Greetings from Salectric

Salectric

Senior Member
Dave Slagle has some Type 50 monos that he brings some years to the Capital Audio Fest. The past couple years he has had his Quad 57s which I guess need more power so the 50 amps stayed home. But at the CAF last weekend he had two rooms, one with the double-Quad panels powered by their built in PP 300B amps, and the other with some cone speakers driven by, I believe, the Type 50s. I had never heard of the speakers before but the amps drove them effortlessly.
 
If you haven’t listened to an all DHT amplification chain, you should try it.....or maybe not!

Todays chain....300b>3b7>45>Altec 605b
 
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Redboy

Knobophobe
@Salectric, a question about your 46 schema...

Why the CCS and the 0D3 gas regulator on the driver tube? Could you get away with using just the 0D3?
 

Salectric

Senior Member
@Salectric, a question about your 46 schema...

Why the CCS and the 0D3 gas regulator on the driver tube? Could you get away with using just the 0D3?
The circuit will work just fine with the OD3 and a dropping resistor in place of the CCS, but it will sound better with the CCS. I experimented with this in a 12b4 linestage. When I first tried the gas tube voltage regulators (I used two gas tubes for the 12b4) I used a dropping resistor and the gas tubes were a modest sonic improvement over the unregulated power supply. But when I added the CCS in place of the resistor the sound quality improved substantially.

While I didn’t try these variations with the 46 amps, I suspect there would be something similar.

A side benefit of the CCS is that it does a great job of filtering ripple in the power supply line. That allows the B+ tap for the 417a to come off the first filter cap rather than the second. I tried it both ways and there was a slight difference in sound quality in favor of using the first cap as the power takeoff point for the 417a.
 

Salectric

Senior Member
WARNING! If you think power supply wiring doesn’t affect sound quality, please don’t read the following.

After using the 46 amps for a while, I was bothered by some minor tonal balance issues. The highs were a tad too bright and the bass was lean, not as warm as I like. Looking under the hood, I noticed the wire connecting the CCS (in the power supply line for the 417a) was a possible suspect. This wire runs from the BlackGate filter cap to the input of the CCS. When I built the amps I used 20g Silver-coated solid copper hookup wire that I bought from Cary Audio many years ago. That wire can sound lean and bright as a signal wire so I wondered if it might be contributing to what I was hearing.

I replaced the Cary wire with Neotech 18g solid copper with Teflon insulation which I have used in power supply wiring in more recent projects. The Neotech wire already had many hours of use in another project.

The Neotech wire pushed the tonal balance in just the right directions: the bass is warmer and and the highs are reduced in level. A side benefit is dynamics are improved as well. To tell the truth the highs are actually reduced a bit more than I would prefer but the overall balance is still much closer to neutral to my ears.

Anyway my only reason for posting all this is to emphasize that everything in a simple amplifier circuit is critical to sound quality. I see that as a virtue in a DIY project because it means that the sound can be tuned to fit a particular system and a particular listener. The folks who buy the latest ARC, CJ or whatever amp don’t have this luxury. If there is something about their new amp they don’t like their only option is to sell it and buy another amp.
 
While I dont have any homemade stereo gear, I can only imagine how rewarding it must be listening to stuff you made. Very impressive!
 

marantzfan

Administrator
Staff member
WARNING! If you think power supply wiring doesn’t affect sound quality, please don’t read the following.

After using the 46 amps for a while, I was bothered by some minor tonal balance issues. The highs were a tad too bright and the bass was lean, not as warm as I like. Looking under the hood, I noticed the wire connecting the CCS (in the power supply line for the 417a) was a possible suspect. This wire runs from the BlackGate filter cap to the input of the CCS. When I built the amps I used 20g Silver-coated solid copper hookup wire that I bought from Cary Audio many years ago. That wire can sound lean and bright as a signal wire so I wondered if it might be contributing to what I was hearing.

I replaced the Cary wire with Neotech 18g solid copper with Teflon insulation which I have used in power supply wiring in more recent projects. The Neotech wire already had many hours of use in another project.

The Neotech wire pushed the tonal balance in just the right directions: the bass is warmer and and the highs are reduced in level. A side benefit is dynamics are improved as well. To tell the truth the highs are actually reduced a bit more than I would prefer but the overall balance is still much closer to neutral to my ears.

