As promised some pages back I have rewired the inside of my FE to be A/C coupled and completed a C13/volume control test rig. Right now I am using the audyn plus caps that Bob has so generously lent me. I am going to compaire these head to head with the K71-4 and see which ones "let more sound through". This setup should allow me to swap the caps faster which will hopefully reduce ear fatigue.
So far I have noticed that the shorter the interconnect between the coupling caps and the amplifier the better the sound, especially for vocals. I also used the blue pc screw terminals at first but the fastons are more convenient and sound much better. I dont think the sound will be as good as having the C13 caps inside the amp enclosure or even in position on the board, but my hope is to test a few different caps and see which ones allow the most natural sound to come into, and out of, the amp
more to come.....
P.S. Dario, are you still working on the DAC9?
So far I have noticed that the shorter the interconnect between the coupling caps and the amplifier the better the sound, especially for vocals. I also used the blue pc screw terminals at first but the fastons are more convenient and sound much better. I dont think the sound will be as good as having the C13 caps inside the amp enclosure or even in position on the board, but my hope is to test a few different caps and see which ones allow the most natural sound to come into, and out of, the amp
more to come.....
P.S. Dario, are you still working on the DAC9?
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Really interesting...and nice confirmation on insisting on using an onboard cap and fastons.
I'll read your findings with interest.
Sure, but I'm still in the middle...
Will,
First of all and once again, you did a beautiful job with the enclosure. Nice!
I look forward to your comments as you experiment. Observations like screw terminals compared to fastons are very interesting. I would have guessed the other way round. Keep up the good work.
Jac
For C13 in a Rev C, I've tried NOS Siemens MKL 2.2uF/630V Cellulose Acetate axials, and the sound is very natural and cohesive, even if it may have lost some micro-detail.
IMHO, the opposite is true of the K71-5 radial polystyrenes - micro-detail is preserved, but loses natural cohesiveness to the point of sounding harsh. Eagerly awaiting your impressions of the K71-4 axials (which may sound different because of differences in construction).
I've also heard good things about the K73-16 PETP film/foil axials - the tube crowd swears by them. I've ordered some from EBay and will give an update later.
On another note, I was also trying some compensation mods on a hunch, and came up with an experimental one which sounds good to my ears:
C10 - 27 pF silver mica (33 pF as in FE should also work fine)
C32 - 150 pF (same as Rev C, FE - I used a KP1834 polystyrene film/foil)
R42 - 47R (not critical, I used a Dale 51R1. Non-magnetic resistors may be better)
C34 - 15..22 pF silver mica, ceramic NP0 or similar (I used a Philips P100 ceramic 15 pF)
R43 - 27k (I used a 26.1k PRP non-magnetic)
Preliminary audible impressions: The sub-100 Hz lows seem extended, better defined and textured, while everything else remains similar to Rev C - maybe slightly improved imaging. I'll audition it further to see if there are any regressions from Rev C, before possible further tweaks to C34.
first of all, thank you Jac. I really enjoy the construction process and the challenges it presents. This amp was a departure from my other components in a design sense. I wanted the enclosure to be servicable and to seperate as many of the A/C components from the amp as possible. I will post more detailed photos as I take them
Now for some initial thoughts on C13. I will say that my impressions of the differences between the audyn plus caps and the K71-4 are preliminary, but I do have some thoughts.
First, my setup is as follows. Sony DVP NC85H DVD player as a source not high end, but it does the job. I have thought about a DAC, but I have not done enough research to decide if it would make a difference. A quick search told me it has a 24bit DAC built in, maybe a 32bit would be audible, others with experience let me know. TKD pot based volume control with C13 caps. FE with standard build. audioquest evergreen inter connects. Basic speaker cables connected to ESS AMT monitors circa early 70s (Mint, seriously). 35 year old holes in my head
My first plunge into the subjective yet revealing test was with a modern recording. Minnesota, wi by bon iver which for those who dont know is full of detail throughout, high mid and low. the K71-4 reveal quite a bit of the mechanics of the music. string noise, etc make you feel like your in the studio. the vocals are "in the room" and the highs are sharp but not piercing. the mids and bass are accurate and detailed. Overall the sound seems warm and enjoyable.
