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6883B as a audio output tube

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Posted on April 9, 2015 at 13:34:11
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Always looking to do something a little different with DIY tube audio, had a pair of monoblocks made with a pair of 6BL7's driving a pair of 6883B tubes.

I've wanted to use a 6146/6883 tube in a power amp for some time. Any tube can provide 100 watts a pair in AB1 has my attention. After reading up on the tube and its history, decided to go with the 12 Volt 6883B version. NOS tubes can still be had for very reasonable cost. As long as one pay attention to the screen limitations, they are a rather stout and linear tube, so to me, it was worth a try.

I'll post observations and pics once they break in some. Initial impression is that this tube has excellent sonic characteristics, and has far exceeded my expectations. Seems to be a very linear and quiet tube with lots of dynamics, bass punch, and very clean sounding. The amp has separate power supply taps for each section (front end, screens, power, bias) and heavy choke filtering.

The 6146B/6883B seems like a excellent alternative to Chinese/Russian 6550's.

Anyone else tty this tube out for a test spin?
" Don't look back. Something may be gaining on you"

Satchel Paige

 

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RE: 6883B as a audio output tube, posted on April 9, 2015 at 15:43:23
Triode_Kingdom
Audiophile

Posts: 10045
Location: Central Texas
Joined: September 24, 2006
 6146 push-pull amps have been around for decades. I've never heard one, but owners seem to like them. The issue for me is the exposed anode cap...

 

Why?, posted on April 9, 2015 at 15:53:20
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Nothing wrong with plate caps. In fact, they have at least one advantage over most other tubes. The plate cap allows for higher plate voltage without the issue of arcing across tube pins.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: Why?, posted on April 9, 2015 at 16:02:27
unclestu
Dealer

Posts: 5851
Joined: April 13, 2010
 for manufacturers the issue is potential liability. 807's are dirt cheap bu rarely used even though they sound good.

 

Agree on 807, posted on April 9, 2015 at 16:06:53
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 In fact, my other power amps (monoblocks) sports a quad of 1625's per side (12V 807). I love the sound from them. They have a mid-range that makes music sound alive, especially with certain recordings. Long lasting and reliable as well.

Besides, this is DIY, so no worries about liability. :-)
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: Why?, posted on April 9, 2015 at 18:56:01
Triode_Kingdom
Audiophile

Posts: 10045
Location: Central Texas
Joined: September 24, 2006
 I don't want 500V exposed in my livingroom. As for the advantage of the cap, my 211 SETs use 1,000V on the anodes with no cap. There's not a chance of arcing across those large ceramic bases. Really, the only the only way I'll use medium power tubes with anode caps is if they're configured as followers, with the anodes grounded.

 

RE: Why?, posted on April 9, 2015 at 20:25:31
GSH
 The tube has no voltage on the plate. It's obviously all under the cap which even turned upside down, still would require intentional poking to be contacted, assuming one uses a decent cap and not a raw wire or uninsulated clip. The fear of plate caps in 500V or less devices is common, the reasons defy common logic.

 

RE: 6883B as a audio output tube, posted on April 9, 2015 at 21:47:35
Paul Joppa
Industry Professional

Posts: 7295
Location: Seattle, WA
Joined: April 23, 2001
 6550 rated 35-40 watts plate dissipation.
6146 rated 20 watts plate dissipation.

 

6883B plate dissipation IS 35 watts, not 20, posted on April 10, 2015 at 02:54:53
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 The tube was re-designed for higher power in the B version.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: Why?, posted on April 10, 2015 at 05:50:43
Triode_Kingdom
Audiophile

Posts: 10045
Location: Central Texas
Joined: September 24, 2006
 I don't know why anyone would argue this point. Using a device with 400-500V outside the chassis is incredibly stupid in a family setting. Even my old ham gear - most of which used HV tubes with plate caps - was never constructed in a way that would allow access to the anodes. To do otherwise would violate simple common sense.

