AudioCircle
Audio/Video Gear and Systems => Tube-o-phile Circle => Topic started by: Presb4 on 6 Jan 2024, 08:53 pm
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Its time for me to void my warranty :icon_lol: and upgrade the coupling caps and tube stage resistors in my stock Schiit Freya+ Pre-Amp. Not sure if this topic has been discussed here on AC, a quick search did not turn anything up. Reading over on Headfi there are a few posts but as I enjoy the AC community better, I figured I would post this process here instead.
The primary goal of this thread is to document my mod process, the results I hear and the value it created for me compared to other mods/upgrades like new/different tubes, cables, power isolation ect.
If anyone else here has modded their Freya's, plus or regular, please chime in and share your experiences.
I will order the parts I need today and complete the mods in the coming weeks.
My list of upgrades to complete are:
*Remove and install new coupling caps for the tube circuit. - the new caps used will be V-Cap ODAM 400VDC 2.2 uf
*Remove and install new resistors in the audio signal path for the tube circuit. - the new resistors used will be Amtrans 47K and 22K Ohm 2W AMRG Series Carbon Film ± 1%
*Add more ventilation to the top of the case above the power transformers to reduce the overall temps the caps see during operation.
*Remove the stock case feet and upgrade with 1/2 tall isolating soft rubber feet.
(https://www.audiocircle.com/image.php?id=260388)
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I would love to hear about the difference that you experience hearing before and after the change.
I did a cap replacing on a new preamp so I don't know what the original unit sounds like. The thing that sticks out in my memories is removing the old caps, I used a flush cutter and cut it out to reduce the heat exposure time when I removed the old solder and the tiny lead.
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This is going to be fun to watch. Just curious, do you use the rca or XLR connections? When I modded a bifrost2 a while back, I heard a good improvement swapping the rca to the KLE Harmony compared to the stock plugs. I've heard the Freya+ boosts performance very well with upgrades so you should be in for a treat. :popcorn:
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I have thought about picking up a different tube pre-amp in-lieu of modding my Freya+ but for the money, I just cant find a better Pre-Amp that has both RCA and XLR inputs and outputs, not to mention, the Freya maintains the discreate balanced circuit all the way through. Who else does this sub 1k??
I have had my Freya+ for almost 2 years now, so I am very familiar with its factory sound signature.
I am very excited to hear what the change will be post mod as I already know what differences my NOS tubes bring to the sonic table.
I have the Bitfrost 2/64 DAC and use the Balanced XLR outs to the Freya+ Balanced Input, I then run balanced out to each of my Schiit Tyr Monoblocks.
I tried using the RCA inputs and outputs, but went back to balanced as I felt the soundstage was a bit better and there was no downside. I can run longer cables to my mono blocks as they offer better shielding than RCA's. But when I output from my Freya+ to my tube power amp I use RCA's, so I might have to take a look at those KLE Harmony plugs.
Now I just have to wait for the post man to deliver my new caps.
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What tubes are you planning on using after the mods?
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new caps used will be V-Cap ODAM 400VDC 2.2 uf
1/2 tall isolating soft rubber feet.
What is the brand and value of stock cap? 2.2 uF seems likely overkill and likely too large to fit if premium caps are used?
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What tubes are you planning on using after the mods?
I have a number of different NOS 6SN7's, RCA, Sylvania, GE's mostly. My favorites right now are the Sylvania GT's from around 1952 (Bad Boys 3 hole)
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What is the brand and value of stock cap? 2.2 uF seems likely overkill and likely too large to fit if premium caps are used?
The stock Schiit Freya+ uses Wima 2.2 uF caps. I have had the chassis open and measured the space before I purchased, the 2.2 uF ODAM caps will fit.
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So in prep for the venting modification, I CAD'd up a simple template that mimics the hole pattern that Schiit uses on their products. I will add it below as an image that if printed on an 8.5"x11" sheet full size, it should scale correctly. I plan on using this and a center punch to locate the holes over the transformers before drilling.
