[bcowen]

Both Keenan and I have bought from the seller in India. They're the real deal and a safe source of L63 tubes. They also have quite a few of the Brimars too which are also a fine choice.

Are NOS 5998s really selling for $500 now? That's insane. I'm almost a little tempted to sell my backup pair at those prices, but somewhere down the line I'll probably wish I still had them........

I picked this one up recently for $100. IBM branded, true blue TungSol 5998. Tests quite well with nicely balanced triodes and GM over bogey. Seller had some pairs up for auction at the same time...they went for less than $250 (pair) IIRC. Timing maybe, or perhaps some potential buyers thinking an IBM labeled tube wasn't a Tung Sol.

Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago. I love the 5998, but the Chatham is my favorite 6AS7G.

 

[bcowen]

It is finally a new speaker day for me, horn style

I ended up having to make two trips to dealer, the Forte IV boxes are huge. Made one trip yesterday, but of course it has been snowing in NE Ohio for like a week straight, so after yet another blizzard, I went and picked up the second one today (couldn't fit both in my car, my girlfriend's hatchback has a tire leak, go figure).

First thing I did was rip apart one of the stock grills and take measurements. Kept the badges in case I want to put them on my modded grills.



Will sand off the residual glue, drill holes for mounting the perforated metal front plate, apply new grill cloth (black), then attach the perforated metal grill on the front. I found an architectural grill company to make the metal grills for me. They are going to machine them to my spec in aluminum, with mounting holes, then anodize them in black satin. Here are the dimensions, blank center is where the pattern will be, which I obviously could not build out in CAD. Gothic pattern I chose on the right (not to scale).



Going to be a six week lead time given the anodization. How to stop those dastardly cats from destroying the speakers for six weeks when I can't supervise? A genius invention.



Magnetic cardboard, that'll stop them.

Before listening to the speakers, I swapped out the garbage jumpers included for some nice DH Labs jumpers.



So that's it, plans are made for the DIY grills, in the meantime I'll put the cardboard grills on when not in use.

Now we can listen



But just for a bit, gotta finish off that Airmid today, just one hour of work left...

Nice!! And not too huge for the space.

 

[L0rdGwyn]

Here is the bronze Airmid. Took me a little longer than expected as I had to troubleshoot an oscillating component. Think I tracked it down, but still need to do some more testing to be certain. So I'm gonna call it 99% done. I already took the pictures though, so here they are.











Sounds pretty good to me!

 

[L0rdGwyn]

Those are really the binding post jumpers they came with? These speakers are going to sound 1000% better when you're done with them.

Yeah those jumpers are pretty crappy! Might end up changing the binding posts too. I hope so, upgrading the crossover will be a project, likely will add damping to the horns as well. That's pretty much what I have planned for them long term - modded grills, new binding posts, upgraded crossover, horn / driver damping.

 

[jgwtriode]

Yeah wow, could have at least done copper buss bars!

 

[bpiotrow13]

I picked this one up recently for $100. IBM branded, true blue TungSol 5998. Tests quite well with nicely balanced triodes and GM over bogey. Seller had some pairs up for auction at the same time...they went for less than $250 (pair) IIRC. Timing maybe, or perhaps some potential buyers thinking an IBM labeled tube wasn't a Tung Sol.

Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago. I love the 5998, but the Chatham is my favorite 6AS7G.

Nice, I got the IBM/Tung Sol 5998 pair from the same seller I believe he sold two pairs and two single 5998 at the same time.

Chatham is the same as Tung Sol I believe.

 

[bpiotrow13]

Are NOS 5998s really selling for $500 now? That's insane. I'm almost a little tempted to sell my backup pair at those prices, but somewhere down the line I'll probably wish I still had them........

I started buying 5998 and some other tubes so that I have a couple of spare pairs. In a year or two I may not be able to afford them...

Somebody really needs to start current production..

 

[whirlwind]

I picked this one up recently for $100. IBM branded, true blue TungSol 5998. Tests quite well with nicely balanced triodes and GM over bogey. Seller had some pairs up for auction at the same time...they went for less than $250 (pair) IIRC. Timing maybe, or perhaps some potential buyers thinking an IBM labeled tube wasn't a Tung Sol.

Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago. I love the 5998, but the Chatham is my favorite 6AS7G.

Oh wow....I would buy the Chatham 6AS7G for $29 all day long, LOL.

 

[Xcalibur255]

I started buying 5998 and some other tubes so that I have a couple of spare pairs. In a year or two I may not be able to afford them...

Somebody really needs to start current production..

I suspect the large and plentiful supply of Russian made 6AS7 tubes would have to be mostly dried up before any current tube factory would take an interest in this. OTL amplifiers are still quite a bit less common too so there isn't enough money to be chased.

 

[Xcalibur255]

Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago. I love the 5998, but the Chatham is my favorite 6AS7G.

Love my Chatham 6520s. I rarely use them because I have only the one pair. That classic tube conundrum of not wanting to use the ones you like the most.

The funny part is I almost gave up on them because they were NOISY the first time I ran them. 24 hours later they settled down and stayed quiet after that.

 

[jgwtriode]

JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 (78/102ma) - JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts 1956
JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 in white box 1 section) 78ma Gm=4850 1...

What do you thinks of these Are they worth $59 each?

jgwtriode

 

[L0rdGwyn]

Got the oscillation situation all worked out, bad batch of FETs, swapped to a near-equivalent part, functionally the same, bingo.

So now 100% done.

And I'm off to work!

 

[bcowen]

JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 (78/102ma) - JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts 1956
JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 in white box 1 section) 78ma Gm=4850 1...

What do you thinks of these Are they worth $59 each?

jgwtriode

Not the best triode balance, but not that bad either. $59 is a good price...most times I see these on Ebay they are going for $75+. Finding an excellent testing one for $29 like I did is pretty rare and pure luck these days.

 

[bcowen]

Nice, I got the IBM/Tung Sol 5998 pair from the same seller I believe he sold two pairs and two single 5998 at the same time.

Chatham is the same as Tung Sol I believe.

Cool! Do you have a way of testing them? Hopefully they are as good as the one I got. I debated getting a pair, but my amp only uses a single....and I'm cheap.

 

[L0rdGwyn]

I recently took some repeat measurements of the red Airmid, inputs were the Russian 6S2S (6J5GT) here are the results if anyone is interested in this type of stuff.

Russian 6AS7G
Output Z - 50ohm
1mW into 300ohm - 0.11% THD
1mW into 120ohm - 0.22% THD
1mW into 80ohm - 0.31% THD
1mW into 32ohm - 0.67% THD

Tung-Sol 5998
Output Z - 30ohm
1mW into 300ohm - 0.032% THD
1mW into 120ohm - 0.094% THD
1mW into 80ohm - 0.15% THD
1mW into 32ohm - 0.38% THD

Frequency response at the two extremes.

300ohm



32ohm



1mW into 300ohm square waves.

1kHz



10kHz



100Hz



1kHz sine wave into 300ohm dummy load just before the onset of clipping. So just about 1W out.