 

RE: Why?, posted on April 10, 2015 at 07:56:22
GSH
 Incredibly stupid without a cage or cover in a "family setting" where some moronic family member chooses a low and accessible location to install the amplifiers, and also offers no instruction to "other family members" to leave it alone.

Yes OK.

If you can't achieve that, then you can't.

But in no remote form whatsoever is the use of plate caps, even in a
"family setting" (properly done) "violating common sense".
If you can't imagine other "settings" beyond your own, then you can't.
So this is why you'll just have to imagine that someone would argue this point. You do Not represent the last word on this subject, period.

 

RE: Why?, posted on April 10, 2015 at 13:27:58
Triode_Kingdom
Audiophile

Posts: 10045
Location: Central Texas
Joined: September 24, 2006
 "You do Not represent the last word on this subject, period."

You're wrong. It's not safe. Period.

 

RE: Why?, posted on April 10, 2015 at 13:38:14
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 OK, so you don't like tubes with plate caps. No big deal. I think you are overstating the issue. I would want not a family member or pet going near ANY hot exposed power tube (especially a 211 or 6C33!)

The original point (which is getting lost here) is that tubes with plate caps like 807/1625/6146B/6883B can and do make great audio tubes in DIY applications (which IS what this forum is all about). Having endured sub-optimum Chinese and Russian 6550's over the last ten years or so, I'm quite happy to not need to use them any longer. I'm quite happy to use genuine NOS tubes with much better overall quality control and longevity (not to mention excellent sonic performance!) The reasonable costs of these tubes is the icing on the cake.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 10, 2015 at 13:48:39
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 the CCS rating is 27 Watts...and it is not a large plate; I'd think more like 25 watts is more like it.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: Why?, posted on April 10, 2015 at 14:21:46
GSH
 It's not safe for fools, who ignore logical precautions, which it's clear you've included yourself amongst.

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 10, 2015 at 14:22:14
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 For audio, ICAS seems a reasonable rating for the 6883B. I'm pretty happy with the audio presentation from them. Getting 90 watts from a pair is pretty good performance in my estimation.

Pretty happy with the build quality, and very happy with the price. Just need to run them in pentode to not worry about the screens.

All in all, it's a good tube, IMHO.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

+1 (nt), posted on April 10, 2015 at 14:30:00
GSH
 .

 

RE: 6883B as a audio output tube, posted on April 10, 2015 at 15:04:06
unclestu
Dealer

Posts: 5851
Joined: April 13, 2010
 6146 was RCA's failure to understand the market. They thought it could compare and hold i-ts own against the KT-88/6550 but it was too expensive for the mass marketers, Same with the 7027.

IIRC, the Greatfull Dead, towards the end, used amps running the big Dyna Transformers (a-440/441, the stuff for the Mk VI's) and using the 6146 Good luck

 

RE: 6883B as a audio output tube, posted on April 10, 2015 at 15:39:23
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Interesting. Thanks for the feedback.

These days, the price of 6883B's are very reasonable, and seem to be readily available. So far, they seem to provide a excellent sonic presentation. Using a pair of 6BL7's as the driver/phase splitter, the 6883B's really sound great. Outstanding clarity, low level detail, excellent bass, and very linear.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

" which it's clear you've included yourself amongst. ", posted on April 10, 2015 at 15:41:02
Triode_Kingdom
Audiophile

Posts: 10045
Location: Central Texas
Joined: September 24, 2006
 Seriously, how old are you?

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 10, 2015 at 15:54:52
Steve O
Audiophile

Posts: 12364
Location: SE MI
Joined: September 6, 2001
 Per RCA, "...ICAS covers applications in which high tube output is a more important consideration than long tube life. The term "Intermittent Commercial" in this title applies to types of service in which the operating or "on" periods do not exceed 5 minutes each, and are followed by "off" or standby periods of the same or greater duration." When tubes were in their prime, consumer equipment rarely if ever used the ICAS system except maybe for CB linears.

