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Inspire by Dennis Had Enjoying Vacuum Tube Audio

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  #41  
Old 05-09-2022, 11:27 PM
Isaacc7 Isaacc7 is online now
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Quote:
Originally Posted by Huduguru View Post
@Isaacc7 : I am beginning to roll tubes in a June 2021-production Firebottle amp w/volume control, and am curious about your experience with 807/5933 power tubes and associated rectifiers. How does the 807 compare to say a kt88? I like the availability of the 807 and the quirkiness of it (adapter and top cap), but am curious about sound. I love more solid low end of the bigger tubes, but want to check out the 807 and any compatible retifier/input tube combo with it.
Sorry about the late reply... The 807 is a great tube! I enjoy a Russian pair I have. They are labeled Firenti but are Russian. I also have a set of 5933 that I have not tried yet but will one of these days.

The 807 is basically a 6l6 with a top cap. Using an adapter essentially gives you access to all the different brands 6l6/6l6gb tubes but cheaper. Another tube you might want to think about is the 6bg6. It too started out as a 6l6 with a top cap though with a different base. What's cool about the 6bg6 is that over time manufacturers ended up putting their newer versions of 6l6 in the 6bg6. GE ended up with 6l6gc guts in their last 6bg6ga. The Philips 6bg6ga actually had the same guts as a Sylvania 7027a! I've bought them for $15 NOS, not going to find 7027a at those prices...

So my suggestion is if you want to play with adapters, get a 6bg6. You'll be able to get the same tubes as the 807 plus some better ones too.
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  #42  
Old 05-09-2022, 11:35 PM
Isaacc7 Isaacc7 is online now
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Let me tell you about my new favorite combo... The GE 6bg6ga with a Raytheon 6f8g is magic! It is a big, open sound but the mids to lows are out of this world. Rock solid bass. The openness gives a great sense of space. There is also a kind of slight, I dunno, coppery? sound to it. A warmish, slightly metallic sound that makes string instruments really come alive. It's a lively, dynamic sound that is super big and detailed. I will say that I almost gave up on this tube. I must have gone through 5 input tubes looking for something that sounded good. Most sounded dry. The Tungsol 6c8g gave a super big and airy sound. So much so it was almost dizzying. The Raytheon clicked immediately, it is a magic combo in my system.

I think both of these tubes have octal equivalents. The Raytheon 6f8g is probably the same as the Raytheon ladder plate 6sn7. The GE 6bg6ga I have looks like it's the same as the GE 6l6gb. There is another GE 6bg6ga that looks like it has the guts of the GE 6l6gc. but I haven't tried those yet. I haven't checked but it wouldn't surprise me if the octal equivalents cost more. I'm a cheapskate so I don't mind using adapters.

Edit: The Raytheon 6f8g tube I love apparently has the T plates. I think there is an equivalent 6sn7. I also have some Raytheon 6f8g with really flat plates. I've been told that they are relabeled RCA tubes.

Last edited by Isaacc7; 05-28-2022 at 11:47 PM. Reason: More inför on plate type
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  #43  
Old 05-09-2022, 11:53 PM
Isaacc7 Isaacc7 is online now
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The cv1102 is a wonderful tube by MOV. Later on it was released as the BL63 with the Marconi label. It is a rich, darker sounding tube. It has the same pin out as a 6f8g, lower amplification and higher heater current. I've been told that the sound resembles the Mullard ecc32. I'm never going to own one of those so I'll take their word for it. It has the sound signature that matches the descriptions I've heard of the ecc32 so I believe it.

Every time I use this tube. I'm blown away by the richness of the sound. It's a very chocolate cake kind of presentation. It lacks the air of some of the other tubes but makes up for it with its vivid timbres.

Lots of amps would choke on this tube because oif the heater requirements but the firebottle kt88 has no problems. The only thing to watch out for is the low gain. My regular preamp has developed a fault so I'm using a passive one right now. When I use this tube with a regular output tube like a 6l6 I just don't have enough gain. My preamp was right at 0db attenuation, full line signal and it wasn't quite enough. It sounds amazing when I pair it with a high gain tube like the el38.

If you're looking for the prototypical British sound but don't want to pay for an ecc32 or British 6sn7 the vt1102 or bl63 is highly recommended. They aren't the easiest things to find but with some patience you can find them at reasonable-ish prices.
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  #44  
Old 05-13-2022, 09:52 PM
Isaacc7 Isaacc7 is online now
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Finally got around to trying the Sylvania 5933. I can characterize these as soft and warm. I've tried 5 different input tubes and while all of them sounded different in terms of bass, soundstage, highs, etc. But in all cases there is a lack of detail and a pleasant warmth. I could also not get any better than fat bass. After the tight bass of the 6bg6 it's tough to live with flabby bass.

