Thanks for the explanation, Lee.
Wow! 😀 I paralleled a 47k resistor to R6 (making it 35.6k total) and paralleled 122k to R4 (making it 95.6k total). The midrange became very solid sounding.
But the micro-detail was lacking. So...
I lowered R2 back to 221ohms. 😱 The results are wonderful! The detail is back and the upper end is solid as a tank.😱 😀 As a bonus, I got to turn down the gain on the x-over one full click.
I'm very happy with the end results and plan to stay here awhile. I'll be assembling my next ZV7-T using Lee's inter-stage coupling technique (basically, remove everything between the gain stages but the stopper resistor). I'm very fortunate in that the pcb allows this process without the severing of traces. I just have to relocate two resistors and omit whatever else stood between the buffer and power transistors. This even places pots P1 and P2 in series with R6 and R6a. This way I can adjust offset at the buffer's inputs.
Happy days,
John
Wow! 😀 I paralleled a 47k resistor to R6 (making it 35.6k total) and paralleled 122k to R4 (making it 95.6k total). The midrange became very solid sounding.
But the micro-detail was lacking. So...
I lowered R2 back to 221ohms. 😱 The results are wonderful! The detail is back and the upper end is solid as a tank.😱 😀 As a bonus, I got to turn down the gain on the x-over one full click.
I'm very happy with the end results and plan to stay here awhile. I'll be assembling my next ZV7-T using Lee's inter-stage coupling technique (basically, remove everything between the gain stages but the stopper resistor). I'm very fortunate in that the pcb allows this process without the severing of traces. I just have to relocate two resistors and omit whatever else stood between the buffer and power transistors. This even places pots P1 and P2 in series with R6 and R6a. This way I can adjust offset at the buffer's inputs.
Happy days,
John
Lee, I finished my second amp last night and got to have a quick listen before bed.
First off, it works!😀 In fact, it came up to speed with very little adjustment (CCS P3 for the most part). This is wonderful considering that the first amp took at least a half-hour with back and forth adjustments to all thee pots.
I configured the pcbs so that P1 and P2 are in series with R6 and R6a. I preset the value to 30K and wound up with 10 volts or so at the gates of the gain FETs. Remarkable; thanks for the drawing.🙂
There is a bit of "grain" in the upper register; probably from the Radio Shack metalized film input caps I used. I'll be replacing them at a later date! All suggestions on good, affordable caps would be welcome.
I'll be tinkering with the amp later, today. More info to come.
John🙂
First off, it works!😀 In fact, it came up to speed with very little adjustment (CCS P3 for the most part). This is wonderful considering that the first amp took at least a half-hour with back and forth adjustments to all thee pots.
I configured the pcbs so that P1 and P2 are in series with R6 and R6a. I preset the value to 30K and wound up with 10 volts or so at the gates of the gain FETs. Remarkable; thanks for the drawing.🙂
There is a bit of "grain" in the upper register; probably from the Radio Shack metalized film input caps I used. I'll be replacing them at a later date! All suggestions on good, affordable caps would be welcome.
I'll be tinkering with the amp later, today. More info to come.
John🙂
Hey John 😀 So, this is a ZV7-T with the gain transistors biased up through the buffer 😕 I guess with no R3 and C2, and with P1 moved???
I would watch the offset stability initially.
What are you useing for R2 and R4 values?
Caps??? I use AC Line rated metalized films up to 2.2uF alot. Then when I really think it's getting towards a final version, I go to Parts Express or somewhere and spend a few to many bucks on an audiophile type.
I would watch the offset stability initially.
What are you useing for R2 and R4 values?
Caps??? I use AC Line rated metalized films up to 2.2uF alot. Then when I really think it's getting towards a final version, I go to Parts Express or somewhere and spend a few to many bucks on an audiophile type.
The newer version sounds almost exactly like the original experimental amp with buffers. I think it has a bit more gain, as I can turn the pre-amp/x-over lower than the other channel which uses the ZV7-T w/buffer #1.
I'm happy as can be with the performance. I use to have a CD boost button (for constant directivity horns) turn on with my Hafler P3000. With the ZV7-T arrangement, I am able to operate without the added boost to the top end. As a result, there's less gain in the upper register--which equates to less hash. Yet, I still have the full spectrum.
I never ceased to be amazed at Nelson's ingenuity 🙂 and at the wonderful help from the members of this forum.
