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Old 19th July 2011, 05:08 AM   #1021
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Join Date: Oct 2004
Location: Adelaide South Oz
Latest Baby picture.
6SL7 and 6V6G

The Chassis and Tranny Cover are from Mabel. This is the full version with CCS loaded MOSFET Source Followers, Fixed bias outputs. Construction into this tiny chassis was a serious pain but I got there in the end. For 6V6 I've chnged the 47K:15K:47K shunt feedback to 39K:18K:39K, the lower (than EL84) gm output tubes need a little more local shunt feedback.

Cheers,
Ian
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Old 19th July 2011, 05:29 AM   #1022
airboss is offline airboss  United States
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What Iron did you choose Ian?

Dan
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Old 19th July 2011, 08:26 AM   #1023
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Dan,
This has "Bog Standard" Hammond 1608 Output Trannies.
I had friends around for drinks last Friday evening just after I'd done the final tweak of the feedback level and the response was not "how soon can you build another one for us" BUT rather "how soon can you build another one for yourself, We want this one".

No kidding - its sounds seriously gorgeous. I'd been listening to some JADIS JA80 80W Class A mono-blocks I'd just finished re-tubing for a local audio nutter, it was a massive relief to get rid of them and fire this up instead.

Some of that gorgeousness comes from the 6V6Gs (Sydney Australia factory AWV circa 1960) but I've also run it with 1980's Russian military 6V6 (the big box they came in still had the KGB stickers on the side) and it was almost as lovely with those.

Cheers,
Ian

Last edited by gingertube; 19th July 2011 at 08:31 AM.
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Old 19th July 2011, 08:46 AM   #1024
Ian444 is offline Ian444  Australia
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I've been running some Russian 6V6 in a small PP amp and keep going back to it, they seem to have a softness, good bottom end and easy listening feel compared to EL84, but thats just my opinion...do you think you will stay with 6V6 for future BH's Ian?
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Old 20th July 2011, 12:52 AM   #1025
Ejam is offline Ejam  Australia
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Default Baby Heuy 6SL7/6V6 Version

Gingertube

Referring back to Page 1 of this thread you stated:

"As a practical exersize I have built a 6SL7 plus fixed biased 6V6G experimental version but low 6V6G Rg1 requirement (imposed by the fixed bias), lower 6V6 gm, higher currents for the 6SL7 etc. have meant that it just isn't in the same league - I keep running into limiting conditions everywhere as parametrers are pushed outside of acceptable limits"

How then (apart from different feedback resistor values) did your new 6SL7/6V6 version overcoming the design limitations?
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Old 20th July 2011, 12:58 AM   #1026
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I still run both 6V6 and EL84 Baby Hueys. The higher gm EL84 is theoretically the better choice but in practice all of the 6V6 BHs have been lovely and there is not a lot to pick between them. The EL84 is probably still better across all music selections, 6V6 are rock and blues tubes. I use these same 6V6G in Guitar Amps I build.

Ejam,
All of the 6SL7 / 6V6 BHs are the latter circuit incorporating MOSFET Source Followers. 6V6 grids are direct coupled to the Source Follower Outputs and Fixed bias is applied to the MOSFET gates. That addresses those problems noted back on page 1. The schematic is pretty much like that of post 602 on page 61, feedback mod as stated above, Mosfet Source Follower currents increased to 3mA. Note the "corrected" schematic at post 604 (f/b from UL taps instead) was abandonned after further listening.

I'm not sure what the next amp will be at this point - you see I have these piles of bits:

Pile 1: Power and Output Trannies, Chokes, Chassis Tubes etc. for 845 SE Stereo
Pile 2: Plitron Power and Output Trannies, Chokes, Chassis and 2 quads of EH300B for PPP Monoblocks
Pile 3: Plitron Power and Output Trannies and 2 quads of Gold Lion KT88 for PPP Ultralinear + Cathode Feedback Mono Blocks.
Pile 4: 2 EL84 BH Monoblocks part dissassembled to have their diff amps rebuilt with 6BR7 pentodes.

Decissions, decissions !!!

Cheers,
Ian

Last edited by gingertube; 20th July 2011 at 01:19 AM.
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Old 20th July 2011, 04:54 AM   #1027
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Actually I do know what the next project is - my preamp needs an update before any new power amp is started.

This will be a Vaccum State SP2, no doubt "compromised" by using a remote control channel selection and motorised Alps Volume Pot. Super Reg will be used.

Cheers,
Ian
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Old 20th July 2011, 01:57 PM   #1028
Ian444 is offline Ian444  Australia
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As long as you are having fun that's all that matters Thanks, Ian.

Edit: oh yeah, I'm into rock and blues, maybe that explains the 6V6 thing.

Last edited by Ian444; 20th July 2011 at 02:00 PM.
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Old 20th July 2011, 10:35 PM   #1029
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Quote:
Pile 4: 2 EL84 BH Monoblocks part dissassembled to have their diff amps rebuilt with 6BR7 pentodes.
This is something I hope you get around to one day as I would love to have a go at building it. In the meantime my chip phono preamp also needs updating so I suppose that'll keep me busy until then......


Brgds Bill
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Old 21st July 2011, 01:27 AM   #1030
rhone is offline rhone  Australia
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I second the vote for "Pile 4" !
I've collected all the parts for my Baby Huey build. Got the iron (James), made up the CCS and SF modules, got the EL84s. Then Ian mentions that using pentodes in the diff amp may be worth persuing! I'm stalled, not wanting to pull the trigger just yet
Come on, Ian, I need some closure
Luckily I have been distracted by a pre-amp project - Vacuum State FVP5A
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