Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: tmills on June 26, 2021, 10:32:38 AM
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Good afternoon
I am considering purchasing an EROS 2 but want to ask a few questions first. I am looking to add a little tube warmth. I am not sure if the EROS 2 will work in my system. My system consists of a modified Rega Planer 3, Nagoaka MP200 cartridge, and a Rega phono 3 for source. The preamp is a Pass diy BA3 running a Pass diy 50 watt class A power amp. Speakers are Totem Staafs. I find the Rega phono 3 a little bright on some albums. I listen to mostly rock music. I do not know the output impedance of my preamp but the Eros gain will be fine as the Rega has 42db and that works great for me.
I also want to ask about upgrades. I am willing to spend the money on mods but I don't want to waste it on just upgrading everything. What parts are worth upgrading in the kit. I have two 1uf Stealth caps already to use on the outputs but wonder what other parts will make a difference.
Thank you
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The B3's input impedance looks to be 47K, which is OK for an Eros. The Nagoaka MP-200 is specified as having 4mV of output, so I think you've got the goods to drop an Eros into your system without any fuss.
The 47K/2W resistors and the 75K 1/2W resistors are worth upgrading. Be aware that any resistor that lives in an "R2" position on the boards is outside the signal path and not at all audible. The 75K resistor is part of the RIAA EQ, so be sure to get a 1% part or buy a batch and hand match them. The 47K 2W resistors are not so critical in terms of tolerance.
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Thank you Paul for the info. I can now make my decision.
Todd
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I just ordered my Eros 2 today. Looking forward to getting and building it.
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Thanks for your order!
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Just received my kit today in great shape and quicker than expected. I am looking forward to soldering this weekend!
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Hey guys
I have my kit completed but am having an issue. The 2 led's on the B side of the regulator board do not light up. They lit up when I did my first check on that board. Now that I have everything wired they don"t. All other led's light up. My tubes light up. My resistance and voltage checks were all good. I checked the wiring and it "appears" correct. Would using the upper solder tab instead of the lower one cause an issue. I wouldn't think that it would matter as they are the same tab. I used Mundorf Supreme silver/oil output caps and the leads wouldn't fit in the lower so I used the upper. I also had to go back and solder a 1072F(left channel) on the upper as I forgot it the first time around.
Any advice would be greatly appreciated.
Thanks
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Can you post your voltages? Just about all the time when there are LED lighting issues, there are voltage issues that follow.
Specifically I would want to know all the terminal voltages on the small board up front, as well as IA, IB, OA, OB, KregA, and KregB on the regulator board mounted back on the D socket.
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Thanks Paul
Here are the readings:
IA=293.5V, IB=293.5V, OA=162.8V, OB=162.3V, OC= 99.6V, OD= 99.2V, OKA= 100.2V, OKB=99.4V, OKC=1.8V, OKD=1.8V, KREGA=126.3V and KREGB=124.7
All lights on the regulator board do not light up now.
Thanks
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What are the voltages on the regulator board above the 12AU7 socket?
Seeing 293V at IA/IB on the front C4S board tells me the regulator board back above the 12AU7 isn't working properly. Was it working during your initial testing?
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The regulator board tested fine when I built it. Voltages between 210 and 230 on the actual regulator tops and all LED's lit up. The voltages now are all between 292 and 294 on all points on the regulator board except KregA is 126.3 and KregB is 124.7. The tops of the regulators now measure 293.5 on A and 292.1 on B.
1A= 294V
OA= 291.6
1B= 293.5
OB= 292.0
bA= 0
bB=0
Todd
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If the Kreg voltages on the regulator board measure that high, you probably have a loose or broken wire on that board or connecting it down to the sockets/terminal strips. I would focus on fixing that before really worrying about anything else.
I would guess that the tubes are still glowing properly? The 12AU7 is a pretty easy one to check, and the proper voltages on the forward C4S board would suggest that the front tubes are being properly heated as well.
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Thanks Paul
I pulled out the regulator board and found a loose wire. Newbie mistake. All Led's light up on all boards and my voltages off of the regulator are 218V. Did resistance check again and redid the voltage checks.Everything okay.
Hooked it up........ and have a large ground hum. Rega's don't have a ground wire. What's going on? Am I missing something?
Todd
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Is the hum there with no TT installed? Did you paint both sides of the chassis plate?
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It is only there with the TT installed. I did not paint both sides of the chassis plate.
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If you play a record, is this noise super present? If you cable up an Eros to a turntable and crack your preamp up all the way, you'd probably hear some hum, but you'd never listen at this level, so it's a good idea to be sure that isn't what's going on.
