Pop quiz. ASL 1006 SET mono 845 amp, what's missing?

RE: Pop quiz. ASL 1006 SET mono 845 amp, what's missing?, posted on August 16, 2020 at 16:40:25
Story Audiophile Posts: 10423 Location: NJ Joined: December 11, 2000	let's see....tubes, bottom cover, HV keep your hands off danger sign. chassis ground? is that the input jack in the corner by the output? what's that piece of foam doing in there? it's getting late and I'm tired but do let us know

RE: Pop quiz. ASL 1006 SET mono 845 amp, what's missing?, posted on August 16, 2020 at 17:13:45
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	The schematic shows 5 bridge rectifiers. They must be in the power transformer can. The leads coming out of the power transformer go straight to the caps. I have never seen that before. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: Pop quiz. ASL 1006 SET mono 845 amp, what's missing?, posted on August 17, 2020 at 03:32:11
Story Audiophile Posts: 10423 Location: NJ Joined: December 11, 2000	Those wires look like they come right out of the trannies but that makes no sense. If ASL is Antique Sound Labs, their builds don't make a lot of sense anyway. What is the B+ measured? 5 rectifiers? Is this a factory build? Are you going to disassemble? The wires are all twisted like they carry AC.

RE: Pop quiz. ASL 1006 SET mono 845 amp, what's missing?, posted on August 17, 2020 at 06:55:52
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	I agree, this design doesn't make a lot of sense. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

After a little repair....., posted on August 17, 2020 at 08:25:39

Tre'
Industry Professional

Posts: 17293
Location: So. Cal.
Joined: February 9, 2002

of the damage caused by shipping, they work!

The one on the left us quite bent up but it works.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

BTW, posted on August 17, 2020 at 11:33:21
Story Audiophile Posts: 10423 Location: NJ Joined: December 11, 2000	I took an old scope out to see if it was still working - so I ran an 800hz sine wave into my Transcendence pre with 12au7's to check the waveform, full volume with 1 volt going in. This is a pic and it looks ok to me. Is there anything else to check for non-linearities?

RE: BTW, posted on August 17, 2020 at 13:11:53

Tre'
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Posts: 17293
Location: So. Cal.
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Do you have a schematic?

Tube Cad does an overview of that preamp.

It's not really a grounded grid preamp and there is a lot of local current feedback in the first and third stages and voltage feedback in the second stage, so that's the answer.

If you were to build a gain stage with a 12au7 (GG or not) without any form of feedback then you would see the non-linearity of the tube.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

RE: BTW, posted on August 17, 2020 at 13:49:10
Story Audiophile Posts: 10423 Location: NJ Joined: December 11, 2000	I took out all the v feedback a couple years ago. So it still has the rest along with some other improvements. Despite the shortcomings it still sounds very nice, perhaps not as dynamic as it could be (too many stages). Euphonic? Yes, compared to others I have. But somehow it hooks you in nicely. Thanks

RE: BTW, posted on August 17, 2020 at 13:58:36

Tre'
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Posts: 17293
Location: So. Cal.
Joined: February 9, 2002

Cool!

I think these amps I'm working on are the first ones. I found pictures of a pair that look just the same (from the top) but have circuit boards under the chassis that hold the diodes and bridges.

On the ones I'm working on the diodes must be in the power transformer can.

I guess I'll have to take it off because the caps for the filament supply are in there also and on one of these amps I can't null the hum. I think I need to replace those caps.

What a weird way to do things.

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

RE: BTW, posted on August 17, 2020 at 14:06:05
Story Audiophile Posts: 10423 Location: NJ Joined: December 11, 2000	it looks like they took a little shipping abuse, especially the bent over choke. All the best Tre'

RE: Pop quiz. ASL 1006 SET mono 845 amp, what's missing?, posted on August 17, 2020 at 14:09:38
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	Some consider it good practice to twist wires (and keep them short) between the rectifier and first PS capacitor; the "DC" can have a lot of ripple at that point. "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

Weird for sure. nt, posted on August 17, 2020 at 14:11:50
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	. "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: BTW, posted on August 17, 2020 at 14:15:54

Tre'
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Posts: 17293
Location: So. Cal.
Joined: February 9, 2002

The funny thing is, it's the one that didn't get "crushed" that needs the cap.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

Update, this has to be the weirdest thing I've ever seen, posted on August 17, 2020 at 20:13:59
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	Not only are the bridges (all five of them) inside the potted power transformer but some of the caps (at least the filament supply caps for the 845 output tube) are inside this potter power transformer, with no way to repair or replace them. It's one of those things that make you think WTF? Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: Update, this has to be the weirdest thing I've ever seen, posted on August 18, 2020 at 06:39:57
Story Audiophile Posts: 10423 Location: NJ Joined: December 11, 2000	yes that is weird because it seems they can only put them between the lams and the can - and then pot it! Anybody who's got one: good luck with repairs 'cause you'll have one helluva time.

RE: sell it ..., posted on August 18, 2020 at 06:44:09
deathtube 667	while the thing is still playing. Or keep it and regret later.

I am totally wrong about this amp, posted on August 18, 2020 at 08:11:16

Tre'
Industry Professional

Posts: 17293
Location: So. Cal.
Joined: February 9, 2002

There are no diodes or caps in the transformer. This amp does not follow the schematic I have. There are no bridges. The DC supplies are all doublers and the heater supplies (including the filament supply for the 845) are all AC.

