Tube pre-amps

virtue · « **on:** 15 Jun 2009, 04:44 am »

There's just no getting rid of the love for that tube sound, even among those who appreciate the power, accuracy, and dynamics of the Virtue power amplifier. Many customers are finding the best of both worlds by pairing the amp with a tube pre-amp. Which products are you using and what do you recommend?

doorman · « **Reply #1 on:** 15 Jun 2009, 10:17 pm »

As noted elsewhere, I'm using a Transcendent Sound GG (tubed) pre with my V-1.
It's dead quiet, blisteringly fast, doesn't require esoteric (read expensive) tubes and the kit price makes it one of the better audio purchases, IMHO.
I've yet to hear it paired with any amp it didn't compliment.
Don

droht · « **Reply #2 on:** 16 Jun 2009, 02:35 pm »

What should be considered when pairing a pre with the ONE or TWO?

I ask the question because I currently have a Keces DA-152 USB DAC/HP amp, which also acts as a preamp. I have been very happy with it sonically with all amps I have used it with. If I use it with the ONE and crank the volume to max on the ONE I have almost no adjustability of volume on the Keces. It is too much almost immediately.

The Keces is not a standard preamp, so maybe that is the issue. I want to purchase a Mapletree 2A SE, but I'm wondering if it will be any different.

Final questions. Does bypassing the volume pot do anything different than simply cranking it to full?

Thanks.

panomaniac · « **Reply #3 on:** 16 Jun 2009, 10:57 pm »

It does raise input impedance a little, as well as make for a slightly cleaner signal path. But I usually find that running the Virtue about 1/2 open and pushing the preamp harder works best.

droht · « **Reply #4 on:** 17 Jun 2009, 12:24 am »

Quote from: panomaniac on 16 Jun 2009, 10:57 pm

It does raise input impedance a little, as well as make for a slightly cleaner signal path. But I usually find that running the Virtue about 1/2 open and pushing the preamp harder works best.

So bypassing volume pot = cranking volume up all the way?

doorman · « **Reply #5 on:** 17 Jun 2009, 01:13 am »

Quote from: droht on 17 Jun 2009, 12:24 am

Quote from: panomaniac on 16 Jun 2009, 10:57 pm
It does raise input impedance a little, as well as make for a slightly cleaner signal path. But I usually find that running the Virtue about 1/2 open and pushing the preamp harder works best.

So bypassing volume pot = cranking volume up all the way

yes

panomaniac · « **Reply #6 on:** 17 Jun 2009, 09:44 am »

Close enough, yes.

bunnyma357 · « **Reply #7 on:** 17 Jun 2009, 12:46 pm »

It seems like the Euterpe kit Bill is putting together would be a good choice. I haven't heard it, but the price seems like a good fit with the Virtues.

http://www.audiocircle.com/index.php?topic=65651.0

http://home.comcast.net/~sonicrevelations/

Jim C

Hogg · « **Reply #8 on:** 17 Aug 2009, 11:25 pm »

What is the input impedance of the Virtue II? I tried a stepped attenuator with the Virtue II without success. I used a Goldpoint unit and the sound was not nearly as good as using a direct connection from the source.

Jim

al128 · « **Reply #9 on:** 18 Aug 2009, 01:41 am »

Quote from: droht on 16 Jun 2009, 02:35 pm

The Keces is not a standard preamp, so maybe that is the issue. I want to purchase a Mapletree 2A SE, but I'm wondering if it will be any different.

Thanks.

in your particular case ... you might want to look into the beresford 7520 DAC/Pre-Amp ... I think that a very unethical man (Mr. beresford has been banned often for shilling his products on audio-forums

) is building a very good DAC/Pre-amp combo for little $$$

incl. 30 days trial ...

or you could wait for the virtue DAC

cheers
al

al128 · « **Reply #10 on:** 18 Aug 2009, 01:54 am »

a technical Q:

what (signalwise) is the function of a pre-amp?

background ... back in the days I connected my Denon DCD1500 Cd player (often thought of as one of the first decent CDP's) directly into my power amp when my pre-amp died on me ...

voila ... its variable output made for instant happiness

that was in the mid 80ies

I never used a pre amp again in my life

what preamp can (signalwise) sound better than "none" it cannot add to the sound, only subtract (IMHO) ... you cant get less phase shifts, less distortion, hum, etc... than none ...

