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Old 20th August 2008, 12:41 PM   #481
Salas is offline Salas  Greece
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Default Initial impressions.

Gave it a long enough first listen. Used a 28dB gain/9dB feedback 20W PP tube amp and 95dB/2.83V speakers. No shortage of drive and level by using a unity gain buffer in other words.
I did sole and AB auditioning tests VS a single stage 6V6 triode wired preamp. That preamp has one coupling capacitor (Mundorf Supreme Silver/Oil) in its output, X5.7 gain, no feedback of any short. I used an SPL meter so to normalize the level and be fair.
The particular B1 version has the zero capacitor advantage over the tube preamp.
Well, the B1 is clean, has good detail, even dynamics, does not jump on your face. I could describe it as cool but not edgy. Its tone is not artificial, yet not really natural or especially transparent. It has some short of pentode and local feedback sound, persistent mainly in vocals, but darker. It takes about 30 mins to warm up so to lose an initially flat and gray presentation.There is a distinct loss of depth, texture, flow, and body VS the tube preamp. Music becomes less interesting. It does not bounce. Also the image won't extend as much beyond the speakers horizontally.
Of course all those things are academic if you consider the value. It can cost peanuts. I would use Auricaps if I had to capacitively couple the B1, I think that their tone will not spotlight its shortcomings. But it will lose detail and become much costlier by using any worthy capacitor. If there is a gate to ground resistor after the pot, there is no chance it will lose reference to ground upon a pot fault and will not produce about 4V DC at at output (I tested such a disaster scenario). So I think that a DC coupled B1 version is a viable, cheap, and most transparent option to consider.

*These are highly subjective initial findings, and by no way are universal for different systems and for different people. Just a report for a particular B1 construction in a particular audio system environment.
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Old 20th August 2008, 04:28 PM   #482
udailey is online now udailey  United States
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Well I try to man up and ask my dumb questions without shame. Here is the next in my string of such questions.
I have 18V dc wall wart. No ground. I can easily take + from it to R1 but do I do nothing with the negative? Do I take ground from the input RCAs? Do I take ground from the output RCAs since they are grounded in the amp?
Uriah
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Old 20th August 2008, 07:54 PM   #483
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Yout wall wart must have at least two output terminals, at minimum a plus and
a minus. Minus = ground.
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Old 20th August 2008, 07:55 PM   #484
udailey is online now udailey  United States
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Thanks Nelson. I thought about using - but I wasnt sure if I could and didnt want to cook anything if I could just ask.
Uriah
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Old 20th August 2008, 08:32 PM   #485
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Default Re: Initial impressions.

Quote:
Originally posted by salas
Just a report for a particular B1 construction in a particular audio system environment.

Very cool review Salas. Many thanks for all the effort. It would be interesting to know how it compares to a passive - just the pot in this case. What's the bass like?
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Old 20th August 2008, 09:53 PM   #486
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Quote:
Originally posted by Nelson Pass


It's just easier. For you, not me. I don't lay awake at night worrying about
the sound of capacitors.




/pass/ Gets a good night's sleep.

I still find it interesting that so many people accustomed to solid state gear get hives even thinking about coupling caps when tube pieces are full of them and still regarded by many as the reference for many aspects of audio reproduction. It's a perfectly valid and (barring parts failure) 100% functional way to nail DC problems to the floor.
Just use a decent cap.


Quote:
Originally posted by udailey
Well I try to man up and ask my dumb questions without shame. Here is the next in my string of such questions.
I have 18V dc wall wart. No ground. I can easily take + from it to R1 but do I do nothing with the negative? Do I take ground from the input RCAs? Do I take ground from the output RCAs since they are grounded in the amp?
Uriah

Using the negative rail as "ground" is traditional in single-ended power supplies, but hardly necessary. You could turn everything upside down and use P-ch devices instead of N-ch, then flip the rails--use the positive rail as ground and negative rail as the "power supply" rail. It would still work.
The thing about ground is that it's relative. I know this seems unsettling to some folks, but there really isn't any such thing as "ground." It's a convenient fiction that we use when we're building equipment. As long as you're consistent within the circuit and don't try to reference anything other than the signal at the input and output, you'll be just fine.

Grey
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Old 20th August 2008, 11:02 PM   #487
udailey is online now udailey  United States
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Grey thanks a lot for that description. It helps. Well, it completely explains it.
I finished it and its running right now.
Now that I know it works I will get some more inputs for it and a few switches.
Click the image to open in full size.

My two year old saw the LED light up. "Cooool Daddy!! Cool!"

Poor Gal got her first music related boo boo today. She was headbanging to some Justin Roberts and her body couldn't hold the forward momentum of her head and she went head first into the little platform that our TV is on. This happens to be brick. She's tough though and is fine except for a bruise on her forehead.
I like that my hobby has her so interested in music. They love to do whatever we do.
UriahClick the image to open in full size.

Here she is pre injury HERE
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Old 21st August 2008, 01:40 AM   #488
Salas is offline Salas  Greece
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Default Re: Re: Initial impressions.

Quote:
Originally posted by analog_sa



Very cool review Salas. Many thanks for all the effort. It would be interesting to know how it compares to a passive - just the pot in this case. What's the bass like?
The bass is not overbearing and runs in lock with the mids. It lacks some slam. Midbass a bit dark.

I have used passive before, since my amp lends for it with its 120k input Z. Nice flow, no guts, boring, a little closed in. The B1 sorts out the dynamics missing, you can feel there is proper drive, and you don't listen to the pot's signature that much anymore. It just has the JFET follower tone. Which is really good versus other silicone. Not edgy. Especially in my DC coupling point to point version, the detail is high enough. But 100% local feedback in a buffer (any buffer) won't give you the top transparency and flow. Add the trademark darker silicone presentation versus glass, but in B1 stays in check.
Its just that when you have a really good and transparent single tube stage with no local feedback, you can't go back.

But I made the capacitor-less B1 not for primary duty. Wanted a trusty, non colored volume control in a little box that I can take with me everywhere. Actually, the performance is excellent for such a simple circuit and low expense. I don't know of a better value project. Highly recommended!
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Old 21st August 2008, 06:17 AM   #489
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Better PSU should give better result - especially in terms of channel separation, if you added a second pair of regulators for second channel. 1000F after regulators relevant reduced ripple.
Have not built B1, but tried this with another buffer. Big difference! And when B1 board is out, I build it this way.

Ernst
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Old 21st August 2008, 09:11 AM   #490
Salas is offline Salas  Greece
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Maybe, dual mono could give somewhat enhanced imaging. But I want it small and cheap. Not for main duty. Ripple is very low already, there is always doing further. But I don't like the tone of electrolytics as last caps. You can make it this and that and add this and patch that, but you will always listen to a JFET buffer, that will not change. But if someone gauges B1 as main preamp, there is scope for cooking up pots, resistors, hook up cable, PSUs, filter caps, even solder type and connectors, until kingdom come. Certainly there is enough basic performance to tune up. Just make it sans caps as I did. 4 rather large caps are going to cost an arm and a leg if you are shooting for top sonics. And maybe you will need to try 3-4 types if you are aesthetically selective enough.
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