2019, 17:02 
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Joined: 22 Aug 2017, 21:57
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Location: Layton, Utah, USA
Sorry but my ARTA system was not calibrated when I made the previous measurements so the gain was way off. Here are the corrected graphs.


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 Post subject: Re: 6V6 Marblewood Amp
PostPosted: 30 Jan 2019, 19:24 
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Joined: 23 Feb 2017, 02:02
Posts: 553
Is there any load on those results, you've said a gain of 45db = 10^(45/20) = gain of 178X
Low drive of 0.25V*178=output v of 44.5V rms into 8R.

Thats a peak power of (44.5*44.5)/8= 247.5W and 123.5W RMS (P=(V*V)/R)


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