NAD! - Airline 62-9023A

[FleshOnGear]

This is the Airline brand version of the Supro 1624T, also built by Valco. I ordered it from GC and it’s waiting at my local store for me to pick it up. I’m pretty excited about this one, hoping that I’ll be able to get in the ballpark of LZ I with this baby.

This is a 1x12 combo, supposedly 18 watts clean output from two 6973 tubes, with two channels and tremolo. From what I’ve read, Page used a 1690T (35 watts) with its 2x10 speaker baffle replaced with a 1x12. My research indicates that the 1690T also had an additional gain stage on the trem channel compared to the 1624T. So, my amp will at least have a 1x12 speaker stock (who knows what speaker was in Page’s amp), but probably less gain.

The Airline I bought comes with a Jensen C12R, which is only rated for 15 watts, so I’m likely going to preemptively replace it with a sturdier speaker to keep from blowing the original. I need to audition this particular C12R and see what type of cone it has before I choose it’s replacement. As far as I can tell from the pics, it will need a 3-prong power cable installed. I’m thinking that its electrolytic caps will need to be evaluated, as well.

I’ll post a quick review and pics once it’s acquired!

 

[FleshOnGear]

So, I finally picked it up, and I’m very pleased! This thing is all original (including tubes) and very clean for a 60-some year old amp. I only found one little nick in the tolex. It works great, with the exception of a voice coil rub and some rustling noise on start up. Once it’s warmed up it’s super quiet. I plan to get a period correct speaker replacement and try new preamp tubes, along with installing a 3-prong cord. That should take care of the issues, which is nice because I was certain the 60 year old Mallory caps would need replacing.

Tonally, it’s warm and punchy, with a pleasing crunch. This light little cabinet has a beautiful bass and low-mid resonance. Does it sound like LZ1? Almost. It has the vibe, though I think the speaker might be different and miking technique on the recordings probably has an influence. It might also benefit from a boost, since the amp is possibly short one gain stage compared to the 1690T. The C12R in it is pretty low efficiency, so the amp’s 18 watts are not offensively loud.

In summary, this amp is less of a project than I anticipated, and it sounds super cool. I’m happy!

 

[Torren61]

That's hot. You forgot to mention the power tubes are 6973. Those are killer tubes and NOS ones are relatively still affordable. Even EH 6973s are around $35 each. I have an amp that uses them and I love it.

 

[FleshOnGear]

That's hot. You forgot to mention the power tubes are 6973. Those are killer tubes and NOS ones are relatively still affordable. Even EH 6973s are around $35 each. I have an amp that uses them and I love it.

What amp do you have that uses 6973s? I had never heard of them before I started researching Valco amps. I think I read somewhere that this tube was often used in jukeboxes. Another positive is that the Airline I got can also use the 6CZ5, which is very affordable and electrically the same (but with a very slightly different pinout).

I’m surprised at the quality of this “cheap” department store amp. The cabinet is maybe put together with a little less care, and they chose a speaker that doesn’t handle the full output of the amp, but it’s otherwise quite nice. I guess it’s a testament to the quality of old tube technology.

 

[Torren61]

I have an amp made by a small builder in Chico, CA. It's that little mofo down at the bottom, a Monkeymatic "Lassen". It's based off a Supro 1624. Just a volume and tone and that's it. He's still makes the Lassen amp but not with 6973s.

 

[FleshOnGear]

Here’s a quick and dirty cell phone recording of the amp. Stumbling through a few early Zep riffs.

 

[solarburn]

Here’s a quick and dirty cell phone recording of the amp. Stumbling through a few early Zep riffs.

Sounds great!

 

[Vinsanitizer]

I think that thing sounds awesome, even via a cell phone clip. I've had a lot of small maps, even a few vintage ones. More often than nart, they run on 6V6's and sound dark and dull. But THAT there map's got character.

BTW, would u happen to be using 9's and a heavy pick? (Just checking my perception.)

 

[FleshOnGear]

I think that thing sounds awesome, even via a cell phone clip. I've had a lot of small maps, even a few vintage ones. More often than nart, they run on 6V6's and sound dark and dull. But THAT there map's got character.

BTW, would u happen to be using 9's and a heavy pick? (Just checking my perception.)

Thanks! I think it sounds great, and it’s a ton of fun to play. I use 13’s, but I’m tuned down to C. I do use a heavy pick.

