Anyone ever build Dynaco Amp Kits?

[klipsch4life]

Mark

How is your ST-120 holding up? Still happy with the results?

Kevin

[mark1101]

Oh yes. Still very satisfied. I fried a rectifier and 1 driver tube so far. I push the heck out of this amp with my avatar 3.6ohm speaker loads.......and so I consider tossing a couple of tubes now and then pretty normal. Other than the tube replacements no issues at all. Holds its bias well and simply sounds great each and every time I turn it on. CLEAN / TIGHT sound in the bass, creamy smooth mids, and crispy top end. I will probably be buying another in 2009 for biamping.

[NOSValves]

Mark,

Keep lots of rectifiers on hand your going to keep burning them up. I honestly think you'd be better off buying a SS replacement performance wise... 120 watts out of a single 5AR4 is the recipe for restricted dynamics and blown rectifiers... Heck the 60 watts a VRD is asking for all the a 5AR4 can produce...this is the one design parameter I have contemplated changing on the VRD(changing it to dual 5AR4's) It really takes dual tube rectifiers to supply the needed juice for the dual KT-88 60 watt stereo amplifier and even then its a raged edge design.

Ideally if it was me I would hard wire some really nice hexfred SS rectifiers and do some serious optimising of the PS for SS rectification.

[mark1101]

Bob Latino recommended a s/s rectifier. If you look on his website the amp is shown with one (tall copper). I read about them and was concerned about the downstream components at startup and about sagging during operation. They were reviewed poorly by a couple of people who measured them. So I haven't gone there yet. Honestly, I push the heck out of the amp and it continues to deliver. It may be running on its rails. I don't know. But it handles it, and it is CLEAN CLEAN and it's a little powerhouse too. My RTA system says I am running flat down to at least 38Hz out of my MWM bass cabinets (34Hz, about -5 db) and when using tones can produce 30 hz. at around -10 / -12db down. I don't think MWM horns will go any lower than that. My TAD 4002 HF drivers mated to the K402 horns are flat to past 19Khz. and I EQ'd them down some (just a little too hot). I'm not short of any top or bottom end. This setup is the very best sound I have ever had. I have finally got a very serious well engineered pair of speakers and that has probably made more of a difference than anything else. I didn't expect a couple of years ago that this is what it would be, but it happened.

Admittedly this is simply a very well built budget amp that has great synergy (with the Peach and the MCM grand cinema speakers). Probably nothing more than that. But it must have been done right. I'm sure it could be improved like anything else. I did get an upgraded power supply. It may be just enough or not. Don't know. But it all works very well right now.

I do keep a couple of Sovtechs on hand for the next time it happens. I know it will happen again at some point. I was surprised I failed a driver tube though. I think the driver board is worked hard on this amp. The caps on it get quite hot. But again, it has been several months now. The amp has long since proven itself. 2 tubes in about 6-7 months is expected with how I am applying it.

[Don Richard]

A customer sent me one of these amps recently - the 35W/ch version. They are really nicely made. The metal works are about as exact clones as you could imagine. The performance was good. The only thing functionally I didn't like was that the amp had really excessive gain making it more sensitive than really makes sense to me for a straight power amp. Nice amps for this kind of money.

There is an available low gain board using 12AU7s for use with preamps.

[mark1101]

I was told you can use 12AU7s in the board I have which is the higher gain drvier board. But I don't see any reason for it. In practical use the performance is great as is.

[NOSValves]

What caps are getting hot to the touch? That should not be unless the heat is being transfered from tubes over to the caps after hours of use.... For instance my Stereo amp where all caps and other related components are under the chassis away from tube heat it never exceed 95 degrees under the chassis even after playing all night. (I measured this once for a customer that wanted to try using audiophile coupling caps only rated to run 55c max. No way should a capacitior ever get hot to the touch on its own.

I bet what you have going on there as far as being able to reach these blistering levels with the amp still sounding clean is you never even remotely come close to reaching the restriction that the 5AR4 rectifier imposes on the amp with those huge efficeint theater speakers. This ain't rocket science a single 5AR4 can only deliver 225 to 250 mA of maximum current http://www.triodeel.com/5ar4_p1.gif and these specs are with a superior NOS 5AR4. If you bias 4 output tubes to say 50, 60 or 70mA each and have 3 12XXX series tubes using around 10ma each add it up........those are idle figures.... play some music it rises, push the amp it rises more....

If anything SS diodes properly done would have a stagering amount less sag... the 5AR4 absolutely has serious sag in that circuit. I'm not advocating using that plug in SS jobby since I have no idea of its internals... I suggested hard wiring a nice Hexfred design in, its really simple to do with some nice bypass caps... But hey if it sound good as your using it then why bother...

Heck you can even build your own plug in SS rectifier with some nice hexfreds diode using a 8 pin tube base like this... you solder them in and then fill the voids with black RTV all for under $10 LOL!! You could even do a bypass cap inside by simply running a ground wire over to an unused pin under the chassis on the 5AR4 socket although the physical size would be limited.

www.tubesandmore.com part # P-SP8-476

[mark1101]

The caps that get hot are the four power supply caps on the driver board in a line directly behind the 3 driver tubes. That may be why they get so hot. The quad cap barely gets warm. After several hours the transformers are just warm. It's only the driver board getting hot and it does have the 3 tubes on it.

