Almarro A318B SET Amplifier Simple Modifications For Improved Performance?

woodnut · « **on:** 16 Nov 2015, 02:22 pm »

Hi there,

I have been a long time owner of the Almarro A318B, 3 years ago I changed the 0.47UF coupling caps for Mundorf Silver in Oils and it was quite a step up in performance.

I need to get in there to make a couple of repairs, namely changing the selector switch which is intermittently causing issues plus the IEC socket which has a crack in the plastic casing. While I am in there I wondered about the potential for any simple upgrades by swapping like for like components.

I have already changed the input valves after tube rolling with a small selection of valves.

Is there anything else worthwhile that could be achieved with a simple swapping of components for better quality ones?

I have seen on some threads on here that some folk replaced the 0.47UF caps for 0.22UF, what was the reason for using a lower value here? I also see from the schematic in the manual that there is a second cap (0.22UF) after the 6H8C (6SN7). Is there anything to be gained by changing that cap?

Many thanks in advance.

FullRangeMan · « **Reply #1 on:** 16 Nov 2015, 02:56 pm »

The most simple upgrade is eleminating the IEC power socket and solder the power cable direct wire in the power transformer or in the power conditioning circuit if there is any.

The same for audio inputs, eliminating rca connectors will reduce losses in music signal.

MarkR7 · « **Reply #2 on:** 16 Nov 2015, 04:24 pm »

My Almarro A318B..... Changed out both sets of stock coupling caps (the .47uF, and the .22uF) with equivalent Jupiter Copper Foil caps. Also took the input selector, and volume pot totally out of the signal path, and made the Almarro into a fantastic standalone amp. Life is GOOD!

jackmonster · « **Reply #3 on:** 16 Nov 2015, 05:15 pm »

If you want to keep it an integrated amp- the biggest improvement you can make is to change the volume pot. My friend did this for me(I forgot what kind he put in, but it was that expensive) and it was a marked improvement in clarity and detail. Also, NOS 6SN7's make a big difference. This is a nice amp

Folsom · « **Reply #4 on:** 16 Nov 2015, 07:11 pm »

Quote from: jackmonster on 16 Nov 2015, 05:15 pm

If you want to keep it an integrated amp- the biggest improvement you can make is to change the volume pot. My friend did this for me(I forgot what kind he put in, but it was that expensive) and it was a marked improvement in clarity and detail. Also, NOS 6SN7's make a big difference. This is a nice amp

Bingo!

Find out what the value of the one inside it happens to be. The chinese DACT's on eBay are literally amazing for the money. They're not just good for what they cost, they're good period. They make known "quality" pots sound like garbage.

Also consider replacing the RCA jacks with something higher grade, based on copper. These guys are really cheap, but do an excellent job.

I'm not sure what your binding posts are, they may be an option too. Having copper conductors will remove grain you may not even know you have.

I'd keep the IEC, but you could replace it with a nice Furutech unit. Direct soldering might be better, but it's also absolute hell.

Mark's recap looks like an absolutely worth wild endevour.

woodnut · « **Reply #5 on:** 17 Nov 2015, 08:18 am »

Hello folks and many thanks for your replies!

I am really tempted to get hold of some Jupiters and give them a try but the cost here in the UK is making me wonder if I can justify changing the pair of 0.47 and the pair of 0.22. Also the crazy amount of heat that the amp kicks out is a concern, it is a harsh environment for these caps to live in.

I had read somewhere that some people had changed the 0.47 for 0.22 which would bring the cost down. Does anybody know what effect this would have for the coupling caps? My relatively uneducated assumption is that the filter frequency would change and move upwards. Perhaps the performance of the larger cap would also be better in terms of ESR?

I use two sources which is a shame because I would love to do away with the channel selector switch as mine has gone bad. On the subject of pots, I was actually looking at some stepped ladder attenuators on ebay at around £15-£20, I need a 250K pot and I fancy giving one of these a whirl. I wonder whether 23 steps is enough?

I am going to make the power cable captive also, this is a great suggestion and hadn't actually occurred to me as an option.

Thanks again.