Beyond that, the Rega TTs send the earth connection down one of the RCA cables and combine it with signal ground. This should work just fine with the Eros and only will cause potential problems with a moving coil cartridge and step-up transformers.
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I can't play a record because the hum is super present. That is all you hear. It isn't noise or a hiss. It is 60hz hum and the more level I give the preamp the louder it gets. This is disappointing. I will figure it out. I have been working all day on it and I think I need to just walk away for a bit.
Thanks for your help'
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Yes, I would take a break. If you have a phone with a headphone jack, you can turn the phone all the way down, then up one click, then use that to feed signal into the Eros to be sure it's all working properly.
Hum issues like this are grounding related, and they are generally pretty simple but they can be tough to find.
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I played a record again just to see what would happen. It turns out that the hum is in the right channel only. The left channel is fine. It was just so loud I assumed it was coming from both channels. I will retest tomorrow and check all wiring in the right channel.
I would think it would be on the input side since there is no hum when the input is not connected. It sounded good on the left channel although I couldn't turn it up very loud.
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What happens with the Eros if you only have the left channel plugged in from the TT?
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If I just have the left channel hooked up the Eros plays fine on the left channel with no hum. I switched tubes to see if I had a bad tube. I don't. I will just have to go through all the wiring on the right channel to find the source of the hum. I will have to wait until next weekend to sort this out.
Thanks again for your help Paul.
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How about if you plug just the left RCA into the right channel?
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After a lengthy inspection, I found another loose connection. That is two newbie mistakes. Now the Eros is firing on all cylinders and it sounds amazing!!!
It will just get better as it runs in and those big Mundorf Supreme silver/oil caps burn in.
Thank you Paul for all your help. This is a solid bit of kit but it takes some time and patience to avoid the mistakes that I made.
Todd
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Waiting a day or two and having a second look is a very good way to approach these kinds of problems.
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Here are some pics of the unit. It sounds really good and will only get better as the caps burn in. The finish is straight out of the videos with black hammertone and high gloss clear coat on the alder. The mods were the resistors suggested by Paul and the Mundorf 1.5uf Mcap Supreme Silver and oil caps which just fit. The leads on the Mundorfs were too thick so I had to solder them on the upper tab instead of the lower tab. Other than that it is pretty much straight from the manual.
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Just put together the Bottlehead power cord kit. My Eros is still burning in but the new power cord seems to make certain things a little clearer. Especially drum hits, cymbals etc.
Nice cord. Recommended.
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Hey Guys
Looking for some advice on purchasing some serious tubes for the Eros 2. Want to spend between $400 - $500. Listen to mostly rock music and like a warmish tone. Some of these new pressings are pretty bright sounding.
Any advice would be appreciated.
Thanks
Todd
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I am using GEC CV4085 (the military version of the Genalex Z729) and a USN-CEP Amperex 7308.
I had better luck finding somewhat reasonable prices for the GEC CV4085 from sellers in the UK (ValveTubes worked well for me--I did not spend anywhere near $200 per tube, but I bought mine over 5 years ago) and I got the 7308 from a guy in Southern California who sells on USAudiomart.
Tubemonger sometimes has the flying leads version of the CV4085, which they fit onto bakelite bases, but I think they have been out of stock for a while. When they are in stock, they are relatively reasonable in price.
Mary
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I use the Mullard CV4085 tubes from Tubemonger that Mary mentioned. I also have a pair of Mazda (France) EF86 tubes that sound warmish. I've liked all the Philips family of tubes (Mullard, Bugle Boy, Mazda) I've tried. The Valvo EF86 sounds very clear but also bright, so I'd stay away from them.
Telefunkens might strain your budget, but they're said to be excellent. Tubemonger had some last I was on their site.
for the 6922 slot, I'm happy with a Amperex Holland 7308. I haven't heard them, but I bet the Mullard CV4109 that Tubemonger sells is worth considering.
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Thanks for the advice. I will check into all suggested and let you know which ones I went with.
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Hey guys
For the 6922 I went with an Amperex USA Gold Pin(40% off from $299.95 - so $179.95 at Tube depot). I got a Telefunken Black Diamond EC82/12AU7($79.95). I am going to wait a little while for the EF86's as the ones I want are not in stock. I want to get the Telefunken EF806S/6267 from Tube Depot. If they take too long I will go with the Telefunken EF86/6267 from Tube depot. Going way over budget but I hope it gives the sound I want.
Thanks for the advice.
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The 12AU7 is vastly less critical in the Eros than the rest of the tubes.