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Old 7th October 2006, 07:12 PM   #1021
tubee is offline tubee  Netherlands
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Hi John. You have been busy again! Thanks for elaborating the diy resistors. I have some enamelled wire to try this. When 1 meter has 9 ohm's you used is very thin wire then, 0.05 mm or so.

Quote:
Also keep in mind that a tube faillure could cause all TDA1541A's connected to be permanently damaged.
Then i will not use this idea, too risky for me, thanks for info.

Off topico againo:

I just did some other try-outs:
Added remote controlled volume control in pre-amp: A 433Mhz signal from a on-off mains switches (12Eu at the shop "Action") switches a 74/08 port and H bridge to a DC motor. This motor and gear is scavenged from video player. With a clutch (otherwise it ruins the pot) it drives the axle. Nice to regulate volume into the listening chair!

Replaced in tubed pre amp the 10uF MKP audyn caps in big 6.8uF Audyn cap "plus" caps. Good depth and detail, less colouration, but i lost some bass, and i like bass. Mids has now a slight distorted "edge" on it. So still not fully satisfied. This cap also shows the weak spots of my speakers more obvious (2 way: cone break up) They costed me Eu 17.50 each.

Another mod: replaced the very old, thick & stiff (low voltage cable for trucks) speakerwire into 24 awg Cat5 cable, 3 cables parallel woven by myself. Used solid core type. Whole other sound again. Bass is some better now (thinner effective cable diameter) but also have some mild enhancement of midbass. Depth is not that obvious anymore. But treble is much cleaner now, this cat 5 cable is every penny worth for the cost of it! (8 euro for 18m)

See also:
http://www.humblehomemadehifi.com/CAT5.html
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Old 9th October 2006, 07:30 AM   #1022
Zoran is offline Zoran  Serbia
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Hi ECdesign...
I was unable to find diagram of
USB interface circuit...
Are You post jpg already?
Thanks
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Old 9th October 2006, 01:53 PM   #1023
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Default Coupling cap's

Hi Tubee,

Thanks for your reply [post#1021]

Yes I use very thin copper wire in order to keep the mobius loop as short as possible, this reduces the parallel capacitance.

Well, nice creative remote volume control construction.

The coupling cap's are not off topic as they are used in the tube output of the octal D-I DAC as well and have a significant effect on sound quality. Can you understand now why I use DC coupling in my audio set, and made the octal D-I DAC DC coupled exept for the single coupling capacitor in the tube output? The Audyn caps work very well in speaker crossover filters, but even the Audyn plus is not optimal for tweeters, you need a tin capacitor to get optimal resolution and detail. But it seems they are not optimal for use as coupling capacitors in a tube amplifier. A good coupling capacitor for this application would be Auricap (you can order them from Automatic Electric Europe).

If a speaker get's damaged that easily, perhaps the crossover filter is not optimal.

Yes, I have seen the network cable speaker cables already. I use 24 solid core enamelled copper wires twisted to one wire, there is a photograph of it on my website. I can only confirm that they result in a much better sound quality.
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Old 9th October 2006, 02:18 PM   #1024
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Default USB interface

Hi Zoran,

Thanks for your reply [post#1022]

If I am correct, I already posted a diagram of the shiftregister reclocker. But I haven't posted the complete schematics of the USB interface yet. So I added the schematics, it's a straight forward bus powered setup using the PCM2706, but it uses the shiftregister reclocker, differential buffered I2S outputs and a common 48 MHz crystal oscillator module. If you want single ended I2S outputs, you can use the differential receivers that are also located within the DS8921 and DS8922 chips. It's preferred to always use these buffers as the PCM2706 can damage easily when the output's aren't buffered.

For single ended outputs, connect the following pin's on the DS8921:

pin 6 connected to pin 8 only DO+ to RI+ (pin 8 NOT connected to GND)
pin 5 connected to pin 7 only DO- to RI- (pin 7 NOT connected to VCC)

pin 2 is BCK output.

connect the following pin's on the DS8922:

pin 14 to pin 16 only DO1+ to RI1+ (pin 16 NOT connected to GND)
pin 13 to pin 15 only DO1- to RI1- (pin 15 NOT connected to VCC)

pin 1 is WS output

pin 12 to pin 10 only DO2- to RI2- (pin 10 NOT connected to VCC)
pin 11 to pin 9 only DO2+ to RI2+ (pin 9 NOT connected to GND)

pin 8 is DATA output
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Old 9th October 2006, 04:20 PM   #1025
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Quote:
Originally posted by adhoc
Anyone else have anything to say regarding software resampling?

My impression was that it was to be avoided in general not only because it used a lot of CPU, but also because the results were often less than satisfactory, especially when compared to hardware resampling.

What sort of resampling algorithm does the Mac use? PPHS? SSRC? LI?

I have found SRC upsampling with a PC to be superior to all other formats, given that the optimum ASIO is used with it. I use:
Foobar 0.8.3
ASIO SSE3 vers. 47a
SRC

All of my customers that use MAC have reported that the MAC upsampling does not sound as good as the 16/44.1 output.

