Are you asking about the new Balanced/SE to Bal buffer or the amp’s input? The amp is already 100k.
Let’s check with Jhofland if that’s possible. The boards have been ordered already. I’ll post the schematics, PCB image and details in a new thread later tonight. It will he called the BTSB (Best Thing Since-sliced Bread) Buffer. It does it all: Bal/SE in to Bal/SE output with selectable 0dB, 12dB, and 20dB gain. All using state of the art low distortion OPA1656 and LME94724 IC’s. Built in dual rail +/-15 PSU requiring only +12vdc input.
Hi guys,
can somebody please help me? I would like to find some project about equalizer or correction ( I don't know how to correctly translate it). For example I am looking for something as Schiit Audio Loki. Is there any project on DIY Audio which is proved and functional?
Petr =)
can somebody please help me? I would like to find some project about equalizer or correction ( I don't know how to correctly translate it). For example I am looking for something as Schiit Audio Loki. Is there any project on DIY Audio which is proved and functional?
Petr =)
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A tone control preamp is something we have considered and actually have a design and layout under development by JPS64. Just never thought people liked it enough as we all use our PCs or DSP for EQ now. I never use it myself. But let me ask JPS64 if he wants to share the design publicly.
Yes, see that tiny black brick in between the two XLR jacks? It has 5kV isolation from the input, and is very low noise. I added a 100uH and 4.7uF CLC output filter in addition to the built in filter.
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The SE/Bal to Bal preamp works great. Just tested it and it works as expected. Clean, no noise and gives the gain needed to drive the TPA3255.
I am using a 12v 1000mA Class 2 wall wart adapter. I am also using RCA to mono 1/4in TR plug adapters in the combo Neutrik jacks to emulate an RCA input jack.
I am using a 12v 1000mA Class 2 wall wart adapter. I am also using RCA to mono 1/4in TR plug adapters in the combo Neutrik jacks to emulate an RCA input jack.
Attachments
That’s good news!!
It turns out I totally forgot that my Traktor s8 DJ control is also a DAC with balanced output. I’m waiting on a pair of CLR cable from Hosa and I’ll be able to make it play some music. Should arrive next Thursday.
Concerning the input impedance of the buffer, did you get some answers from Jhofland?
It turns out I totally forgot that my Traktor s8 DJ control is also a DAC with balanced output. I’m waiting on a pair of CLR cable from Hosa and I’ll be able to make it play some music. Should arrive next Thursday.
Concerning the input impedance of the buffer, did you get some answers from Jhofland?
Typo is 0.047uF 100v X7R 1206 should be 0.01uF 100v 1206 X7R. Please use this cap for C133, C261-264:
VJ1206Y103KBBBE31 Vishay / Vitramon | Mouser
For R1021 to R1024, use anything from 10R to 220R. I have found 51R to be a good compromise.
The common mode impedance is quite a bit higher than the 75K you would calculate looking at the input circuit because of the bootstrapping. While I haven't tried it, it would surprise me if you would have an issue using even a 50K pot.
Okay, first sound check conpleted, everything is working as it should and it sounded good. I’ll do a real listening session as soon as I can.😀
Would a 4.1V rms (full scale - not sure what that means) preamp be powerful enough to drive this amp bearing in mind the low gain?
15dB gain is 5.62x gain x 4.1vrms is 23.0 Vrms output. That’s good for 66w. Quite loud but not close to the typical max of 120w at 8ohms. You want 31.6 Vrms output to hit clipping.
So you need a preamp capable of 5.62 Vrms. That’s about 16Vpp.
The new SE/Bal to Bal preamp that I just tested will serve that purpose well and give you SE to balanced conversion.
If you replace the the PFFB 2k7 input resistors ( A, B, C, D) with a jumper (0R), your gain will be 22dB and 4.1vrms should be fine. THD increases about 6dB, but still very low.
So you need a preamp capable of 5.62 Vrms. That’s about 16Vpp.
The new SE/Bal to Bal preamp that I just tested will serve that purpose well and give you SE to balanced conversion.
If you replace the the PFFB 2k7 input resistors ( A, B, C, D) with a jumper (0R), your gain will be 22dB and 4.1vrms should be fine. THD increases about 6dB, but still very low.
I got a spacer for the heat-pad machined today.
It provides the required clearance for the chip and the capacitors.
Fine adjustment is possible by filing down the bolt pads to exact height.
I'm attaching the GibbsCam file.
If someone has access to a machine shop it should be a breeze to make.
I used a 2"x0.25" flat bar of aluminum.
It provides the required clearance for the chip and the capacitors.
Fine adjustment is possible by filing down the bolt pads to exact height.
I'm attaching the GibbsCam file.
If someone has access to a machine shop it should be a breeze to make.
I used a 2"x0.25" flat bar of aluminum.
