Got the Dynaco....

organ · June 2003

Well I finally got the amp. My friend came over after work to check out my system, play video games and listen to the Dynaco driving my LSi. We hooked up the 9's to the 4-ohm output and let the amp warm up for about 10 mins.

The first thing I put on was some opera and I was able to tell the difference immediately!(remember, this is my first time with tubes) It's something I've never heard before on any SS gear. The thing that grabbed my attention fist was the extremely smooth vocals it produced and the there's the "air" around the vocals, music, etc. It gives this illusion like you can hear the air in your room, it's very hard to explain. My friend couldn't believe how smooth the sound was and kept commenting on it. I really love the sound.

When he went home, it was time for me to do some critical listening. I couldn't believe how good this 40yr old amp sounds. It blows away every SS amp I've heard to date. I'm not saying that SS sucks but it sounds like tubes and SS like to focus on differeent harmonics. SS likes to focus on the higher freq harmonics while tubes focus on the mids. I heard so much stuff in the mids that I thought never existed on the recording. And all this harmonics in the mids makes the presentation sound very realistic and more natural to me. In one song that I tested which starts with a bass guitar, it felt like the front wall was warping back and forth with the bass guitar. The soundstage was that good! Another thing I really like about tubes is the ultra fast upper bass. When asked to, the amp could sound very hyper. I'm not getting any spongy bass. The bass is tight but won't reach as low as my NAD.

The one thing I like most about this amp is it's ability to convey emotions especially in the vocals. I'm just hearing so much more stuff in the vocals that I missed before. At times I could hear the harmonics produced by the frets on electric guitars even though the artist didn't mean to do it. It just picks up every detail.

As of now, I will not be going back to SS for 2ch amplification. It seems like I found what I've always been looking for in tubes.

While cleaning the tubes, the brand name dissapeared right before my eyes as I was wiping them clean. They're not dynaco tubes though. The ones still visible is one of the small ones which is sylvania, and GE for the rectifier. I will replace them but first I need to know how to bias this thing. While reading stuff on the net before, I thought I could do it. Now that I have the amp, I just don't understand a thing. The only thing I know is 1.56V on socket #8. I don't know where to adjust anything.

If any of you are thinking about getting a new amp, give tubes a try. It may be the sound you've always been looking for. They sound so different than SS.

Well, thank you for reading my post. I will post a review in about a month, after I get to play around with different tubes.

Maurice

pjdami · June 2003

Hey Maurice,

Nice review. Who's working for Stereophile now heh?

Congrats on your new discovery. Its been about ten years since I've heard a really good tube amp so I'm trying hard to remember but can't anymore except for warmth.

So does the Dynaco have similar dynamic range as the NAD C270? Or is just quality over quantity (though the C270's quality is pretty damn good too).

Very interesting indeed. .... Enjoy and keep us posted.

Paul

madmax · June 2003

Sounds like you have crossed over to the other side. Welcome!
madmax!

gidrah · June 2003

Good to hear. Mine is disconnected once again. This time it'll probably be for a few months though.:(

HBombToo · June 2003

Originally posted by organ

While cleaning the tubes, the brand name dissapeared right before my eyes as I was wiping them clean. They're not dynaco tubes though. The ones still visible is one of the small ones which is sylvania, and GE for the rectifier. I will replace them but first I need to know how to bias this thing. While reading stuff on the net before, I thought I could do it. Now that I have the amp, I just don't understand a thing. The only thing I know is 1.56V on socket #8. I don't know where to adjust anything.

1.56V is most likely the filament voltage. The filament is what heats the cathode for thermionic emission of electrons. If you now the model amp and find a schematic I'll be more than happy to help figure out what tubes and what replacements will work.

Good job on the amp and I hope to be there withya someday.

