best tube preamp for about $500

ckwase · « **on:** 13 Jun 2006, 07:05 pm »

I am looking for the best bang for my buck tube preamp for my IRD MB-100 monoblocks. ones i have considered are listed below.

norh aca 2b
ming da mc-7r
dodd audio basic
easterm electric mini-max (if i can find one used)
dared sl2000-a

I am leaning towards the norh because the price ($400 to your door) and i have heard good reviews. Altough i have heard the company is also fairly unreliable.

Please let me know what you think. Thanks.

p.s. this is my first post

dado5 · « **Reply #1 on:** 13 Jun 2006, 07:28 pm »

You may want to reconsider.

Those chip amps already have 30dB or so gain. That is more than enough for most home systems fed with a CD/DVD output. A tube pre will add 12dB or more on average and that will likely leave no room on your volume control (the old 9 o'clock is too loud syndrome).

If you are only looking for volume control/switching, go passive.

If you are looking to relax the sound a bit with tubes, try buffers or very low gain designs:

http://www.decware.com/linestage/zp1.htm

http://www.electra-print.com/ultrapath.html

DARTH AUDIO · « **Reply #2 on:** 13 Jun 2006, 07:31 pm »

Call Bill @ Eastern Electric. He may have a show demo. He's located in Arlington Heights. He's a great guy to work with, a class act!!

http://www.morningstaraudio.com/

chadh · « **Reply #3 on:** 13 Jun 2006, 07:42 pm »

I recently bought my first tubed component, a QA-001 pre-amp from Albert at Space Tech Labs ( http://space-tech-lab.com ). I can't compare it to any others, as I've never really listened to any others. But right out of the box it sounded wonderful to me. If you try hard, you can find a couple of reviews scattered through Audio Asylum and maybe one or two here. In it's most basic form, I think the QA-001 goes for around US$400.

The Dodd Audio ELP (Entry Level Pre-amp) is meant to be wonderful too. But it's out of production now, so you'd need to find it used.

BTW - I'm using my QA-001 with Channel Islands VMB1 chip-amp monoblocks (which give around 30dB gain), and my speakers are around 89dB sensitivity. The pre-amp is currently using a pair of 6SL7 tubes, and I don't find the gain too overwhelming. Which is a relief, as this was a problem I lived with for a long time with my old solid state pre-amp. What's more, the QA-001 will allow me to swap directly from 6SL7 tubes to 6SN7 tubes, which will lower the pre-amp gain by a factor of 1/2. So I think, with careful selection of pre-amp design and the tubes you'll be using, excessive gain need not be an issue.

Chad

Bob Reynolds · « **Reply #4 on:** 13 Jun 2006, 09:34 pm »

I agree with dado5, the Decware tube buffer would be a good choice. The problem with having too much gain is that you lose fine level control -- 9am is too low and 10am is too loud. Typical potentiometers are not linear across their entire range. You usually get the best performance on either side of the middle position.

chadh · « **Reply #5 on:** 13 Jun 2006, 09:42 pm »

Like I said, I have no problem using my tubed pre-amp with my 30dB gain chip amps (and 89dB sensitivity speakers), and listen at around 10 or 11 o'clock without any trouble. My source is a 2v output source (stock squeezebox 2). What's more, I can lower the gain on my pre-amp by switching to 6sn7 tubes. If you choose carefully, you can certainly get a tubed pre-amp that will not leave you with too much gain in your system.

Chad

Gvt1911 · « **Reply #6 on:** 13 Jun 2006, 10:19 pm »

Well here is my 2 cents...I have the Dared SL2000a, it is a great preamp,but I found that it can put out some DC ( About 40mv)...This will affect the IRD monoblocks since one cap is now removed for better sound quality..I have the IRD's also...Too bad, it does have a cool remote control..The result was my midrange driver "popping" at below average listening levels...I also had the Space Tech preamp ( which was wired wrong at the factory), inverted left/right channels,but was great because of the octal tubes used...Old School states octal tubes are the BEST preamp tubes around...If you do not need the remote,go with the SpaceTech and get yourself some nice RCA blackplate SL and SN7s...It would be a great combo...You would have a nice soft sounding preamp to go with those IRD mono's...
Best yet: Find a preowned Mapletree Octal 6 !!!!

