I'm still waiting for Mr. Eddy's Buffered Passive Pre-Pre, with >60dB step-up transformer (1:1+1+1). 
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I'm still waiting for Mr. Eddy's Buffered Passive Pre-Pre, with >60dB step-up transformer (1:1+1+1).
Will you settle for 14dB?
se
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You guys make me laugh! Everybody's full of criticisms, and nobody has any idea what it takes to make a successful preamp.
PMA, please put up your schematics for me to criticize. It's only fair! '-)
PMA, please put up your schematics for me to criticize. It's only fair! '-)
Oeww, love the volume knob of that one, big enough to club someone with.
(but the case longs for 2-tone anodised aluminum, with the box joints)
3 of those in series then please, with 1:10 Haufe transformers (to keep it all-nostalgic).
JC mentioned iirc that the configuration with the 1k output termination of DMOS drains was particularly robust against loading-induced instabilities, and such circuits particularly useful for problematic line-driving applications like performance venues and their ilk. Note also that RFI/EMI induced into the output will be less likely to find its way to rectifying junctions, unless quite high-level.
Of course the standard technique is to throw down a high-loop-gain opamp circuit and put a fairly low-value resistor in series to the output connector. Note that the same interference considered above will likely find its way back to the input of the opamp via the feedback network and get demodulated to some extent.
The load-compensated JFET buffer I showed a while back is also rather well-behaved with reactive loads --- the bandwidth degrades gently but it doesn't readily break into oscillation. The trick is to know what the loading is for proper compensation. The buffer linuxguru showed and related circuits is nice as it compensates for loading more-or-less automatically, as long as things stay in class A, nothing "running dry". However I think it is a little more temperamental with reactive loading. I still mean to get round to showing some enhancements of his approach, using some DMOS in place of some of the bipolars.
yet you recommend a device that places the very shiny pot at the other end of a large mostly empty chassis connected with very shiny wiring, when it could have easily made the line level signal path at least 2' shorter... i'd rather make a toy than a vacuous show pony
And you should see them fly! They make great shurikens once you've ground down the skirt to a razor sharp edge.
There is a time and a place for two-tone anodized aluminum. This is not one of them. I'll stick with the ebonite.
Sure thing. What's the rated input on those Haufe's?
se
If I sell as many 515's as you've sold Blowtorches, will that make it "successful"?
se
Dollar volume yes, unit pieces no.
If I sell as many stadium sound systems as Blowtorches does that make me successful? Yes if unit quantity, no for dollar volume!!! 🙂
Just for fun here is a "Million Dollar" circuit. Any guesses as to why and what it does?
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Well, cusp, the passive preamp has the same problem, you know, too much room.
However, the ORIGINAL CTC Blowtorch was EXPANDABLE, and you could order all balanced input and output, an added output buffer to create a LOW Z drive for extra long lines, as well as an added Vendetta phono stage. Very few people actually wanted the extra stuff. We added a few phono boards, a few all balanced inputs, but most people just got single ended input and single ended and balanced output, with polarity reversal. It got pretty lonely in there with just the single ended input and a single ended output, but we were committed to the box, and we did not know what the customer would want until they ordered one. Unfortunately the power supply box is pretty full when a phono stage is added, and the boxes were roughly the same dimensions.
However, the ORIGINAL CTC Blowtorch was EXPANDABLE, and you could order all balanced input and output, an added output buffer to create a LOW Z drive for extra long lines, as well as an added Vendetta phono stage. Very few people actually wanted the extra stuff. We added a few phono boards, a few all balanced inputs, but most people just got single ended input and single ended and balanced output, with polarity reversal. It got pretty lonely in there with just the single ended input and a single ended output, but we were committed to the box, and we did not know what the customer would want until they ordered one. Unfortunately the power supply box is pretty full when a phono stage is added, and the boxes were roughly the same dimensions.
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