I was using a Quickie that had the Speco transformer mod for high impedance headphones, which is about 3dB down at 80Hz, as a line stage.
Is there going to be a package deal?\
Give me a little time and I will get the order buttons up on the website.
could you also put in a button for ordering the Seduction base with the Quickie?
... I'm using the Specos there too. Do you know of a high quality 4K:500 output transformer or have any plans for working with Mikey on one?Yes, I have asked Mike about the B7 parafeed line output, in either 5K or 8K primary, 500CT secondary (with a 125 ohm tap available). It would cover a wide range of headphones as well as being a decent driver of 500 ohm loads, balanced or single ended. If you have the bucks, this can even be stacked with 80% nickel laminations for extremely high inductance and low distortion.
PJ asked me to mention that since this current source compensates for the B+ changing as the battery runs down PJCCS stands for the Paul Joppa Compensating Current Source.
Is it worth bothering with these if we've already loaded the plates with chokes, though? (I mean, in place of the chokes - are CCS's better for sound quality?).What if Nicad's were used for power, would there be an advantage of the PJCCS over a choke?
...I see I may have been too consistent in my responses lately ... :^) It's not an experiment I have done. But here's one I did do:
I can almost hear the response of "try it and let us know" ...
I assume you can use the PJCCS with the headphone design?
I think I posted on the old forum but can't find it right now. Anyhow, the problem is the battery voltage will drop as they age. Using the fixed bias of an LED in the cathode will cause an exaggerated change in tube current as the battery ages; the cathode resistor provides negative feedback at DC to maintain the appropriate operating point.
A quick look at the curves shows the plate current dropping from 2.5mA to 1.0mA as the battery drops from 36v to 24v.
A reasonable solution would be to use a current source to replace the plate load - that way the tube maintains a constant operating point, and operation will cease suddenly when the battery no longer provides sufficient compliance for the current source. I'd suggest 1.5mA as a good value to use. Note this will not work well for headphone operation where a substantial output voltage is going to be needed, unless you also add more battery voltage. Now this is starting to get complicated!
I assume you can use the PJCCS with the headphone design?Yes, it is designed to adjust the current as the battery ages.
No, that post is old - it's actually what started me thinking about a self-adjusting current source. The PJCCS should work well and give fairly good battery life whether implemented as a preamp or as a headpone amp with output transformer.......
Would the above long post apply with the PJCCS, too?...
No, that post is old - it's actually what started me thinking about a self-adjusting current source. The PJCCS should work well and give fairly good battery life whether implemented as a preamp or as a headpone amp with output transformer.......
Would the above long post apply with the PJCCS, too?...
Does the PJCCS offer the same gain increase as the Hammond choke modification?Yes. :^)
I have a choke mod Quickie and can't give up a db of gain.
I'm having trouble with wiring up the PJCCS I just received. The PCB is a bit different from the one pictured in the manual and some solder points are missing/not the same. The partially stuffed board is here:
http://picasaweb.google.com/103078014592468973736/Bottlehead#5537786106126040610
In short, p.13 talks about soldering a wire from points bA to bB with an "S" shaped wire. My board has no such points, though it has all other solder points in different orientations from the manual. I can't make sense of the solder points that DO exist to match them to the board as represented in the manual. Can anyone help me figure out what points are the bA and bB on my board?
Thanks.
Edit: Hnmm. I can't seem to get the pics to post, so I've tried just posting the link.
Thanks, guys. In looking it over, I just assumed though different, the two boards could both be wired to work. The only issues I figured I'd have are the "s-shaped" wire connector between bA and bB and the connections to the quickie circuit. If there is a way to do this without the Queen having to send a replacement board, I'm happy to take instructions for how to wire this board properly. If all traces are visible on the board I have, I may be able to figure it out from the manual photos and schematic. If I can't work it out, I'll call her.Yes, the board you have should work just fine. I'll dig up the board designs and try to describe how to hook it up, but it may take a few hours.
Oh, note too that the transistors I got don't have the metal ground plate on the back for orientation. I assumed the side opposite the one with writing was the same as the metal plate (per most transistors I've used). If anyone thinks I've got it wrong, please let me know.
Carl
.
old board new board
O OA
I IA
- (-reg)
K Kreg
- -reg
+ breg connected to rreg
G bA
Of course for the PJCCS you only use the I, O, and G connections; the rest are for the shunt regulator function which is not used