Just saw a Mapletree Audio Octal 6 on the 'Gon for $475obo - WOW

Curt · « **Reply #7 on:** 15 Jun 2006, 01:07 pm »

Quote from: dado5

You may want to reconsider.

Those chip amps already have 30dB or so gain. That is more than enough for most home systems fed with a CD/DVD output. A tube pre will add 12dB or more on average and that will likely leave no room on your volume control (the old 9 o'clock is too loud syndrome).

If you are only looking for volume control/switching, go passive.

If you are looking to relax the sound a bit with tubes, try buffers or very low gain designs:

http://www.decware.com/linestage/zp1.htm

http://www.electra-print.com/ultrapath.html

26dB

Curt · « **Reply #8 on:** 15 Jun 2006, 01:11 pm »

Quote from: Gvt1911

Well here is my 2 cents...I have the Dared SL2000a, it is a great preamp,but I found that it can put out some DC ( About 40mv)...This will affect the IRD monoblocks since one cap is now removed for better sound quality..I have the IRD's also...Too bad, it does have a cool remote control..The result was my midrange driver "popping" at below average listening levels...I also had the Space Tech preamp ( which was wired wrong at the factory), inverted left/right channels,but was great because of the octal tube ...

MB-100s will pass a DC-Offset since they are ALL DC coupled (no MB-100 ever had DC blocking caps installed at the factory) but NOT amplify it like some amplifiers will.

In many loudspeaker systems 40 mV is not a problem, actuallu <100mV in many is not a problem.

Hope this extra info helps you make your decissions. Enjoy.

avta · « **Reply #9 on:** 15 Jun 2006, 02:17 pm »

ck:
I've got a Norh ACA 2b. I'm using it with an old Pass Aleph3 pure class A ss amp. and Magnepan 1.6's. I use a Squeezebox(wireless) for source along with Apple iTunes lossless ripped files. The sound is lush and quite enjoyable to my ears. I have no problem with volume. It's hard to imagine a better value for the money as the Norh is $400 delivered to your door. Good luck.
Guy

R_burke · « **Reply #10 on:** 15 Jun 2006, 03:43 pm »

Quote from: avta

ck:
I've got a Norh ACA 2b. I'm using it with an old Pass Aleph3 pure class A ss amp. and Magnepan 1.6's. I use a Squeezebox(wireless) for source along with Apple iTunes lossless ripped files. The sound is lush and quite enjoyable to my ears. I have no problem with volume. It's hard to imagine a better value for the money as the Norh is $400 delivered to your door. Good luck.
Guy

What tubes are you using in the ACA 2b, and what have you tried?

steve k · « **Reply #11 on:** 15 Jun 2006, 08:10 pm »

I'm curious too.

I had an ACA 2B for 5 months and couldn't get any other tubes to work in it but the stock EH's, which I didn't care for the sound of. I tried: Amperex PQ's, Russian Rockets, Siemens/Sylvania 7308's, Ei Gold Elite 6DJ8's, JJ 6922's, National 6922's, and Matsushitas and all of them went microphonic after anywhere from 1/2 hour to 2 hours of use.

I tried pairs of Herbie's Halos, Vibrapods, double Vibrapods, small fans on the tubes and nothing seemed to stop the squealing. I finally sent it back for a refund. As much as I loved the sound of the ACA, I could not keep any other tubes from going microphonic but the Electroharmonix.

A friend just tried Jan Phillips 6922's in his ACA2B and they went microphonic on him so he's back to using the EH's.

I also tried the ACA in a friend's system thinking it might be something incompatible with my system. Same problem.

I'm no electrical engineer but I think they're running these tubes way too hot and the microphonics are the result.
steve

Gvt1911 · « **Reply #12 on:** 15 Jun 2006, 08:42 pm »

Curt wrote:
MB-100s will pass a DC-Offset since they are ALL DC coupled (no MB-100 ever had DC blocking caps installed at the factory) but NOT amplify it like some amplifiers will.

In many loudspeaker systems 40 mV is not a problem, actuallu <100mV in many is not a problem.

