Search found 35 matches

by mseddon
Mon Mar 26, 2012 3:38 pm
Forum: Transformers
Topic: OT for 801A driving 340Hz horns
Replies: 1
Views: 5471

OT for 801A driving 340Hz horns

Hi Dave, I am looking to buy or try winding a pair of Nickel OT for 801A driving 8ohm TD2001s on 340Hz horns. 30mA for about 1W, 380v B+ self bias. I have got the amp up and running using some small Akai RtoR OTs, and it sounds worth it. Is a 1/2" core going to be big enough? ( 80% Nickel lams ...
by mseddon
Mon Nov 29, 2010 1:43 pm
Forum: Transformers
Topic: OT to drive Fostex T900A Tweeter
Replies: 3
Views: 5482

Yes, looks to good to believe (even thought about air coil) - I guess challenge is how best to use all the slack one gets cut. Gap / turns / rolls of teflon tape (self capacitance). To consider inductance first - where does one set the lowest frequency one wants low phase angle? 0.5H puts the 15 deg...
by mseddon
Sun Nov 28, 2010 4:18 am
Forum: Transformers
Topic: OT to drive Fostex T900A Tweeter
Replies: 3
Views: 5482

OT to drive Fostex T900A Tweeter

Hi Dave, I am looking for a transformer to drive Fostex T900A Tweeter. 8 Ohms, 6KHz - ??, 6dB HP cross over (max BW case). Lots of good quality off the shelf OTs to choose from - however I suspect this is just where one needs a specialist high resolution design. I know I am really picky about sound ...
by mseddon
Mon Nov 22, 2010 2:09 pm
Forum: Resistors
Topic: I/V resistor for TDA1541 Vishay Bulk Foil
Replies: 1
Views: 9238

I/V resistor for TDA1541 Vishay Bulk Foil

I recently direct wired the audio out from the TDA1541A chip in my old Kinergetics CD player to a simple choke loaded valve stage using a 100 Ohm grid resistor for I/V. (In fact the 2nd stage of my LCR phono designed here on Intact. Thanks guys). Great improvemnt on the stock discrete transistors (i...
by mseddon
Sat Jul 24, 2010 2:27 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Thought I would close this with the finished phono - sounds very rich and alive, compared to CR phono stages I have built. LRC is definitely worth doing. And it's quiet. Cart is Denon 103 to Cinemag 1:14 MMMI-7C input trannie. I used cathode bias to get it going, with OS-Con caps, but can mod to bat...
by mseddon
Thu May 27, 2010 12:47 am
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Then what we obviously need is a large selection of models for each type of tube, so that we can do some tube rolling... martin still flushed with success having got my LTSpice phonostage model running... Just thought - the inverse riaa on the front of teh riaa model, fed into ones real life phono (...
by mseddon
Tue May 25, 2010 3:23 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

azurahorn.com - have sent 2 pairs to Norway. martin
by mseddon
Tue May 25, 2010 2:32 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Halleluya! Praise the Lord - I think I finally got it. Only took 4 days. All currents running and riaa looking good. Will never have to make a real amp again. You gotta go into the ascii file and find out how to name the parts, then it's all hunky. well signing off for now, might even get a phono st...
by mseddon
Mon May 24, 2010 2:23 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Hi Lars, I can get to see the numbers for the DC op points, but there is no voltage drop across the loads.

The AC sim seems to do plot the output graph OK (looks like neg riaa).

What is the procedure to check if the riaa EQ is correct?

thanks, martin
by mseddon
Sun May 23, 2010 2:41 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Heyhey! OK, it runs! - was doing it OK, just didn't include the word 'triode'. Doh!

Unfortunately no current - jeez its easier breadboarding...aargh

martin
by mseddon
Sun May 23, 2010 1:09 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Hi Lars, I entered the name of the name d3a tube as per dmtriodep 'D3a/7721' on the component attribute editor line 'Value'. However LTSpice doesnt seem to pick it up. What am I doing wrong? I tried 2A3 and also doesnt recognise it. What did you change and where? Sorry for newbie dumb questions - I ...
by mseddon
Sat May 22, 2010 1:27 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Hi, I have updated the schematic (attached), but I cant get it to run - it says there is an unknown subcircuit. I have got all the subfiles uploaded from Stephies 101. I think.
martin
by mseddon
Sat May 22, 2010 10:22 am
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Thanks Lars, Some delay - I ordered and just received plate chokes to load the anode of 2nd d3a - I guess to extend the iron phono philosophy, equalise the ps B+ and hopefully get some more PSRR. I wonder if you could load it up into spice? Any changes? I am sorry, I should do it myself, but not yet...
by mseddon
Mon Apr 12, 2010 4:22 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

>However, that circuit produces 40dB gain, the original 3 stager had 60dB

Guess d3a is a pentode so could increase the gain on the second stage... how does this affect things? I guess not too good for hte Zo and driving a autoformer vol control....

martin
by mseddon
Mon Apr 12, 2010 3:41 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Hey thanks Stephie - that looks really great, it's a wrap. I like the idea of an 'EQ module' - can then play around with front end gain stages / step up trannies, or maybe opportunity for another go at line level preamp - I just have a passive autoformer / selector at the moment. And several other s...
by mseddon
Mon Apr 12, 2010 11:08 am
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Hi all, Yes, it's true I planned the first stage 75uS EQ to be high impedance with a nice convenient air core adjustable C. But Dave got me thinking, if we go all Low impedance, stay split EQ - why not pull the same trick twice? A simple LR filter is going to have (ignoring Zo for now) a L= 0.75H fo...
by mseddon
Sat Apr 10, 2010 1:59 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

hooray! I can read the dwgs now I have downloaded LTSpice. Yes, I like it - it was my first idea, but the gain seemed to be a bit low, using a DL103 cartridge and 1:3 SUT ~54dB ? I always think one should be able to tickle the power amp a bit more than the 1st watt. ( I thought of adding a 12B4a or ...
by mseddon
Sat Apr 10, 2010 2:31 am
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

