Tube guru's help me out here - Almarro 318B content.

ICTWoody

No longer a junior member
So first a little story:

I keep a list of gear I would like to own/try someday. For several years the Almarro A318B tube integrated has been on my list. Don't know where I came across it originally, but I just liked the idea of it and have overall read positive things. It was on the list and I have saved searches etc... for them.

I almost pulled the trigger awhile back when @ralfoto was selling his, but the timing wasn't right for me. Well this one popped up on the 'bay a while back and was listed without tubes, with some cosmetic issues to the wood and for a WAY TO HIGH price. I looked at the sellers previous listings and it was pretty clear they were NOT hifi people. Who knows where they got it... likely an estate or something. Well it didn't sell, they relisted it at a lower (still too high) price... it didn't sell. They relisted it at a lower (slightly still too high) price and I finally had a couple too many whiskies one night and I made a low-ball offer. They accepted it. It was a good enough score, even without tubes, I was willing to gamble on what it might need.

Well it arrived last week. Good news is overall it arrived as it was shipped, which is good... cause the packing was as you'd expect from a non-audio person, but not the WORST i've received. The damage to the unit was only what was there before shipping. I had messaged them asking them to please pack it well since even without tubes it weighs 42lbs.

I took off the wood chassis to have a wood-worker buddy take a look at it and see what the repair options might be. If he'll even take it on or have time. Hoping to find a local wood person willing to spruce it up a bit... but if one of you HFH family guys with your crazy talents want to help me out... I'd ship it out.

The steel and the rest of the amp is in good shape. An interesting note is this seems to have applied braille stickers on the back... wondering if this was owned by someone with a visual impairment? Mysteries.

When I took off the bottom plate it was missing a couple feet, I had some nice aluminum ones on hand that are nicer than the stock plastic feet and I just had to go to my favorite local hardware store and get some little M3 screws. Check that off. I saw inside this has been "upgraded" with Jupiter wax caps. At first I was like "double score!" but in my googling I found a couple guys who had done that upgrade with those caps and both had them MELT because of the high heat the 6C33C tubes put out... I looked closer and sure enough... melted caps. They need to be replaced. Other than that... internally it looks fine... I see nothing that was of concern.

I am into it for short money... I am thinking modding it. I don't feel confident to do the work myself, so first off is I need to find someone willing to take it on for me. For most of you more savvy tube guys this is probably cakewalk work.

I am wanting to replace the Jupiter caps with Duelund's. They are spendy, but like i said, I'm into it for short money, so I figured why not splurge a little. I did notice that two of the Jupiters are .022 caps, where I think based on the schematic in the owners manual, and posts online, they should have been .22. I don't know how this might have affected things for the PO. The other caps seem to be correct at .47.

Next, I see many guys saying the volume pot should be replaced or bypassed. Seems like the only swap availible is a Alps Blue Velvet 250k pot. I would like to make this swap unless you guys know of something better -OR- I'm considering modding to a stand alone power amp since I have my Bent Audio TVC I could run with it. If I go this route, I would also remove the selector switch and make it a single input. Thoughts?

I would also like to upgrade the binding posts and RCA's perhaps while someone has it.


I still need to source the tubes, but being just a pair of the 6C33C's and a single 6SN7 and single 6SL7, that should be quick.

So, who wants to work on my amp? Or knows someone who will?

- Woody

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The Packing

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The Braille

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The Guts and melty caps...

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The Amp

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Here is the damage to the wood case. Who wants to tackle this? The lips that lap the top of the steel chassis have broken, and then there is the damage to the back corner. Open to ideas. I was thinking perhaps taking the top 1/8-1/4 off with a nice table saw, adding 1/8" hardwood to the top, routeing it flush with the existing profile and adding the 1/8" round-over back on? It would change the aesthetic a little bit... but not much.

But... I don't have the skill to do it. Wood experts? @Wardsweb wanna help a brotha' out?

- Woody

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... and the old feet, small plastic, next to one of the new ones I installed when I put it back together.

- Woody

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Here is a schematic from the owners manual... looks like a pair of 0.47 and a pair of 0.22 on the coupling caps... not 0.022.

- Woody

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I'm no expert but yeah was gonna say .022 seems more like a bypass usage, than a normal coupling cap.

Maybe it melted not because it was too hot but it was extremely wrong value?

Beautiful amp btw
 
I have worked on one of those before. I think when they build them that they pre-assemble a fair amount of what goes into there, them mount things after they are built, as there are some tight spaces in there! The one I repaired had melted cathode bypass caps on the 6C33 but was otherwise mostly OK. I would replace the coupling caps with decent metalized poly caps and call it good. Super expensive coupling caps don't generally belong inside a global feedback loop. If you post where you're located, there may be someone close by who can do this work for you.

The 250K volume pot should be considered a mistake by the designer and a 10K substituted in its place.

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This is what I found in the one I worked on, but yours looks to have been produced at a later date.
 
Here is the damage to the wood case. Who wants to tackle this? The lips that lap the top of the steel chassis have broken, and then there is the damage to the back corner. Open to ideas. I was thinking perhaps taking the top 1/8-1/4 off with a nice table saw, adding 1/8" hardwood to the top, routeing it flush with the existing profile and adding the 1/8" round-over back on? It would change the aesthetic a little bit... but not much.

But... I don't have the skill to do it. Wood experts? @Wardsweb wanna help a brotha' out?

- Woody
Not something I would want to tackle. Whatever you do, it will be noticeable. Replacing the sides is hampered by the front splines. that and the pieces were CNC machined. Creating the curves manually is a PIA. You might try some synthetic wood filler (bondo) and furniture stain pens to blend it all together. Any route will not be easy and require a lot of time and patience.
 