The same tune with the audyn plus instantly has different characteristics. Most notable is the bass. The bass is full deep and tight. It really brings the AMTs to life on the low end (an aspect that has always been just ok).
There is a warmer tone to the sound, but it does lose a bit of the high frequency detail and much of the background detail. However I am reluctant to say that even though I really like to hear the "mechanical" sounds of the music, the warmth and musicallity of these caps is really pleasing.
Next up was Miles Davis, Kind of blue (remastered edition). Many of the same observations of the previous recording rang true. The K71s had a sense of being "in the club" but there is an amount of hiss from the recording that reminds you of your location. the Audyns mask much of that hiss, but again sound warm and pleasing.
Both of these caps have their benefits and drawbacks, but tonight my preference is with the audyns. (tonight....preliminary)
One observation that remains is that with both of these caps this amp is so detailed and enjoyable it makes great recordings sound amazing and bad ones, well....revealed.
P.S. swapping the caps and listening to the same song four or five times is a bit tedious, but quite interesting.
Now for some initial thoughts on C13. I will say that my impressions of the differences between the audyn plus caps and the K71-4 are preliminary, but I do have some thoughts.
First, my setup is as follows. Sony DVP NC85H DVD player as a source not high end, but it does the job. I have thought about a DAC, but I have not done enough research to decide if it would make a difference. A quick search told me it has a 24bit DAC built in, maybe a 32bit would be audible, others with experience let me know. TKD pot based volume control with C13 caps. FE with standard build. audioquest evergreen inter connects. Basic speaker cables connected to ESS AMT monitors circa early 70s (Mint, seriously). 35 year old holes in my head
My first plunge into the subjective yet revealing test was with a modern recording. Minnesota, wi by bon iver which for those who dont know is full of detail throughout, high mid and low. the K71-4 reveal quite a bit of the mechanics of the music. string noise, etc make you feel like your in the studio. the vocals are "in the room" and the highs are sharp but not piercing. the mids and bass are accurate and detailed. Overall the sound seems warm and enjoyable.
The same tune with the audyn plus instantly has different characteristics. Most notable is the bass. The bass is full deep and tight. It really brings the AMTs to life on the low end (an aspect that has always been just ok).
There is a warmer tone to the sound, but it does lose a bit of the high frequency detail and much of the background detail. However I am reluctant to say that even though I really like to hear the "mechanical" sounds of the music, the warmth and musicallity of these caps is really pleasing.
Next up was Miles Davis, Kind of blue (remastered edition). Many of the same observations of the previous recording rang true. The K71s had a sense of being "in the club" but there is an amount of hiss from the recording that reminds you of your location. the Audyns mask much of that hiss, but again sound warm and pleasing.
Both of these caps have their benefits and drawbacks, but tonight my preference is with the audyns. (tonight....preliminary
) One observation that remains is that with both of these caps this amp is so detailed and enjoyable it makes great recordings sound amazing and bad ones, well....revealed.
P.S. swapping the caps and listening to the same song four or five times is a bit tedious, but quite interesting.
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I haven't heard any of the Ks yet but I plan to do so later this summer. Let me suggest that those qualities you find missing with the Plus caps are what the TCs add for ~ an additional $30. The TCs retain that warmth and musicality but add some brilliance, definition and seperation -IMHO. Each builder has to determine if that is a worthy investment. I think it is, but then I come in a little short on the self discipline scale with these amps.
A basic cost/benefit analysis should suffice.
One can spend $200 or so on parts to build an amp that sounds as good as or better than any $500 amp, if such a thing exists in the modern marketplace.
Or one can spend $250 or so on parts to build an amp that equals or exceeds the performance of most $1000+ amplifiers available commercially. I can't write "all" with any conviction because, of course, I haven't heard them all, but it does outperform the ones I have heard.
