I recieved test data on the oscillator and it does seem to meet the advetized spec. That's great news. Now I just need to be able to measure it here... and then I can get the true harmonic level of the headphone amp.
Well, now that everyone has gone to sleep! 
The n jfets sourced from Tayda2009 turned out to work just fine.
My ebay source had some p fets (mark on body shows CAL???) and those turned out to be pretty good. I have several matches now between .8 and .9 volts as Mr. Marsh indicated.
I've tweaked the board layout enough, so I will print up some sheets this weekend and get ready to do some etching. Photos to come.
Oh, and the transistors I bought from Jan are matching quite well... Vbe very close to one another...not much difference..about 1/100 of a volt...nice.
I'll have more info coming up...there are sources out there that have good pricing on the transistors but I'll post that when I get my order in!
The n jfets sourced from Tayda2009 turned out to work just fine.
My ebay source had some p fets (mark on body shows CAL???) and those turned out to be pretty good. I have several matches now between .8 and .9 volts as Mr. Marsh indicated.
I've tweaked the board layout enough, so I will print up some sheets this weekend and get ready to do some etching. Photos to come.
Oh, and the transistors I bought from Jan are matching quite well... Vbe very close to one another...not much difference..about 1/100 of a volt...nice.
I'll have more info coming up...there are sources out there that have good pricing on the transistors but I'll post that when I get my order in!
And here I thought you had been seduced away by the sweet, sweet talk of discrete op amps!
Stock tip!
Well, not a stock tip, exactly, but a tip, nonetheless!
Now that I have my transistors on order, if some of you don't know already, here in the States you can get some parts much cheaper at Avnet Express. They have the BJTs in stock for a very, very good price. The SMT jfets are also in stock and I ordered a very small amount (25 each) to see how they measure. The small signal BJTs can be had for just over a penny in large quantities. You can get hundreds of 'em and not break the bank!
Well, not a stock tip, exactly, but a tip, nonetheless!
Now that I have my transistors on order, if some of you don't know already, here in the States you can get some parts much cheaper at Avnet Express. They have the BJTs in stock for a very, very good price. The SMT jfets are also in stock and I ordered a very small amount (25 each) to see how they measure. The small signal BJTs can be had for just over a penny in large quantities. You can get hundreds of 'em and not break the bank!
Some back-up numbers -
I got to use Demian Martin's ShibaSoku gear as another crosscheck --
THD ref 1 volt at 1KHz was .0005% 2nd and 3rd --- other harmonics are approx -20db or more down from the 2nd and 3rd (viewed via FFT).
S/N ( 1v and input shorted but 30KHz cutoff) = -106dB. It can reach -110db if a quieter power supply was used and with a reduction in fb and gain resistor values (but same ratio-gain).
Thx Demian -Richard
I got to use Demian Martin's ShibaSoku gear as another crosscheck --
THD ref 1 volt at 1KHz was .0005% 2nd and 3rd --- other harmonics are approx -20db or more down from the 2nd and 3rd (viewed via FFT).
S/N ( 1v and input shorted but 30KHz cutoff) = -106dB. It can reach -110db if a quieter power supply was used and with a reduction in fb and gain resistor values (but same ratio-gain).
Thx Demian -Richard
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Very nice feedback!
I couldn't resist buying some more pfets. As it turns out, this fellow has had them for some time from a video game company that closed in '96. When I got the package a couple of days ago, I was shocked to find they had gold leads and a little M logo. The good stuff!!
I'll have some pics soon on my actual progress....finally.
I couldn't resist buying some more pfets. As it turns out, this fellow has had them for some time from a video game company that closed in '96. When I got the package a couple of days ago, I was shocked to find they had gold leads and a little M logo. The good stuff!!
I'll have some pics soon on my actual progress....finally.
So many things going on and very little real meat to report, but here goes:
I found someone selling some LT1963A regs for half normal price on ebay and I got 8 pieces on the way. A really nice find!
I also placed an order to Digi-Key to get some transformers. I bought a pair of Triad Magnetics dual bobbin types so each channel gets its own xformer. I also will keep them in a separate box on a floor and not in an all-in-one configuration. But I will have the regs right up against the amp circuit, as you recommended.
This weekend was way too hectic to do anything useful as my 5 year old celebrated her birthday and that was a real adventure! But I want that board etched and drilled ASAP because I have all the other parts available now to build the amp circuit. It really is time to get the show on the road!