FullRangeMan · « **Reply #6 on:** 17 Nov 2015, 11:05 am »

Wow these Jupiter caps are 600V, the usual for a commercial 6C33 SE amp are 250V.

Charles Xavier · « **Reply #7 on:** 17 Nov 2015, 12:02 pm »

Quote from: FullRangeMan on 17 Nov 2015, 11:05 am

Wow these Jupiter caps are 600V, the usual for a commercial 6C33 SE amp are 250V.

Does the voltage make a difference ?

FullRangeMan · « **Reply #8 on:** 17 Nov 2015, 12:18 pm »

600V are more than the double from a cheap cap.
Bass needs energy, a powerful PS.
A power supply are more from 50% from the amps sound.

Charles Xavier · « **Reply #9 on:** 17 Nov 2015, 12:38 pm »

Quote from: FullRangeMan on 17 Nov 2015, 12:18 pm

600V are more than the double from a cheap cap.
Bass needs energy, a powerful PS.
A power supply are more from 50% from the amps sound.

So then it is better with 600v

FullRangeMan · « **Reply #10 on:** 17 Nov 2015, 12:47 pm »

Much better, but at a cost.

Charles Xavier · « **Reply #11 on:** 17 Nov 2015, 01:13 pm »

Quote from: FullRangeMan on 17 Nov 2015, 12:47 pm

Much better, but at a cost.

Financial cost or quality cost ? Lets get it out for the laymen

FullRangeMan · « **Reply #12 on:** 17 Nov 2015, 01:19 pm »

Finance $$ cost, the sound quality is improved w/these caps.

Charles Xavier · « **Reply #13 on:** 17 Nov 2015, 01:31 pm »

Thanks

woodnut · « **Reply #14 on:** 17 Nov 2015, 04:22 pm »

MarkR7 :

What would you say changed with the addition of the Jupiters? The Mundorf Silver sounded a tad forward in the mid range (not unwelcome in my system), very transparent and made the amp alot more exciting in my system. I have read that the Jupiters are very neutral and wondered about the balance and the fact I might get a less involving presentation versus the Mundorf. Has anyone compared these two caps in any way?

MarkR7 · « **Reply #15 on:** 17 Nov 2015, 04:58 pm »

I did not try the Mundorf SIO in my Almarro, so I can't comment on the difference between the Jupiters and the Mundorfs. I do run the Mundorfs in my Dodd preamp, and I like them there. I was thinking of putting Jupiters in the preamp, but at 2.2uF, that will be costly.

There is no loss of energy or involvement in my system, so no plans to replace the Jupiters in the amp!

Quote from: woodnut on 17 Nov 2015, 04:22 pm

MarkR7 :

What would you say changed with the addition of the Jupiters? The Mundorf Silver sounded a tad forward in the mid range (not unwelcome in my system), very transparent and made the amp alot more exciting in my system. I have read that the Jupiters are very neutral and wondered about the balance and the fact I might get a less involving presentation versus the Mundorf. Has anyone compared these two caps in any way?

FullRangeMan · « **Reply #16 on:** 17 Nov 2015, 11:56 pm »

Found this cap test at Lampizator site afew years ago;

Abby356 · « **Reply #17 on:** 18 Nov 2015, 03:21 pm »

I have owned the A version of this amp for the past 7 years or so and have always been interested in making worthwhile improvements to the caps and volume attenuator. Switching out the caps in the Almarro A205a MKII that I owned previously made a marked improvement.

I was glad to see this timely post surface just in time for winter projects.

Does anyone have experience with the value of the stock volume pot ?

Would something like a 48 step KHOZMO fit ?

Its been a few years since I looked under the hood (skirt) of this beast.

Thanks,

Daniel

Charles Xavier · « **Reply #18 on:** 18 Nov 2015, 03:25 pm »

I would like to know about the pot also. Every once in awhile I get a scratchy sound in my right channel when moving it

FullRangeMan · « **Reply #19 on:** 18 Nov 2015, 05:31 pm »

Maybe this help> my tube amp builder asked me a 100K log volume pot for my 6C33 amp.