• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Building monoblocks, go Dynaco MKIII or.....?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Greetings all!

I have a Music Angel XD800 Mkiii that I have been modding over the years and I'm now interested in moving up.

The MA 800 is 30 W (Class A) which is a little on the low end for my Martin Logan Spires. Therefore I'd like to build a pair of monoblocks that put out at least 40 W (each).

I've been looking at the Dynaco MkIII kits from Triode USA but am willing to listen to other options and see what this community would recommend!

Thanks for any and all comments!
 
JMO, the Dyna MK3 is rather ordinary.

A good deal more work, but would yield better results, is to build along the lines of the H/K Cit. 5. The Cit. 5 is a superior implementation of Mullard style circuitry. The 12BY7 H/K used as the voltage amplifier is getting scarce, but you can use the provided 6922 cascode instead.
 

Attachments

  • Citation-V-full-final.gif
    Citation-V-full-final.gif
    273.3 KB · Views: 541
  • Cascode 6922 Mullard Front End.jpeg
    Cascode 6922 Mullard Front End.jpeg
    636.5 KB · Views: 485
The MA 800 is 30 W (Class A) which is a little on the low end for my Martin Logan Spires.
Therefore I'd like to build a pair of monoblocks that put out at least 40 W (each).
I've been looking at the Dynaco MkIII kits

Agreed that the MKIIIs are not so good, partially due to the output transformer.
I'd keep what you have now. If you can bi-amp, try a good LF amp on the woofer.
 
Last edited:
Greetings all!

I have a Music Angel XD800 Mkiii that I have been modding over the years and I'm now interested in moving up.

The MA 800 is 30 W (Class A) which is a little on the low end for my Martin Logan Spires. Therefore I'd like to build a pair of monoblocks that put out at least 40 W (each).

I've been looking at the Dynaco MkIII kits from Triode USA but am willing to listen to other options and see what this community would recommend!

Thanks for any and all comments!
An Mk III is an excellent starting point, all hardware is there, it's easy to
assemble and it's a good base for further experimenting if one desires.

Also have a look at dynakitparts.com who also have a Mk III , and tubes4hifi.com that has a M-125 which is a new model that could deliver 120w
 
Last edited:
I've had many MKIII's cross my path. In the speakers I've owned, I've preferred a stock ST-70 to the stock topology of the MKIII.

The real issue with the MKIII is that the chassis is small. It's plenty big enough for the marginal driver circuit, but if you want to do anything better, you get cramped for space pretty quickly. Putting in a better power supply also means diving under the chassis as well. Which is OK because all the modern good quality electrolytic caps want to be on a circuit board anyway.

I've never really been in love with the monoblock thing, seems like needless complexity. I tend to stick with stereo amplifiers when given the choice.

Since you are doing your own thing ultimately, the stuff that matters is the best output iron you can get, and a good power transformer or two (a choke for the power supply is also a good thing). And the last piece is a chassis (or two) that allows you to realize the design you want.
 
Eli is right.

Rather then spend that kind of money on rather bland Dynaco amps that are going to drop in value,the Citation 2 or a Citation 5 makes much more sense and I use a pair of Citation 2s to run my Martin Logan CLXs.
I did the McShane mods to them but the wonderful thing about the Citation2 and the Citation 5 is,they have no problem driving difficult loads especially the Deuce.
 
The citation II is a great amp, I've got one driving my ESL-63's now. I've had 4 or 5 of them over the years and in my blog are a number of installments on things I've done to my latest one: Sheldon’s World

The output iron is outstanding, and I'm a fan of the driver circuit, but lots of people aren't.

They are pretty spendy these days, so the cost of admission isn't trivial.

Sheldon
 
It's not a state secret that, the better the "iron", the better the amp. The Cit. 2 is absolutely creme de la creme, but sourcing "iron" of the bandwidth needed by Stu Hegeman's all pentode small signal circuitry is, unfortunately, almost impossible. OTOH, Mullard style circuitry squeezes maximal results out of not absolutely stellar O/P trafos. Dyna O/P "iron" is a good value, but not stellar.

