Bottlehead Eros Phono Preamp

mrbiron

I know its too late now but I painted all of the screws gloss black and even the silver ring that holds the socket down. It drove me nuts.

Otherwise, it looks OK....

audiocr381ve

Wow, phenomenal work!

ALL212

SHA-WING!

That last little part is the pièce de résistance.

Sometime later this year the Reduction vs. Eros will happen.




(is Rich gonna be pissed when the Reduction wins!!! )

SCompRacer

Thanks all!

ALL212 wrote: »

Sometime later this year the Reduction vs. Eros will happen.




(is Rich gonna be pissed when the Reduction wins!!! )

If that happens, I'll remind you I had a Reduction/Integration ordered but you convinced me to send another 200 to Queen Eileen for the Eros.

How much later? August?

ALL212

I've got two weekends committed now for August (fishing and move a kid to college) so it might be even into September.

mrbiron

I'll send you my Hagerman Bugle2 and then you'll both be pissed

SCompRacer

ALL212 wrote: »

I've got two weekends committed now for August (fishing and move a kid to college) so it might be even into September.

Sunday! Sunday, July 26...we're gonna drag 'em out! Stock Eros against modded Reduction/Integration!

Last touch, add the Cardas ground lug. Working on wide top shelf for rack. No room! Cell phone pic. THIS is one amazing phono pre SQ wise!

mrbiron wrote: »

I'll send you my Hagerman Bugle2 and then you'll both be pissed

That Bugle2 is pretty amazing! I'm scared!

mrbiron

Now that right there is sexy!

agfrost

Probably sucks.

ALL212

No suckage. Eros has better bass, better image placement, better soundstage.
Reduction isn't bad at all but Eros does ramp it up another notch or two!

Send the Bugle!!!

SCompRacer

Thanks for the kind words!

Aaron, it was a relief to hear the extra $200 was well spent.

agfrost wrote: »

Probably sucks.

It sucks lemons and makes lemonade.....lol

agfrost

With all the solder flux fumes you two have been huffing, I'd be surprised if your brain can still process sound well enough to tell.

Seriously though, fun comparison. It's been fun seeing both of your builds take shape.

mrbiron

ALL212 wrote: »

No suckage. Eros has better bass, better image placement, better soundstage.
Reduction isn't bad at all but Eros does ramp it up another notch or two!

Send the Bugle!!!

Get me a shipping address....it's game on!

voltz

Do you still have a Bugle? I though Doc did

analog97

Carl just told me about this.....wowee!!!!! Unbelievable work. Kudos!!!

How does is sound as compared to the Cornet2? Still using mine...

Regards, Larry

SCompRacer

Hi Larry! Long time! Thanks for the kind words!

It's been a long time and lots of gear since the Hagerman Cornet 2 which did sound excellent. I did have a hum with it paired with a ModWright SWLP tube pre amp. Tried everything I know to get rid of it, but failed to. I used the then latest and greatest grounding scheme in the Hagerman too. IIRC Carl had a hum with it and his pre amp too. George Daniel eventually got it and he had no hum in his system. Impedance between gear looked good based on specs so I dunno.

The Eros is a good design. One could stick it in a metal chassis if desired. Folks claim the circuit board is better than point to point wiring but the Eros is quiet and sounds fantastic. It has some fine tubes in it now. Plenty of gain (50dB).

I'd like to build a lower gain SUT to use with it though. I don't need much volume on the pre for 80dB.

No room on the rack so I built a hangover...

SCompRacer

Second upgrade for the Eros, the first being tubes.

Sonicap Platinum's used as coupling caps. I've used and loved Sonicap Gen I and II's, so I am looking forward to these. Jeff and I decided on a pair of L3 (1/2 %) matched .33uf Platinum's to replace the included 1.5uf Solen's. Anybody that has dealt with Jeff knows he knows his way around a crossover or component circuit. Very helpful fellow.

