Intact Audio

Now I realise this is not anything to do with a slagleformer AVC but here goes anyway. I have a Olson style Raven preamp/headphone amplifier with a Sowter 9335 TVC on the output driving Senn HD650 headphones. So I got the clip leads out and disconnected the primary and connected the secondary up dir...

I must try that too one day. I like the idea of no series resistance however I had read that there might be an issue with HF overload though whether that is an issue IRL is another thing.

cheers,

Stephen

I mean an RIAA EQ network with a series resistance of about 15-20k vs higher Z networks with a series R inthe region of 50-100k. I prefer the sound of the lower Z network. If I could go lower, I would.

cheers,

Stephen

D3a and E810F are good to drive lowish Z EQ networks which IMHO sound better than high Z networks. They are lowish noise too and sound good. I don't find them microphonic or noisy and are relatively easy to tame wrt oscillation.

cheers,

Stephen

I don't believe in a generic sound within reason. Things tend to work when you use them right. I use a pentode, D3a, in my phono. I like it But then I don't know anything about the C3G.

cheers,

Stephen

www.izzy-wizzy.com/audio

I really enjoyed your contribution in that thread. Blinded em wiv science

cheers,

Stephen

There's one on an old web page of mine http://www.izzy-wizzy.com/audio/demag.html

Some of the links are broke as it isn't current but I stuck it back up in response to your query.

cheers,

Stephen

I wouldn't have thought so but in practice it would seem it is. Maybe I've looked at it for too long and not seeing an obvious mistake. I'm going to go pull a tree out of the ground and come back to it later.

CurveCaptor outputs a bunch of LTSPICE stuff that I think represents the plate curves for the valve. The attached text file is a number of Koren models from the most accurate to the least. I see in the triode file for the 6H30 a similar syntax that looks nothing like the others. I haven't tried to u...

Yes I suppose I could if I knew the syntax. The models in the triode file that look like the definition I have created from curvecaptor don't have inter electrode capacitance figures either.

So this makes me wonder how good these models are too.

Hi, Does anyone have or know of any models for the above valves? Since writing the above, I went and used CurveCaptor to get a LTSPICE model. All seemed to work OK and got a bunch of results. However I can't quite see how I translate the results into the triode_nh.txt file. I can see models in the t...

Hi Dave,

Were you able to compare your crossover to the unmodified one?

Impressions?

cheers,

Stephen

Hi Dave,

Having seen the crossovers boxed up, I'm wondering why 3 switches. Is it because the hi level tapped autoformer has the resistor switched seperately from the tap setting switch?

cheers,

Stephen

I had a quick play about and changing the coupling cap from 0.22u to 2.2u makes a huge difference. Oh and keeping the 100p at the 2nd stage input also improves things. Maybe get rid of it altogether. It gets quite close then. After that, fiddle about a bit with the other values if you fancy in a rea...

Hi Andrew, We tried on the 5687 out of my phono, one of Gary P's battery biased cascode CSS thingies vs a Lundahl choke. The sound was very very close between them and I wouldn't have wanted to blind pick them but my friend did have to blind pick a winner in my system not his own and he chose the ch...

Hi Andrew, Was in a similar position to you. I had tried anode chokes instead of CSS and liked the result although it was close. If I had the money, I would have gone for one of Dave's nickel 1:1 output txs. I went for a PP output stage as I had a PP tx lying around. Not sure what Rp the E180F has. ...

Went looking through some schemos on the pooter, found Jim Hagerman's SKP (Simple Killer Phono) which uses an E280F in pentode and shunt EQ. Not sure if the circuit is on the public domain though. Bit more traditional WRT coupling and biasing. That's quite a departure from you trad build style. How'...

Hi Lars,

The models that I used are fine but I was using the first circuit you posted and couldn't get that to bias up at all. The second one was fine. With the IRF510, I changed the EQ parallel Z to 39k for good response. All food for thought

cheers,

Stephen

Hi Lars, I didn't have an IRF610 model handy so subbed an IRF510. That might have led to a problemette. I ended up with a lot of current down the valve; about 45mA and so about 12W dissipation. Is that what you get? I also messed about with my para EQ circuit and found it very sensitive to G2 volts....

Hi Lars, I got a bit carried away when I saw a phono thread and the LTP comment and posted what I was currently using :D From scratch, I agree mine won't be cheap but it was cheap for me as the output tx was just lying around on the shelf :wink: I've often thought if I got rid of it, I could have a ...

That's why I though a long tail pair stage at the output could be interesting, though I suspect your scheme has the potential for better sound. And like Lars, I have no idea how I missed this thread. The comment from Shines is very relevant for me as that is what I run at present. See attached. I d...

Thanks Stephie! The new model works much better and closer models the DC conditions I get in reality over a spread of valves. Before I had to fudge the G2 circuit for DC conditions but now I don't :) I was attempting to model a DC coupled fully differential phono and have been messing around with an...

OK I did make an error in adjusting things but I still don't get the right screen current in the model compared to the datasheet. I will go back to the real circuit to look at it closer to see exactly what I've done. In the model, if I make the anode R 5k6 to get 180V on the anode and make the scree...

When using the D3a, the DC conditions as quite a way off reality and the data sheet as far as I can make out. Is the model more suited to AC and not DC?

I get 190V on the anode while the sim suggests 162V. That is quite a difference. Any ideas?

cheers,

Stephen

Yes I was stepping a parameter I didn't think of that as the param I was stepping wasn't on the circuit i.e. it was a hangover from when that component was there and now it isn't.

cheers,

Stephen

Have been using LTSPICE for ages and when using the .op command, the results appear in a window. Except for one circuit I sim'd and the .op command doesn't produce the window but the .raw graph as if it was a .tran or .ac. When you click on the circuit with the probe or current meter the results app...

Checked your circuit and unfortunately the filter isn´t capable of driving a 600ohm RIAA. The figures you get are off. To make it work, a buffer has to be inserted. As is below shows your filters response whatever load you add. Compare with the ideal RIAA at the bottom. No need to use your overly c...

Hi Lars, See below for my invRIAA. I have it seperate from the 50k pole so I guess I confused you when I said that I'd checked my invRIAA circuit. I removed the blocks and have reverted to a raw .asc. You should have all the models as part of a standard LT SPICE install as IIRC, that's what I did. I...

Hi Lars, Didn´t you read hagermans pdf ? Well to be honest, I skim read it and then forgot about it. When the RIAA curve ends up being "derived" into some kind of formula to be represented in SPICE and I don't fully understand how it came to be, I lose trust in my ability to use it properl...

Hi Lars,

Can you please include the .asc for the last 2 posts you show graphs for?

And what does P/T stand for?

Thanks!