I found someone selling some LT1963A regs for half normal price on ebay and I got 8 pieces on the way. A really nice find!
I also placed an order to Digi-Key to get some transformers. I bought a pair of Triad Magnetics dual bobbin types so each channel gets its own xformer. I also will keep them in a separate box on a floor and not in an all-in-one configuration. But I will have the regs right up against the amp circuit, as you recommended.
This weekend was way too hectic to do anything useful as my 5 year old celebrated her birthday and that was a real adventure! But I want that board etched and drilled ASAP because I have all the other parts available now to build the amp circuit. It really is time to get the show on the road!
No major updates other than fine tuning my board layouts, including changing the layout a bit for the voltage regs. I wanted the LT1963A thru hole part but found the great deal on the DD package.
Work has been hell but in 2 weeks we're done with our major project. So I'm taking several days off in November and December and get this all done! I'm tired of sitting there just looking at the parts.
Work has been hell but in 2 weeks we're done with our major project. So I'm taking several days off in November and December and get this all done! I'm tired of sitting there just looking at the parts.
Hi everyone, I'm quite intrested in putting one of these together and understand that the build & schematic etc. is covered in issue 3 of Linear Audio magazine. Until I'm ready to start I'll leave the technical questions to one side...
PCB's .... are any available to purchase, or like Sonidos is doing, does the layout and making of the boards need to be done one's self?
Paul.
PCB's .... are any available to purchase, or like Sonidos is doing, does the layout and making of the boards need to be done one's self?
Paul.
This site/forum is just to answer questions and offer advice on building. The design is not here, either. The design is shown and described in Linear Audio publication. The pcb have been available for quit awhile thru the publisher. The design offers superiour performance with minimal parts cost. This site here is more about DIY designing and modifying and collaborating on design and on the construction et al. This one is all done. Nothing to do but built it and listen to music. Thx for your interest - Richard Marsh
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Once again, thanks. A copy of LA #3 has been purchased, are the pcb's only available to order directly through the publication and not the web site? [not including jackinnj's offer]
Without having yet read the article, is there scope for changing the gain of the amp. Is that something that's covered within the publication, or something that can be discussed here.
Paul.
Without having yet read the article, is there scope for changing the gain of the amp. Is that something that's covered within the publication, or something that can be discussed here.
Paul.
I had some time last night to mess around and I decided to measure the hfe on the small signal BJTs I purchased from Avnet. The npn's are Fairchild and the pnp's are OnSemi. So the good stuff.
I sampled about 10 each. Like previous experience, the NPNs were all pretty closely grouped, and the PNPs as well.
Unfortunately, the NPNs all measured around 538 and the PNPs around 438. That's a pretty big difference. I'm hoping that I can find a few that meet somewhere in between that range.
Mr. Marsh, any comments on the difference? I'm assuming that's fine but I don't know how closely yours matched on your proto build.
I sampled about 10 each. Like previous experience, the NPNs were all pretty closely grouped, and the PNPs as well.
Unfortunately, the NPNs all measured around 538 and the PNPs around 438. That's a pretty big difference. I'm hoping that I can find a few that meet somewhere in between that range.
Mr. Marsh, any comments on the difference? I'm assuming that's fine but I don't know how closely yours matched on your proto build.
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ac and dc match
Its been a couple years since I measured my transistors. I believe I used same mfr for npn and pnp. I try to match both dc (Vbe) and ac (Hfe). BUT, the heavy local degeneration being used means matching isnt super critical. However, it never hurts to do a reasonably close match, though.
Its been a couple years since I measured my transistors. I believe I used same mfr for npn and pnp. I try to match both dc (Vbe) and ac (Hfe). BUT, the heavy local degeneration being used means matching isnt super critical. However, it never hurts to do a reasonably close match, though.
Thanks. Great info. I'll be sure to look at vbe. The problem I had is that neither OnSemi or Fairchild make the npn/pnp combo available anymore. I even tried to place a large order from OnSemi and it was rejected and I was directed to order an alternative that was a 20,000 piece min.
But there are plenty of these on ebay and maybe I'll try some at a later date that are a better match. As you noted, they are heavily degenerated locally and the matching is not as critical. Thumbs up!
But there are plenty of these on ebay and maybe I'll try some at a later date that are a better match. As you noted, they are heavily degenerated locally and the matching is not as critical. Thumbs up!