(https://www.audiocircle.com/image.php?id=260478)
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I don't like this thread.. I love it! I will certainly be watching closely and can't wait to see your progress!
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as a Freya+ owner, i appreciate the sharing of the info including the tubes you are using.
Thanks.
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Are the RCA and XLR's active simultaneously? As in running the second active line to a sub processor.
Thx
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I am feeding 2 ea. xlr's to my main speaker amps and 4 ea. rca's to my sub amps.
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Hi,
I'll be watching this thread with interest :). Good luck with your modifications.
Cheers Rod
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Can you explain how you opened up the Freya+ to replace the caps? I would like to replace the fuse with an audiophile fuse but after an attempt, couldn't figure it out.
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Can you explain how you opened up the Freya+ to replace the caps? I would like to replace the fuse with an audiophile fuse but after an attempt, couldn't figure it out.
Sure, I will take a few pics and show you how to open the cover and get at the fuse.
I have tried a number of mods on other equipment I own and have settled on only upgrading components in the audio circuit path. Modifying other components, like in the power circuit, I don't find to be worth the effort, or money. So I will not be upgrading my fuse, unless it blows :lol:
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Ok, the mail man delivered and today the mods start. Of course it is also the coldest day of the year so far, so it will take me 1/2 of the day just to heat my shop up where I will work :o
But until I get going, here a few pics of the components I will be installing.
(https://www.audiocircle.com/image.php?id=260578)
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Close up.
BTW, I am really hoping I get similar results installing the Amtrans resistors, that I have on other Amps. Very smooth and warm sounding resistor in my experience.
This will be the first time using V-Cap ODAM's, but I have heard nothing but good reviews.
(https://www.audiocircle.com/image.php?id=260579)
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Sure, I will take a few pics and show you how to open the cover and get at the fuse.
Thanks so much. I bet those VCaps are gonna sound great. I like the Freya+. Nice little preamp. I like the balanced in and out, and no frills. Much to my surprise I've found that an audiophile fuse can make a difference, but I'm sure won't come close to those VCaps.
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Close up.
BTW, I am really hoping I get similar results installing the Amtrans resistors, that I have on other Amps. Very smooth and warm sounding resistor in my experience.
This will be the first time using V-Cap ODAM's, but I have heard nothing but good reviews.
(https://www.audiocircle.com/image.php?id=260579)
Hey!
Oh! Damn! :lol: Look like you have over $400 worth of V-Caps there :o
Anyway, I've never use V-Cap so I'd be curious to hear your feedback on them.
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OK, time to crack this puppy open.
Step 1 = Pull the volume knob, it just pulls off. Then remove the plastic knob gromet. Then remove the volume pot nut and washer.
(https://www.audiocircle.com/image.php?id=260609)
(https://www.audiocircle.com/image.php?id=260610)
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Now, if you use tube socket savers like I do, you will need to remove them. I use socket savers to save my sockets from wearing out and to lift the tubes out of the casing to lower the internal pre-amp temps.
You need to remove them so you can slide the cover off. This can be a real pain and after messing around I found that this "L" pick worked great. Just angle it a bit and slide it down inside the tube socket key way and hook the underside of the socket saver and pull up. They pop right out.
(https://www.audiocircle.com/image.php?id=260611)
(https://www.audiocircle.com/image.php?id=260612)
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Step 2 = Remove the top of the case.
To do this flip the pre-amp upside down so you are looking at the bottom and gently pry the front lip of the top/front cover forward. The top cover will slide forward about 1/4 inch. At this point the front push buttons will fall out, don't let them hit the floor and roll away. Now wiggle the top case a bit and it will lift in the back and slide the rest of the way forward over the volume pot stem.
(https://www.audiocircle.com/image.php?id=260613)
(https://www.audiocircle.com/image.php?id=260614)
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And here we are, looking at the internals of a bone stock Freya +.
(https://www.audiocircle.com/image.php?id=260615)
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Step 3 = Remove the PCB from the bottom case.
But before you do this a word of warning....
