ASL, Antique Sound Lab AV-20, wave 20? (or 25)

Anyone ever have any of these, or mod any?

I find it at least a bit interesting, I'd had 1 for so long, used it for a center channel.
Just recently swapped a bunch of stuff with a guy an acquired another pair of them.

The pair are wired PP PENTODE 6L6 from the factory with a 12ax7 driver, BUT they
also have UL taps taped off inside, would be rather easy to convert them over to UL.

The single was wired in PP PENTODE 6L6 from the factory with a 12at7 driver, BUT it
did not NOT have UL taps on it's output tranny.

Probably do 2 filter stage, more then likely drop/remove the loop feedback an change
the driver down to a 12at7 or less gain tube like an E80CC or something and UL wired.

Anyone by chance have the schematic from the AV-20 or AV-25, supposedly the same?

Any thoughts on these?

Hi, I had a set of the ASL 105 watt tube monoblocks and was very pleased with them, they have a very good quality to price ratio. The ones you are looking at are nice amps, but you may want to consider some of their other amps, they are quite reasonable used and have larger transformers.

I also have an ASL 300B amp, it is a decent amp, I find there build quality pretty good.

I generally build my own gear and am not "looking" for more off the shelf stuff, if it does
come my way it's some kinda deal, what I find lacking is some of there design choices of
how they approach certain things and mainly there power supplies lacking solid filtering.

I also would not build an amp with output transformers that have UL taps an not use it
to my advantage in the circuit, I've seen it done a few times by others as well. :scratch2:

Just curious if others have found anything on these type amps and have done any mods
to them for improvement besides just the switching of caps an resistors for same values.

OK I got the Audio an PS circuit traced out, after I measure voltages I'll post the schem.
(Just for the heck of it, never know when it may be handy/wanted)

OK here is the orig Power Supply and the orig Audio Circuit.

With this low (by usual standards) 312v supply some nice output tubes
are usuable here, like 6L6G, 350B, and 6BG6G's with adaptors I have, an
there are a few other 7AC pinout tubes that can be messed with as well.

You can see the 100 ohm resistor in the PS where you could sub in a choke.
(For now I'm leaving it until I listen to them a bit more after the audio mods)

You can also see the output trannies have UL taps but does not use them.

For the fairly simplistic power supply it's not all that bad, just over .5v of ripple
on the main B+ and after the driver RC stages .004, so it is quite useable as is.

(Not a ton of changes but significant ones I feel)
Hooked up the UL taps, removed the Loop feedback, removed the driver bypass
cap, reduced the plate load on the driver and installed a 12AT7 for the 12AX7.

By using the UL taps the output impedance has been lowered verse pentode, so
by removing the loop feedback would be raising it back somewhat similar to stock.

By not having the loop feedback not as much voltage gain needed from the driver
so a 12AT7 can be used instead, also removing it's bypass cap gives a little "local"
feedback and we can still spare a bit more gain.

Paralleling in the 120k resistor with there 270k plate load drops the load which is not
needed for the lower plate resistance 12AT7 and provides a bit more voltage/current
available to the driver section.

There's more current available with the 12AT7 to drive the 6L6's then with a 12AX7
an that sections output impedance is lower as well, which should improve linearity.

I ran various 12AT7 tubes to get the most voltage I could an still stay under the 100v
heater to cathode ratings, this was also done so other tubes, such as 6829, E180CC,
5965's among others would have decent operating points as well an could be rolled in.

I have the second amp to finish making the changes, listen to them for a while, do the
power supply mods an update an evaluate whether to make any more changes, I hope
no more feedback mods need to be done for satisfactory performance but we will see.

The single amp does "sound" better then it did before all of the changes, now to put
the pair in the main system (after finishing the second) for some extended listening.

I'll post an update when I have more info, just in case anyone has been following.

I had a pair of Wave 25's for a while. I loved them. I sold them because I broke an LCD TV and needed the cash to buy another. I wish I still had them.

They sounded real nice for very little cash.

Scott

Hey Keg, your modded topography might make a good start for the Impedence Bridge amp!!! ???

Sure Dennis, when you figure out what tubes your running and what voltage we'll have
we can tweak the circuit to fit the needs.

I finally got the amps in my system, tried a few different drivers, settled on the E180CC
and I gotta say these things really do sound pretty good!

I'll play them a bit more the next few days, but at this point I think there done!

That is a clean circuit Keg. The base for this amp is going to take me a couple of weeks to build, but once I am done with it, I'll be ready to go. As we talked, I want to focus on a clean CLCLC power supply with big cans to ensure I have the stored energy as this amp will be driving my woofs only.