My pre amp SE input impedance is 300K Ohms so we are close to the suggested -3dB Frequency of 2 Hz with the .33uf caps. With couplers, they say less is more.... When you buy gear that has coupling caps, (pre amps, CD players, DAC's) they stick a value in there that will work with a wide range of input impedances, like from 2 to 10uf. This can cause issues like phase anomalies or a dB bump at a particular frequency.

You can calculate the lowest value needed by finding the input impedance of the device you are plugging into and using a calculator, like the one V Cap offers on their web site. They also explain the reason for coupler optimization. Or ask Jeff.

http://www.v-cap.com/coupling-capacitor-calculator.php

vcwatkins

I'm very interested in your thoughts on improvements that come with the cap upgrade. I am just now getting around to painting my Eros plate and can order the same Sonicaps to use from the start if you think it's worth the cost. The Eros will be used with DL-103r and Budgie.

Thanks for sharing your experiences,
Craig

SCompRacer

Hi Craig! I got the caps in and will start burning it in this weekend.

The only bad thing about the Platinums is the cost for higher values. If I had to use 1.0uf as couplers, they are $132 each! 33uf are $61 each. L3 matching (1/2%) is $5 each. L2 (1%) and L1 matching is less. You have to go direct to the individual cap page to add matching. If you add direct to cart, there is no matching option available.

You can also request suggestions from Jeff. He had suggested a Jupiter copper foil as a second choice and a Mundorf RTX as a budget choice. The Mundorf S/G/O is a good cap but it's a 3 section metallized Polypropylene that will really flavor the sound. I'm into neutral true film and foil sound qualities, and Jeff likes to suggest those caps for phono pre amps.

If you use the Platinum's, there is a long and short lead. He suggests connecting the long lead to the RCA out side of the circuit. Have you cut any of that small coax yet? You need to use good strippers as one tiny nick in the solid wire will make it easy to break if you bend it.

SCompRacer

One other thing regarding coupling caps in the Eros. Paul Joppa, the circuit designer, had posted this...

"I have to thank long-time Bottlehead and occasional poster VoltSecond, who first brought this to my attention. The output interconnect is exposed to electromagnetic fields, many of which can impose hum through capacitive coupling. Thus hum is reduced when the impedance of a conductor is low, so a rational criterion is that the impedance of the output capacitor should be no greater than the output impedance of the source at 120Hz, the most common (non-magnetic) hum frequency. The output (source) impedance of Seduction/Reduction and Eros is around 4000 ohms, so doing the numbers we get 0.33uF. That's why Seduction uses a 0.47uF cap. The Seduction cap is a 250v part, so we need a different part anyhow, and the 1uF/630v part was in inventory for the then-current version of the SEX amp - that's how it got into the Eros.

Bottom line - the minimum voltage rating is 400 volts, and the minimum capacitance is 0.47uF. A higher rating ion either variable will not hurt, but it will not buy you any technical (performance or longevity) benefit. That's not to say it won't buy more subtle subjective benefits - if we truly understood those, they would be technical benefits, but they are not there yet."

Since this seems to be theory as test results have not been mentioned or posted, I went with Jeff's suggestion of .33uf couplers instead of .47uf. So I may or may not have an issue. Someone posted there that they used as little as .22uf as couplers in the Eros.

So best to keep that in mind when figuring for your couplers using your pre amp input impedance. I'll let you know if I have any adverse problems.

vcwatkins

Very interesting. Many thanks for the helpful info and heads-up on stripping the coax! I'll try to read up some this weekend. Cheers!

[Deleted User]

Wow! That is real nice. I'm in the market for a new phone pre to try but I couldn't pull this project off so well. I liked the burnt wood look but have to admit this is better.
A show piece in my book.

BlueMDPicker

Rich,

Your undertakings are consistently masterworks in attention to detail. I'm in awe (once again).

SCompRacer

Thank you all for the kind words!

