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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: 06 Nov 2013, 01:57 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Isophon wrote:
Hi,

The 807 is indeed a great amp, I have built mine a few years back based on many trial with different set up...cathode feedback, led bias on driver, RH807, UL and the best sound for me was the UL setup. Here is a recent pic for fun (just came back from a friend's and it's quite dusty)

Image

BR,
Isophon

Nice.

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PostPosted: 07 Nov 2013, 09:31 
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Joined: 23 Mar 2013, 12:18
Posts: 38
Location: New Belgrade
Isophon wrote:
Hi,

The 807 is indeed a great amp, I have built mine a few years back based on many trial with different set up...cathode feedback, led bias on driver, RH807, UL and the best sound for me was the UL setup.


It is rather strange that of all the listed variations you actually prefer the UL version... which version was it?

While the RH807 as originally published was optimized for lower B+, low anode dissipation, and console output transformers... if you had applied a higher B+ to the schematics you would have obtained more power with the same, hopefully good, sound.

The only reason why people went ahead from the original RH designs (RH84 and RH807) was output power, since most do not own highly efficient speakers: myself included, that is why I have designed more powerful amplifiers since then... That is why I wonder what was wrong with your RH807? Have all the versions of 807 amps that you built had the same output transformers, the same power supply... or was it different amps altogether?

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PostPosted: 10 Nov 2013, 19:04 
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Joined: 20 Sep 2008, 19:49
Posts: 171
Location: Montreal, Canada
Hi Alex,

Why is this strange ?

I really like the original RH84 design but not so much the RH807, this is MY taste.

I didn't go for the RH design because of the increase output power (96db speaker), I tried the RH807 because I enjoy the RH84.

All the versions of my 807 amp that I have built had the same output transformers and same power supply.

I enjoy the sound that a UL set-up provides.

Rgds,
Iso

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DIY SS Amp : LM3875 GC | TA2024 | TA2020 (AMP-6) | TA2022 | Amp Camp Amp | JLH
DIY Tube Amp : RH84 SE | 6V6 SET | 13FD7 SET (Chinook) | 807 UL SE | 6BQ5 Class A PP UL | 6LR8 SE
DIY Spkrs : Cyburgs Needle | MLTL (FE206E) | CSS EL70 BR | Open Baffle (Alpha 15A + FE206En) (in process...)
DIY Pre-Amp : MooseFET.
To come : MLTL (CSS enabled EL70) + more tube amp...


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PostPosted: 11 Nov 2013, 00:29 
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Joined: 23 Mar 2013, 12:18
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Location: New Belgrade
Isophon wrote:
Why is this strange ?

I really like the original RH84 design but not so much the RH807, this is MY taste.


TASTE is always a good explanation - for all choices that are not empirical.

It is strange, because the RH amps all sound very similar, yet with varying flavors. Thus if you like the RH84, you should like the RH807. Those who particularly like the 807 tube usually like the RH807 even more, due to a "golden sound", as they describe it.

That is what makes your statement slightly incoherent. It reminds me of the way politicians explain their choices.

Of course, you are free and welcome to prefer either, or even neither of the two.

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PostPosted: 02 Oct 2015, 20:05 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
I listen to my 807 amp every day for at least a few hours - abcclassicfm. The other day when I turned it on it hummed terribly. When I tapped the choke the hum stopped. You would think then that something is wrong in the PS. The PS proved faultless. But when I touch the left 807 (never been out of the socket since day one some years back) noise and hum ensured.

Switching the power tubes to see if there was a faulty tube the hum and noise vanished and (thankfully) has never returned. It appears there may have been a little oxidation between the tube pins and socket. Simply removing and re-inserting the tubes would have fixed this. Maybe part of a maintenance routine would be; once a year remove and replace all tubes to gain fresh connection between tube and socket.

All good now and no problem for a day or so or when tapped hard. Luciano lives - well in my amp anyhow.

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