Caps can have very high amounts of DC voltage still stored in them. Take care to no touch them until you have verified they are discharged with a DVOM. Your Pre-amp will bleed off this voltage over time, so its best to totally unplug your pre-amp and have it sit for a few hours before you go messing with it or be ready to safely discharge the caps with a resistor across the caps. If you are not experienced in doing this, just don't do it. The caps in the Freya + can hold up to 300VDC.
I had unplugged mine the night before and the caps still had 5 VDC on them when I checked them with a DVOM.
Ok, warning out of the way.
Now you need to remove all of the black screws from the back of the Inputs / Outputs and power socket.
Then flip the pre-amp over and remove all the silver screws from the bottom. Support the PCB a bit with your hand on the last few screws as it will want to fall out of the casing after you remove the last screw.
(https://www.audiocircle.com/image.php?id=260616)
(https://www.audiocircle.com/image.php?id=260617)
(https://www.audiocircle.com/image.php?id=260618)
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Another word of warning.
This thread and all of these steps are for a Schiit Freya +, not the original Freya.
The Schiit Freya + has a very different tube circuit topology than the original Freya.
Ok, lets get this Mod going....
Here are the tube circuit resistors you can swap out. The ones marked in Yellow are the resistors between the voltage gain tube cathode pins and the coupling caps going to the cathode follower tube stage. They are 47K ohm 1 watt 1% resistors. The resistors marked in blue are the tube plate B+ dropping resistors. They are 22K ohm 1 watt resistors.
Until I had the PCB pulled I was not able to figure out the audio path, so I had both resistors on hand. In the end I only swapped out the 47K ohm resistors marked in yellow as they are part of the audio path. No audio signal flows through the 22K ohm resistors, so no need in upgrading them in my opinion.
I replaced the resistors in yellow with Amtrans AMRG 47k ohm 2 watt 1% resistors.
I did not replace the 22K ohm tube B+ plate resistors.
Unless you have a lot of experience working soldered PCB's, I would not recommend replacing the tube circuit resistors, they were an absolute pain in the back side to get to.
(https://www.audiocircle.com/image.php?id=260619)
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Here are the factory 2.2 uF coupling caps in the Freya+.
I replaced these with the V-cap ODAM 2.2 uF 400V caps.
Replacing the caps was fairly easy. There is plenty of room to work the old ones out and the new ones in.
(https://www.audiocircle.com/image.php?id=260620)
Out with the old.
(https://www.audiocircle.com/image.php?id=260621)
In with the new.
(https://www.audiocircle.com/image.php?id=260622)
(https://www.audiocircle.com/image.php?id=260623)
Yes, those resistors were a very tight fit, like I said painful to get them in, but I got them in but it does not look pretty.
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Note... The V-Cap's have a metal housing that are part of the cap circuit. So you need to make sure the leads and any other components on the PCB or the case cannot come in contact with the Capacitors or they will short. :nono:
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Hi,
Thanks for your post. Its really interesting and I'm so envious of your skills.
:popcorn:
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So that's the end of the Mod. I will save the drilling of the new vent holes over the transformers for another day. I am ready to get this guy connected back up to my system and see how it sounds. But before that, lets take a look around the stock Freya +.
The Freya + has 2 transformers. The one with the yellow arrow is the tube stage transformer, it supplies the 300VDC and the 6.3VDC to the tube stage. She runs hot!
The one marked with the blue arrow is the discrete power supply transformer for the all the other circuits in the Freya +. It runs warmish...
(https://www.audiocircle.com/image.php?id=260624)
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The mains fuse is located with the blue arrow. If your Freya + will not turn on, it might be because this fuse blew. Just pop it out and replace it.
The tube stage B+ 300VDC power stage smoothing caps are marked with the red arrow. They are all 450V rated.
The tube stage 6.3VDC power stage smoothing caps for the tube heater filaments are marked with the green arrow. This was one of the significant changes from the OG Freya to the Freya+. The OG Freya used 6.3VAC for the heaters, whereas the Freya+ uses 6.3VDC. The use of DC for the heaters reduces the noise floor significantly in a pre-amp.