John😀
I'm happy as can be with the performance. I use to have a CD boost button (for constant directivity horns) turn on with my Hafler P3000. With the ZV7-T arrangement, I am able to operate without the added boost to the top end. As a result, there's less gain in the upper register--which equates to less hash. Yet, I still have the full spectrum.
I never ceased to be amazed at Nelson's ingenuity 🙂 and at the wonderful help from the members of this forum.
John😀
I don't exactly have a favorite. I have tried their Kimber Kap, their Jantzens and the solens have been around a while. I think the Film/Foil types like their Audiocap PPT Theta is of higher qulity though. But you pay for them too😀 😀 😀
I'm sure you can find good recomendations here on the forum in many threads...
I'm sure you can find good recomendations here on the forum in many threads...
The Kimber Kaps are considerably more expensive than the Jantzen or Solen counter-parts. I won't even consider the Audiocap at this point in time--very expensive!
Lee, are you able to comment on the various sonic qualities of these caps?
I hope you can,
John🙂
Lee, are you able to comment on the various sonic qualities of these caps?
I hope you can,
John🙂
I've been reading for several hours on the "net" and came across what appears to be a fine capacitor. It's called Sonicap. 1uF @ 200 VDC cost $5.80 each. Dimensions: 0.47" x 1.3".
Anyone familiar with this product? I'm about to order four.
John🙂
Anyone familiar with this product? I'm about to order four.
John🙂
The only actual A-B test I did was replacing some Solen's with Kimber's in my Zen4. I could honestly say there was a noticable improvement. My Zen4 did not seem to have much high end anyway but it cleaned up what it had nicely 😀 😀 😀
As I said, I ussually use one or more in ll, "MKP" style, Metalized PolyProp rated for AC Line filtering until I think the amp is tuned up well in the prototype stage. Then I rebuild it into something more finished with the bigger $$$ Caps. I don't think the solen's are much better than your basic Evox-Rifa AC line cap. Ideally, No Cap is good 😀 But, I really hate poking my soldering iron around in a circuit that has $30 caps in it.
Hey, I just happenned to notice something??? Where did that Z2 come from??? Depending on its Zv that could be a problem???
And, I still think you need to change that 221 ohm for a real input resistor like 10k or so. Without a large enough resistor there you are running open loop(No Feedback).
Your high end would improve with R1 being 221 ohms, put them there...
As I said, I ussually use one or more in ll, "MKP" style, Metalized PolyProp rated for AC Line filtering until I think the amp is tuned up well in the prototype stage. Then I rebuild it into something more finished with the bigger $$$ Caps. I don't think the solen's are much better than your basic Evox-Rifa AC line cap. Ideally, No Cap is good 😀 But, I really hate poking my soldering iron around in a circuit that has $30 caps in it.
Hey, I just happenned to notice something??? Where did that Z2 come from??? Depending on its Zv that could be a problem???
And, I still think you need to change that 221 ohm for a real input resistor like 10k or so. Without a large enough resistor there you are running open loop(No Feedback).
Your high end would improve with R1 being 221 ohms, put them there...
carpenter said:
carp
look in your drawer and find dirtiest oilers you have;
if they are too dark for your liking,just solder across them 10n wimas and you'll be there
spend 20 bucks for empty cds and make some burnies at your best friends place ,then musak will sound best......at least better than with 98% of boutique caps
if your health condition allow you that ........look at surplus places and buy few older caps intended (or pulled) from telco equipment ;it's really hard to find better even today
all the best from me
😉
edit: ps.
seems that Apex Jr have some dirt cheap film caps .........
(somebody someday will ask me -what you Serbian boy have with that guy from US o fA............I just like his site .......looks as Dream Junkyard with 5***** (stars) ) hehe
Hi Lee, hi Choky,
Lee, the input zener is for static protection and hasn't been implemented, yet. I was thinking of something along the line of 10 volts considering that more than one volt input will drive this amp into clip mode--or at least it did with the old air-core choke. I haven't measured its voltage output with the transformer that's taken its place.
I tried changing R2 to 10k awhile back and the amp didn't sound very good--dull, muted. It sounds terrific with R2 at 221 ohms. The top end is very articulate--and I do mean VERY. It's so clear, I could probably hear a mosquito fart in the recording studio.😀 😉 😀 Perhaps I could try something around 2.1k?
