My new Pre-Amp project


#1

With this new project I will try to build a high end pre-amp and hope it will outperform my Classé CP-700. I started a week ago so it is already partly assembled.IMG_4286.JPGIMG_4274.JPGIMG_4275.JPGIMG_4277.JPGIMG_4278.JPGIMG_4280.JPGIMG_4283.JPGIMG_4284.JPGIMG_4285.JPGIMG_4287.JPGIMG_4288.JPG

I got help on this project from the Pink Faun engineers for components and schematics. The Pre-Amp will be single ended, but this way it is more easy to afford better parts and reach the best.

The powersupply is separated in a left and right channel (which will be very very stable) and so will the Pre-Amp. The volume control they selected is a Tribute inductive control which is only 0 to 33Ohm. The transistors are specialy matched pair. The capacitors in the signal and a big pair in the power supply are Paper oil capacitors. Which will be compared with V-Caps and output transformers in a later stadium.

The biggest challenge is to cut a hole in the front for the display, but maybe I better find somebody for the milling. The display will be connected with a arduino one. The arduino will check the input voltage and protect the Pre-Amp and my speakers.

I’m planning to use a pair of XLR inputs and output so I still can use my expensive cabling. It also will have 1 or 2 RCA inputs and output for my Sub.

Please bring in your idea’s I could use all the help!

Enjoy the pictures!


#2

Hi Wijnand,

This i real interesting!!

Can you share the schematic of the design?

Or describe why you choose this configuration.

Did you hear already a amp build his way?

I build several amps in the past from SS, hybrid and full tube.

The A&T yearsnerd_gif


#3

Forgot to say.

The results with external PS for the amps where in my case not good.

The shorter the signal path and PS lines the better IMO


#4

Thanks!

I’m curious about your projects so please add some pictures if possible! Were you able to outperform your formel commercial equipment, with your own amps?

Well I choose for this design, because I’m very impressed by the Pink Faun equipment. They follow their own pad in design and engineering. I never heard that much rest and blackness in music than with Pink Faun equipment. They do not use connectors in their equipment, no 20mm fuses, but big 38mm fuses with a very thight clamp. These will outperform any high grade 20mm fuse easely. When my amp is complete I will install some high grade 38mm fuses. Their equipment is that well engineerd that they don’t use any feedback in the amps. So I got my inspiration for this amp. I went to Pink Faun to buy some part’s and a Pink Faun inductive volume control. Their volume control is probably one of the best, but they told me that the Tribute was even better. So one followed the other and schematics were drawn. About 6 hours later I had a box with parts and schematics.

I’m not sure if I may share the schematics I don’t want to throw in my own glasses, so I will ask them first. The paper oil capacitors are old military stock, which they once bought. The capacitors have a very open and natural soundstage, but V-Caps probably will outperform them.The capacitors are very good to build filters for speakers, i’m going to replace the filters of my focals.

about the external PS I already use one with my CP-700 and it works great in this case. In my project I use high grade wiring and 48volts so this won’t be a problem I hope!wink I will keep it short just in case and thanks for making me aware.


#5

I was still thinking how and why the external PS would not work. I’m planning some capacitors in the preamp itself to get a buffer. Was this the case for you?


#6

There are a few things left to be found out. I would like to add a headphone output. The preamp is now layed out to drive a 50KOhm poweramp, but the output impedance will be pretty low so I could try how it will sound if I drive the headphone through the exact same circuit.

In case of the PWD there was a clear difference between the balanced and unbalanced output. So I quess the PWD is ment to be used balanced in the first place. How would this be for the DS I have not compared the outputs yet. I hope they will be of the same grade. Because of my cabling I like to use the XLR output anyway.

A question for the PS audio experts.

Would it be okay to short the cold and ground of the DIrect Stream XLR. I like to do this on the XLR inlet of the pre-amp.


#7

You wont hurt the DS itself by shorting the outputs, but you’d be better off sound quality wise to use a balanced input on your pre if it has one.


#8

Thanks Ted!