HBomb

organ · June 2003

Paul,
OK, we'll both start our own magazine then LOL I still love my NAD and I will try bi-amping when I have more time. I was going to save the comparisons for the review but what the hell. The NAD blows away the Dynaco for dynamics especially in the low bass, slam, and high high freq. The Dynaco has better mids and upper bass. The highs are very nice and mellow too. I feel like the C270 has better HF extension and more detail up there. The NAD sparkles and the Dyna shimmers. I'm not saying the Dynaco don't have slam or dynamics. It's there but it won't deliver them with authority like the NAD. I also keep getting this feeling like the Dyna has better micro dynamics but it could be my head. You're right about tubs being warmer. I also find the NAD quite warm and the Dyna is slightly warmer.
Are you going to check out some tubes also or are you still going for the B&K?

madmax,
I thought this "other side" was reeserved for old snobby audiophiles who are too lazy to listen to transistor amps. Now I know why they prefer tubes. I had no idea I would like tubes this much, I thouht I was SS for life.

gidrah,
Perhaps you could help me bias this thing. I keep reading about adjusting a potentiometer but can't find them anywhere. I read all the articles about biasing this amp and I still have no clue how it should be done.
Why won't you be using it for a few months?

HBomb,
I found a schematic somewhere. I'll look around again and I'll post the link when I find it. Glad to know you'll help me out with the tubes. I want to replace them but I need to know how to bias first. Thanks man.

Maurice

madmax · June 2003

When I got my first tube amp I looked at it like kind of a joke. You know, an antique to play with then delegate to a bedroom system or something. As soon as I powered it up it became obvious that it was far superior to many high dollar SS amps (way more in cost) I had been collecting. The next day I decided I needed to sell off some of the SS stuff and concentrate on tubes. That was with SDA's. When I tried the Lsi's I was less than happy. It is my opinion that if you are at all happy with the tubes and Lsi's then you would be estatic with tubes and some other speakers. Just a thought.
madmax

HBombToo · June 2003

Originally posted by organ

HBomb,
I found a schematic somewhere. I'll look around again and I'll post the link when I find it. Glad to know you'll help me out with the tubes. I want to replace them but I need to know how to bias first. Thanks man.

Maurice

don't worry about biasing right now. we'll just get a tube list going.:cool:

HBomb doing his Twin imatation.:D

Tour2ma · June 2003

Originally posted by organ
Now that I have the amp, I just don't understand a thing. The only thing I know is 1.56V on socket #8. I don't know where to adjust anything. Maurice

Here you go.... I've circled the screws for the bias adjustment for you.

BE VERY CAREFUL... long screwdriver is a must and be sure to stay on its insulated handle only... ST-70's have a mean bite...

Also be patient, as adjustment can be sensitive and be sure amp is warmed up or setting will drift on you.

Edit: I was assuming you have the ST-70 pictured below, but you did not specifically mention the model. If yours is the 35, let me know.

Also, Paul, you were asking about the dynamics. Don't know the NAD, but the 70 is a nominal, 35 wpc model that with new tubes can muster 40+. And with tubes, as with any pure class A, it's doing max out all the time. If not as music, as heat... can almost double as a toaster...

organ · June 2003

madmax,
What was it about the tubes and LSi you didn't like? Did you try it on the 9's or 15? I've never heard tubes on any other speakers but would love to hear them powering some Klipsch. Maybe I'll try it out with my 800i's.

Hbomb,
The schematic for the amp can be found at www.dynaco-doctor.com It is in the original instruction book located on the left side of the page in pdf format. You must be a tube freak to know this much about them. I can read the schematic but there's no way in hell I'd know which tube will work best LOL. I'd like some tubes that gives good dynamics and transients. I'm not really into the spongy bass thing right now. Thanks.

Tour,
Thanks man, that really helped. The only problem I have is that with the least resistance setting on the pots, I can only get 1.44V max. I think the tubes are dying or the rectifier may be bad. Before biasing my left channel was 1.02V and the right was 0.70V. Now both sides are at a constant 1.44 +/-.01

I think I'm going to need new tubes very soon. Last night while listening to my music, I heard distortion from the right channel and when I looked at the amp, one of the tube was ready to go. It was glowing brighter and turned red. So I ran to the amp, turned her off for a few seconds and back on. Everything's cool now.