While one of the benefits of one-off, non commercial design is that you can choose your own set of tradeoffs and compromises, operation under ICAS conditions puts a very high premium on output at the expense of short tube life. Compounding the ICAS tradeoff is the fact that the 35W rating you reference is under the "Absolute Maximum" system and not the more conservative "Design Center" system. For audio, the 27W design center rating would seem more applicable.

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 10, 2015 at 16:02:46
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Well, I'll have to see how long they last in the application I'm using them in. My primary goal was to get between 80 to 90 watts per channel, which the amps achieve. If I get 2-3 years out of a quad under moderate use, I'll be happy with that. I have lots of them on hand.

The amp has 600V on the plates, and the bias is set at 50ma.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: " which it's clear you've included yourself amongst. ", posted on April 10, 2015 at 19:31:05
GSH
 Surprised you took the bait, but you did. Feel better now?
Or are you struggling with English grammar, again?

 

Check out this link..., posted on April 10, 2015 at 19:41:05
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 There is a link on the Mastero amp, which sports a pair of 6146 tubes that makes 90 watts a side (circa 1952).

The Acrosound To-350 schematic uses a pair of 6146's for 100 watts a channel.

This tube can provide some clean high wattage.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 10, 2015 at 20:56:49
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 You can expect very short lifetime at those operating parameters. The plates will turn red, the heat will have nowehere to go, and the internals will go belly up. If you're unlucky, this can take out your output transformer in the process.

There is a CCS operating point for 82 Watts. That's about 1dB less than 100 Watts.

For reference, there's a Class A1(!) operating point for a pair of 6550's or KT-88's that makes 100W. It takes similar plate and screen voltages to the beefy 6883B operating points, but at higher current.

In the end, I say go for it! But don't build something that may melt down when you're not looking (at least don't do that intentionally).

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 10, 2015 at 21:04:44
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Good feedback.

If I run the tubes at 600V (560 loaded) and 50 ma, are you saying that will be a short tube life? That's what they are running at now, and it sounds great!
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: Check out this link..., posted on April 10, 2015 at 21:11:44
Steve O
Audiophile

Posts: 12364
Location: SE MI
Joined: September 6, 2001
 I'm quite familiar with the "Maestro": it was part of the Sarser & Sprinkle trilogy of amps beginning with the "Musician's Amplifier", the U.S. version of the original Williamson and ending with the Maestro. They were featured in the "Audio Anthology" series published by Audio Engineering (Audio mag).

You'll note that the operating point chosen for the Maestro's finals is firmly within the ICAS region of operating conditions @ 750V on the anodes and ~ 22W dissipation (25W is max under the "absolute" rating system). Also note that the reader was not informed of this detail nor was there any discussion of the potential consequences this operating point might have on finals life. Thei primary objectives were to achieve higher power than the "Musician's Amplifier Senior" more efficiently and in a more compact package.

It's also interesting to look at RCA's use of the 6146 in audio apps. One relatively common product was the MI-12182 power amp. This one ran the 6146 finals at ~ 570V and 28 mA (16W) and 210 reg V on g2 for short term output of 70W or 35W continuous. Clearly RCA chose to stay within CCS ratings for their commercial offerings. Legend has it that even under these relatively conservative operating conditions there were reliability issues such that conversion to 6550s was a common mod not unlike what happened to the Ampeg SVT, another 6146 amp.

The bottom line here from my perspective is that tubes are extraordinarily forgiving wrt how they're used but with tradeoffs. The tube manuals had operating points for EL34, 6550 and 8417 where 100W could be obtained if one wished to push ratings to the limit. Most commercial products avoided the extremes to gain reliability. In this case the tradeoff is probably power vs life. If you have a large stock of finals, the possibly shorter life may be a good trade for the resulting power and compact packaging. You be the judge.

 

That's Pipsqueak Stuff, posted on April 10, 2015 at 21:28:50
Triode_Kingdom
Audiophile

Posts: 10045
Location: Central Texas
Joined: September 24, 2006
 A pair of 811As can output 400W plus, and Hammond can provide OPTs for this service at reasonable cost. No little 35W pentode can even come close to the sound quality of 811A triodes running at 1.5KV.