(https://www.audiocircle.com/image.php?id=260625)
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The Schiit Freya+ has Balanced XLR inputs and Balanced XLR outputs, this means the audio signal coming in maintains the positive and negative on different channels. So for a 2 Channel Pre-amp to maintain its true balanced topology, it has to have 4 audio paths, + and - for both the right and left channels.
This was another significant change from the OG Freya to the Freya+, the Freya+ maintains those 4 pathways all the way through the pre-amp and they never cross.
This also means you have to have 4 volume controls for the balanced channels and why the pre-amp has 4 tubes that need to be matched, not only in pairs, but each tube needs to have matched sections (triodes) to sound its best.
Note* Don't mistake the need for matched pairs, for matched quads. The Freya+ does not need a matched quad of tubes to sound great IMO. Only matched pairs for the voltage gain pair and the cathode follower pair are needed. But if you only have one matched pair put it in the voltage gain section.
Each 6SN7 tube has 2 triodes in it, one is used for the + wave and the other is used for the - wave for each channel L and R in the Freya+.
The voltage gain stage (right side tubes) are the most important for good sound as they do the amplifying.
The (left side tubes) are the semi-circlotron output follower stage. Those tubes are not as important for sound quality and I often use my LISST tubes in that position to save my good NOS tubes for the voltage gain side.
This balanced path can be seen throughout the PCB. The red arrow is the right channel leaving the tubes, the relay (little white box) is the switch to either use the tubes stage or the 1x buffer stage, which passes to the volume relays. The audio output is run through a volume relay ladder to control the output volume voltage (the many white boxes in the top section of the picture). From the signal input to the output there is a dedicated right and left channel pathway all the way through. Its a very well laid out design, and for the money, a home run.
(https://www.audiocircle.com/image.php?id=260626)
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To put this back together, simply reverse the process above. Put the PCB back in, put all the screws back, black screws in the back, silver screws in the bottom.
Then put the silver front panel buttons back in the front cover. They are all the same so it does not matter the order. I found that adding a strip of painters blue tape to the front of the top case plate and pressing the silver buttons into the tape holds them in place while you re-assemble the top case. It keeps the buttons from falling out. Now just side the case top back on. It will sit flush when it is 100% back in place. Then re-install the volume washer/nut and knob.
(https://www.audiocircle.com/image.php?id=260627)
(https://www.audiocircle.com/image.php?id=260628)
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Time to hook it back up and listen for awhile. In fact that's exactly what I have been doing the whole time I was typing this "how to". I will give more details on how it sounds after burn in, but I can say it is a significant change from stock so far. More to come :drums: :guitar: :rock:
(https://www.audiocircle.com/image.php?id=260629)
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Presb4, thanks so much for taking the time to post these photos and the "how to". Very informative. Much appreciated. Well done.
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Presb4, thanks so much for taking the time to post these photos and the "how to". Very informative. Much appreciated. Well done.
You are welcome. This is a hobby that is fun for me and I enjoy sharing what I learn with others. Enjoy.
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My initial impressions and a few things I have noticed so far.
So first off, what I hear and what I like is a product of the components in my sound system. What you hear and what you like will most likely be different. This does not make any one right or wrong. I only say this because when I first got into this hobby a few decades ago I use to always read in Absolute Sound and say to myself, if I just had that, I would be happy. For those out there still on this quest, a word of advise. Keep it fun and enjoy the music. The moment you stop either one of those 2 things, you might be going down the wrong path.
I have an almost full Schiit system now, I have had many others, but Schiit provides 90% of what I am looking for and at a reasonable price. Because of that I have sold most of my other gear and built an almost all Schiit system. I use it for both 2 Ch and HT in our family Den. So what I like is a jack of all trades system. I stream via Qobuz or Android TV to a MiniDSP Studio -> USB Digital Out -> Schiit Bifrost 2/64 -> XLR Balanced -> Schiit Freya+ -> XLR Balanced -> to twin Schiit Tyr Monoblocs -> GR Brutes. I used this in a room that is 12'x 14', aka. smallish room. I also have a custom built ST-70 tube power amp that I use when I am in that tubey mood.