Maurice

Tour2ma · June 2003

Good catch, organ. Did the problem occur before or after the bias adjustment?

What follows is a bit of a stretch for me, still a novice, but I am learning.

It maybe tube time, but if the unit was down as long as I think you were saying, the Cap probably did not reform properly if the unit was powered up suddenly. If this is it, then Im not sure if it is salvageable. Jumping it out of the circuit with a modern cap is another common tweak and will make the bias much more stable.

The old rectifiers were selenium (toxic) and replacing with silicon is a common tweak of little consequence sound-wise.

As for the tubes, Svetlanas are very popular and affordable, Russian made EL34 output tubes.

Please post what you learn/ do. Id like to compare notes. And thanks for the Dynaco Dr. link had been a while since Ive been there. Just read about 30 minutes worth of the Q&A forum

madmax · June 2003

I tried the tubes with the Lsi15's. Seemed like the power ran out before the speakers really woke up. The SDA's go WAY further before that happens. It seemed like all the real glory of the tubes was lost.
madmax

organ · June 2003

Well, I've been doing a lot of thinking lately. Now I want to mod the amp slowly. I will start with new circuit board from Dynaco Doctor that use three small tubes(SET?). I'm not planning on selling the amp so the sound quality is more important to me than higher value non-modified version.

Tour,
The problem occured after the bias adjustment. One of my friends, who is no audiophile but a musician who have tube gear told me that it's usually a sign of a broken seal on the tube. I was a little worried about the cap, but after checking the inside, it doesn't look too hard to replace. I just need to start learning how to solder first. I don't think I'm going to change the rectifier to SS because I want to keep it 100% tube amplification. I heard changing the rect to a SS will take away the warmth but give more bass.
I will look for some Svetlanas at the tubeshop.com thanks

A funny thing is happening. It seems like the bias voltage is going up slowly each day. For the past three days it has gone from 1.44 to 1.50 to 1.67. Maybe it's taking a long time for this unit to break in again. (Oh yeah, my meter is off by 0.1 so that 1.67 is like 1.55). I always check the bias at least 1 hour after power up.

madmax,
I feel the same way too but only with the bass. It's not as punchy with less dynamics, slam and deep bass. But the mid range makes up for it. I hope this improves when I get some new tubes.

*edit* Tour, how did you get your amp so shiny? Mine has a very thin layer of dust that's very hard to take out. Holy **** man, that amp looks brand new.

Maurice

madmax · June 2003

Organ,
Check out the "something interesting" thread. The article is long but they talk about the dynaco at one point. Interesting. It's worth the read considering you have one.
madmax

Tour2ma · July 2003

Originally posted by organ
A funny thing is happening. It seems like the bias voltage is going up slowly each day. For the past three days it has gone from 1.44 to 1.50 to 1.67. Maybe it's taking a long time for this unit to break in again. (Oh yeah, my meter is off by 0.1 so that 1.67 is like 1.55). I always check the bias at least 1 hour after power up.

*edit* Tour, how did you get your amp so shiny? Mine has a very thin layer of dust that's very hard to take out. Holy **** man, that amp looks brand new.

Sounds like the cap may be continuing to reform, which surprises me some...

As for the shine.... Once upon a time cars actually had chrome bumpers and trim... still can find the polish in auto stores... The plating may actually be nickel, but nickel is one of the metals in chrome. Good old auto chrome polish will do the trick. Just be very careful around the lettering. You can use Q-tips around and in between the words, if you wish.

organ · July 2003

Tour,
Thanks for the info. I'll go check out some auto shop for polish. I'll polish the amp while I'm modifying it.

I thought the caps were doing good but it looks like the quad cap crushed and burned. I posted this at the dynaco-doctor forum. The thread is called "really need some help guys". I got some great responses and I will buy the upgrade cap which raises the voltage from 500V to 600V. Maybe this will really wake up the LSi. I'm thinking about getting the upgrade board as well. I'll get either a replacement stock board or the premium.

Maurice

Got the Dynaco....

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