Search found 120 matches

by Wolfgang
Thu Sep 19, 2019 11:52 pm
Forum: Everyones Projects
Topic: Valve DAC
Replies: 22
Views: 385

Re: Valve DAC

"The actual digital to analogue conversion, reconstruction filtering, time reference and voltage reference must therefore be regarded as critical analogue and mixed-signal functions. Because of the reasons explained in section 1, they must be realized in valve technology." If the word “critical” in ...
by Wolfgang
Thu Sep 19, 2019 1:52 am
Forum: Everyones Projects
Topic: Valve DAC
Replies: 22
Views: 385

Re: Valve DAC

If I can ask an honest and perhaps devils advocate question, what's the reason for using valves in the DAC cores? Curiosity? Or is there a genuine expectation that valves will bring something special to this Don’t know if that answers the question but this is in a nutshell the reason for using valv...
by Wolfgang
Mon Sep 16, 2019 2:30 pm
Forum: Everyones Projects
Topic: Valve DAC
Replies: 22
Views: 385

Re: Valve DAC

I think Ray's new project would deserve better than two off topic comments about funny Pachelbel sketches. I wonder what would have happened if he had used a CD with Bach music for showing the size of the PCB? When I read the original article about the tube DAC in Linear Audio many months ago I was ...
by Wolfgang
Fri Sep 06, 2019 3:51 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

I am closing in on my DC protection circuit for a final test in the amp. But I have still some open questions. I could use a single mechanical relay for disconnecting/connecting the speakers or two SSRs, one for the 250V (Vishay LH1540/350V max/20R on resistance), the second for the speakers (IXYS L...
by Wolfgang
Wed Sep 04, 2019 5:59 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

That took a brave man! I tested all the functions at different voltages before I hooked it up to the DX4 for a final test under real conditions. The reaction time was ok. DC protection.png Now I will find out with some listening tests whether it has any side effects on the sound. If it all works ou...
by Wolfgang
Tue Sep 03, 2019 7:15 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

That's how it looks and sounds when you connect -250V to a 8ohm Lowther driver using the DC protection circuit:

https://drive.google.com/file/d/1FXX17p ... sp=sharing

Not bad. I am satisfied with the result.
by Wolfgang
Sat Aug 31, 2019 4:54 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

The DC offset is 100% under control and doesn't drift. Only during the warming up of the tubes and the resistors(about 10min) it slowly settles down to the once set value. One can set it to 0V with +/- 20mV. The problem was clearly a bad tube. It was the first tube in line and from my listening posi...
by Wolfgang
Fri Aug 30, 2019 11:41 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

I asked not because of a relative sound quality perspective but from that of the DC offset; I assume that, because of the asymetric voltages needed at the output stage, that any drift in the mains voltage would result in those voltages varying by different amounts and therefore changing the DC offs...
by Wolfgang
Fri Aug 30, 2019 7:39 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

Is the issue with the Neurochrome/XRK solution suitability down to them being unable to handle the 250V scenario or is there something else? I know the XRK board specifies that it can handle upto 48V of DC and assume the neurochrome will be similar as the designs are quite alike. It is the -250V is...
by Wolfgang
Fri Aug 30, 2019 7:33 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

You currently use the SLB modules; these give you a very clean supply but are not regulators so I assume that you keep them stable, with respect to the output voltage, because you use a mains conditioner so your amp always has the same supply voltage? If so, in the absence of a mains conditioner, w...
by Wolfgang
Fri Aug 30, 2019 7:12 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

I assumed the diodes on the input would protect the CMOS from over voltage. And at worst, socket the IC and buy a bag of them and include a test button to bleed voltage to the output. With this circuit it's clear: The DC level will be controlled by the diode bridge to impose a forward bias polarity...
by Wolfgang
Fri Aug 30, 2019 2:03 am
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

can you run a spice sim with a 74 series logic library? I did only simple things with spice. Would probably need some time to get useable results. if you have a trigger at +- 40v, then that will also trigger at +250v? If the problem is the voltage limit of the solid state relay, why not use a mecha...
by Wolfgang
Thu Aug 29, 2019 4:07 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 116
Views: 7069

Re: Inverted OTL with 6SN7/6AS7

Nick's mention of Mike's E-choke project reminded me that I have a couple of the boards in my spares box - I might just dust them off and use them in my 300B HPA project. It will improve things as it has been shown on the Tentlabs page but it's not the same as the SLB. I think the active bridge rec...
by Wolfgang
Tue Aug 27, 2019 4:26 pm
Forum: Everyones Projects
Topic: Latest DSD Decoder Project
Replies: 42
Views: 4786

Re: Latest DSD Decoder Project

Ray, I can see that you use 3 psus for your DAC. How did you resolve the problem with different potentials of the ground planes? Any minor hum or not fully "open" sound? And how will you resolve this when you use the tube output stage? I had to struggle with my DAC for a while to clean everything up...
by Wolfgang
Fri Aug 23, 2019 4:14 pm
Forum: Speakers
Topic: Fane 12-250TC Retro Speaker.
Replies: 284
Views: 32326

Re: Fane 12-250TC Retro Speaker.

For full-range drivers like these, the cone(s) will be bending all over the place. Correcting for that by altering the signal at the voice coil would be immensely difficult. You are right. I was under the impression that Backes& Mueller active speakers would have used in the 90ies already some cont...