He is correct,I only had this problem with the Von Schweikert VR4 gen III speakers...Large complex crossover in them...Wish I could get them to work with the MB100s and the Dared SL2000a preamp...Great amps from Curt, going to pickup the Purist preamp for a go round...So it depends on your speakers, the combo of the MB 100s and the Dared SL2000A may work great...Lot's of tube rolling there...Good Luck....

R_burke · « **Reply #13 on:** 15 Jun 2006, 11:31 pm »

Quote from: steve k

I'm curious too.

I had an ACA 2B for 5 months and couldn't get any other tubes to work in it but the stock EH's, which I didn't care for the sound of. I tried: Amperex PQ's, Russian Rockets, Siemens/Sylvania 7308's, Ei Gold Elite 6DJ8's, JJ 6922's, National 6922's, and Matsushitas and all of them went microphonic after anywhere from 1/2 hour to 2 hours of use.

Currently they are shipped with Sovteks, or at least that's what the web site says

steve k · « **Reply #14 on:** 15 Jun 2006, 11:49 pm »

R_burke wrote:

Quote

Currently they are shipped with Sovteks, or at least that's what the web site says

That's what it said when my friend and I bought ours but we both got EH's. I never tried Sovteks in it--never cared for them.
steve

texasphile · « **Reply #15 on:** 16 Jun 2006, 01:41 am »

I purchase a used Dodd Audio Intro-level preamplifier on Audiocircle.com and it turns out that it was the first one that Gary made! He upgraded the capacitors to Sonicaps and it is the nicest sounding preamp that I have owned (Perreaux, Plinius CD-Lad, a Monolithic Sound PA-1 with outboard power supply). I guess I just like the "tubes/valves" sound more than solid state in a preamp.

Regards,
Chris

avta · « **Reply #16 on:** 16 Jun 2006, 02:47 am »

I'm using Amperex 6038's Holland 1967's. They're a bit softer sounding than the 6922 EH's that came with the unit. I haven't tried any other tubes. What are you folks hearing that you're calling microphonics?
Guy

steve k · « **Reply #17 on:** 16 Jun 2006, 04:14 am »

Microphonics, in my case, started when you tap the top of the tube and you can hear it amplified in the speakers. A lot of my tubes would start to whine a high-pitched whine when they got really hot. The whine got loud enough that you could hear it over the music. If you tapped on the tubes, they would stop whining for a few minutes and start to whine again. With a pause in the music, you could hear the whine from quite a distance from the system.

truant · « **Reply #18 on:** 16 Jun 2006, 05:01 am »

I used to have the ACA 2b and IRD MB100s. I had the same tube rolling issues. The only tubes that would not whine were the stock Sovteks. A pretty dynamic little pre but too harsh and uneven to my ears over the long haul. I also had the Dodd entry level pre for awhile but then tried a couple of passives which I liked alot. I was also trying to stay around $500 but when you end up buying 5 or 6 preamps looking for that certain synergy your original budget turns into something else altogether. I was finally going to buy the Purist thinking it would be the right mate for the MB100s but stumbled on the ONIX SP3 on sale and decided to get away from separates altogether. So while I never got to experience the Purist I'd give it a good look.

Curt · « **Reply #19 on:** 16 Jun 2006, 08:57 am »

Quote from: Gvt1911

Curt wrote:
MB-100s will pass a DC-Offset since they are ALL DC coupled (no MB-100 ever had DC blocking caps installed at the factory) but NOT amplify it like some amplifiers will.

In many loudspeaker systems 40 mV is not a problem, actuallu <100mV in many is not a problem.

He is correct,I only had this problem with the Von Schweikert VR4 gen III speakers...Large complex crossover in them...Wish I could get them to work with the MB100s and the Dared SL2000a preamp...Great amps from Curt, going t ...

I actually believe there should be no DC offset sent to the loudspeakers, even if it doesn't hurt anything. This is simply a matter of good engineering.

If there is an offset going into an MB-100 from upstream (i.e. from the preamp) I consider anything less than or equal to 5mV normal and acceptible and anything above 5mV a problem.

I believe any line-level component putting out more than 5mV of DC-offset is defective and should be repaired. This is my opinion.