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Old 6th February 2013, 01:46 AM   #921
bcmbob is offline bcmbob  United States
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Hey Jac,

You and others are no doubt very familiar with my feelings about the FE. I'll just do a guick list of my builds:

BrianGT

MyRef V1.2

MyRef V1.3

BP-150 dual chip

FE Beta

FE RC

Pass Amp Camp

TDA7294 Stereo Kit

BJT/Jfet discrete (Pass type)

They all sound very good but the FEs just sound more "real" to me. IMO, the TDA kit (a big suprise since it's only ~ $30 for a stereo kit) comes the closest to what the FEs do for musicality and warmth. There is a new thread dedicated to optimizing a design for that chip, but I would guess that is many, many months away from completion.

Just last week I finished and auditioned the discrete amp. I have read years of raves about those and the only way to compare was to build one myself. There is no way I could judge the many flavors of discrete/Pass/Burning amps, so I simply asked my vendor for his top of the line discrete kit.

Upon completion I heard exactly what so many had stated - a super clean, relaxed and well blended sound. I would say it is almost perfect for listening to some forms of classical music and small acoustic groups. For my tastes there was a deficiency in punch and stage. I installed a pair of Audyn Plus input caps and the presentation brightened up considerably. I was very impressed - till I plugged the FEs back into the system. The difference was similar to moving from the back of the auditorium up to the third row. The discrete was like listening through a very long, very wide tube - great sound but restricted. I'll be doing some more tweaking in the weeks to come.

The FEs suffer no such stage/presence limitations. The characteristic I have never found with any amp, DIY or commercial, is the sparkle and shimmer of Dario's design. With high quality components on-board, I would still put the FEs up against any DIY power amp and probably most commercial offerings. During all this I also rebuilt/upgraded two Hafler DH-120 amps but even they fell short.

I've been keeping Dario up to date on developments with the last three builds/trials and in the end, I always sounds like " I've been on a journey, but when I plug the FEs back in it just feels like coming home".

Now, next week I'll do a post on how I really feel.!!!


P.S. The only other power amp I want to try is Siva's dual LM3886 design - if/when he pumps it out.
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Last edited by bcmbob; 6th February 2013 at 01:56 AM.
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Old 6th February 2013, 08:28 PM   #922
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Bob,

Thanks a lot. It is what I kind of expected to hear, but as you say, you just don't know until you build 'em. The temptation to add a few more boards to Dario's group buy continues.

Anybody else with other thoughts?

Jac
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Old 6th February 2013, 09:24 PM   #923
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Originally Posted by bcmbob View Post
On another subject - while searching the stash for parts to another project I found some 3.25 mm brushes cables I salvaged from a former employer. They look like Litz to me. Think they would be any good for output to post ???
If they're litz, sure.

BTW my personal preference goes to solid core OCC copper.
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Old 10th February 2013, 01:22 PM   #924
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Talking A few more thoughts on C13, Capacitor Choices

It is well known that C13, the input cap to block DC, has a strong influence in the sound of the FE amp. For the last several months, I have been enjoying a 1 uF Russian K75-10 paper-in-oil with a small bypass cap in that position. Recently, I've been doing some playing with the bypass cap and learned a few things.

First of all, the K75-10 alone is not my choice. It has a full and liquid mid-range and a well balanced bass, but the top end lacks sparkle and the detail, while there, seems recessed and a bit quiet. Actually, I find the mid-range more attractive than all of the caps I have tried, so it is worth the effort to improve the top end.

Adding a small value, bypass cap offers the opportunity to improve the high end because small caps act like capacitors to higher frequencies than larger caps. The question remains, what value bypass cap and what type of cap sounds best. Looking around my workbench, I found that I had the opportunity to do a little science experiment.

For about 2 months, I had enjoyed the K75 with a 1 nF Amtrans polypropylene cap. I honestly didn't find much to dislike in this set up, although using the tiny radial Amtrans as a bypass on the 52 mm long K-75 was a challenge. Initially, the 1000 to 1 ratio (1uF/1 nF) seemed on the high side. I doubted if the little cap could have much affect on the much bigger caps sound, but the sparkle and detail improvement are clear from the first moments.

My first experiment was to compare the Amtrans with an FT-1 teflon and a K71-7 polystyrene, all of them about 1 nF. In general, I would have expected the teflon and styrene to have better high frequency performance than the polypropelene. The result of this experiment is that I couldn't tell significant differences between the three 1 nF bypass caps. All three did what was needed, that is, brightened up the top end a bit, added some sparkle and attack to transients, added a nice measure of detail, and expanded the sound stage and image separation. Very nice.

My second experiment was to keep the design the same and vary the bypass cap value. In this case, I had FT-1 caps available in 1, 3, and 18 nF. I thought, if a little cap is good, maybe a bigger one would be better. This turned out to be a much stronger influence in sound than the cap design at 1 nF.

Using the 18 nF, the detail and imaging improved, but so did the strength of the whole higher frequency range, swamping the mid-range and bass and resulting in a sound that was tiring to listen to for long periods. Overall, 18 nF was too strong for my system.

Comparing 1 and 3 nF was naturally a smaller difference, yet one that was clearly audible. I would characterize the 1 nF as slightly laid-back and relaxed and the 3 nF a little more forward and detailed. Both would be good and it comes down to personal choice. That said, this difference is as large as the difference between C13 capacitor choices, as big as the difference between an Audyn True Copper and K71-4.

