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A tubeNoob enters => I bought a Dynavox VR-70E

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Hi all,

After reading some enthousiastic reviews of this integrated tube amp, I decided to buy one to test if I'd like the tube sound and take my first step in Tube land. (I've never even listened to a tube amp)

It seemed like a very tempting affordable starting point (perhaps also for possible diy improvements) . Which also would prevent any real pain if this is going to be a disappointment.

It's got 4 EL34 tubes for the power amp and 2 6F2 for the preamp.

I've been playing around with the Tripath chip based amps lately, which I like very much. They are often described as having a tube-like sound. So I really felt I need to experiment with these as well then...
:D

Any experiences with this amp?

I hope this trip will be a good one. In the mean time, I'll dive into the 'Tube learning for newbies' thread
 

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kevinkr said:
I looked up the 6F2 and found that it is a triode/pentode so what I am thinking is that this amplifier both looks physically like and is probably a knock off of the Dyna ST-70.. The 6F2 is an obscure chinese/russian type which may be a little hard to get, but seem to be available from
http://www.diyhifisupply.com/

Kevin

thanks for the lookup!

On a german board, they are speaking about a replacement for these tubes.

There's some more info on that thread as well

http://www.hifi-forum.de/index.php?...ort=lpost&forum_id=100&thread=138&postID=last

I'm really anxious to find out how this chinese amp will sound...
 
Well, I don't really know what to say. I'm stunned, speechless.

Without having any tube experience as a reference: This amp sounds really, really good. And I've only run it for just one day.

I've been toying around a lot with the Trident chip based amps lately, so that's my latest reference. With very good results as well. I was really impressed (and I still am) by the performance of these little tripath amps in terms of dynamics, analytic and precise sound, very transparant, great stereo image and so on. The biggest challenge has been getting the LF dept right with these babies. Their biggest strengt h lies in the mid/high department. Before That I was mostly listening to a Cyrus Amp + PSX and my Yamaha. Both got blown away by the tripath amps.

Some remarks about it sounding 'tube like' really brought me to want to try out a tube amp, without really 'heavy' investing. Than this amp came on my way.

A first impression:
This is a totally different ballgame. Definately even more dynamic, excellent stereo image, nice warm sound in the low department, maybe not yet as defined here, but that may come. Amazing rich 'musical' sound. Voices and acoustic sounds really jump out in dynamic music (perhaps here's a comparison to be made with the t-amps) but it sounds more balanced, whole, rich. This is very, very good. I was listening with a friend and we both just kept quiet after the first couple of songs, just stunned and amazed. Very interesting to experience such a total different character compared to the t-amps, quite on the other side of the evolutionary time-line.


What will this baby have in stock for me weeks and months to come?

The last amp I listened to the most has been the unmodified reference 2021b tripath board on a 13,8V PSU. I like it a lot, but I really fear for it's place as 'resident amp' in the near future. Thank you Russia (or was it China :D ) I'm really happy I bought this, because I'm experiencing magic here, just like the first time I listened to a T-amp.

I'll take the opportunity to ask some questions which I didn't find a good answer to yet;

- One tube sometimes seems to produce a high pitch sound (like in an old telly, fortunately nothing near so loud) which comes and goes. This a sign of a bad tube or part of the burn-in period?

- It's got 4 EL34B tubes and 2 6F2 tubes. Can these just be replaced with any brand tube of the same type? Do you need to adjust the bias then? (For when I want to buy some spares. Recommendations?)
Obviously you can't judgde, but what kind of differences can one expect changing tubes with better ones? (not that I feel that I'm missing something right now, just curious)

- What's a normal burn-in time for these tubes?
 
Heh, welcome to the world of tubes! :D

Glad your new amp is good. Is it actually brand new? If so it may take a few days to a week to settle down.

In answer to your questions-

1) One tube may be microphonic. Take a pencil, and with the amp on but no music playing, *gently* tap the tubes, each in turn. A clunk sound is normal, a ringing sound indicates a microphonic tube which may need replacing.

2)Any EL34s and 6F2 types should just plug straight in. If it is auto-bias (cathode bias) amplifier it won't need to be adjusted, or have any adjustments. If it is adjustable bias (fixed bias), you may need to adjust for a new set. RTFM I believe :D

You should try and get matched pairs and preferably matched quads for the power tubes. Original British Mullard EL34s from the 1960s are awesome, but expensive. Some of the new re-issues are supposed to be good.

Good luck :)
 
In the German magazine Klang + Ton from Januari 2006 there is a intresting artikel for users of this cheap but very good VR 70-E.

In this artikel the Dynavector is modyfied in 7 steps. The artikel explains every step and illustrates this with pictures.

After modyfication there is much more basefundament and a gain in all the way precision.
 
I've just bought a Dynavox VR-70E modded as a power amp and i'm very impressed....the trouble is the manual's in German and being an ignorant Englishman can't read a word...hangs head in shame....

I've had a look at the bias voltages and i'm getting.

top left=340mv
bottom left=310mv

top right=256mv
bottom right=278mv

From what i can see from the manual the range is 250mv to 270mv...is this correct....and are the voltages way out or is this acceptable?

As you can see i'm new to valves and it's a whole new world for me.
Your advice and knowledge would be much appreciated.

Cheers,

Tim.
 
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