 

RE: That's class B2..., posted on April 10, 2015 at 21:56:24
Steve O
Audiophile

Posts: 12364
Location: SE MI
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 ...significant drive power necessary. Not a typical audiophile mode...for tubes at least.

 

RE: That's class B2..., posted on April 10, 2015 at 22:29:01
Triode_Kingdom
Audiophile

Posts: 10045
Location: Central Texas
Joined: September 24, 2006
 "Not a typical audiophile mode..."

It's less common because it's more difficult and costly to do right. The reward is that a pair of 811As will simply squash lesser tubes. I do rather like the idea of trying a 6146 as a grounded-anode preamp though.





 

RE: 6883B as a audio output tube, posted on April 11, 2015 at 04:27:46
sony6060
Audiophile

Posts: 1465
Location: USA
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 The 6146 group of tubes have limited screen voltage. Thus UL operation is not an option and when operating in pentode a separate power supply is needed. In my opinion a PITA.

 

Good Feedback, posted on April 11, 2015 at 06:04:26
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Thanks, Steve. Some good insight provided.

The purpose of this project was to come up with an amp that would provide between 75 to 90 watts that had excellent sonic character, used quality tubes that don't break the bank and are readily available, and good reliability. Also was looking for a slightly different variation from the 1625 amp sound.

The choice of the 6883B was made because the "B" version is the most rugged version of the 6146 family, and it's 12 volts. The 12 volt tubes are generally less to purchase, draw only half the current of the 6 volt types, and in this case, plentiful, as it was used in FM gear extensively.

The amps succeed on all counts. I got tired of shoddy performance and questionable longevity from the current production Chinese/Russian 6500/KT88 types (not to mention cost).
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 11, 2015 at 07:16:21
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
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 Yeah, lifetime will be really low. ICAS ratings for tubes are provided for purposes like public address, where there are long resting periods. I don't think I'd run them any harder than 35mA.

 

RE: 6883B plate dissipation IS 35 watts, not 20, posted on April 11, 2015 at 08:08:08
Freo-1
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Location: Florida
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 Interesting. I've been running the 1625 amps at 40ma for well over a year now under heavy use, and the tubes still measure very near NOS. I would have thought the 6883B could run at 50ma all day long.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: 6883B as a audio output tube, posted on April 11, 2015 at 14:26:19
unclestu
Dealer

Posts: 5851
Joined: April 13, 2010
 funny I seem to prefer an independent screen supply as per older Peerless transformers (Altec 340/350's, Allen organ amps and such). In converting UL trannies to regulated screens I get better detail and dynamics... Just my observation, of course the additional circuit needed is what killed those amps

 

Me too..., posted on April 11, 2015 at 17:47:00
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008



This amp has separate windings for screens, front end, bias, and power, complete with separate choke filtering. Very clean and detailed sounding.

I have had trouble in the past with screens going in ultra linear setups, especially with current production Chinese/Russian tubes. Give me NOS tubes and true pentode any day.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: 6883B as a audio output tube, posted on April 11, 2015 at 19:39:46
RS Steve
Audiophile

Posts: 3
Location: South Florida
Joined: August 8, 2014
 Great information Jim, how about sending my Scott 340B receiver back to me, or the 1200.00 I'm out because I trusted you. Until you make things right, this will be what your known for, a crooked tube guru! Explain to everyone how you can treat someone like this that has sent you work, and told others to use you, and still act like someone that deserves listening to? Sorry (honest people) to have to post here, but I guess there are many reasons he was banned from AK. Chow!

 

That was out of left field..., posted on April 12, 2015 at 11:54:15
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 First, sony6060's view is not shared by all here. I think pentode IS a better option over ultra linear in many applications. This is DIY after all.

Second, while your complaint is out of left field, I went over to AK, and sure enough, your complaint is valid. Sorry you having to experience this.