My conclusions are;

+ 1000:1 is probably a good ratio to start with for a bypass cap, at least for C13
+ Bypass capacitor value is a better tuning tool than cap design
+ Certain caps can benefit from a small bypass cap and may result sound quality very close to much more expensive choices.
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Old 10th February 2013, 02:32 PM   #925
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Originally Posted by lehmanhill View Post
My conclusions are;

+ 1000:1 is probably a good ratio to start with for a bypass cap, at least for C13
+ Bypass capacitor value is a better tuning tool than cap design
+ Certain caps can benefit from a small bypass cap and may result sound quality very close to much more expensive choices.
Thanks for the intersting post, Jac

I've had similar experience with the russian paper in oil, delicious but, IMHO, too much colored and lacking detail.

My experience with bypasses is a bit different, though.

A well sized bypass can do miracles and let shine a lesser cap.

But most of the times I've found more coherent a single cap.

Obviously a single high quality cap is much more costly than a lesser one with a well sized bypass and difference is quite small... so we face the usual dilemma:

Best performance or best quality/price ratio?

IMHO best quality, in a price no object context, is obtained using a single high quality cap.

But if we consider price/quality ratio using quality bypasses could be the way to go.
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Old 10th February 2013, 03:54 PM   #926
bcmbob is offline bcmbob  United States
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For a single cap solution let me suggest that Audyn Plus line. I used a 1uF. It is very close to the True Copper caps and the price has actually dropped $3 since I bought them. The pluses also did wonders for the input cap on the discrete amp build.
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Old 10th February 2013, 08:32 PM   #927
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Originally Posted by ClaveFremen View Post
Thanks for the intersting post, Jac

I've had similar experience with the russian paper in oil, delicious but, IMHO, too much colored and lacking detail.

My experience with bypasses is a bit different, though.

A well sized bypass can do miracles and let shine a lesser cap.

But most of the times I've found more coherent a single cap.

Obviously a single high quality cap is much more costly than a lesser one with a well sized bypass and difference is quite small... so we face the usual dilemma:

Best performance or best quality/price ratio?

IMHO best quality, in a price no object context, is obtained using a single high quality cap.

But if we consider price/quality ratio using quality bypasses could be the way to go.
Dario,

I understand and respect your experience and opinion.

Just curious, which Russian PIOs have you tried? I remember you mentioning K40Y-9. Have you tried the K75-10? I ask because a lot of people over on Jon L's Capacitor Thread continue to like the K75 with a bypass. Not being a pure paper-in-oil but a mix of paper and polymer, most people feel it sounds better than the K40 or K42. I'm interested because I haven't tried any the other Russian PIOs in a controlled comparison as I have with the K75s. That said, I'm not getting colored at all in my system, but then we already know that I get slightly different answers than others. For contrast, I found the Sonicap Gen 1 colored the sound.

In the end, it may just come down to personal preference, which is cool.

As for one high quality cap being the most coherent choice, I don't disagree. It makes sense one well designed cap should have the best compromises designed in. A DIY guy would have to be very lucky to combine just the right characteristics in a bypass cap that would make up for shortcomings of a cheaper cap. I suspect that it may be a case certain caps combine smoothly with a bypass and other don't.
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Old 10th February 2013, 08:34 PM   #928
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Originally Posted by bcmbob View Post
For a single cap solution let me suggest that Audyn Plus line. I used a 1uF. It is very close to the True Copper caps and the price has actually dropped $3 since I bought them. The pluses also did wonders for the input cap on the discrete amp build.
Thanks for reminding me. I'll have to see if they have the right value for a tuning gap in the subwoofer board. Audyn Plus would be an interesting choice.

Jac
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Old 10th February 2013, 08:51 PM   #929
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Just curious, which Russian PIOs have you tried? I remember you mentioning K40Y-9. Have you tried the K75-10?
As you mentioned I've used K40Y-9, never tried K75-10
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Old 10th February 2013, 10:40 PM   #930
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As you mentioned I've used K40Y-9, never tried K75-10
Dario,

I just reread Jon L report on K75s (Orgy of Capacitors Thread, Head-Fi.org, page 14). He says that they are quite different from K40s or other PIOs, "a very saturated, colorful, textured, and detailed midrange........yielding an apparently more detailed and forceful presentation." ......"but the leading edges are not razor-sharp and precise like premium film caps" and "a bit dark overall"....."The line dividing "colorful" and "colored" is thin, and while K75-10 likely leans a bit to the latter."

Then he did something crazy and bypassed the K75 with a V-cap teflon. "With many caps, bypassing with teflons often sound terribly disjointed and incoherent, but K75-10 sang beautifully with VCap teflons.......This pair is so attractive-sounding that I believe the combo belongs in the league of the best of the breed."

So I guess its OK to say that the K75 is different from most PIOs, still colored when used alone, but a cap that likes a bit of teflon on top.

Regardless of the choices made or individual preferences, this part is fun. I have had the music turned up all weekend and enjoying my FEs immensely. I just wish we could get some of these other DIY inmates to give them a try. I'm sure they would be surprised. Thanks again to you and to Mauro for the journey.

My next step will be to understand how an FE sounds with a balanced input.

Jac
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