These particular 5933 tubes are from Vintage Tube Services so I know they are in great shape. They did come in the old green Sylvania boxes though. I do have some gold brand 5933 which are newer but I'm not sure when I'll get around to trying them.
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  #45  
Old 05-19-2022, 08:21 PM
Isaacc7 Isaacc7 is online now
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I have given up on the 6aq5. No matter which ones I try and the input tube used there is a distortion in the upper midrange that I can't get rid of. I was using them with a 5y3 rectifier but I think I was still feeding them too much voltage on the plates and the screen. Oh well. I have an amp coming later in the year that will be able to use them.

I saw an older post that mentioned using 6k6 tubes with a 5w4 rectifier. My friend gave me a pair of GE 6k6gt tubes. I popped them in with a Tungsol 5w4gt rectifier and a tall 7n7 in the input. Sounds quite nice. The initial impression might just be from getting rid oif that distortion lol. I'll listen for a while and try some other input tubes too.
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  #46  
Old 05-23-2022, 08:52 PM
Isaacc7 Isaacc7 is online now
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I have been very, very impressed by these 6k6 tubes. I'm now using the Raytheon 6f8g as the input tube. The combo has a great clarity and is solid up and down the frequency range. Like the 7c5/6v6 tubes I've used there is a "rightness" to the sound that I find compelling. 6k6 tubes are so cheap I will definitely try some other brands at some point and see how they compare.
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  #47  
Old 05-23-2022, 08:55 PM
Isaacc7 Isaacc7 is online now
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I truly have a problem lol. Just placed a big order with Billington for a bunch of tubes. In addition to RCA and Sylvania 6k6gt I have Mullard and Brimar 807, GEC Kt61, and Mullard ecc31 tubes on the way. These won't come till the middle of June though. I really am done buying tubes for at least the rest of this year. Dennis has made it just too much fun to roll different tubes!
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  #48  
Old 05-27-2022, 10:37 PM
Isaacc7 Isaacc7 is online now
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I'm still listening to the 6k6g tubes but have moved to a short 7n7 with angled plates. Should be the equivalent of any run of the mill Sylvania 6sn7a/b. Sounds great. This is among my favorite tube combos in this amp and it's certainly the cheapest of those favorites! I've got 6k6g tubes from RCA, Sylvania, and Tungsol coming next month.
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  #49  
Old 05-29-2022, 12:01 AM
Isaacc7 Isaacc7 is online now
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Default I have actually gone insane

I have posted in the main thread about my desire to use 12v tubes for the input of my amp. Turns out the guy that I usually get my adapters from has just the thing for me. He can make adapters that use an external power supply just for the heaters. The power supply has connections for up to 6 tubes and can supply up to 10 amps. I opted for the ability to change the output voltage. Initially I plan on using this just so I can use my collection of 12sn7/2c50/12sx7/14af7 etc. in my Firebottle. I could potentially also try some 12v output tubes like the GU50.

In the future I might explore the world of 4v output tubes. I don't think I can get the plate voltage low enough on the Firebottle but I will be able to in another amp I will be getting in the fall.

This may be why finally causes friends and family to stage an intervention and/or have me committed lol.
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  #50  
Old 05-30-2022, 01:43 PM
Isaacc7 Isaacc7 is online now
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Default Audio memory is weird and tube burn in is BS

Decided to switch back to the GE 6bg6ga that I liked so much. Put them and the Raytheon 6f8g in and… something’s not right. When I had first tried those GE tubes I had to try 3-4 input tubes to combat a “dryness” to the sound. The Raytheon was an obvious improvement and I listened happily to that combo for a while.

When I switched from the 6k6gt back to the GE 6gb6/Raytheon 6f8g combo I noticed that dryness immediately. WTH? My best guess as to what is going on is that in the time it took for me to find an input tube that minimized that problem my brain had just gotten used to the sound. The Raytheon was the best fit and I latched on to it.

Going back fresh, I heard the problem immediately. I have always been a bit skeptical of the concept of tube burn in and this experience cements it in my mind. I think our brains adapt to what we hear much more than any changes actually happening to the tubes themselves. Those particular 6gb6 tubes are going into my get rid of pile.
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