Steve N.
Empirical Audio
Manufacturer
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Old 9th October 2006, 06:00 PM   #1026
tubee is offline tubee  Netherlands
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Default Coupling cap

Hi John

I just decided that tomorrow i will refit the old standard 10uF MKP Audyncaps back again in the tube preamp. They where paralled with KS, but now i will do that with some small PIO's .I'm not satisfied with the sound of the "plus". Some closed in and a distorted edge in mids, treble seems cleaner, but also softer, and not " fresh". The Plus has 2 windings in series, that must be the problem, to many borders to cross or something.
Indeed found out a cap for tweeters works totally different then as coupling, in special in tubed amps. It has to keep 110V DC away of my preamp.
I will order 2 caps from AE in Schagen, see how they perform.
Btw, my tweeters are filtered with huge metal can 3.4uF PIO's from a tube light of the seventies!

I have at the moment a Quad 33 and 303 to service, some small problems. The sound is rather good, very clean highs. But soundstage is flat(transistor + lytic coupling cap to speakers)
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Old 10th October 2006, 05:27 PM   #1027
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Default Coupling cap 2

Refitted the standard Audyncaps; yes, thats more like it.

In meantime swapped the Panasonics in cathode of phonostage in Standard black Gates. I was sceptic about BG's, but now i am a believer too: This cap is a lot better than any other lytic. So John if you search a good cap for cathodedecoupling in your tubestage...

And someone interested in 2 MKP Audyn Cap "plus" caps6.8uF 425AC 800V DC?
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Old 10th October 2006, 08:01 PM   #1028
tubee is offline tubee  Netherlands
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Very peculiar, the slight hum in the phonostage is gone! Even without the top cover. I can tell now, those Black Gates are worth every penny. Now they have to burn in a while.
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Old 12th October 2006, 06:18 PM   #1029
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Default K4040 mods

Hi Tubee,

Thanks for your reply [post#1027 / #1028]

Little bit off topic here, since you are talking about tube amplifiers, guess what I have been doing? I needed a tube amplifier to test both the sonic resonators and the octal D-I DAC, but I didn't have one. I didn't want to spend a lot of money on a High-End tube amplifier, and there wasn't time to design one from scratch, so I decided to buy a K4040 kit (shame on me). I knew there were some design problems, and I might need to do some minor modding in order to get the sound right. Some JJ KT77's were ordered, just in case...

Then the kit arrived, it didn't have the ILP transformers I hoped for, the EL34's were from Svetlana, the ECC83's from Sovtec and the ECC82 from Electro Harmonics. The housing looked very impressive with the massive chrome plates, even the feet and the decoration rings for the tubes were chrome. It comes with a a huge single-sided PCB. I planned to use Beyschlag metal film resistors instead of the cheap carbon resistors, Spectrol cermet's for bias adjustment and Panasonic electrolytic capacitors. After a few hours the PCB was assembled, wiring the EL34 sockets cost a lot of time. Then it took me another day to squeeze-in the transformers and wiring as there was very little space.

I continued with the bias adjustment, there is a LED indicator for this, but it's readout wasn't very good, a lot of LED's burning and flashing at the same time, so I had to solder a 100nF across the LM3914 input to get it working correctly. Finally it was time to listen to this 2 X 90W rms tube monster, well in fact the sound it produced wasn't that good. Perhaps the Svetlana's needed some burning-in time, but after burning-in one full day without significant sound improvement I lost my patience. Measurements showed relatively high distortion and a huge peak at around 40KHz.

Next lot's of different tube brands were tested, but it became clear to me, the design wasn't optimal, so I could prepare myself for some serious modding. Starting with the input stage, what's a ECC82 doing here? I replaced it with a JJ ECC83 and changed the resistor values for maximum linear drive. A concertina phase splitter using a ECC83 to drive 4 X EL34 ?? out it went and replaced with a modified Schmitt phase splitter with a constant current source (2 X J508 in parallel) to ensure fully symmetrical drive. The ECC83 wasn't capable of driving 4 EL34's, so I replaced it with JJ ECC81. The EL34's were replaced with JJ KT77, next the 22nF coupling cap's were replaced with LCR 100nF/1KV polypropylene capacitors, yes tubee, coupling cap's can make a world of difference. Oh yes, the overall feedback was removed, only using local feedback. The bias voltage was stabilized with a 47V zenerdiode (22K series resistor lowered to 10K).

After these modifications there wasn't much left of the original K4040 design, but the sound quality was stunning, what a difference. The K4040 turned into a beautiful sounding High-End power amplifier. Distortion is much lower, it sounds crystal clear, transparent and open, with a deep impressive bass and a wonderful sounding midrange. Unbelievable what a few modifications can do. By the way, the sonic resonators work very well with this tube amplifier, same with the octal D-I DAC. I added a photograph of this modded K4040.

Beside from this K4040 intermezzo, I also spend a lot of time on the octal D-I DAC, the housing is ready now (side panels and ventilation slots in the top cover) so it can be annodized. The PCB's are almost verified, so a small batch of PCB's can be ordered soon.
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Old 13th October 2006, 09:28 AM   #1030
tubee is offline tubee  Netherlands
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Hi John

Nice to read about your Velleman kit experiences. I have been thinking to buy one too, but what i did till so far was a cheaper. I have a SE two EL36's in series amp design and part lying somewhere, it has to be finished. Tubed amps can give such fine sound, reasonable easy to modify. Yes a E83CC cannot drive everything, but has a large amplification factor. Allmost all old schematics use an ECC83 somewhere. Are endtubes in penthode?

Btw the Cat 5 cable sounds spacious, but not perfect. Maybe Supra cables?
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