No it won’t have a true balanced input. I was planning to build a true balanced pre, but I was told to better build a single ended pre with the same budget to achieve a higher coal. For example I would need four Tribute volume controls instead of two. That would be to expensive so I would make a concesion on the volume control. Etc.

in my case My interconnects are only 1meter between the DS and the Pre. The other is just half a meter from the pre to the poweramp. So I hope there won’t be to much trouble for the signal.

But I hear you! Thanks for the advice I probably will use it in the next project.


#9

Hi Wijnand,

I stopped with DIY 5 years ago but i will look if i have some pictures.

Yes i was able to outperform commercial equipment but till a certain level.

That’s why i ended up with Spectral right now.

The best sounding diy power amp was a hybrid (tubes/mosfet) and a full tube amp (triode).

The pre and Phono amp were also based on tubes.

I didn’t get the tube Phono quiet :-(

Spectral outperformed everything i build (at very high prices)!

But i do also like Audio Note (total different from Spectral)


#10
adimon said

Spectral outperformed everything i build (at very high prices)!


Well let me try4_gif!

Spectral probably is unreachable, but the brand have many single ended equipment at the highest level. So that is a good thing for me.

i’m very curious about the pics!


#11

Some random thoughts.

o- Do you indeed need a pre-amp? Since I tried the DS directly into the power amp, I removed all cables from the pre. Though in my system the PWD sounds MUCH better with a pre-amp. DS is another story.

o- Is the rest of your equipment also single-ended? I would go balanced, unless absolutely not feasible.

o- Capacitors in the signal path? Any chances to get rid of them?

o- I would go for tubes ;)

o- Yes, everything takes time, energy, money and money…


#12

Thanks Alekz,

Well I don’t realy need a pre-amp and I did not tried the DS directly into the poweramp yet. I can still hear a little pop when I switch a channel on the DS. My poweramp will probably reach it’s maximum volume at 75% volume when connected direct to the DS. 1.88V reaches the clipping point. Below the clipping point it can easely throw 600W power through my speakers. I realy became scarred after my poweramp once tripped connected to the PWD. Beside that the volume can go from 100 to zero by a single touch on the display. It doesn’t always stop when I release my finger from the display. I’m scarred this will happen the other way around

When I get rid of the capacitors out the signal path. What would you recommend to put back?

The rest of my equipment is balanced, but why is everybody so convinced about balanced solutions. I don’t drive long cabling. The signal of a balanced solution is twice as strong as a single ended solution, but what happens to this stronger signal when you use the volume and go 6db down. Than you have the same signal strenght as with a single ended solution. When I use the volume of the DS between 70 and 100. There’s still a very good signal quality. So when the equipment has the same good parts for the single ended solution as it uses for the balanced solution than it should nearly sound equal. So for my poweramp It makes no difference same path, but using half the circuit. Single ended my poweramp is 6db down so I can take the volume 6db up and there’s the stronger signal back and the pre can be build with better parts for less money. With better parts the SQ will bennefit even more I think, but maybe I’m wrong i’m not sure.

Tubes maybe in a next project, I’m very curious what they would bring me. But indeed it will cost more money.sad-029_gif1_gif


#13

In general a balanced design will automatically cancel the even order harmonic distortion (perhaps not always a good thing :) )

IMO most of the difference people report in cables are lessened by balanced connections - a balanced connection will help a lot with interference and radiation : i.e. picking up noise and sending out noise. Also things like ground loops have less of an effect with all balanced connections.

The DS is inherently balanced so IMO it would be a waste to not provide a balanced output.

Some manufacturers believe they can do more to improve the sound of a device with the budget of a truly balanced design than the balanced version gets.


#14

Wijnand, try the DS directly to amp (with all precautions, of course ;) ) At least you will have some benchmarks.