C13 is that critical. In the case of this capacitor (and, to a lesser extent, many other parts), we have found from experience that there is generally a relationship between cost and performance. It is difficult to quantify but easy to identify. How far does the curve extend? No one has been crazy or rich enough to define that limit, but I wish someone were. I'm sure there are better caps than TC that cost far more. I'm not sure there are better caps for C13 that cost much less, but we should keep looking and listening.
Done cheerleading.
Peace,
Tom E
One can spend $200 or so on parts to build an amp that sounds as good as or better than any $500 amp, if such a thing exists in the modern marketplace.
Or one can spend $250 or so on parts to build an amp that equals or exceeds the performance of most $1000+ amplifiers available commercially. I can't write "all" with any conviction because, of course, I haven't heard them all, but it does outperform the ones I have heard.
C13 is that critical. In the case of this capacitor (and, to a lesser extent, many other parts), we have found from experience that there is generally a relationship between cost and performance. It is difficult to quantify but easy to identify. How far does the curve extend? No one has been crazy or rich enough to define that limit, but I wish someone were. I'm sure there are better caps than TC that cost far more. I'm not sure there are better caps for C13 that cost much less, but we should keep looking and listening.
Done cheerleading.
Peace,
Tom E
I think a well made 16/24 bit worth more than a poorly done 32 bit dac.
32 bit is usually done to make the volume control digitally. 32 bit is not really usefull as you will not find much 32 bit data anyway. More 24 bit, but most of the CDs are 16 bit. So a well made 24 bit DAC approved by others what I would suggest.
On the way of improvements
SMC RCA 816U sockets and DACT type 21 step SMD potentiometer were recieved and installed today. For connections 0.6 mm single core twisted pairs were used. Though this ebay potentiometer is far from perfection tactically, the sound improvement is audible. The audyophyle resistors and capacitors are also already on the way. I strongly suspect that K71-4 is what I need as C13, judjing from descriptions. Now with the industrial BOM it remains to be desired a bit of breathing to the strings and some substantionality to the brass instruments.
SMC RCA 816U sockets and DACT type 21 step SMD potentiometer were recieved and installed today. For connections 0.6 mm single core twisted pairs were used. Though this ebay potentiometer is far from perfection tactically, the sound improvement is audible. The audyophyle resistors and capacitors are also already on the way. I strongly suspect that K71-4 is what I need as C13, judjing from descriptions. Now with the industrial BOM it remains to be desired a bit of breathing to the strings and some substantionality to the brass instruments.
SMC RCA 816U sockets and DACT type 21 step SMD potentiometer were recieved and installed today.
CMC816?
Mmh, they're not so good... I've tought you ordered CMC805-2.5F... there is a not small difference between the two.
Absolutely, the price/quality ratio is nearly unbeatable
C13 and C9 can help you.
Yes it was my mistake. I understood, when the post arrived. Will order the 805 copper ones.
But it makes minor difference, for at present I also don't have good RCA cables. Sane advise is highly desirable
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Pay attention.
805-2.5F are brass made (really good sounding for the price)
The 'pure' copper ones are:
805-2.5-CU-G
And have the Swiss CU marking.
Prefer the -G (gold plated) over the -R (unplated copper), the latter oxidise easily and you'll pass your time cleaning it...
I also appreciate Dario's approach to suggesting multiple cost levels. I did not mean to imply that one must spend a lot of money to get good performance from this design. It is superb with all but the very cheapest components, and will surpass the expectations of many builders.
You do not need to max out your credit card to buy C13 to make this amp sound better than most others.
Peace,
Tom E
Hi Dario,
I am not easily seeing the Swiss CU mark in the online photos. I am also seeing a wide range of pricing for what is listed as CMC 805-2.5-CU-G. They seem to range from $10 to $60 for a pair. Do you have a favorite supplier or one to watch out for?
Thanks.
Jac
Once it was Valab... but it seem out of activity.
If I remember correctly I've bought also from hanshare-electronics
Recently I've bought them only from hificollective.co.uk, price is honest and you're sure you're getting the real thing...
Those are really good sounding connectors at a very good price but, if you're willing to spend more than double, WBT NextGen are better
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