The schematic I have shows bridges for all the high voltage supplies and bridges for 2 of the 4 filament/heater supplies.

Sorry for wasting everyone's time.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

If it was mine I would, posted on August 18, 2020 at 16:59:47
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	but it's just a repair. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

Not waste: learning. Glad you got it sorted! nt., posted on August 19, 2020 at 00:39:39
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	. "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

Might explain the hum..., posted on August 19, 2020 at 05:56:43

Ivan303
Audiophile

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Location: Cadiere d'azur FRANCE - Santa Fe, NM
Joined: February 26, 2001

Why one side worse than the other? Maybe a bad cap?

OTOH, no apologies required, at least to us here at AA

Maybe a small one to designer and Antique Sound Labs founder Joseph Lau?

Met him at CES a couple times more than a few years ago when I attended regularly. He seemed like quite a nice guy and was well regarded by tube audio folks back in those days.

Can't speak for the sound or reliability of his designs as, with the exception of an OTL headphone amp which still works after 10 years of not much use, I have little experience with gear he designed.

First they came for the dumb-asses
And I did not speak out
Because I was not a dumb-ass

That's very kind of you. Thanks. , posted on August 19, 2020 at 08:18:52
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	There's a little hum but that is to be expected with AC on the filaments. The bent up chassis is sad, but they work! They don't sound bad for what they are. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: Might explain the hum..., posted on August 19, 2020 at 08:25:37

Tre'
Industry Professional

Posts: 17293
Location: So. Cal.
Joined: February 9, 2002

Yes, the hum is to be expected. I can't even get away with AC on a 5 volt 300b. With 10 volts AC for the 845 there's no way not to have hum.

They do play and they don't sound bad. The worse thing is the appearance of the bent chassis. I just hate when things get damaged in shipping. For anything this heavy, a lot of attention is needed when packing.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

RE: Might explain the hum..., posted on August 20, 2020 at 09:30:07

elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004

.

what's all the buzz about?

RE: Might explain the hum..., posted on August 20, 2020 at 14:56:00
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	Bench is a very smart person. Thanks. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

you're welcome, posted on August 20, 2020 at 17:13:10

elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004

I have a pair of these I got at an estate sale for $500 about 15 years ago. I was the only bidder. One of the guys running the auction tried to bid cuz he knew I was stealing them. His mother, who was running the auction, grabbed him by his ear and told him that was unethical. I should have asked her to bend the chassis straight with her bare hands.

One was damaged from being dropped on its end with cord plugged in as evidenced by broken IEC socket. Replaced socket, beat chassis straight, new 'lytics in both amps and applied the Bench hum mod. I remember putting higher voltage rated lytics cuz the doubler runs the stock ones too close for my taste. I guess since they stay cool topside they figured they could go right to the limit.

Last time I turned them on they still played fine.

RE: Might explain the hum..., posted on August 20, 2020 at 18:23:49
elblanco Audiophile Posts: 3486 Joined: August 20, 2004	Yes, she has an unmatched facility with electronics. did you find a schematic? if I remember correctly, one of the 6sn7 is an error amplifier for 6l6 regulator/pass. it has a lot of interesting implements. I always wanted to mod it, but decided not to mess with the Lau-Lau.

RE: you're welcome, posted on August 20, 2020 at 18:31:07
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	Thanks for all the info. The owner picked them up today. I had them playing on some bench test speakers, nothing great but he liked what he heard. If he's happy, I'm happy. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: I am totally wrong about this amp, posted on August 22, 2020 at 17:04:11
engineer@baymoon Audiophile Posts: 16 Location: CA Joined: April 30, 2011	>The DC supplies are all doublers If indeed it is a diode-capacitor voltage doubler ... where are the two diodes in this a.c to 2xdc doubler ? Thanks.

RE: I am totally wrong about this amp, posted on August 22, 2020 at 17:29:11

Tre'
Industry Professional

Posts: 17293
Location: So. Cal.
Joined: February 9, 2002

In line with one of the secondary wires, just as they are reaching the capacitors, hiding under shrink wrap, with one doide going to ground and the other going to the top of the two doubler caps and the other secondary wire (without a diode) going to the point between the two doubler caps. Just like the conventional voltage doubler circuit shown above.

This is followed by a filter choke followed by another filter cap then off to the output transformer.

The raw B+ for the series regulator circuit (6l6 pass tube with a 6sn7 control tube referenced by a zener diode) taps off the doubler supply at the center point between the two doubler caps.

The bias supply is half wave with one diode also hiding under shrink wrap in line with one of the bias secondary wires over by the rest of the bias supply parts.

All three heater supplies and the one filament supply for the 845 are just AC.

I am ashamed to admit how long it took me to see all of this.

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

don't be ashamed, posted on August 23, 2020 at 17:29:54
Story Audiophile Posts: 10423 Location: NJ Joined: December 11, 2000	you are a legend here at AA, and I've had an encounter with an ASL preamp. There is a bunch of crap squeezed into that small chassis.

Thanks. nt, posted on August 23, 2020 at 18:13:34
Tre' Industry Professional Posts: 17293 Location: So. Cal. Joined: February 9, 2002	. Have Fun and Enjoy the Music "Still Working the Problem"

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Pop quiz. ASL 1006 SET mono 845 amp, what's missing?

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