The gain is set by the input resistors (Ri) from the DIP switch and the feedback resistor Rf . For non inverted opamp, gain is (1+Rf/Ri). Default values for BTSB are for 0dB, 6dB, 14dB, and 20dB. Simply selecting the 14dB switch will get you what you need.
Note that for the 14dB setting, Ri is 1.24k and Rf is 4.99k. So G=(1+4.99/1.24)=5.0x or 14dB.
Note that for the 14dB setting, Ri is 1.24k and Rf is 4.99k. So G=(1+4.99/1.24)=5.0x or 14dB.
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Have you made a Yarra preamplifier? It can accept different preamp core modules (7 and counting). This changes the sonic signature. Very useful and capable preamplifier.
The YARRA Preamplifier/HPA for Melbourne DB Group Buy
If you have the Yarra already, other good things to have on hand:
SFP soft start board
SLB Class A PSU board
Aksa Lender preamp
Lately though, one of my favorite amps is the FH9HVX 100w Class AB for many different uses.
The YARRA Preamplifier/HPA for Melbourne DB Group Buy
If you have the Yarra already, other good things to have on hand:
SFP soft start board
SLB Class A PSU board
Aksa Lender preamp
Lately though, one of my favorite amps is the FH9HVX 100w Class AB for many different uses.
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Thanks.
Yes pretty much finished the Yarra, just waiting for the new MOSFET's after my little screw up the other day, need to find a case for it however.
The FH9HVX AB amp looks interesting, I saw it on your Etsy page the other day, never thought I'd consider a class AB amp but it would be nice to compare and contrast next to your reference TPA3255 and the 3E mono blocks I put together.
Yes pretty much finished the Yarra, just waiting for the new MOSFET's after my little screw up the other day, need to find a case for it however.
The FH9HVX AB amp looks interesting, I saw it on your Etsy page the other day, never thought I'd consider a class AB amp but it would be nice to compare and contrast next to your reference TPA3255 and the 3E mono blocks I put together.
I am working on a verification build of an ultra compact BTSB with XLR/TRS and RCA panel mount jacks. It will be ideal as a universal front end input for a lot of projects. It’s going to be mostly 0603 SMT components for compactness. Jhofland is using an OPA1637 now for the balanced driver. One very cool feature is that this board has auto switching relays that control whether or not single ended RCA’s are being used and switches the RCA off when a TRS or XLR is inserted. Everything will be powered with a single 12v input as usual. I am not sure how many people want to attempt building an 0603 SMT project so I am exploring how much interest there would be in a RTR prebuilt and fully tested unit.
Panel jacks will be Neutrik XLR/TRS combo with lock. RCA jack will be premium Elecon (gold plated with Teflon insulators and high density thermoplastic body - same as on Yarra preamp). Board simply hangs off the panel jacks which are screwed in with own mounting screws and RCAs have main body nut.
Schematic:
Panel jacks will be Neutrik XLR/TRS combo with lock. RCA jack will be premium Elecon (gold plated with Teflon insulators and high density thermoplastic body - same as on Yarra preamp). Board simply hangs off the panel jacks which are screwed in with own mounting screws and RCAs have main body nut.
Schematic:
Attachments
Each XLR/TRS jack has 11 pins to secure the board to the jack which takes all the stress of insertion and removal. The RCA jacks have two mounting pin bosses and two conuctors for a total 30 soldered points of mechanical connection to support the relatively small PCB. Adding holes on the back edge of the PCB would require exact holes on two 90 deg surfaces to line up perfectly. I don't think screw support holes for extra standoffs are necessary.
All assembled and waiting for the combo 90 deg Neutrik XLR/TRS jacks to arrive. A new Meanwell isolated DC/DC converter provides regulated +/-15v rails for some extra headroom to drive low gain power amps.
Detail of new OPA1637 balanced line driver:
Detail of new OPA1637 balanced line driver:
Attachments
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Wish I had waited for the new board now as this would have been perfect for the current project.
Any plans to do a version that incorporates a volume control ?
Any suggestions for a simple volume control with the current boards ? Ideally after the BTSB Buffer but I am sure there are other points of insertion such as before the output stage.
Any plans to do a version that incorporates a volume control ?
Any suggestions for a simple volume control with the current boards ? Ideally after the BTSB Buffer but I am sure there are other points of insertion such as before the output stage.
Search on eBay for
CS3310 volume
Apparently some of the finished units are very transparent
include a remote and source switcher
I was hoping to find a way to integrate with the BTSB board, to get choice of SE or fully balanced on input or output
also allowing for wiring over long distance between the preamp and power amp(s)
Some say they prefer a VCA for volume control, but none have actually tried the CS3310 solutiin, and afaik there is no way to control a VCA with remote
CS3310 volume
Apparently some of the finished units are very transparent
include a remote and source switcher
I was hoping to find a way to integrate with the BTSB board, to get choice of SE or fully balanced on input or output
also allowing for wiring over long distance between the preamp and power amp(s)
Some say they prefer a VCA for volume control, but none have actually tried the CS3310 solutiin, and afaik there is no way to control a VCA with remote
Hi X, I am very interested in this last BTSB version and for example I personally don't have any problem with 0603 size. BTW is there any benefit from OPA1637 vs LME49724. And aproximetly with prices components in EU (mouser store) is a little advantage for me buy bare PCB with non populated components.
Let me make sure this board works and if you are interested I can certainly offer it as a bare board. Many people shy away from stuff smaller than 0805, and in some cases 1210 causes heart palpitations. 
I think specs on OPA1637 are better from low idle current standpoint (~1.5mA). The THD is not as good as LME47924 (0.00003%) - but 0.0001% is fine for audio use. It doesn’t have a belly pad so technically could be soldered without using paste. Although the pin pitch is tiny.
I think specs on OPA1637 are better from low idle current standpoint (~1.5mA). The THD is not as good as LME47924 (0.00003%) - but 0.0001% is fine for audio use. It doesn’t have a belly pad so technically could be soldered without using paste. Although the pin pitch is tiny.
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The new BTSB Panel Mount edition checks out beautifully. Everything works as it should. The relays auto click and clack to disengage the RCAs when a balanced plug is inserted (XLR or TRS). Gains check. The polarity of the SE outputs check as well. Even mono in via the TRS with RCA adapter checks. The relays do indeed disconnect the RCAs as that was checked. Another super design from Jhofland!
