Re: B1
One point related to this question is the load has an effect on the source performance. I'm referring in this case to the load as what the upstream source sees at the linestage/attenuator input.
If you use a 10K attenuator, this presents a 10K load to your CD/phono stage/tuner etc. If you use a B1 with 25K pot, the load is now about 25K. This may not seem like a lot, but I have measured a change in distortion when going from a 10K to 25K load. When playing around with circuits, I vary the load and output level while watching distortion. For sources that have tube or no feedback discreet outputs, it is something to be aware of. Most tube output stages would be happier with at least 25K, if not 50K.
Bob
sparky6 said:
One point related to this question is the load has an effect on the source performance. I'm referring in this case to the load as what the upstream source sees at the linestage/attenuator input.
If you use a 10K attenuator, this presents a 10K load to your CD/phono stage/tuner etc. If you use a B1 with 25K pot, the load is now about 25K. This may not seem like a lot, but I have measured a change in distortion when going from a 10K to 25K load. When playing around with circuits, I vary the load and output level while watching distortion. For sources that have tube or no feedback discreet outputs, it is something to be aware of. Most tube output stages would be happier with at least 25K, if not 50K.
Bob
some/many tube (valve) pre-amps do not have much in the way of output current. These usually prefer a high load impedance, anything upto 500k.
Your findings of a change from 10k to 25k load would fit with this.
Another example is the removal of the 1M0 ground reference resistor at the output of a Croft (valve) pre-amp, this is supposed to sound better due to the very slight raising of load impedance without the 1M0//load.
Your findings of a change from 10k to 25k load would fit with this.
Another example is the removal of the 1M0 ground reference resistor at the output of a Croft (valve) pre-amp, this is supposed to sound better due to the very slight raising of load impedance without the 1M0//load.
Thanks and PCB/JFET set available
Thanks for the R1 answer.
I bought two PCBs w/JFETS (NOT to hoard, but to balance!) but plans have changed - I'd be happy to give one up for the same rate as I got them from Pass plus paypal fee if anyone is interested... CONUS is easier, but International a possibility...
-Bill
Thanks for the R1 answer.
I bought two PCBs w/JFETS (NOT to hoard, but to balance!) but plans have changed - I'd be happy to give one up for the same rate as I got them from Pass plus paypal fee if anyone is interested... CONUS is easier, but International a possibility...
-Bill
Hi Bill
Tried to email you, but can't access your email address. I guess you have not been on the board long enough. Please post your email address.
Thanks
Jim
Tried to email you, but can't access your email address. I guess you have not been on the board long enough. Please post your email address.
Thanks
Jim
and there are few valve pre-amps with a recommended load impedance of less than 50k.Nelson Pass said:
Arrrrr... 'Tis a pitiful preamp that a few micro-amps cannot source,
sez I.
That is not an invitation to list ten valve pre-amps that can, it's just a statement of the general requirement for many valve pre-amps.
My power amp needs a bit more "pedal on the metal". So, how can I add around 9-12 dB gain at the B1 or should I wait for B3?
Without the addition of extra parts or a complete change of the topology, the b1 has no voltage gain, it is common drain. So you have to wait for the subsequent models or use the J-BOZ.
With best regards
Flo
With best regards
Flo
single sided B1 Buffer Layout
Offered here is an image of an alternate single-sided B1 Buffer layout. Input capacitors are axial lead, and pads for up to four inputs are included.
Offered here is an image of an alternate single-sided B1 Buffer layout. Input capacitors are axial lead, and pads for up to four inputs are included.
B1 Buffer single sided pc board image
oops, picture was too large. here it is compressed. This board was etched at home using a solution of one part muriatic acid and two parts hydrogen peroxide (3%), and Techniks "press and peel blue" toner transfer sheets to form the etch resist mask.
oops, picture was too large. here it is compressed. This board was etched at home using a solution of one part muriatic acid and two parts hydrogen peroxide (3%), and Techniks "press and peel blue" toner transfer sheets to form the etch resist mask.
Attachments
Can anyone recommend a source for the 25K Ohm Linear Taper Mono Pots?
Also a good switch for 4 sources?
Looking for good quality on a budget.
Also a good switch for 4 sources?
Looking for good quality on a budget.
ebay-i bought 2 mono pots with 24 step discrete resistors for i believe 30 bucks for my b1 and they work great.mouser has a good "cheap" selector switch and parts connexion has a better one or try---you guessed it---ebay
I've used a Grayhill rotary switch before for input selection and they seem nice. I'll have to double-check, but I think this is the model I used:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=GH7102-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=GH7102-ND