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In Reply to: RE: I get confused posted by sony6060 on November 05, 2014 at 13:30:38
- And, the best PP amp I built was triode connected PPP 6V6GT that was slightly better than the PP 45. G glass 6V6 were the best
That one took me by surprise! The cost difference is shocking! Do you have a schematic?
Dave
Follow Ups:
The PPP amp is thr Eric Kingsbury Music Machine with changing the phase splitter to a Raytheon 6CG7 black plate. I also added two more 6V6 per channel for 10 watts output per channel. The audio transformers were Dynaco DT-70 replacements (Triode Electronics) using the 4 ohm tap on 8 ohm speakers. This is critical using 4 ohm tap on 8 ohm speakers as the reflected plate to plate impedance is double or about 9K ohms. I used K40Y-9 coupling capacitors.
If Sylvania 6V6G glass are not affordable, use Sylvania 7C5 with the oval plate. The oval plate sounds identical to 6V6G. These are usually marked with a JAN military number. The later 7C5 with a plate having a square extension on each end are bad news. The Raytheon 6CG7 USA are critical. You can also use a Sylvania 6SN7 with the Y plate vs the rare Raytheon 6CG7.
The 45 amp & this 6V6 sounded almost identical, but the 6V6 in triode has better dynamics. A faster sounding amp.
10 watts of near 45 sound, seems like a good thing to me! Eli like the 6V6 too. You are getting the gears turning!
Dave
Wow, isn't 9k about twice as high as PPP 6v6's would normally call for? Interesting.
Dave
Yes, a quad of 6V6 should perform well at 5K+ and did not sound good at 4.3K PP as spec'ed in the ST-70 audio transformers. I recommend 6K minimum, but compromised with the Dynaco transformers I had in the parts bin'. 6V6 triode does not like same impedance as tetrode connected. And, IMO are not so great sounding UL either.
I advised Eric Kingsbury the pair he designed in the Music Machine with 6V6 in triode should be 10K P to P. Eric followed up a year later with recommending 10K audio transformers.
But pp that should be 18k to be the equivalent impedance to your ppp amps, no?
I have a pair of pp 6v6 amps with 10k opt's, I've been meaning to try the MM circuit so sounds like I should do it.
Dave
In simple terms paralleling tubes drops the impedance in half of a single tube.
Not only does it affect you output transformer choice, but it also allows you to get a away with a very simple driver stage.
dave
Right, sorry I'm confused. One tube SE - 5k. Two tubes PP - 10k. Four tubes PPP - 5k. PPP with 9k is the equivalent of PP at 18k, no? Did I misunderstand?
Dave
Correct. 9K PP is rather high. 6K-7K for PPP 6V6 triode would be best with a good balance of power & dampening factor.
~!
The Mind has No Firewall~ U.S. Army War College.
Cool, makes sense, thanks.
Dave
Interesting! That gets me pointed in the right direction. Thanks!
Dave
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