I use a bit of DSP to correct for a room mode I have below 150Hz. My system has plenty of power for my needs with loads of clarity and bottom end for HT use. But for 2Ch use some times I want a bit more smoothness and warmth. This is often when I switch on my ST-70 power amp, fed by the Freya+ tube mode. In the past though I have felt that the Freya+ vailed the sound stage a bit and muddied the attack of mid bass instruments, and yes this was with NOS tubes.
After reading a number of posts and talking to friends, I aligned on the caps and resistor upgrade detailed above to help lift that vail and sharpen that mid bass attack I felt I was missing.
So the manufacture of the V-Caps stats that they test and burn in every cap they make in the ODAM series. I can say that the new caps do sound really good right out of the gate. I find that new caps can sound a bit shrill when new and that they smooth out after around 100 hours of use. But as of right now the new ODAM caps are pleasant and if they are going to get better over break in that's just icing on the cake for me, because I like them already.
I have used Amtrans resistors in my ST-70 build and know they need a little time to burn in. I have no doubt they will add that extra bit of smoothness to my system that they did in my tube power amp.
Also, it is very common that Freya+ owners report a audible pop through the speakers when turning the volume pot, generally found around 12oc on the dial. I have had this pop ever since new, it never bothered me enough to seek repair under warranty. After the cap upgrade yesterday, that issue is gone in my Freya+. I don't know how changing the caps out would effect / fix that issue, but it did -> Bonus :P
So what do I hear?
Well, the change I got is greater than the amount of change I get with a fancy set of new NOS tubes. So as good tubes these days can be 100 bucks a Pc, dropping 400 bucks on caps and resistors might not be too crazy as they will last forever and work with all tubes. The change in sound for me is mostly noticed in string bass and kick drums and in the decay of cymbal hits and the echo's in live recorded events (think concert halls). So I'm not hearing more details, but the details I am hearing now just sound more real (sound stage has widened and increased in depth).
The bass has tightened up, the leading edge of a bass guitar plucks or the strike of a piano key, is sharper and the trailing reverberation (decay) hangs longer and decays smoother over time.
More to come.
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Nice! Thanks for documenting and sharing. :popcorn:
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OK, I have around 100 hours on the caps now and will do my best to provide a short and to the point description of the changes.
First off, these caps did not need much time to burn in. As I said in an earlier post the OEM claims that they burn them in and test them to sell in matched pairs or quads. They must as I would say the amount of change over the last 100 hours of use has been very small <10%, if anything, they have smoothed out a tiny bit. The edge of sharp details have smoothed out a bit. Otherwise I would say that the ODAM's are what they are the day you first power them up.
The change to the Freya+ was mostly in the sound stage width and depth, everything has a more 3d effect with these caps vs the stock WIMA caps. The tone did not change much if at all in my system.
Clarity and Resolution has also increased significantly. The best example I can provide is to listen to this song on your current system.
(https://www.audiocircle.com/image.php?id=261130)
It is basically a recording of objects being dropped and bouncing. Ask yourself, where in space, depth, side to side do you hear the different objects being dropped. Does it sound like it is all around you or just in front of you? Now count how many different objects you can identify and what they are being dropped on (surface).
The sound stage in this recording went from in front of me and wide, to now being twice as deep and all around me after the cap change. Also the number of objects being dropped that I could identify before the caps change was around 4 or 5 and they all sounded like they were being dropped on a big table top in front of me. After the cap change the number of objects I could count went to around 10, and the surfaces they were bouncing off of that I could count was now 4 or 5.
Have a listen and tell me what you count?
Basket balls, ping pong balls, marbles, pebbles, playing dice, exercise balls, just to name a few that I hear.