I should add that I can re-wind the choke for other values of DCR and Inductance (within quite a wide range - though with obvious constraints on the L, R and BW)

martin
by mseddon
Sat Apr 10, 2010 1:52 am
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

Sorry forgot to include that

Inductor is 31 Ohms DCR
adjustable to about 3.5H at 100Hz (and still measures 2.2H at 10KHz)

martin
by mseddon
Fri Apr 09, 2010 5:22 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

The transformer primary measures 28.7H at 100Hz (21H at 1K Hz) 84 Ohm DCR. Secondary is 38 DCR (2.9H as a check). I downloaded Pspice LT, thanks for advice. Will get to grips. I built a rough and ready phono stage like this once before , with a 5842 - but ignoring all the inconvenent Rs and Zs. thou...
by mseddon
Thu Apr 08, 2010 5:25 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

wow, thanks Stephie , Wish I could say ah well that expains it :-) The schematic is correct. I did think of using a 7K:15 ohm output trannie to get hte Zo low as poss. Must get PSice. does one download the Student free version? Is that what people have? I do petro process modelling at work - fun. ab...
by mseddon
Wed Apr 07, 2010 1:01 pm
Forum: Phono
Topic: help with calculation of a LR 318 / 3180uS riaa stage?
Replies: 42
Views: 37312

help with calculation of a LR 318 / 3180uS riaa stage?

Hi, Can anyone help me with calculation of a LR 318 / 3180uS riaa stage? I have a 6DJ8 loaded with 6K:600 step down trannie driving a simple L//R1: R2 filter, to grid of next stage. The 10:1 step down is easy enough to calculate incorporating the r out, DCR of the inductor, and R1 and R2, but how do...
by mseddon
Sun Apr 06, 2008 3:04 am
Forum: Transformers
Topic: OT optimised for a bass horn amp
Replies: 10
Views: 15779

I had a look at the Hornresp impedance plot vs the spl plot and pretty clear the 'ripples' are in opposite phase. So I guess 'negative output impedance' amp would be a good thing to to try. ie at frequencies that draw less current from the amp (and have less horn spl) due to higher acoustic and driv...
by mseddon
Fri Apr 04, 2008 3:41 pm
Forum: Transformers
Topic: OT optimised for a bass horn amp
Replies: 10
Views: 15779

Nice spreadsheet Lars, thanks. I wondered if this is about horns not transformers, and we should take it off line - but realised this is exactly where the transformer design should start - as part of an acoustic / electrical circuit of the horn / tranducer / transformer. Unfortunately the maths is o...
by mseddon
Fri Apr 04, 2008 9:34 am
Forum: Transformers
Topic: OT optimised for a bass horn amp
Replies: 10
Views: 15779

Hi Lars, I found your website - looks great - but cant get the to the spreadsheet. Can you post it to me at mseddon@eftel.com.au ? My bass horn is designed using McBean to a 0.6 Hypex : have a look on azurahorn.com Not sure I undersand why one needs very low impedance - can you explain? But In fact ...
by mseddon
Thu Apr 03, 2008 3:24 pm
Forum: Transformers
Topic: OT optimised for a bass horn amp
Replies: 10
Views: 15779

OT optimised for a bass horn amp

Hi Dave, What might an OT optimised for a bass horn amp look like? Horn used up to Fc of around 320 Hz and 100 - 104dB sensitive. To narrow things down a bit I have a nice quad of SV811-10s and a power trannie. willing to try pentodes. Have been thinking pp - but open minded. At present using a ss a...
by mseddon
Tue Apr 01, 2008 11:20 am
Forum: Current Cancellation
Topic: mic pre circlotron ?
Replies: 6
Views: 12437

Hi Dave C, Neat - once you unravel it it's pp - with an equal cathode load. Move the taps down and its normal 1:1 pp. Focussing on the ccs with shared winding (for my application) it is conceptually similar to the circlotron in that AC and DC have separate paths. But the benefit is one ps at tube vo...
by mseddon
Mon Mar 31, 2008 12:04 pm
Forum: Current Cancellation
Topic: mic pre circlotron ?
Replies: 6
Views: 12437

mic pre circlotron

Hi Dave, Pls find sketches attached showing tertiary winding morphing into circlotron. I guess the other way of describing it is - DC goes round the long loop, AC goes round the short loop. This is only for a few milliamp - maybe a simple fet ccs would work? and adjust tube bias to match it. Best rg...
by mseddon
Thu Mar 27, 2008 1:50 pm
Forum: Current Cancellation
Topic: mic pre circlotron ?
Replies: 6
Views: 12437

mic pre circlotron ?

Hi, I have been thinking about winding a small Nickel OT for a mic pre project - basic design has been cinemag input and various output trannies with many iterations both bal and SE, fet and tube and hybrid in the middle - but never been really satisfied with it. Have done it parafeed , but want ser...
by mseddon
Thu Nov 16, 2006 4:49 pm
Forum: Inductors
Topic: Double filament choke wound on single core
Replies: 8
Views: 11972

Not at all Dave, it's quite apposite. DaveS opened up my specific application pointing out one might as well share a common conductor too. However as my filament circuits will be at different DC potentials I will need two windings. The circuit drawn appears to cancel the whole half wave ripple - ing...