Check out my 200w Guitar Amp with KT90s

[jelle]

Well, in all fairness...I'm not talking about those here, am I?

[dynamo]

[quote="jelle"]Welcome fellow ampbuilder. Would you care to tell us a bit about your transformers for the 200W? Are they customs, built by who and what are the spec?

Thanks,

Jelle[/quote]

I used Onetics Output transformers custom built for me. They make the best SLO, Marshall, Blackface, and Blues voiced PT i've found and they have some PT Stuff out of this world levels above what we commonly used for Guitar Amps. I'm working on a pure metal amp to use the next level OT because they are too fast for other guitar playing styles.

For power I started off with Onetics PT but I had Heat and noise issues, primarily because we reached a design Max for that style and size transformer. I had to switch to Toroidal to add more windings, run super cool, and reduce noise. plus the are so efficient they peak my amp way over 200w. I use 2 companies. Toroid of MD and PLitron. Both make excellent Transformers, i like Toroid of MD because they have the best service and one-on-one during the design process and they have a small family team. Plitron has a higher reputation in the Hi-Fi community, they cost more, but i chose to continue with them because they have a few in-house process I require for my transformers to reduce noise. My amps are double the power and thus potential double the noise so i must reduce it by going to the next level. They are 750v@600ma built around a KT88 power section

[Gaz]

Can you please explain double the power being equal to a doubling of noise? I'm also curious about what kind of transformer noise you were/are dealing with? I can't recall a properly positioned transformer causing noise...

[dynamo]

[quote="Gaz"]Can you please explain double the power being equal to a doubling of noise? I'm also curious about what kind of transformer noise you were/are dealing with? I can't recall a properly positioned transformer causing noise...[/quote]

Being that it a double the power is would make since that the noise is louder. So must make amp even quite to prevent.

Mechanical Noise. My first IE Laminated PT's sounded like a Fridgerator(due to being push to its design MAX and it was super Hot), had to mount on Rubber washers and use Nylon aluminum core screws to stop, When you pressed your hear to the cabinet you could still hear noise. So I switched to toroidal. My First Toroidal sounded like a fish tank. I had to encapsulate it in epoxy to kill it. Now I buy pre encapsulated PT from Plitron i have no mechanical noise. I also filter the power inside the amp with a DC blocker for the Toroidal because they hate stray DC voltage on the line

[Cliff Schecht]

Your understanding and my understanding of noise are very different. The noise we deal with in guitar amps is mostly thermal noise and 1/f noise, both of which are really side effects of our using low gm triodes throughout our amps coupled with a LOT of gain. This is why we are so anal about the tube choice in the first stage of really high gain amps, especially single channel amps like the Express that rely on a great tube in V1 to give you a /decent/ SNR*. We are dominated by these two noise contributors though (thermal and 1/f), both of which can be predicted well before you put solder to wire. Thermal noise is relatively easy to model. I won't go into the details of the origins but it can be calculated with noise power=4ktRB where 4kt is -174 dBm at room temp, R is the equivalent resistance and B is the circuit bandwidth. Just looking here it can be seen that the easiest way to decrease the noise power is to either decrease the equivalent resistance (as you do when you add additional output tubes!) or decrease the circuit bandwidth (something you don't do with additional output tubes!). So to be noted here is that when you add additional output tubes in parallel, you decrease the output resistance (equivalent to increasing gm) and effectively reduce the noise the output stage contributes (the bandwidth increase is mostly negligible). But really, on top of this, the amps noise floor is dominated by the first stage (or few stages) of the amp. The later stages are push-pull and have relatively high power supply rejection when compared to the preamp stages. If you are having noise issues then it's in the early preamp, not in the power amp! If anything doubling the power in the output stage will (theoretically) increase your SNR.. Your whole thought process is a bit off..

As for the mechanical issues, it's no surprise at all that you had to go to such extremes to keep mechanical noise at bay. You're pumping a lot of juice through that iron and you can't rely on the typical guitar amp construction methods. With that said, I still think that you should have no problem getting a modern custom wound transformer that can handle the power you are looking for without having to switch to toroidal cores and epoxy potting. That's additional processing that is expensive and almost never necessary for what we do (at least the potting, toroids can be cheaper). I can see the toroid maybe helping because when you're pumping out 200W from an output stage, you're putting a lot through an EI core which tends to spew any flux that is not coupled through the core. As that core heats up, you saturate easier and get more stray flux spewing out. In this regards toroids are super quiet because they leak very little.

I guess it's up to you to decide what to put where though, it's your amp and all, but unless we are getting gutshots you probably just lost more customers than you gained by coming here. Not trying to be rude about it but we see right through the bullshit and could probably have your amps deciphered in about an hour if we really wanted to. You aren't fooling any of us with any claims you have made, unless you can substantiate them with something meaningful then you are just as guilty as the rest of the amp industry for blowing smoke up peoples asses! I wouldn't buy an amp from you simply because it's obvious already that you don't understand them enough to build something worth my money.



*The first stage of any amplifier has the most significant noise contribution of noise to the circuit, later stages of said circuit will divide down the noise by the gain. This is predicted by Friis formula, although we must modify it slightly because this formula assumes a matched input and output impedance. But still you will eventually find that this idea still holds true, even the ultra-high gain and highly non-linear designs that we work with nowadays. This is assuming that noise contributions from a bad grounding scheme or coupling lines are dealt with properly, i.e. are non-existent.

