Hello Scott,
I also want to know why we need to use big resistors the maximum current i saw on LT spice simulation is 3.5mA which is less than 55mW for 15v ps. I really dont get it.
Jack - NMJ6HF-S Neutrik | Mouser
1/2 watt resistors are great! You can always use bigger dissipation resistors. And the difference between a .4W and a 1/2W is minuscule.
1/2 watt resistors are great! You can always use bigger dissipation resistors. And the difference between a .4W and a 1/2W is minuscule.
to Dneu2011
And - it is an excellent sounding preamp!
I tested it yesterday driving the BA-3 poweramp (BA-3 input board + complementary outputstage) and with my 50W-SE-Schade-amp (which is difficult to drive). Both combinations sounded wonderful!
It has a clearance without any harshness. Bass is also solid and controlled.
Great preamp from Wayne!
Greets
Dirk
And - it is an excellent sounding preamp!
I tested it yesterday driving the BA-3 poweramp (BA-3 input board + complementary outputstage) and with my 50W-SE-Schade-amp (which is difficult to drive). Both combinations sounded wonderful!
It has a clearance without any harshness. Bass is also solid and controlled.
Great preamp from Wayne!
Greets
Dirk
Yes.
Here's a schematic with some notes, I'm going to include these in the parts kit, but it needs to be here as well.
Parts kits? What parts kit? I need to stuff new Diystore board and don't want to strip parts off the old boards you passed out a while ago.
Maybe you mean in Diystore? Guess I should check!
Russellc
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It's not there yet.
If in a rush there are two pre-populated carts in this thread, one Mouser that I made in post #508 a while back, and a Digi-Key cart avdesignguru made in post #1069. (To see that one you'll need to have an Digikey account and be logged in.)
The circuit works just fine with normal metal films and common caps. There's nothing special about the parts in the kit, aside that it has all the parts required to configure it with either the big or the small output devices.
If in a rush there are two pre-populated carts in this thread, one Mouser that I made in post #508 a while back, and a Digi-Key cart avdesignguru made in post #1069. (To see that one you'll need to have an Digikey account and be logged in.)
The circuit works just fine with normal metal films and common caps. There's nothing special about the parts in the kit, aside that it has all the parts required to configure it with either the big or the small output devices.
Mouser has the KSC1845FTA back in stock so I have worked up a Mouser Project BOM for the BA2018. I did some research on Vishay resistors and found that the quietest ones are actually the Vishay/Beyschlag MBA-series. Quieter than the SFR-series typically spec'd by Papa. They are also slightly less expensive and generally more available than the RN55-series preferred by 6L6, with the downsides of no printed values on the body and 100% tin plating on the copper leads instead of tin/lead plating.
This BOM does not have the high power output transistor option. It does have everything in stock as of this posting. I've included a separate excel spreadsheet that includes the device numbers from both channels of Wayne's schematics.
Spreadsheet also has lead spacings and critical part dimensions in case you want to do substitutions. Due to space limitations, the Mouser BOM only shows device key numbers for one channel but the quantities are correct.
Mouser Electronics
This BOM does not have the high power output transistor option. It does have everything in stock as of this posting. I've included a separate excel spreadsheet that includes the device numbers from both channels of Wayne's schematics.
Spreadsheet also has lead spacings and critical part dimensions in case you want to do substitutions. Due to space limitations, the Mouser BOM only shows device key numbers for one channel but the quantities are correct.
Mouser Electronics
Attachments
And - it is an excellent sounding preamp!
I tested it yesterday driving the BA-3 poweramp (BA-3 input board + complementary outputstage) and with my 50W-SE-Schade-amp (which is difficult to drive). Both combinations sounded wonderful!
It has a clearance without any harshness. Bass is also solid and controlled.
Great preamp from Wayne!
Greets
Dirk
Awesome. I am excited to try this out and compare it to my BA3FE. Not sure if it will be powerful enough for an F4, but I am also building M2x mono blocks to use this linestage. A couple more questions I have:
- Can resistor 11 and 12 be changed to 18 ohm instead of 15 ohm? I have a few in my stash.
- As for matching, I saw a few posts that matching is not needed for any of the devices. I just wanted to make sure this is correct.
Those resistors will work just fine and you are correct no matching is needed.
@avdesignguru, assign a "HV" net to all your 115V & 230V traces, and give it a much larger clearance. Otherwise, over time airborne contaminants can collect on the board causing leakage at higher voltages. This is called "creepage", and you can find lots of creepage calculators on the web to help you come up with a value.
Note: for the most part none of them agree with each other.FWIW, I use 2mm but I'm an amateur too....
Thanks for the advice, Jeff. I've modified the power supply board for wider HV trace clearance. For anyone interested, I've attached a zip file with the schematic and the gerber files. Also, a picture of my BA2018 preamp built to match my Whammy HPA.
I split the feed from the preamp input selector switch using isolation resistors and fed it a pair of RCA jacks that connect to the Whammy input. Not sure I needed the iso resistors. Each unit uses a 50K pot, effectively 25K in parallel. They are there in case other setups might create too much source loading and to prevent or reduce possible control interaction.