SCompRacer

My concern with this upgrade was the designer said .47uf was the suggested lowest coupler cap to use due to the output interconnect being exposed to electromagnetic fields, many of which can impose hum through capacitive coupling. I had also read that with resistors to ground after coupling caps like the Eros has, bass will roll off with use of lower value caps. Jeff at Sonic Craft was very patient with my concerns and explained his doubt that the .33uf coupler would be an issue for me. You just don’t get a hopeful guess, Jeff really knows his way around crossovers and circuits and explains why. He even offered to cancel my order and send the .47uf but I trusted him and went with the 33uf. My pre amp SE input impedance is 300k Ohms.

My system is diy heavy plinth/heavy platter Lenco idler drive - Advanced Analog MG-1 linear air bearing arm w/ Ultra P arm - AT33PTG/II cartridge (.3mV) - Park’s Audio Budgie SUT (CineMag Blue 1:8 / 1:16 set at 1:8) - Bottlehead Eros - ARC Reference 3 pre amp - Krell KSA-250 - Salk SoundScape 8 speakers - NHT B-12d subs (10,000 cubic feet open listening area) - GIK acoustic treatments.

I used my Granite Audio MC phono burn in CD to put some hours on the Eros before the weekend after installing the Sonicap Platinum .33uf couplers. I am very happy to report the 33uf couplers have introduced no noise in my system. Low level listening is greatly improved. My vinyl is more transparent than before. System is more coherent, and exhibits more realistic ambiance and air. There is no roll off of the bass. I am very pleased with the Sonicap Platinums! A huge upgrade over the Solen 1.5uf couplers. Thanks Jeff!

Vinyl played:

RTI Limited Edition 180 gram 45rpm Melody Gardot / My One and Only Thrill.
Telarc Michael Murray Bach / The Great Organ at Methuen.
Talk Talk / The Colour of Spring remastered import
Skrillex / Bangarang (yeah, I like some dubstep now and then…lol)

SCompRacer

rednedtugent wrote: »

Wow! That is real nice. I'm in the market for a new phone pre to try but I couldn't pull this project off so well. I liked the burnt wood look but have to admit this is better.
A show piece in my book.

It is considered a difficult build. They do provide a nice manual with pics that comes in handy. I'd hate to build one by description/schematic alone.

They have folks that will build kits for pay at Bottlehead forum. If cost is out of budget, one can consider the Bottlehead Reduction with Integration upgrade.

vcwatkins

OT thanks to @SCompRacer . I'm almost done with changes to the den vinyl rig and I'm REALLY diggin the sound so far. The last four simply mimic SComp. Changes made:
- upped the RP6 subplatter to Groovetracer Reference RP6
- upped to Rega white belt
- upped the counterweight to Michell Technoweight
- modded the Jolida JD-9 (op amps, caps, Dynamat)
- switched to AT33PTG cartridge (second DL-103r on way to compare on this TT)
- added Parks Audio Budgie SUT
- bought BH Eros kit and hope to finish Christmas week
- ordered Sonicap Platinum .33uf per posts above

So, thanks SComp for the inspiration to learn and improve!
Craig

SCompRacer

Kewl Craig! Thanks for the kind words! Carl loves his Budgie too! BlueMD is taking a chance on the AT33PTG/II as well. He should have it sometime this week IIRC. I sent him my diy SUT so he can try the LOMC cart with his phono set to MM.

Regarding the .33uf couplers. What is your pre amp input impedance? Did you run it by Jeff?

You're gonna love the Eros! Even with the stock tubes it sounded darn good.

Is the 103r in oem form or does it have a wood or aluminum body? I have a 103r I stuck a Midas aluminum body on mounted on a second arm. As good as it sounds, I love the AT33PTG/II more.



My next project, build a PTP5 top plate Lenco idler drive turntable to match the Eros walnut enclosure.

FTGV

Outstanding project Rich.It has me wanting to build something with those glowy things.

SCompRacer

Thanks Fred! Bottlehead has some nice circuit designs, for tubes. : 0

The Eros sound has very low distortion. I prefer the Eros over the Krell reference MC phono stage I had. The Eros is one of the better phono stages I have heard.

A builder posted a frequency response measurement of his Eros.