Anyway my only reason for posting all this is to emphasize that everything in a simple amplifier circuit is critical to sound quality. I see that as a virtue in a DIY project because it means that the sound can be tuned to fit a particular system and a particular listener. The folks who buy the latest ARC, CJ or whatever amp don’t have this luxury. If there is something about their new amp they don’t like their only option is to sell it and buy another amp.
I have some of this same wire and used it in speaker builds as well as just recently in my Aleph J. It’s really nice stuff!
 

Salectric

Senior Member
It’s time to take a short break from vinyl and listen to some CDs. Yesterday I finished building my first DAC and I am busy putting it through its paces. It’s an old school DAC with AD1865 and No Oversampling. The digital board feeds a simple one-tube audio stage (Western Electric 407a). The power supply uses a pair of 6x4 rectifiers, choke input filtering and a BlackGate cap.

So far I am really happy with the sound of the new DAC. I will post some photos soon.
 
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Salectric

Senior Member
There’s a lot of iron under the hood. The digital board uses three 12v transformers, and the B+ supply uses an old PT from an Eico tuner and a Hammond choke. In addition there is a small 20v transformer for the heaters of the 407a. The 407a is a sleeper—a great sounding tube with the WE sound but you can buy it for peanuts because it has a 20v heater. The 407a works just fine with AC on the heaters so it’s quite simple to use. The rectifiers are Tung-Sol 6x4.

In keeping with my lack of originality, the audio circuit and power supply were designed by my son Michael who first used them with a RAKK DAC digital board. That DAC always impressed me so I figured copying the tube portion of his circuit was a safe move.

The digital board was designed by a fellow in Italy (Bruno) who also sells complete DACs under the Sound Monogamy brand name. His board uses an AD1865 DAC and CS8414 with several shunt PS regulators. The passive parts are unusual for a digital product since Bruno used vintage capacitors and resistors he selected for their sound quality (Aerovox, Panasonic, Allen Bradley).

Since I literally finished this yesterday, it still needs some cleaning up. The blue painters tape will be replaced with some tie warps once I am confident I won’t need to access the bottom of the circuit board. And the Mundorf coupling caps will be replaced with Copper V-Caps. I will also replace some of the resistors with Audio Note Silver Tantalums. The only other change I have in mind is trying an Audio Note input transformer.
 
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Salectric

Senior Member
Time to pimp my ride! Two pairs of Audio Note Silver Tantalum resistors just arrived and they should make a nice improvement to the DAC. These include my first pair of the new 1/2w series of Silver Tantalums.CCE5B497-04DC-4950-9BE7-C05D4FD29DF2.jpeg I hope they sound as good as the older 2w Silvers.

I already replaced the Mundorf Silver/Gold/Oil coupling caps with larger value copper V-Caps. The new resistors are the final component swapping I have planned. But that still leaves one big variable: an input transformer. So far I have been running the DAC with the digital input going straight to the DAC board, but I have an Audio Note copper input transformer that I want to try.
 

je2a3

Junior Member
Cool project! Are those resistors for the I/V stage?

I also have a WIP DAC - generic Chinese TDA1541 board using a CS8412 receiver, oversampling disabled, op-amp outputs bypassed and replaced by loctal tubes.
 

Salectric

Senior Member
Cool project! Are those resistors for the I/V stage?

I also have a WIP DAC - generic Chinese TDA1541 board using a CS8412 receiver, oversampling disabled, op-amp outputs bypassed and replaced by loctal tubes.
The 1/2w resistors (270R) are for the I/V and the 2w resistors (1M) are loading or bleeder resistors for the output coupling caps. They will replace Caddocks of the same value.

The Audio Note Silver tantalums are the best sounding resistors for loading applications (input loads, interstage loads and output loads) but not necessarily other spots. For example, Riken carbon films are still the very best for gridstoppers. All IMHO, of course.

Any pix of your DAC? It sounds like it might be somewhat similar to what I'm using.

I am far out of my element when it comes to anything digital. I have no idea how my DAC will stack up against something else, but I intend to haul it around to make some comparisons after I get to know it a bit better.
 
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