Bottlehead Kits > Eros Tape

Finally assembled, but not sounding great

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vakman:

--- Quote from: Doc B. on November 05, 2019, 05:06:48 AM ---It's not super clear from the images but I am guessing that you pull the gray repro head cable plug from where it is plugged in to the internal preamp as shown in the photos, and re-plug it into the little header on the RCA jack board, which feeds the RCA jacks closest to the header to create a direct head output. Is that correct?

That looks like it should work. I would suggest running a tone tape and determining what the frequency response is like. You can use a Y adapter at the output of the Eros and feed the signal from the extra output of the y adapter back to the line input of the deck. That way you can monitor the line in signal on the Technics meters. This would help determine of the issue is between the head and the Eros or the Eros and the rest of the system.

Do you know the input impedance of the preamp that the Eros output is connected to? It is best if it is above 15K ohms, and short cables, like 1M or less are best. Interconnect cable capacitance is usually spec'd by the manufacturer or if you have something DIY you can usually look up the spec of the cable used. It is spec'd by the foot, ideally something low like under 20pF/ft. You want the lowest capacitance possible from head to Eros, and low capacitance from Eros to preamp as well. If you DIY cables, there are several foamed teflon coax cables that are around 17pF/ft that work well.

--- End quote ---


Thanks Dan, I'll try and give it a go by running a tone tape (if I can find one) and will try and pick up a set of low capacitance cables over the next few days.

But otherwise, guessing the Eros has been built correctly, if all the voltages are in line with specifications. I mean is there a chance the resistors are not correct, as my construction manual for the Eros is dated October 6, 2013.

I've included a slightly better resolution photo of the circuit board if that helps.

vakman:
Ok, I think it’s fixed. Just needed to flip a switch on the main preamp to increase the gain. Not sure why, as I would have thought the Eros had more gain than the inbuilt Technics preamp.

Now, because I increased the gain, now have a very noticeable hum coming from the speakers

Paul Birkeland:
I would recommend taking a smart phone and playing a 60Hz tone into the Repro with your phone's volume set to the lowest setting above mute, then use your meter to measure the AC voltage coming out of the output jacks. 

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