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PostPosted: Sun Apr 15, 2018 11:28 am 
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Location: Calgary, AB, CA
brianmedia wrote:
Brooster wrote:
brianmedia wrote:
Trying to decide on .22uf Mundorf silver oils or .33uf

I will be using high efficient Zu Omen speakers. Do you think the .22 will be best or .33 will work best will forward HE speakers?



Brian? Welcome to the modding thread.
Just my 2c, but the silver oils might be a little overkill for the 301. Even if you go completely ballistic with tubes and caps and mods your still left with the basic 301.
Also, I dont think the silver oils are a particularly forgiving cap.
Again IMHO,YMMV and all the rest.


Thanks Bruce!

Which caps do you have in yours? Any suggestions? Understand about the Silver Oils Since they are almost 1/2 the price of the 301 itself. Have contemplated just the supremes as well.


My thoughts on modding the 301 are that you should try and balance out your expenditures through the power supply the caps and tubes, and not get too carried away in any one area. There is a lot of information on caps and tubes in the thread and elsewhere, so the choices are a little intimidating but also fun.
In my own 301 I use the Obligato Golds. I think its a good cap for the money, pretty neutral in character and a good match for the 301.( they are also a nice fit as far as size) Its a good enough cap that it wont hold the amp back in any way. Past a certain point I think the caps are really about flavor differences and what you like personally, and also about finding some synergy between the tubes you use and the rest of the mods.


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PostPosted: Sat Apr 21, 2018 9:36 am 
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Posts: 648
Location: Calgary, AB, CA
My amp arrived a couple days ago and it's been interesting comparing it against my current Massdrop CHT (a collab amp with Cavalli Audio). I use this as a headphone primarily but since my new power amp for speakers hasn't arrived, I am using it with my Tyler Acoustic speakers (90db @4ohms).

The stock EL34 power tubes sounded like a wet blanket, super closed in, way too bouncy bass and hollow, I can't believe someone would actually sell these to anyone! Likely for me, they're now in the garbage lol. Fortunately the amp also came with the stock 6L6 which are quite a bit better but still lacking in detail and space. I picked up some Tung Sol 5781As here on CAM that should be here Tuesday, looking forward to those. Tempted to pick up some winged C SED but the cost seems a bit compared to the amp cost.

I don't have appropriate tubes for the preamp sitting around to roll but the amp came with the stock black metal 6SJ7. Without going overboard and spending more on tubes than the amp itself...is there much point/difference in replacing these?

The single bottom filtering cap is fortunately the green 180uF 450V Nichicon, so I don't think I have to replace this one...right?!

As for a mod list, this is what I have in my cart at Digikey:

x2 https://www.digikey.ca/scripts/DkSearch ... 0284564160
x1 https://www.digikey.ca/scripts/DkSearch ... 0284574161
x1 https://www.digikey.ca/scripts/DkSearch ... 0284574161
x2 https://www.digikey.ca/scripts/DkSearch ... 0284574161

Which size of resistor is appropriate for discharging the various caps?

I might pick up 4 of these...I have decided yet. I wish I was ordering more than that from Sonic Craft to make shipping more sensible...

http://www.soniccraft.com/product_info. ... vdc-p-4200


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PostPosted: Tue Apr 24, 2018 12:26 pm 
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Matthew.

If you can redo the links for Digkey, we could have a look.
You dont have to replace the 180uf, but you can.

I use 20k for discharge but a lower value will work as well.

One of the main issues with the caps, is to make sure they fit without too much grief.


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PostPosted: Tue Apr 24, 2018 12:48 pm 
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The issue with C8 and C8A is that they are the cathode bypass caps for the output stage. The result is that you have a fair sized electrolytic sitting pretty much directly in the signal path. Unlike the bypass caps for the preamp stage they can not be removed, nor can they be changed to film caps. Its a good idea to upgrade the cap, but the other option is to bypass it, with some poly films. Bypassing is not the be all end all but it can be effective.

My 301 with cascade bypass on C8 and C8A.
The leads are kept as short as possible.


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PostPosted: Thu Apr 26, 2018 4:53 pm 
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Location: Toronto, ON, CA
My apologies if this should be a separate thread.

Is anyone using the MP301 as a power amp only, as in connecting a preamp to one of the inputs? I'd love one, but 2 line level inputs doesn't come close to meeting my needs. I do however, have 2 SS preamps. I searched AK and other sites, but the acceptable/not acceptable ratio seems about 50/50 with some saying its terrible and others saying the tube integrated amp (not the MP301) may overload but may work OK.

So, anyone doing this?


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PostPosted: Thu Apr 26, 2018 6:01 pm 
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I use a passive RCA selector switch. 3 RCA pairs in / 1 RCA pair out.


