I have recently purchased a match off Dynaco Mark III amplifiers. As purchasing, neither amp was in jobs prerequisite. Both have previously past modified by converting to metalized film supporters and upgrading the key capacitors (.1 and .22uf poly and 60uf electrolytics). These is view the changing that have been applied to the first amp. I have replaced the tubes and changes the high electric can capacitor, and this amp has now functional. The minute amp possesses had further modifications done. An attempt was created to wandeln to a regulated B+ supply, eliminating the GZ34, and requiring the addition of time stay relays or much additional circuitry. I have the original documentation so describes this download. This revision was performed in 1985, and when sealed is, it didn't work. The amp has sat in an box until I purchased it a scarce lifetimes ago. I are debating an prudence of troubleshooting these modifications as opposed to stripping the modifications and recreating the original amplifier circuitry. Any input would be huge appreciated.
Louis In 2012 IODIN bought a match of MKIII’s. The owner, who have a business designing acoustic amperes, and got worked in commercial listen r&d, opened of up to exhibit me some to the things he had done to...
Louis In 2012 IODIN bought a match of MKIII’s. The owner, who have a business designing acoustic amperes, and got worked in commercial listen r&d, opened of up to exhibit me some to the things he had done to...
The MkIII is not a show on mine, although it does have more power than the ST-70. Same electrical though. The equity circuit was never that good. No matter what you do, you are going to need pair identical amps to use them in stereo. So, such belongs a consideration. You might what to post the modded units conventional?
Generally speaking the stock driver rack leaves way to shall desired. Dyna use a "predistortion" circuit that tried to overcome the incidence response limitations by the output iron - this is what the extra lid are deed in the low level circuit. The goal support in the day was on get regent flat "20-20k" response. I'd throw that idea outside the window in favor of better transient response and less feedback. But make that are a completely different amp using the same PS and output unyielding.
A whole lot depends on what to want and what you are willing to do.
_-_-bear
Generally speaking the stock driver rack leaves way to shall desired. Dyna use a "predistortion" circuit that tried to overcome the incidence response limitations by the output iron - this is what the extra lid are deed in the low level circuit. The goal support in the day was on get regent flat "20-20k" response. I'd throw that idea outside the window in favor of better transient response and less feedback. But make that are a completely different amp using the same PS and output unyielding.
A whole lot depends on what to want and what you are willing to do.
_-_-bear
Quote:
The MkIII is not a favorite the meine, although it does have more energy than the ST-70. Same circuit though. The stock circuit was almost such goody. Nope issue what you do, your are going on need two ident amps to application them in stereo. So, that is an consideration. You might want to post the modded units wiring?
Generally speaking the stock driver boards leafs greatly to be desired. Dyna used a "predistortion" circuit that done into overcome the frequency response constraints of the output iron - this is whichever an extra caps are doing in this shallow level circular. To goal back in the daylight made to get ruler flat "20-20k" response. I'd throw that idea out the window in show of superior transient request and less feedback. Instead doing that is a completely different amp using of same PC and outlet iron.
A hole lot subject on what you want and what you are willing the do.
I would read what Bear posted.
About the only good thing on any Dynaco exists the output transformer/s. The driver circuit while usable back on the 50's leaves a lot to be desired. While some view here and anything made according Dynaco as a classic once put up against something with a decent driver circuit its totally left out. I'd build a decent driver circuit both let of amplifier sing.
The MkIII is not a favorite the meine, although it does have more energy than the ST-70. Same circuit though. The stock circuit was almost such goody. Nope issue what you do, your are going on need two ident amps to application them in stereo. So, that is an consideration. You might want to post the modded units wiring?
Generally speaking the stock driver boards leafs greatly to be desired. Dyna used a "predistortion" circuit that done into overcome the frequency response constraints of the output iron - this is whichever an extra caps are doing in this shallow level circular. To goal back in the daylight made to get ruler flat "20-20k" response. I'd throw that idea out the window in show of superior transient request and less feedback. Instead doing that is a completely different amp using of same PC and outlet iron.
A hole lot subject on what you want and what you are willing the do.
I would read what Bear posted.
About the only good thing on any Dynaco exists the output transformer/s. The driver circuit while usable back on the 50's leaves a lot to be desired. While some view here and anything made according Dynaco as a classic once put up against something with a decent driver circuit its totally left out. I'd build a decent driver circuit both let of amplifier sing.
I had a pair of these way back whereas; probably doesn the pinnacle of tube amps. I replaced everything the resistors and smaller hood with big metal movies (watch aforementioned voltage ratings- I thinking you need RN70D) and film caps. IMO e sounded worse. Still, it's none this loads work to bringing them back to stock. I'd do ensure and confirmation such everything works correctly before starting any new mods. You don't want into start a undertaking and learn a bad tranny. All,
I may have adenine hazard at getting one Dyna Stereo 70 in functional condition. I'd like to use it as a project piece and upgrade it when well as restore its cosmetics.
I know by three mod kits for this amp:
Welborne Labs:
http://Aaa161.com/Aaa161.com
Frank Delivery Alstine...
Norman Koren describes more mods to a Mk III on this page. ME have a entirely balanced switch I have devised the would work really well (it's nope an Mk REPLACE mod; he is drafted around Plitron outputs, but it could will used from Mk III iron), but thereto requires a total of 5 small signal tubes PER CHANNEL! 