I'm leaving R1 at 1k because Nelson mentions that the amp can oscillate with inductive loads, which is exactly what that big ol' transformer is, right?😕
The top end is a bit bright, almost to the point of bruising the "golden ears" in my family. They love what I've come up with, though. That's why I thought of trying an audiophile type input cap. Ok, a cheap, audiophile cap.
My step-daughter, the woman who can hear through walls and tell me who's leaving a message on the phone downstairs, was listening to a Mariah Carey CD on my system last night. She mentioned that she had attended the concert that featured the song being performed and that it sounded exactly like the concert. Now, that's quite a compliment, and this woman doesn't mince words. If it's not good, she'll be honest.
Choky, I don't own a drawer of oil caps. Darn. I'll check out the site you mentioned.
Now for something weird: while the amp was operating, I disconnected a clip lead from the grounded pin of C3 (the lead was for the negative lead of my volt-meter). An odd sounding static began to transmit from the horn. After 5 seconds, it didn't sound as if it were going to quit, so I shut down the amplifier. When I fired the amp back up, the static had disappeared. What was that?😕
Anyway, the stereo package is wonderful, just peachy. Thanks for the help along the way, guys. 🙂
Lee, the input zener is for static protection and hasn't been implemented, yet. I was thinking of something along the line of 10 volts considering that more than one volt input will drive this amp into clip mode--or at least it did with the old air-core choke. I haven't measured its voltage output with the transformer that's taken its place.
I tried changing R2 to 10k awhile back and the amp didn't sound very good--dull, muted. It sounds terrific with R2 at 221 ohms. The top end is very articulate--and I do mean VERY. It's so clear, I could probably hear a mosquito fart in the recording studio.😀 😉 😀 Perhaps I could try something around 2.1k?
I'm leaving R1 at 1k because Nelson mentions that the amp can oscillate with inductive loads, which is exactly what that big ol' transformer is, right?😕
The top end is a bit bright, almost to the point of bruising the "golden ears" in my family. They love what I've come up with, though. That's why I thought of trying an audiophile type input cap. Ok, a cheap, audiophile cap.
My step-daughter, the woman who can hear through walls and tell me who's leaving a message on the phone downstairs, was listening to a Mariah Carey CD on my system last night. She mentioned that she had attended the concert that featured the song being performed and that it sounded exactly like the concert. Now, that's quite a compliment, and this woman doesn't mince words. If it's not good, she'll be honest.
Choky, I don't own a drawer of oil caps. Darn. I'll check out the site you mentioned.
Now for something weird: while the amp was operating, I disconnected a clip lead from the grounded pin of C3 (the lead was for the negative lead of my volt-meter). An odd sounding static began to transmit from the horn. After 5 seconds, it didn't sound as if it were going to quit, so I shut down the amplifier. When I fired the amp back up, the static had disappeared. What was that?😕
Anyway, the stereo package is wonderful, just peachy. Thanks for the help along the way, guys. 🙂
dunno for static...I'm sure that you'll figure out what happened.......
there is it:
http://tiny.pl/w95n
and http://tiny.pl/w952
there is it:
http://tiny.pl/w95n
and http://tiny.pl/w952
carpenter said:
look at lower links (in previous post) and I'm sure that you'll find few more alternatives...
who knows-if you mail Steve,mebbe he'll find something else for you
ps.
decent cap is decent ; good 90% at least as 50x costlier one......I think that these caps are decent
if you click on lower link,you'll find some poly and mylar caps in range of 8-10UF............certainly worth trying for that money
hehe.......this days I'll buy printing machine and spend few hours with Photoshop.......doing attractive logo for cap rebadging ................
.............mebbe soon I'll have my own forum.......
Choky, you're a bad boy
😀I called Steve; he'll get back with me tomorrow morning. Thanks so very much for the link. This one a keeper for sure.
John🙂
So, I guess Mundorfs would be out of the question too😀 😀 😀
http://www.partsconnexion.com/catalog/CapacitorsFilm.html
http://www.partsconnexion.com/catalog/CapacitorsFilm.html
now you are bad boy..........who's talkin' about silver?
if that s**t was good for Kondo......................
if that s**t was good for Kondo......................
I'd love to have a pair, actually 4 for stereo ZV7-T, but that'll have to wait until I'm back at work.😀 and have some bills paid.
That was a great link, too. Thanks, Lee.
John🙂
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