The volume control does not work THAT fast. And you can get the same effect even if you have a pre-amp in the chain. Think about a wrong movement when the volume in one touch goes to 100. Something what is not currently possible with the DS (provided there are no funny bugs, of course :D )


#15
Ted Smith said In general a balanced design will automatically cancel the even order harmonic distortion (perhaps not always a good thing :) )

IMO most of the difference people report in cables are lessened by balanced connections - a balanced connection will help a lot with interference and radiation : i.e. picking up noise and sending out noise. Also things like ground loops have less of an effect with all balanced connections.

The DS is inherently balanced so IMO it would be a waste to not provide a balanced output.

Some manufacturers believe they can do more to improve the sound of a device with the budget of a truly balanced design than the balanced version gets.


Well I do believe in truly balanced disigns and also that they will always be better than single ended designs. But I still have the hope that the gap between balanced and single ended will be reduced in case of very short cabling. The noise a cable from 50cm will pick up or send out will be far less as big as longer cabling. Besides this I think the design of a high end cable like the Kimber KS1136 will send and pick up less noise than less good cabling. For the cable between the DS and the pre I use an Audioquest Sky XLR with active screen. So I hope it won’t pick up a lot of noise. The ground loops are the biggest concern, but again a grounloop on longer cabling would be a bigger concern.

So you probably or (better said) are right on all points. I try to balance on a single ended disign so the bennefits of a trully balanced design will be as small as possible. Beside this I try with the budget that came free of the parts I don’t need to invest in better single ended parts and so to close the small gap or bridge this gap that is left.

When this would not work. I learned a lot and have a single ended pre for sale.frown

Still thank you very much for your comments they are worth a lot and realy appreciatedsmile


#16

IMG_4289.JPGIMG_4293.JPGNew Pictures

The axis of the volume control wil find it’s way to the frontpanel. Below the signal capacitors and will pass between the big powercapacitors and the smaller powercapacitors


#17
Alekz said Wijnand, try the DS directly to amp (with all precautions, of course ;) ) At least you will have some benchmarks.

The volume control does not work THAT fast. And you can get the same effect even if you have a pre-amp in the chain. Think about a wrong movement when the volume in one touch goes to 100. Something what is not currently possible with the DS (provided there are no funny bugs, of course :D )

Thank you Alekz I will try!

Building a new preamp is hobby and I already spend a lot of money on it. So I will finish it single ended. When it doesn’t work I always can build a second one and make it two balanced mono’swink

It happend with the volume control of the DS a few times, but indeed is isn’t very fast so I probab;y can stop it in time!


#18
Alekz said Wijnand, try the DS directly to amp (with all precautions, of course ;) ) At least you will have some benchmarks.
Hi Alekz,

Today I have tried the DS directly to the poweramp. The sound is very good and there’s a bit more clearance. There are some ++ and some - - in comparance with the Pre-amp. The Pre is still favorite.

The volume of the DS is at 100 while the PWD was at 94% to reach the same level, but on the lower end the PWD was somewhere around 3% volume while the DS is at 1%. While the DS is at 1% it is not loud, but I would like some levels below 1%.

My serious listening range with the DS would be between 15 and 30. It is already pretty loud than.


#19

Well finally I have finished my pre-amp laste weekend. The first impression with my poweramp was not so good, but it sounded great with my headphone amp from the start.

It is playing for 48 hours now and it is already very open and neutral with a very strong organic soundstage getting better and better.

The volume control makes pretty big steps in combination with my poweramp so I still need the digital volume of the DS for background listening. My Classe pre-amp has some points where it still outperforms my home build pre. But this pre has some great points too. Far more organic power and much closer to live music.

The amp is only single ended, but using balanced cabling. The input for the Directstream has a resistor of 58K between cold and ground. The XLR output to the poweramp has a 100 Ohm resistor between cold and ground.

The power supply is that strong that it took a bite out my screw driver when I exidentely made a short circuit. When Both power cables are pulled the amp can play for almost 5 minutes when all safety circuits are down. Both power circuits are 63Volts close to the shottky diodes. The voltage is lowered to 43Volts in the Amp itself. The safety will take the Amp down when one of the circuits come below 60Volt.

Later I will replace the paper oil capacitors with a matched pair of V-caps on the outputs.


#20

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