[jelle]

Hi Dynamo, Thank you for your contribution. Jelle

[dynamo]

[quote="Cliff Schecht"] I wouldn't buy an amp from you simply because it's obvious already that you don't understand them enough to build something worth my money.[/quote]

Thanks Cliff for the feedback. I don't understand everything about guitar playing and hell I don't even read music. but it does not stop me from getting my music on the radio or featured in Rock Hard magazine best band CD Unerhort Vol 5. one of many other reviews and features on my music. Mike Soldano and Bogner were not amp experts they were Pioneers who experimented with an existing design and made it better. When I say better I mean for players like me who only played hard rock stuff!!! I doubt B.B.King would agree with me. Every guitar player in my circle, love what I've done with the GTS/GT-6 and those players cant wait to get their hands on it. I have a long list of amps I plan to build for everyone else including a special Texas edition Blues amp, 18watts, 30watts, combos, and more 100w-200w heads!

As far as my noise issues, I have never had any noise in the first gain stages or in the pre-amp period. So don't make it sound like i don't understand how to build a noise free amp. I am Anal about noise I even took it to Guitar Center to demo and they said it sounds normal to them they don't hear what I'm talking about. It has always been mechanical noise from my first versions of this amp. I switched to Toroid for less noise and as I stated before in other post, they ran cooler and i was able to add windings back that were removed from the IE PT to make room for my power requirements that required me to use a small 2nd PT for my switching circuit. My Toroids are awesome I slept with one under my pillow waiting to install it!! They are expensive but not as much as you think when it comes to custom manufacturing.

As far as my ability to build a Amp. Why are you attacking me instead of posting negative feed back about how bad my amps sound??????

[xtian]

As far as my ability to build a Amp. Why are you attacking me instead of posting negative feed back about how bad my amps sound??????

Because you're still not participating in the spirit this forum is meant for. That is, to share your work with schematics, photos and such, and in return, to benefit from the deep expertise of our generous members.

So far you've just used this thread to promote your expensive, and still mysterious, gear. If you just want to blab, thegearpage.net is great for that.

EDIT: Oh, wait…you did that too: http://www.thegearpage.net/board/showth ... p?t=975438

…but no one bit. Guess the joke's on us!

[John_P_WI]

First of all torroids are great for the reasons that you have mentioned. I wish they were as plentiful and as reasonable priced as other transformer options.

In keeping the spirit of this site, would you please enlighten us on your output topology? Is it similar to a Marshall Major, SVT, SSS? How are you driving the output tubes? Cathode followers, intermediate drive tubes etc - what type of tubes. Anything special with the PI? How are you handling the feedback loop - conventional or like the Major? UL connections etc? Hey, we are not looking for specifics, just generalities so we can dialogue and understand your directions as a designer.

Just trying to keep things fun here, and seriously good luck with your amps.

John

[markr14850]

I understand the strong reaction to what appeared as spam. But Jelle asked Dynamo a question about what transformers he uses and why, and got a pretty straight-forward and open response. Do we really need to go so far as to say that every detail of someone's commercial products be explained here in order for them to participate?

Times are pretty tough for everyone, but let's not make attacking each other be our default response.

My 2cents,
--Mark

[SoundPerf]

I understand the strong reaction to what appeared as spam. But Jelle asked Dynamo a question about what transformers he uses and why, and got a pretty straight-forward and open response. Do we really need to go so far as to say that every detail of someone's commercial products be explained here in order for them to participate?

Times are pretty tough for everyone, but let's not make attacking each other be our default response.

My 2cents,
--Mark

+1

[M Fowler]

I just don't see this as spam.

Dynamo amps have been around for awhile advertised in guitar/amps circles so it's not like he just started out and needs to advertise on TAG

The more builders on TAG the better to answer questions and help trouble shoot.

Mark

[Tone Junkie1]

Sounds like an awsome amp Dynamo. I can see how you would be proud of that

[VacuumVoodoo]

I for one am surprised by problems with EI core PT he had.
My question is: who skipped the homework on PT specs?
Problems like the ones you had usually stem from botched spec job and/or lack of communication with manufacturer.
Such situation is very common where there is more ambition than technical knowledge on the part of aspiring future amp builder combined with reluctance to ask for specialist help in fear of having his "secret revolutionary project" exposed. I've seen this enough times to be blunt about it.

[eddie25]

I for one am surprised by problems with EI core PT he had.
My question is: who skipped the homework on PT specs?
Problems like the ones you had usually stem from botched spec job and/or lack of communication with manufacturer.
Such situation is very common where there is more ambition than technical knowledge on the part of aspiring future amp builder combined with reluctance to ask for specialist help in fear of having his "secret revolutionary project" exposed. I've seen this enough times to be blunt about it.

Sure, but let's not pretend that pure technical knowledge is what creates great amps. What some see as a mistake might be a breakthrough for others. I for one, would rather listen to a sloppy old school heavy metal band than a super tight jazz group.

Not to say that I don't totally appreciate what you guys bring to the table. It's all good.

Let's let an amp be an amp though, and just slag on the guy for his questionable marketing techniques.