Might be a good time to do a total rebuild into a new chassis. You have a good schematic, all the transformers etc. Commission a nice chassis from scratch and whip out the soldering iron. make it a few inches bigger and you'll have more room.
 
Wot wntrmute2 said. It would also be a good time to change the "flying trapeze " component mountings too. Although it is pretty good point to point in the amp itself.

Joe
 
The issue with re-chassising the Almarro 318 is that it no longer is an expensive Almarro 318, but Woody's 318 project that probably only has value in the iron. The only way to do they project w/o losing significant value to the 318 is to cleanly pull the iron and purchase new components for your build, which could prove costly too.
The 318 is a rare, and unique amp and I would certainly think twice before I tore it apart to transplant.
 
How much of the electronics, aside from a couple caps, is beat? It doesn't strike me as enough to rechassis, but maybe I missed something.

The wood trim is bad, but it's all on the back and out of sight in a lot of instances. Rather than bondo it, I would glue down that back splinter, and sand down the back rail. The worst part is the chewed up corner, but if one planes the damaged corner flat, glues on a replacement piece with a similiar fine grain, and reshapes and finishes it, it may pass muster. The color matching can be done on the piece the replacement was harvested from and that could be the hardest part of the entire project. BTW, I'd practice this procedure on some scrap wood before the case; it's always better to learn on disposable, not irreplacable, pieces.

The wood damage isn't visible in this view; I think it looks great and brings back memories of that legendary night one of these was singing in Ray's room at one of the early AKFests. I left early, but others were there MUCH later...


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Andyman has an idea too!!. You did ask for advice and it seems you are getting it. From ALL directions.
The only bits that are costsly are the Jupiter caps ( and of course the iron ). BUT, that said hide the damage in the corner of your rack???, maybe. After all, its not falling apart as such.


Joe
 
The one I repaired had melted cathode bypass caps on the 6C33 but was otherwise mostly OK. I would replace the coupling caps with decent metalized poly caps and call it good.
Suggestions for caps?

Super expensive coupling caps don't generally belong inside a global feedback loop.
Why is this? Seems like guys who have these amps have updated the coupling caps in many cases, and they say they hear a noticeable difference. Like I said, I scored this amp for a GREAT price, so I want to make it as good as it can be. I hate that "I wonder / What if" feeling if I don't do something that might make a difference.

If you post where you're located, there may be someone close by who can do this work for you.
I'm in Wichita, Kansas

The 250K volume pot should be considered a mistake by the designer and a 10K substituted in its place.
I don't really understand the difference in what happens with 250k vs. 10k. I'm still debating turning this into a stand alone power amp... but why would they have done this if the 250k wasn't the correct choice?
 
How much of the electronics, aside from a couple caps, is beat? It doesn't strike me as enough to rechassis, but maybe I missed something.

The wood trim is bad, but it's all on the back and out of sight in a lot of instances. Rather than bondo it, I would glue down that back splinter, and sand down the back rail. The worst part is the chewed up corner, but if one planes the damaged corner flat, glues on a replacement piece with a similiar fine grain, and reshapes and finishes it, it may pass muster. The color matching can be done on the piece the replacement was harvested from and that could be the hardest part of the entire project. BTW, I'd practice this procedure on some scrap wood before the case; it's always better to learn on disposable, not irreplacable, pieces.

The wood damage isn't visible in this view; I think it looks great and brings back memories of that legendary night one of these was singing in Ray's room at one of the early AKFests. I left early, but others were there MUCH later...
It's not really beat at all. It's actually in great shape. I just don't know it's provenance and I want someone who knows more than me to do the work on the inside and make sure it's A-OK.

I'm not that worried about the woodwork. I have a local guy I think I'm going to be able to come up with something with. It might be just a new build. The wood is 100% cosmetic on this amp. 4 screws attach it to the metal chassis. It's just lipstick and rouge.

- Woody
 
I would go with something simple and not huge like a Relcap. When you have a global feedback loop, the differences between a pedestrian part and an exotic part is mitigated by the feedback loop itself. This is part of the point of the feedback loop in the first place ;)

The issue with the 250K pot is that the first gain stage is a 12AX7, and there's substantial miller capacitance there to cope with. At anything other than very high and very low positions on the volume control will result in treble rolloff that shouldn't otherwise be there.

I don't know anybody in KS who does this work. I have a customer in Topeka who mails me things like this regularly.
 
Might be a good time to do a total rebuild into a new chassis. You have a good schematic, all the transformers etc. Commission a nice chassis from scratch and whip out the soldering iron. make it a few inches bigger and you'll have more room.
This amp is not a basket case at all. That seems like an overreaction to me for a few caps that need swapped out. I would be so upside-down in this amp if I paid to have that done... I just want to minimize the work here... but also optimize it as best as we can.

I think eliminating the Volume and Input Selectors seems like a good way to make the already simple singled-ended circuit as simple as possible, and I have no doubt my TVC is a MUCH better volume control than a standard pot. I also think simplifying the signal path from the inputs to a single wire and no selector switch is making sense to me.

Since I am going to do something about the wood chassis anyway, I can just rethink the "set dressing" to make it not appear as a modded integreated. I like the idea of making it look like it was a stand alone power amp from the get-go without holes where the volume and selector switches were.
 
The issue with the 250K pot is that the first gain stage is a 12AX7, and there's substantial miller capacitance there to cope with. At anything other than very high and very low positions on the volume control will result in treble rolloff that shouldn't otherwise be there.

I don't know anybody in KS who does this work. I have a customer in Topeka who mails me things like this regularly.

This doesn't use any 12AX7's... this uses a 6SN7 and a 6SL7 in addition to the 6C33C pair.

The little A205 integrated uses a 12AX7 and the pair of EL84's... this is it's big bro.

- Woody
 
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