The OP seems to be interested in PP KT88 "finals". Excellent results would be achieved following along Cit 5. lines using PP KT88s and Edcor CXPP-100-MS-3.3K O/P trafos. Stu Hegeman's concept of high gm small signal types works. Modernizing tweaks would be a CCS in the LTP tail and yet higher gm in the LTP by using an ECC99, instead of a 6CG7.

BTW, monoblocks have an advantage in the weight dept. From personal experience, I can tell you moving heavy stuff around becomes more difficult, with advancing age.
 
Last edited:
Eli -

You are correct about the weight. I keep questioning how much longer I'll be lifting that Citation II before I hurt myself.

I had a Citation V many years ago, and it was a great amp as well. I never gave it enough time in my system because I also had a Citation II at the same time.

You are right about the mullard topology, it's stable and good sounding in my opinion. That 6CG7 phase splitter should be able to drive a set of KT88's as well, but the ECC99 is interesting to me. I'll have to play with them one of these days if I ever get time away from repairing quads.

Sheldon
 
Well, the Citation certainly sounds interesting! I've searched the web,
but can't find anywhere that sells a kit? Is it built from a circuit diagram?

That's a classic amp from the 50s/60s that was originally available as a kit. Used ones are
quite expensive, and will need extensive rebuilding to work well, being over a half century old.
It's also not a given that an electrostatic speaker will work safely or reliably with it.
 
Last edited:
When I started building amps about 4 years ago, my first couple were from pcbs. In retrospect, they were dead easy. At the time, I found them challenging, I learned a lot, and I was stoked when they amplified music. Just because they weren't ultimate fidelity didn't mean I was left wanting. Had I tried to build my ultimate amp back then, no doubt I would have failed and maybe even given up the hobby. My second amp was a stereo effort based on Mullard 5-20 from diytube. Push-pull EL34 Ultralinear on a tidy pcb. Strongly suggested. Maybe you are well beyond the skill level I was at when I started (even now!). If so, go for gold. If not, mid-level kit or pcb offerings are viable alternatives.
 
When I started building amps about 4 years ago, my first couple were from pcbs. In retrospect, they were dead easy. At the time, I found them challenging, I learned a lot, and I was stoked when they amplified music. Just because they weren't ultimate fidelity didn't mean I was left wanting. Had I tried to build my ultimate amp back then, no doubt I would have failed and maybe even given up the hobby. My second amp was a stereo effort based on Mullard 5-20 from diytube. Push-pull EL34 Ultralinear on a tidy pcb. Strongly suggested. Maybe you are well beyond the skill level I was at when I started (even now!). If so, go for gold. If not, mid-level kit or pcb offerings are viable alternatives.

I'm not looking to tackle my "dream" amp quite yet. Just interested in going from tweaking to building. Thanks for the post!
 
My views may be not the same as others.

MkIII or MkII are amongst the worst of the Dyna offerings.
Possibly, just possibly the earlier "potted" versions of that output iron were better, but I am not a fan of the output iron at all. Have yet to personally hear one, modified or not, that sounds "good" to me. Have owned them too.

Citation II, highly over rated output iron and design. Sure looks good.
I have had discussions with someone who worked at H-K as a design engineer at the time that they were being developed and made. Nothing special about KT-88 tubes back then, in fact they went away from KT-88 to 6550 because of reliability issues. Maybe people "like the way they sound", but I suspect that it's mostly because it sounds exotic to say "KT-88", and also it's not a 6550, which is a ubiquitous USA manufactured tube.

Also, nothing special about the output iron. It's a good design, but it's not widely known that they were wound/manufactured for them by more than one company...

Personally, I'd shy away from the AB1 type amp and always go for an AB2 type amp.
If you have big tubes, don't mind the heat then PP Class A2 may be sonic king.

I am a non-fan of the normal Mullard or Williamson circuits. They were used at the time because they were good enough and importantly cost effective. A good example of why this is so is the cascode circuit suggested above, it improves the performance. So, basically that's what I am saying, just about every stage can be "improved".