I hope you get some positive results yet with your issue.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: That was out of left field...And I will share, posted on April 12, 2015 at 17:45:40
sony6060
Audiophile

Posts: 1465
Location: USA
Joined: August 8, 2014
 The Scott repair is a charity case. No money has exchanged hands. No charge for this repair when finished.

I am very late by months on this Scott. It was rebuilt and packed to shipping standards 1A. All items I shipped have been undamaged before this Scott. The Scott was speared by USPS by a sharp object. After blaming me for poor packing I stated I would repair it for free.

After I received the Scott, I got ill with an unknown virus. 3 months of low functioning & sleeping up to 20 hours per day. My retired friend suffered the same illness. Being told it was likely brought in from foreigners, I decided NYC was a health risk with LaGuardia & JFK being a hub for foreigners. After my health improved enough, I moved an hour north of Detroit (healthy area). But, another delay.

My new home in MI had issues- yet again another delay. Finally I stared to move in. Then, I tore the muscles in my right arm. I will post a picture if necessary via my email for the curious.

Finally, my lab was to be set up by others last Saturday to install a heavy bench from Home Depot plus lab gear. I can not lift 20 lbs right now.

I do not have any other outstanding work or owe anyone services or money. I had been prompt before my illness.

I did not damage the Scott, USPS speared it and bent a steel transformer with high force. Perhaps a wood crate may not have protected the Scott.

The Scott will be fixed and mailed at my expense soon. I was also told if not I owe them money. Lesson learned- no good deed goes unpunished.

I am honest but not in good health right now. I do not accept audio work now and unlikely in the future. My past audio work has been performed with quality & no returns or complaints.


 

RE: 6883B as a audio output tube, posted on April 13, 2015 at 09:33:29
TimFox
Audiophile

Posts: 697
Location: Chicago
Joined: January 14, 2006
 RCA intended the 6146 series for RF use, with audio ratings as well.
Note:
1. Low screen grid voltage rating: good for better efficiency in RF (class C or AB)
2. Short dimensions: less parasitic inductance, etc. extends frequency to VHF.
For many years, the typical ham hf SSB exciter used two 6146s in parallel into a pi-network for ballpark 100 W PEP.
See:
http://frank.pocnet.net/sheets/049/6/6146.pdf
Specifically, p 14 of 29:
"High power sensitivity
90 W CW Input (ICAS) up to 60 Mc
60 W CW Input (ICAS) up to 175 Mc"

 

RE: 6883B as a audio output tube, posted on April 13, 2015 at 19:53:41
RS Steve
Audiophile

Posts: 3
Location: South Florida
Joined: August 8, 2014
 Charity case?

So here is where I'm at,

receiver purchase - 329.00 (purchased from auction)

shipping to Jim - 56.00

His bill for work performed, and shipping to me - 798.00

shipping it back for repair - 57.09

TOTAL - $1240.09

You can't wrap a 50 lb tube receiver in bubble wrap and one box and expect it to not get destroyed. It was your responsibility for shipping it back safe, if it would of been isured you could of filed a claim. The X101 I got from you had damage also, luckly I was able to bend the door on the front back into shape.
I'm out the above amount, and nothing to show for it but pictures of what it looked like before. Do you think I enjoy having to post something like this? It's real simple, you packed it poorly, it was damaged, you said to send it back and that you would repair it for free. Now your saying it is a favor? And that it was speared? OMG It has a dented power transformer,crushed phase switch, and somehow it's missing the large tuner knob brite. It had a hole in the box from the sharp corner punching through.

I don't care who you want to blame Jim, all I want is what you promised me, my Scott restored to the point to which I paid you, and any damage caused by shipping to be repaired. You have left me in the dark since last September, your lack of concern for someone you practically begged to send you his Scott, really is upsetting. I have every email you sent me to back up my story, and the lack of emails the last 6 months, but I'm not going to clutter up AA's threads anymore with this, I thank AA for letting me explain myself, sorry to any AA members also.

Thanks for at least responding Jim, now I know where your head is on this. Maybe someone will do this to you someday so you can grasp what it's like to be on this end. I had to do something, I have been more than patient to the point all the excuses mean nothing anymore. Fix it and it all goes away. I'm done, thanks again AA.





