Building Started...

[Jim R.]

Just ask for/look for a tube with matched sections.  That said, I think you'll be very hard pressed to hear a difference with the tube you have.

-- Jim

[Paul Birkeland]

"Matched" tubes can mean a whole lot of things.  You can turn the volume knob all the way up, then put 60Hz of tone into the amp input, then measure the AC voltage at 4 and 12 to see how well the tube is gain matched. 

[drewh1]

Replying to your earlier post - I want to build some speakers too, likely Full range in a Transmission Lline -  too bad you are not in the Bay area, I am more of a wood worker than analog elec. guy, so I could help you with the speakers and you could help me with all this other stuff. 

There are some kits that let you buy the wood pre-cut, so all you have to do is assemble. At any rate, let me know when you want to get started and I will offer any advice that I can.

drew.

[Paul Joppa]

The plate voltages of the 12AT7 are unusually close together already. Normal tubes will vary +/-30% or so - the circuit is designed to accommodate this variation. (Transistors are much worse, the gain of the 2N2907A for instance is between 50 and 300...)

The output tube has some DC feedback in the form of the cathode bias resistor, which more tightly controls its operating point. The bypass capacitor removes teh feedback at audio frequencies.

One of the unique things about SET designs is that they generally do not use negative feedback, at least in the audio band. This makes them more susceptible to parts variations, and to various sources of noise and distortion - but it also makes them sound more natural, at least to the ears of very many observers.

[rlyach]

Drew,

I was also looking at building a full range single driver using a fostex 4" driver. I also looked at the available kits but it is hard to find high efficiency drivers. This is why I ordered the Orcas in the first place. The added benefit of the Orcas is that Blumenstein also sells bases for the Stereomour that match the speakers. This helps the wife acceptance factor  .

Paul,

After looking at what is available in balanced 12AT7's, my 3.3% difference is indeed looking pretty good. I am amazed that everything else in my amp matches to less than 1V. I did go to the extra trouble of measuring all my components and using them in the A or B side in order to keep the total DC resistance identical. I got within one ohm through the choke, the hum circuit, and the cathode circuit. I am also glad I purchased the Goldpoint Attenuator. The sound is smooth and matched all the way down to low listening levels. I also do not hear any switch noise while changing the level. This was probably an extravagant upgrade but I am glad I did it.

Randy

[rlyach]

My Blumenstein base arrived but I am still waiting for the Speakers. Here is the amp from the top. I really like the dark base contrast with the plate and the polished chokes and transformer bell. 

[Doc B.]

We got a new carmelized base in from Clark and Molly a couple days ago. It was done to a really nice deep brown too. Looked sexy, wish I had thought to take a pic before shipping it out.

[Grainger49]

Randy,

The polishing looks great in these pictures.  I can see the end bell and frames better in these pictures.  Exactly, great contrast!

[rlyach]

Just for fun I built this removable pilot light for my amp. I took a 9 pin socket saver, removed the center screw, and placed a 12-16V amber grain of wheat lamp in the hole, soldereing the wires between pins 4 and 5. I can use the adapter if I want the pilot light or remove it if I don't. I haven't heard any difference in the sound yet but I will listen more closely when my Orcas get here tomorrow. Can't wait.

[drewh1]

You must be so excited to hear those speakers - just like christmas.  I can't believe my kit hasn't shipped yet, it better ship soon or will have spent all my money on stuff before it even gets here.  I am still looking at drivers, have found a number that are 96db and higher, expensive though.

Hey, let me know if you want to do DIY interconnects. I have built about 6 different versions and really like the fine magnet wire versions.

drew.

[rlyach]

Yes, I am really looking forward to finally hearing the system. I ordered the kit and speakers on the same day (1/11/13). I guess Blumenstein has been very busy with a lot of backlog to build. Now the only decision is what song to play first  .

[drewh1]

well, I am not a big fan of the idea of electronics "breaking in" but speakers sure do need a break in, so if they sound great right away, just know they will only get better.  Also, if you are like me, you'll spend at least a week moving them around to get just the right listening position and bass response.  All in all, you are going to busy with them for a while!

[Grainger49]

   .   .  .    Now the only decision is what song to play first  .

I always go with CS&N the first LP.  I have a Classic Reissue Remastered.  It is better than my first pressing of the LP.

[drewh1]

Now available in 24/96 khz remix on HD tracks. 

[rlyach]

My Orcas came! WoW. I have never heard anything like what I am hearing from the amp and the Orca speakers, and it keeps on getting better the more I listen. My wife even commented on the sound. Now I really notice the difference in recordings. I guess all recordings are not created equal. I am streaming my music digitally through a tos link cable to a Cambridge audio 24 bit DAC, and then to the Stereomour. I know many of you are cringing because I am streaming digital music, but I can't get over the sound. I am a very happy camper. I have this system in my bedroom and it fits perfectly. It even looks nice.