Bottom line on any tube amp: output iron & power supply. Get that right and everything is much better.

_-_-
 
Last edited:
NordicNorm, sorry I have no information on current "kits".
However Lundahl and a few other output iron makers (some Japanese ones) are highly regarded. I've got no personal experience with Lundahl, and have found that the import Asian iron varies, and depends on the specific transformer and maybe even the period of time it was manufactured in some cases.

Perhaps if you post up with a new thread, but giving real specifics of the proposed application - not just something like "60 watts with tubes" you might get some useful responses. The output iron is highly dependent upon the load impedances intended, the actual tubes AND the operating point for the tubes, if it is for limited range (like midbass and up?) or if for "full range" how LOW?

For example if you were going to biamp, and you wanted something for the top end, then you might consider amorphous core, or nickel core. Things like that.

My 2cents worth says that the ST-70 iron works out to be better to listen through than the larger Dyna iron.

If you browse through various tube projects here, you'll see a range of projects that include certain design "methods & features". They may be found to be for example in broad categories. Like "power supplies" - in which there will be a range of methods and options. The simplest 3 are: Choke Input, Cap Input, and Regulated. So you could look at projects with an eye to that, to start with. There are also broadly speaking other "major categories" like Input Stage, Phase Inverter Stage, Driver Stage and Output Stage. In each of these you'll find there are many projects that use methods that can be grouped together. You can look at Phase Inverters for a while. They are a whole lot of fun, since they range from simple one tube (with maybe a dozen or so variations there) to things that are 4+ tubes! And of course phase inversion can be done with a single transformer (always a good, stable and simple option!).

I know it is a deep and seemingly bottomless pit - but the question to ask in every case might be best stated as "what are the benefits & what are the compromises?" Then you can try to figure out why should one pick one method over another, and what might that do to the resulting sound.

Having said all that, there are two ends to the spectrum: most simple, fewest parts & tubes <---> most complex & greater number of parts. There must be a reason to have such a range, other than for the sake of doing an exercise in complexity! ( I guess ) :D

On the simplest side it can be said that a 100% transformer coupled amplifier is arguably an incredibly simple way to get an amp that "sounds good".

Btw, I vote for Triode over Pentode - and this is yet another thing that has sonic ramifications, they do sound different.

Boy, aren't you glad you asked a simple question now?? :D :D
 
NordicNorm, you might want to look at edcorusa - they offer transformer packages for several Pete Millet and Bruce Heran designs. I have no experience with those projects in particular, but both of those designers have been well received in the DIY community. I'm sure someone around here will have an opinion on those circuits.

I recently moved a MKIII setup to the upgrade/rebuild shelf after finishing my first solid state project (the MOD86 does sound great); this thread has my interest as I'd like to find a better PP tube design to pursue for my next power amp project.
 
I realize you are looking for something simple like a kit, and Bear has a lot of experience and maybe muddied the waters a bit. There is a lot of wisdom in that post, but I'm thinking you may be looking for a more pragmatic answer.

Here's my view of the tube amp world which I've been meddling in for almost 30 years. I'm not about to think that my views and my way is the best way, it's just my path...

I've considered scratch building tube amps many times over the years, and that's really appealing because I would build a high quality chassis that looks like I want it. I would use output iron and a power supply that is top notch. The issue that has turned me away many times is cost vs. rebuilding a classic amp. Modern high performing transformers are quite expensive (transformers have lost the economies of scale).

So I've gone the refurbish vintage and enjoy route. There are a number of amps that have good (enough) output iron and I've been able to buy an amp in reasonable consmetic condition. I add a few bucks and a lot of sweat equity and I've got a very nice amplifier.

I've avoided some nice quality amps like McIntosh, and Marantz because they are way too collectable and I'd be devaluing it by modernizing the parts.

One of the amps that has my attention are some of the chinese tube amps. I'm imagining the output iron is dismal, but China has the ability to make good iron and if they did, one of those amps (Yaqin MC-10 and such) could be a really interesting hobby project.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.