or am I missing something??? (except the obv. conveniance factor of input selection, etc...)

even my trusted NAD 320bee sounds a whole lot better when the DAC drives the "power in" input leaving the whole pre-section out of the signal path (yet it is still somewhat dull, liveless and unrefined)

thoughts??? or am I way off base here?

cheers
al

virtue · « **Reply #11 on:** 18 Aug 2009, 03:51 am »

Michael doesn't recommend using on the ONE/TWO a POT > 20k impedence, which is what you might have experienced with the GoldPoint. You would need a very high level input source to have the amp work well with a 50k or 100k POT... Of course, 20k or 10k is completely non-standard, sorry. The current pot in there is 20k...

panomaniac · « **Reply #12 on:** 18 Aug 2009, 12:06 pm »

Correct, 20K is the right value for the input pot. You can use other values, but 20K works best.

As for preamps, they often are not needed. But a good one can be a help in some cases. A good preamp or line stage can often add a lot of "drive" to the music, especially in the lower midrange. If done right, the loss of detail in minor and more than made up for with the more musical sound. Not all sources have enough current to drive an amp well. Many users have found that T-amps (Virtue included) do well with a preamp up front.

Then of course there are the input selections, balance, volume, loudness control, etc.

Hogg · « **Reply #13 on:** 18 Aug 2009, 04:20 pm »

Thank you for the answers. I'm not as interested in changing the sound, as adding the ability for additional sources. Is there a better solution short of the to-come "Sensation" model?

Jim

Cheerwino · « **Reply #14 on:** 19 Aug 2009, 12:31 pm »

Quote from: panomaniac on 18 Aug 2009, 12:06 pm

Correct, 20K is the right value for the input pot. You can use other values, but 20K works best.

As for preamps, they often are not needed. But a good one can be a help in some cases. A good preamp or line stage can often add a lot of "drive" to the music, especially in the lower midrange. If done right, the loss of detail in minor and more than made up for with the more musical sound. Not all sources have enough current to drive an amp well. Many users have found that T-amps (Virtue included) do well with a preamp up front.

Then of course there are the input selections, balance, volume, loudness control, etc.

Michael,

How's the new Virtue pre sounding with the Virtue amp?

-Guy

panomaniac · « **Reply #15 on:** 19 Aug 2009, 01:39 pm »

Well the DAC section sounds great. The analog section is still being "tuned."

Hogg - there are simple selector boxes out there, AKA a "bang box". or you can get a passive preamp that has volume control. I'm sure some members here have suggestions. I always just build my own.

Cheerwino · « **Reply #16 on:** 19 Aug 2009, 11:13 pm »

Quote from: panomaniac on 19 Aug 2009, 01:39 pm

Well the DAC section sounds great. The analog section is still being "tuned."

Analog sounds great as a schematic in your head?

panomaniac · « **Reply #17 on:** 20 Aug 2009, 12:39 pm »

Analog sounds great as a circuit we already used on our ICEpower monoblocks.

rhing · « **Reply #18 on:** 25 Sep 2009, 02:33 am »

Just received my Aikido Octal All In One kit from John Broskie's Glassware Audio. The All In One kit includes the PCB and components for constructing the widely acclaimed Aikido line stage amplifier. I will be using four (4) Tung-Sol 6SN7 (reissued version). I have other parts on order from Mouser including a Hammond chassis, separate power transformers for the B+ and heater supplies, and a pair of Epcos MKV B25834 3.3uF/600V film in oil caps bypassed with a pair of Russian FT-3 0.1uF/600V Teflon film caps that I got from Dweekie.

Once I complete the build, I'll post photos and listening impressions with the Aikido feeding the Virtue Two as a power amplifier.

TRADERXFAN · « **Reply #19 on:** 25 Sep 2009, 05:08 pm »

Quote from: panomaniac on 20 Aug 2009, 12:39 pm

Analog sounds great as a circuit we already used on our ICEpower monoblocks.

Hi, I am not very familiar with your company, so I have to ask to what icepowered monoblocs do you refer? I didn't find any on the website?

Also, thanks for the info on the attenuator substitutions... I was looking at a goldpoint preamp to use with the virtue 1, that helps a lot.

-Tony