[jacksonbart]

nope

[garyrc]

I built two Mark IVs (40 wt power amps) and a PAS 3 (preamp) in the '60s .... easy, good sounding, BUT I hear that people upgrade them with highet qulity caps and other parts now, so I would look into that, somehow.

The PAS 3 survived about 15 years of constant use at home, followed by 21 years on loan to the Psych dept. at San Frncisco State Universitym followed by 4 years of storage here in Oregon. I still pull it out and use it whenever a newer preamp conks out and is sent out for repair. It sounds as good or better than my NAD T163 home theatre preamp/tuner, as good or better than my old McIntosh C28 preamp, and almost as good as my late, lamented Luxman, EXCEPT for one thing: It sends a little too much hiss through the Klipschorns .... I don't know whether it developed that hiss while it was serving time at S.F. State, or if it always had it, but my old JBLs passed through less hiss than the K-horns (doubtrful).

[thebes]

Hey Mark, don't I recall you recently went through a whole solid state thing. Could what you are hearing with this kit be simply your ears rediscovering the advantages of tubes? I heard some Dynaco's before, and properly modded, they do indeed sound great, but I'm still wondering if it's the changes in approaches (SS vs Tubes) that is accounting for your new love.

Trust me when I tell that I'm not trying to stir the pot, but simply reflecting on my own experiences as I've switched back and forth.

Gary, after all those years, the hiss may simply be ther result of tired and drifted caps (long out of spec) a noisy resistor, tired tube etc. A few bucks and a little soldeirng oought to keep it going for another 40 years or so. Of course, it could be a number of things and the Khorns are very sensitive so it could be they always had that back ground noise. With help from my friends here I've rebuilt a couple of pieces and they always sound way better after a rebuild. I think it's become almost universally accepted here, and on other audio forums that decades old stuff needs some tlc.

Indeed I think this also applies to humans. Just last month I went to a doctor and told him it's time for a tuneup. I said I needed all my caps replaced and while they are at it check the tubes, resistors and power supply. He looked at me kinda funny and sent me to this wonderful home for "an evaluation". It's seems my components are still in fine fiddle though for I was soon released. They gave me something called "happy pills" they said were designed to keep my capacitance in check, but they sure do make me feel sleepy.

[mark1101]

Thebes, over the last couple of years I did make changes from tubes to s/s and then back to tubes. But during that time I still had (have) a couple of tube amps on my second system and never really got out of tubes altogether. I did make the most significant changes to my speakers though. I'm sure that is my biggest improvement.

However, I still feel the performance of these Bob Latino amps are very very good. I've made many positive comments and my opinions are still the same. I honestly believe they are somewhat of an undiscovered secret for the prices he charges. The problem is that I seem to be the only one on this forum that has one and no others have a way to comment yet. Eventually, someone else will provide their comments. These things will be around. Bob has sold quite a few this year.

As you probably know I used to have VRDs, and I've had numerous tube and s/s amps come through here. Some mine, some brought over by others. So I feel pretty comfortable about my comments. Again, I am saying great amp, but also system synergy and a big speaker improvement are all playing together here. I also forgot to mention that I purchased some room measuring equipment and room treatments. These have helped me tremendously in improving the room and that extra little EQ tweaking that escapes my "tuning by ear" that I have done over the years.

[jwc]

Mark.

What does this Latino guy think about passive biamping with his amps? I think you had told me that the two of you had discussed this before.

Can you have a mono dyno kit amp just doing 500Hz and up through a two way passive network?

If so..this would be something interesting for me to try on LS II's.

jc

[mark1101]

I have discussed this with Bob via email and he has quite a lot to say about it. He says it sounds best using VERTICAL biamping with his amps so that each amp handles a LF and HF channel. This is supposed to provide better channel separation and allow more power for each LF section.

The thing we did not discuss is if it is safe to passively filter after the amp or how his speakers are wired.......so I don't know. I could find out easily enough.

[jwc]

I forgot...are these mono or stereo? I guess stereo by your last comment.

It would be nice to know if "vertical" biamp would work.......either way...curious to know about tube amps only playing a limited frequency spectrum.....w/o "dangers".

jc

[Mike Dubay]

Last winter I build a pair of MK IIIs from Dynakit. Very happy with the results. I have not done any modifications, but plan on replacing the existing pp caps with high end replacements, maybe this winter. You don't need much tube back ground, can be assembled 'cook book' style. A week of evenings and they were assembled.

[thebes]

Thanks Mark. I very much appreciate your reply. Sounds like a lower cost sleeper for sure. Also sounds like you have your system about where you want it to be and that's always a treat.

It'll be interesting to see if anyone else here gives these a whirl.

[klipsch4life]

Bump.

[Nailbender]

I have one of Bob's 60wpc stereo amps I built from a kit. It works great after warming up with the copper cap rectifier, genelex gold lion Kt-88 reissues and mllard cv4024 12AT7s. I can't turn the volume over half way on my Blueberry. Sorry I don't have anything to compare it to. I haven't experimented with tube rolling yet either.There is a lot of power in these to drive my efficient Cornscalas. I think I could have gotten away with 35wpc.

Brian