Intact Audio

Hi Dave. I think I mentioned this to you before, but I am in the market for a pair of beefy output tramsformers. Output valve STC 4212 and friends. B+ 1500v Max current 160ma. Maybe looking at 80W at 25Hz as a target. I think 7k looks like a good starting point, and there will be 6A DC available via...

This is the source of the idea behind the driver stage http://www.jrossmacdonald.com/jrmpubs/040CathodeFollower.pdf In the scope picture, the center line of the display as the 0v line, idle bias was about -7v, I think we were looking at 60v P/P, going 25v into A2, the limit on volume was the loudspe...

Though in the interest of accreditation, its far from my design, loads of prior art on it

Ahh, SUT = Step Up Transformer.

It all becomes clear now.

... that I am tempted to try another DAC. Anybody has a spare CPLD? Properly done SUT peaking could take care of most of the sinx/x correction and some of the roll-off above 20kHz. Regards, TonyB PS: Do not forget to re-clock signals after the CPLD. I must admit to not fully understanding what you ...

No, I just got very good ears...

Woops, ok, so maybe I need to talk to you about some filter chokes next then Dave

Looks hopefull, I tried to get somewhere near the #3 setup, but using a pair of 1:10 MC setups I had on hand. It works, and sounds better than I expected, so its certainly got promise. I think I can hear the fact that the step ups are being driven about 40dB harder than they were designed for. So Da...

That response is doing half the work for us :-). I was thinking in the order of 1:10, so 1:7 is fine, takes it to the point where something like an aikido can be used to drive the output. I3 looks good, the step up might need to handle a little DC, the DAC's idle current varies a little, I have seen...

Hi Dave, Myself and another couple of the usual suspects (Andrew and Tony) have been looking at creating a new DAC between us. Having heard and decided we prefer the TDA1541 we want (for the moment) to go with that one. There are a couple of additional features involved like interfacing to a squeeze...

I must admit both of the previous (interesting) graphs are why I have been spending a lot of time building and listening to amps with various regulated supplies. Have you tried the same sort of thing but with a two stage filter? I found it very hard to convince myself that the variations of impedenc...

Well, I own a example of the first, big cap into 600R, I would be happy to try replacing with the third option Dave if you want a test subject.

Mark, I'd be tempted to try again with 1Meg on the grid and 100R on the primary. Yes, from the sound of only the primary being loaded, I was sure that there was RF stuff going on in there, it was the same change in sound as I had got using my Lundahl stepups, but this time with the S&B's, so I ...

I also wonder what the inductance and capacitance of the cartridge will be?

It may be worth looking at the LTSpice help for inductors, there seems to be more than just idealised elements avalable. Most of what I read makes little sense to me at the moment, but I suspect it will to you Dave for modeling non-linear behavour. It also does suggest that the parasitic capacitance...

No, I use the same PD chain that T did, but with altered values to get the correct results.

I will play with the sim's later, I wonder if its worth adding Ckg to the model as well, I know its small in the case of a pentode conected E810F, but what value is it in the case of your (and Mark's) phono?

It may be adding too much to the complexity, but it could have bearing as to why its not the clear success Andrew found. I have been thinking about the input of the phono stage, but from the perspective of the first grid. Andrew, you know that when I built the TL LCR stage as T's original design, it...

Just FYI, I have tried your suggestion, loading the primary (lundahl step ups), it certainly made a difference, but I have gone back for the moment, I will try again later. It seemed to my ears to bring up the lower midrange, also there was a lot more lower bass, and the top end was more detailed as...

Sorry brain fade, it was and is 300hz. I must get some better better cable and rerun the connection between the listening room and where the computer is to try and get rid of that 50hz. The card I am using is a m-audio 2496. I don't know what the noise floor in 24bit mode will work out, but its good...

OK, I don't know if these are any interest , but I wanted to get some idea of the S/N ratio I am getting out of the E810F Pentode front end in my LCR phono. This is a Denon 103 (0.3mv) into lundahl TX's wired for 1:20. The first graph is the background noise, with the phono stage off. It does show I...

I think Max worked out that the E810F noise was equivalent to a 100R resistor in series with the signal, I assume. Yes, the E810F spec gives its equivilant noise resistance as 110R, however I think that will just be 1/f (it must be, I guess, as its specified by the equiv resistance), I don't think ...

I am not at work next week, and was planning to get set up for some loudspeaker measuring. I should be able to do some tests on the pentode driver LCR phono I am using, to try and get an idea what the S/N ratio is. At the moment using a Denon 103 (0.3mv) and 1:20 TX's noise is certainly not an audib...

Argh, I have been looking in on the forum on a regular basis, and thinking that there were no posts and it was all a bit quiet. I just noticed my browser had decided to stop logging me in, so I had missed all these posts about RIAA. Poo.

Thats it, I will go away again now

and at what point AC becomes DC

I would guess that DC would become AC just after 10 seconds.

(sorry couldn't help myself).

Oh,

I don;t think I have altered that model, do you want to mail me a copy of your circuit, and any other .inc's you are using in it and I will see what I have broken.

nick at lurcher dot org

will get to me.

Ok, it was only a single line change to get the models working in LTSpice, I have created a new inc file containing them and the original models, and a 6c45pi I found somewhere. I should find the 6n6p model I saw,as I am using one in my phono stage, so I can bring the model up to date. http://www.lu...

I have a 6c45 model that does work with LTSpice, Its not mine, so I would have to find where it came from before posting it to,make sure they get the credit. I suspect to get the Koren models to work,I am going to have to sit down and work out how it actually works, instead of mindlessly cutting and...

I tried adding to dmtriodep as suggested, but spice doesn't seem to like them (the gm70 model anyway),this was lateish last night so I haven't had chance to look further, I will take another look tonight and see why they don't play together. If they do I will create a new .inc with them in if that h...

Hopefully its of use, a standard three stage RIAA stage, with inverse RIAA on the input.

Usefull for finding the effect of changing the RIAA values.

Hi,

I may be missing something, but I think at 800v on the plate, you will find 100ma requires more like -70 on the grid of a GM70.

Or I may be misreading your post, in which case, sorry.