 

Differences with 6146B/6883B, posted on April 14, 2015 at 08:47:58
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Here is a link which covers the redesign on the 6146B/6883B over the original 6146:
" Don't look back. Something may be gaining on you"

Satchel Paige

 

Update on amp-excellent results , posted on September 4, 2015 at 12:20:16
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 I've been using this amp for several months now, with the following results:

1) Dropped the bias to 40 ma, and the results have been fine from a reliability standpoint. I had a couple of tubes go early in this project. The failed tubes all had a mid 80's date code from the same time frame. Swapped in tubes with 70's date codes, dropped the bias to 40 ma, and it's been great since.

2) Swapped out the coupling caps to Jupiter Copper foils, and that improved overall performance significantly. The mid range is much more open and life like sounding, and the treble sounds clearer as well.

3) The 6BL7 is a great driver tube. MUCH quieter than the 12SN7. In fact, it is so much better, I'm going to change out the driver tubes in my 1625 DIY amp to run 6BL7's.


All in all, this has been a worth while project. The sound from this amp is outstanding. Very happy with the results.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: Can you post a schematic of the 6bl7 front end to the outputs, posted on September 4, 2015 at 12:49:08
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
 I have a bunch of them and have not seen a scheme that I like using them. Specifically, I wanted to try them as a driver for an 813 SE project but don't have the skill to make a design. Maybe your schematic could be adopted to the 813? thank you, Dak

 

RE: 6883B as a audio output tube, posted on December 18, 2015 at 11:43:06
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Update:

Made a couple of changes to enhance performance.

1) Changed out the coupling caps to Jupiter Copper Foil units. Made a signifigant improvement with the overall sonic performance. Midrange and treble sound much more open. Outstanding clarity and 3D soundstage.

2)After good feedback and additional research, dropped the bias current to 30ma to extend tube life. The sonic character of the amp did not change as a result.


The 6883B does indeed make a excellent output tube for audio, as long as one pay attention to the tube design specs. I had read in one of the old Vacuum Tube Valley that the 6146 family was initially going to be the high end audio tube for use. However, it was deemed too expensive to use for commercial audio, so Tung Sol developed the famous 6550.

Since NOS 6550's are now vey scarce, the 6883B tube is a excellent option for DIY audio.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: 6883B as a audio output tube, posted on February 19, 2017 at 08:27:03
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Thought I would bring this back for a quick update. After using these amps for an extended period, they have turned out to be excellent performers. The 6883B has demonstrated itself to be an great audio tube. The only update was to drop bias current to 30 ma to get the required longevity out of the power tubes.

I've been very satisfied with the 6883B tube, as it has displayed excellent playback of dynamics, low level detail, and a very low noise floor. It's hard to believe that these tubes can provide 80 clean watts of power from a pair.

In summary, the 6883B is a excellent choice for an output power tube, as long as one pay attention to not overdrive the screens, and keeps the tube bias sat 30ma or lower. I do not consider plate caps to be an issue. There is a benefit to plate caps, in that it allows for higher operating voltages without concern for arcing.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

RE: 6883B as a audio output tube, posted on June 5, 2021 at 13:24:39
Freo-1
Audiophile

Posts: 1327
Location: Florida
Joined: June 14, 2008
 Wanted to post a follow-up on this. Wound up dropping the bias current to 22 mato extend tube life. Been using the amps daily for several months now with no longevity issues.
I am now using a Chord M-Scaler/Hugo-TT2 as the front end preamp driving the amps directly. The amps are connected to Tyler Acoustics Linbrook Signature floorstanding speakers. There's also a SVS PC 4000 sub for the bottom octave balance.
The sound from this setup is incredible. The 6883B/8552 output tube really sounds great driving the Tyler's.
Although it took some time to get the amps dialed in, they now sound extremely clean, clear, dynamic, quiet background, and reliable.
" Don't look back. Something may be gaining on you"

Satchel Paige

 

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