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PostPosted: Thu Apr 26, 2018 8:02 pm 
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Location: Little Britain, ON, CA
cryogenie wrote:
Is anyone using the MP301 as a power amp only, as in connecting a preamp to one of the inputs?


My stereo speakers are tri-amped.
Signal path...
Source(s) >
Sim Audio I5.3 preamp output >
dbx Driverack PA >
MP301 MKIII > HF Horns.
MP301 MKIII > MF Horns.
TOA IP-450D > LF Woofers.

The system works very well. I use the volume controls on the MP301's as gain controls and use the preamps volume control to set listening levels.


Last edited by HiLift on Sat Apr 28, 2018 4:36 pm, edited 1 time in total.

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PostPosted: Fri Apr 27, 2018 5:34 am 
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Location: Toronto, ON, CA
HiLift wrote:
cryogenie wrote:
Is anyone using the MP301 as a power amp only, as in connecting a preamp to one of the inputs?


My stereo speakers are tri-amped.
Signal path...
Source(s) >
Sim Audio I5.3 preamp output >
dbx Driverack PA >
MP301 MKII > HF Horns.
MP301 MKII > MF Horns.
TOA IP-450D > LF Woofers.

The system works very well. I use the volume controls on the MP301's as gain controls and use the preamps volume control to set listening levels.



Thanks for that. My idea was to use a SS preamp for phono and line level and feed it into the MP301. I was thinking of doing it the way you are doing it. Good to know it works!


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PostPosted: Fri Apr 27, 2018 10:22 am 
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As an alternative, there is a fairly simple way of bypassing the volume control and some of the switching in the 301. Taking the vc out of the signal path is a good thing if it is redundant in your system.


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PostPosted: Sat Apr 28, 2018 4:27 pm 
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Brooster wrote:
As an alternative, there is a fairly simple way of bypassing the volume control and some of the switching in the 301. Taking the vc out of the signal path is a good thing if it is redundant in your system.


Great idea. Are there any links showing how to do this?


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PostPosted: Sun Apr 29, 2018 2:02 pm 
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1) Remove bottom plate of your amp.
2) Remove the 4 screws holding the front faceplate and rotate as in picture.
3) Disconnect the short jumper cable that runs from the daughter board to the " in " on the main board.
4) Take either of the input wires marked cd in or aux in and plug one of these directly to the " in" on the main board where the jumper cable was connected.
5) Reassemble. Everything works as before but the volume control and and input switching are out of the signal path. Only 1 input is active and no volume control.


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PostPosted: Mon Apr 30, 2018 5:40 am 
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Location: Toronto, ON, CA
Brooster wrote:
1) Remove bottom plate of your amp.
2) Remove the 4 screws holding the front faceplate and rotate as in picture.
3) Disconnect the short jumper cable that runs from the daughter board to the " in " on the main board.
4) Take either of the input wires marked cd in or aux in and plug one of these directly to the " in" on the main board where the jumper cable was connected.
5) Reassemble. Everything works as before but the volume control and and input switching are out of the signal path. Only 1 input is active and no volume control.


Attachment:
IMG_20180429_154335260.jpg


Thank you.


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PostPosted: Wed May 02, 2018 10:12 am 
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Posts: 11
Location: Denver, CO, US
Brooster wrote:
1) Remove bottom plate of your amp.
2) Remove the 4 screws holding the front faceplate and rotate as in picture.
3) Disconnect the short jumper cable that runs from the daughter board to the " in " on the main board.
4) Take either of the input wires marked cd in or aux in and plug one of these directly to the " in" on the main board where the jumper cable was connected.
5) Reassemble. Everything works as before but the volume control and and input switching are out of the signal path. Only 1 input is active and no volume control.


Attachment:
IMG_20180429_154335260.jpg


This is great! Thanks so much. I was wanting to add a Pre at some point and this solves the "2 volume controls"


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PostPosted: Wed May 02, 2018 10:59 am 
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Location: Calgary, AB, CA
You're welcome guys.
Its a simple change and the amp does sound better,if for some reason you dont need the vc.


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PostPosted: Wed May 02, 2018 6:14 pm 
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Location: Calgary, AB, CA
devon58 wrote:
Brooster wrote:
I had never come across this before. If you've read it already my apologies.
Not sure what its worth, but it does relate directly to the 301 MK 3
http://wallofsound.ca/audioreviews/ampl ... store-com/

Yep, that review is the reason I tried the Tung-Sol 7581-A, and I’m glad I did.
It’s a great tube in the MP301, bringing a blend of authority and musicality that bests the KT88, EL34, and 5881 that I have tried in my amp.



Thank you for the great link !

I have got a matched pair of the Tung-Sol 7581-A tubes on the way!


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