Supposedly the 6973 tube sounds like big bottle American tubes. I don’t have any 6V6 or 6L6 amps to compare, so I can’t verify that. The character you’re hearing might be the Jensen C12R speaker. This speaker has a lot of ribs, lightweight paper, and a 1” voice coil, so it may be on the brighter side despite the 10oz magnet.

Sounds great!

Thanks, solarburn!

 

[BlueX]

Here’s a quick and dirty cell phone recording of the amp. Stumbling through a few early Zep riffs.

I really like this sound! Has the right vibes, sounds raw and tight at the same time.

 

[Torren61]

Thanks! I think it sounds great, and it’s a ton of fun to play. I use 13’s, but I’m tuned down to C. I do use a heavy pick.

Supposedly the 6973 tube sounds like big bottle American tubes. I don’t have any 6V6 or 6L6 amps to compare, so I can’t verify that. The character you’re hearing might be the Jensen C12R speaker. This speaker has a lot of ribs, lightweight paper, and a 1” voice coil, so it may be on the brighter side despite the 10oz magnet.

Thanks, solarburn!

The speaker is ribbed for your pleasure. I LOVE 6V6 tubes. They're my favorite. I can't say my hearing is good enough to be able to tell you the difference between a 6973 and a 6V6.

 

[ibmorjamn]

Here’s a quick and dirty cell phone recording of the amp. Stumbling through a few early Zep riffs.

Sounds good , congrats, you have a nice sounding amp.

 

[FleshOnGear]

Somehow the voice coil rub went away. I have no idea how that’s even possible, but it’s gone. Also, there’s no more crackling on startup. The only problem left is an intermittent fuzzy ringing oscillation. I narrowed that down to the power tubes, which sucks because old stock 6973 tubes are expensive. I just ordered a matched pair of old stock 6CZ5s to try out, and they were cheaper than a pair of current production EH 6973s.

I did some research on early 60’s American style speakers. I couldn’t find anything that had a cone similar to the one on my C12R that could handle more power, so I took a chance on a cheap used Jensen C12R reissue. They handle 25 watts, so it will be safer, but the cone is different. We’ll see how it sounds. If I don’t like it, I can turn it around and not lose too much money. At that point I could maybe find an old C12Q (which might also sound too different). I feel like I have a duty to keep the original speaker preserved.

 

[FleshOnGear]

I put in the Jensen reissue C12R today. It doesn’t sound drastically different to me. Maybe a little less upper mids and a bit more extension in the treble, but it’s a good sounding speaker. To me, it sounds good enough not to bother with any of the more boutique replacements available, like Weber or Jupiter. It’s staying and the original is being safely stored.

All I really need to do now is pop in some fresh output tubes and wire in a 3-prong cord.

 

[FleshOnGear]

Ok, the 3-prong cable is in and the death cap is gone. I have also replaced the power tube cathode resistor with a 330 ohm so the amp will run cooler, and rewired the screen supplies from pin 8 to pin 1 so the amp will run 6CZ5s and 6973s. A pair of new EH tubes will arrive on Monday, and the vintage 6CZ5s will ship that day.

 

[FleshOnGear]

Quickly, I’ll also mention that this little amp sings pushed with my treble booster.

 

[FleshOnGear]

I discovered that you get the most gain out of this amp when you plug into Ch. 1 High and jumper from Ch. 1 Low to Ch. 2 Low. I’m getting a bit of hum from plugging into Ch. 2 Low, so I’m thinking I need to check the grounding on that input.

I tried the new production Electro-Harmonix 6973, and they’re not bad, maybe a little less dimensional than the RCAs that were in it. It’s not a night and day difference to my ears.

 

[FleshOnGear]

I received the vintage 6CZ5s today. I really can hear the difference between these and the Electro Harmonix tubes. They clip more sweetly. It’s a slightly rounder sound that lets more of the fundamental through at clipping. The EHs aren’t bad, but they’re not this good, and I got the 6CZ5s for less.

 

[FleshOnGear]

Here’s a schematic for the amp. I put a 4.7uF bypass cap on the cathode of the first half of the phase inverter (paralleling R31 and C18). This turned the amp into a rock monster! So crunchy, and the mod is easily reversed. The only downside of the mod is a slight reduction of treble response in the phase inverter due to Miller capacitance, which could easily be compensated by putting a small cap across R30.

I’m never letting this baby go! It sounds too good.