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Very cool. This is all reaaallly fascinating to me. On a 1-10 scale, how easy/hard would you estimate the modifications were to do?
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Have a listen and tell me what you count?
Basket balls, ping pong balls, marbles, pebbles, playing dice, exercise balls, just to name a few that I hear.
Definitely the rubber kickball/dodgeball was in there. I'd know that sound anywhere.
(https://cdn.mos.cms.futurecdn.net/JDCLGLsVwwjeHsBkYQUbqm-320-80.jpg)
Definitely a cool track for testing and geeking out on our systems. :thumb:
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Like! I'm using the N version of the Freya+, nine pin triodes. I totally agree with Stereophile on the A rating. Thanks for the informed thread, you make it look very doable.
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Very cool. This is all reaaallly fascinating to me. On a 1-10 scale, how easy/hard would you estimate the modifications were to do?
Sorry, goggle1824,
I just noticed your question from a couple weeks ago.
Well I think I covered what you need to know in my pics, if your are still uncomfortable, I would say you might not want to try it. The Schiit Freya+ is not cheep, and I would hate to see someone damage theirs with a soldering iron, easy to do if you don't have a fair bit of experience tinkering with this kind of thing.
The aim of my post was to publish the parts needed, and to show how I did it and what my results were. None of this is rocket science and I recommend the learning of new things, so if you want to, have at it. But, if you have some old junky stuff laying around the house, maybe start with taking that apart and removing some soldered parts to make mistakes there first.
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Like! I'm using the N version of the Freya+, nine pin triodes. I totally agree with Stereophile on the A rating. Thanks for the informed thread, you make it look very doable.
Without looking at the Freya N pics online, they pulled them from the website, I dont know how much room is in the N vs + models. But from what I remember reading the Freya N was the same Pre-amp but with the nine pin tube. Did they use 6N1P's?
Other than the tube socket change, they might have dropped the plate voltages 50vDC. Many of those 9 pin driver triodes like to run between 200 and 250vDC where the 6SN7 and 6SL7 run around 300vDC. If that is what they did, it might explain why many liked the sound of the 9 pin tube more than the Freya+ octal tubes. Tubes run at lower plate voltages often have the side effect of more distortion, even order distortion. AKA, more tubey sound.
BTW, I'm rocking my Freya+ right now with some NOS 6SL7 Sylvanias from 1962, and I think I like them better than my Bad Boys 6SN7's from 1952. Even sweeter, the 6SL7's were less than half the price :rock:
(https://www.audiocircle.com/image.php?id=261693)
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Thanks much for sharing your experience Presb4. It’s inspiring. I have a 30 year old Optimist receiver needing some help that I’m considering restoring. Given your advice I think I’ll scrounge up some old pcb’s to practice on first.
As a place to start would you please share what you use as your soldering kit? I have basic skills that are out of practice.
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Presb4,
I just want to drop in and say thank you for a beautifully put together modification thread. I will be saving this for inspiration for my own Freya+, but even if I didn't own one I would have loved your write up on this. Top shelf work!! :thumb:
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Presb4,
I just want to drop in and say thank you for a beautifully put together modification thread. I will be saving this for inspiration for my own Freya+, but even if I didn't own one I would have loved your write up on this. Top shelf work!! :thumb:
Thank you for the kind words. :thumb:
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Thanks much for sharing your experience Presb4. It’s inspiring. I have a 30 year old Optimist receiver needing some help that I’m considering restoring. Given your advice I think I’ll scrounge up some old pcb’s to practice on first.
As a place to start would you please share what you use as your soldering kit? I have basic skills that are out of practice.
AllanS, any iron that runs 650-750F temp will work. So dont think you have to have a super nice iron to have fun modding.
I use a HAKKO 1 Channel 70 W, Soldering Iron.
(https://www.audiocircle.com/image.php?id=261748)
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AllanS, any iron that runs 650-750F temp will work. So dont think you have to have a super nice iron to have fun modding.
I use a HAKKO 1 Channel 70 W, Soldering Iron.
Many thanks.