EAR834 Clone Phono Stage Pre-amps: Chassis Layout Explained.

This is a two part video about the EAR845 clone preamps I have featured on two different build series, showing some tricks I have learned and why they are laid out the way they are. This is in response to a bunch of emails and forum traffic from people trying to build these and having problems. I hope this helps explains why they are built specifically like they are!
Here are some affiliate links I mentioned in the video.
Here is a great book explaining how and why of tube amp construction:
amzn.to/3NHd0JN
Here is a link to the peak meter I use:
amzn.to/3NoxlTN
You can contact me at stephe(at)skunkiedesigns.com
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[@ericlane5949]

Turning the unit sideways magically moves the rca’s to the side, the power switch to the front and triples the visible glow of the tubes. Pure sorcery!

[@dennismag]

I just purchased one of these Phono Preamps from Skunkie. I have a Project Debut Carbon turntable with an Ortofon 2M Bronze moving magnet cartridge. Just Great!! My setup has never sounded this good! Not sure how you could ever beat this phono pre at this price range!! WELL DONE!!!

[@SkunkieDesignsElectronics]

Thanks for the review and I do agree, it sounds amazing!

[@abxaudiophiles]

Let’s go!! Happy Saturday peeps. Morning Skunkie. 😊😊

[@VinylRescue]

Yeppers! 🤠🤠Makes sense, like you explained in your earlier videos. I do like it that your newer build have the tubes up a bit higher. I have your series saved for future reference.

[@andyfarmer2661]

"Are we listening to this or are we looking at it?" Quote for the day. Thanks for a brilliant video on pre-amp layout issues. Really good stuff here. That EAR clone board I bought so long ago keeps staring at me while I busy myself with other projects. Perhaps this will get me moving. I particularly think your layout of the RCA jack locations is helpful. I was tempted to move those but I think you are right. I recently built a Coronet3 with one of Jim Hagerman's boards and took the risk to move the input RCA jacks to the rear panel. I was prepared to move them back to the front if it made noise but in this case it worked. The amp is dead quiet. However, the board is quite compact and I have room in the case I employed to move the shielded cables away from everything. Also, this design lacks a traditional power transformer, but instead takes DC from a separate power brick and employs a boost converter to get it to tube operating levels. With the larger EAR clone board and a traditional power supply and transformer your layout is just perfect. These signals are so low level it doesn't take much to stir up trouble. You did a nice series on the Little Bear phono pre. In that design the power switch is in the front and the wires run right past some very low level signals. You twisted the cables to good result. I tried that, and wrapped them with some shielding tape, but still notice a slight hum, not one you can hear from the listening position, but not dead quiet. I have thought about putting a switch in back and just running dc to the front switch for the light. That might be too confusing for the user though. Maybe just remove the front switch altogether. Too many projects, too little time.

[@andyfarmer2661]

My mistake. It wasn't a pair of RCA jacks that I moved on that Cornet3, but rather the power input. Given the way this amp works perhaps not such a risky move.

[@SkunkieDesignsElectronics]

Yeah if the input voltage is filtered DC from a brick, that changes things for sure.

[@johnstuchlik5828]

​@@andyfarmer2661 how do like the cornet? Which tubes are you using?lm considering building something similar but power by linear supply.

[@andyfarmer2661]

@@johnstuchlik5828 This thing is fantastic. It uses a two stage passive EQ similar to Allen Wright's designs. Brilliant. I have this sort of long term project of a tube preamp with a phono stage and I wanted to explore this type of EQ. Here it is super detailed and natural sounding. Everybody notices the bass, accurate and not lacking or muddied. I am using the tubes Steph recommends for her phono stages (EH7205) for the amplification stages and a similar quality 12AU7 for the output buffer. I was a little afraid of the power supply design but I have to admit it is super quiet, like put your ear up to the speaker with the volume cranked to even detect noise from it. Since it sounds good I think it has slowed me on the EAR project, but I am still quite curious to see how they would compare. It sounds much better than the modded Little Bear T11, but I think the EAR is going to be much tougher competition. I won't know until I try.

[@김바-b4z]

It's the phono amplifier that I put together in August 2022 The output is high.

[@SkunkieDesignsElectronics]

Yes it does have a hot output, and the problem is?? It's actually hot enough where it works well with HO/MC carts.

[@cobar5342]

Well done. Thank you

[@ClearOutSamskaras]

Steph, a couple of questions: This is of course a clone of the EAR 834p. The original EAR never had a mono switch as some phono stages do, and so naturally you have not included a mono switch on the clone either. I plan on getting some vinyl records that will be mono pressings. With the EAR/EAR clone if one plays a mono record with them and uses a mono cartridge is that enough to get the intended sound from a mono record? Are mono switches on phono preamps unnecessary? Is a mono cartridge sufficient?

[@SkunkieDesignsElectronics]

I can't honestly answer that one, sorry.

[@836dmar]

All well-said!

[@plinkyplanky9651]

Hi is there an advantage to using this kind of transformer than a toroidal one that was on the original 834? I'm new to all this and trying to learn Thanks

[@SkunkieDesignsElectronics]

I'm personally just not a fan of toroidal transformers.

[@plinkyplanky9651]

@@SkunkieDesignsElectronics Ok , thanks, i'll investigate further....i'm building your 'colour' pre and ear834 type phono stage amps...thanks for posting the info needed to build them. Appreciated.

[@danielbal5272]

I have two questions. Will this pre-amp work with moving coil cartridge? Where can I buy the kit? Thanks - I enjoy your videos

[@SkunkieDesignsElectronics]

You would need a SUT. I would never try to do a tube only MC pre-amp, it would be too noisy. There is no kit. You can find these boards on ebay and it's DIY from there.

[@jackstanley3529]

As a long time audio hobbyist with electrical eng background who has built & modified several phono preamps, I cannot agree with you more on the importance of the layout. Preamps can be plagued with hum issues and can easily be set into oscillation in the hundreds of kHz which may only appear as a hum but can result in damage to downstream equipment. The bottom line to those not technically knowledgable and equipped with the necessary equipment, as you have stressed repeatedly, is to not deviate from a design that works well and most of all is stable.

[@aquaescape411]

Wondering if the BOM on your website for this is up to date for the new build? I.E. new chassis size/ standoffs/ fuse?

[@SkunkieDesignsElectronics]

probably not, I'll take a look at updating it.

[@cured808]

I used it recently and all went well. I think some parts are discontinued but replacements worked fine.

[@SkunkieDesignsElectronics]

That's the problem listing part numbers, many, especially semiconductors and caps, change all the time.

[@jangrinaert]

Correct grounding was the finishing touch. I had the ground on the PSU side connected, and when I connected the ground on the other side of the board the noise floor was slightly lowered, which for the life of me I can’t explain🙂. I had already lifted the signal ground with 100R/100nano paralleled, but that had no effect.

[@PhetrusX]

Hi and thank you for all the great things shared in this channel, I'm in the process of building one of these 834p kits, I don't know how's it in the other pcbs sold on ali, but I just discovered in mine the grounding point (little triangle) for TT isn't connected to anything, it's isolated on both sides of the PCB so connecting it via wire to the chasis doesn't probably change anything, and if so should it be rewired to the PCB's ground or just left unused?

[@SkunkieDesignsElectronics]

I covered this in one video, that's an error on some of the boards, that pad needs to be connected to the ground plane on the bottom next to that spot, opposite side from the tube sockets. Just scrape off some paint and add a jumper.

[@PhetrusX]

@@SkunkieDesignsElectronics ouch I must have missed that one, gonna look for this video right now, thank you.