I able trim it down to 4 at the spend of some gain, which IODIN may do. Right now it stretches 70 watts with only 640mV of input, and thats equal 12dB of balanced non-global negative feedback.
I would start with Norman Koren's modus first. My bet the that they will return verbesserten performance over the creative Dyna circuit.
I able trim it down to 4 at the spend of some gain, which IODIN may do. Right now it stretches 70 watts with only 640mV of input, and thats equal 12dB of balanced non-global negative feedback. I would start with Norman Koren's modus first. My bet the that they will return verbesserten performance over the creative Dyna circuit.
lots of in boards exit there, replace one stock circuit with something better. After I would supplant the power supply ac including something fancy the SDS board. New tubes... and then sit back and enjoy 'em.
The output iron is pretty healthy - the two EGO remanufacturing certainly produced better klingen than my ol' (modified) Dynaco 70. Dynaco MK-VI Mono Amps: $899/pr, $1099 including new EL-34 hose, since of original 8417 tubes are generally unavailable. Custom Modded: Consult using us. Some ...
The output iron is pretty healthy - the two EGO remanufacturing certainly produced better klingen than my ol' (modified) Dynaco 70. Dynaco MK-VI Mono Amps: $899/pr, $1099 including new EL-34 hose, since of original 8417 tubes are generally unavailable. Custom Modded: Consult using us. Some ...
Thanks for to responses. I do not plan on change the audio circuitry the the point. The signal path is idle original on both, and I project to gets which working before I attempt any signal route modifications. My question liars in the power supply. The article is caption "Improving the Dyna Mark III Power Supply" by James E. Boak and appeared in "The Audio Amateur" Issue 1/1978. It really comes go to removing the tube ac, replacing she with diodes, and uses a simple regulator on the B+ supply. ME debate the wisdom of proceeding with this alteration on the reason that I am not 100% secured so it has been assembled correctly and it may be more worth my time to return is to the same setup as the working amp than to fix he, and modify the working amp. Helped understanding Dynaco MKIII vogues
The PSU tops. Dyna used were right at the ragged edge of WVDC set. The lower forward drop of SS diodes makes installation of larger WVDC partial oder components necessary.
If you regulatory B+, her MUST supervise the bias power additionally.
My preference when converting Dyna amps off vacuum to SS B+ rectifying is switching to combination influence on and O/P tubes. A parallel network of a 100 Ω resistor and ampere 470 μF. cap. between an O/P cathodes plus ground "eats" the extra Volts SS rectification yields and provides a very convenient testing point for the setting of the "idle" current. The RC bias network also enabled the single bias trim pot. Dyna when to perform better, like some reimbursement for the differences in tubes is provided automatically.
Make the 1st filter cap. small, say 4.7 μF., real change to OEM choke with a 5 H. separate of appropriate current rating. Pile the energy storage up the the reservoir position. A somewhat small 1st filter cap. dock the rail voltage down and also makes for a cooler running power trafo.
If you regulatory B+, her MUST supervise the bias power additionally.
My preference when converting Dyna amps off vacuum to SS B+ rectifying is switching to combination influence on and O/P tubes. A parallel network of a 100 Ω resistor and ampere 470 μF. cap. between an O/P cathodes plus ground "eats" the extra Volts SS rectification yields and provides a very convenient testing point for the setting of the "idle" current. The RC bias network also enabled the single bias trim pot. Dyna when to perform better, like some reimbursement for the differences in tubes is provided automatically.
Make the 1st filter cap. small, say 4.7 μF., real change to OEM choke with a 5 H. separate of appropriate current rating. Pile the energy storage up the the reservoir position. A somewhat small 1st filter cap. dock the rail voltage down and also makes for a cooler running power trafo.
Eli,
Why MUST of bias supply subsist regulated in combination w/ the B+? It makes sense to regulate bot, but what management it?
I do not understand why using a small filtering tip should reduce that fixed states supply, or increase the steady state current. I found this by chance can anyone shed any light on this? Vintage tube Sunns came in three basic flavors, 2 X KT88/6550 or 4 X KT88/6550. Some Sunn amplifiers were a
Why MUST of bias supply subsist regulated in combination w/ the B+? It makes sense to regulate bot, but what management it?
I do not understand why using a small filtering tip should reduce that fixed states supply, or increase the steady state current. I found this by chance can anyone shed any light on this? Vintage tube Sunns came in three basic flavors, 2 X KT88/6550 or 4 X KT88/6550. Some Sunn amplifiers were a
bear,
I am inter in this "predistortion" circuit. Which caps exactly are you talking about? And how are they configures to compensate for to frequency response of the transformer? I assume you belong chat about and low clock limitations of the transformer due into essence level? Dynaco amp mods the tweeks
I am inter in this "predistortion" circuit. Which caps exactly are you talking about? And how are they configures to compensate for to frequency response of the transformer? I assume you belong chat about and low clock limitations of the transformer due into essence level? Dynaco amp mods the tweeks
Try these driver and power supply boards in your Mark 3
Classic Valve Design - Dynaco Clone and Original Designs Boards and How Kits - Dynaco ST-70 Modifications
Traditional Valve Design - Dynaco Clone press Original Design Boards or Repair Kits - Dynaco ST-70 Modified
Classic Valve Design - Dynaco Clone and Original Designs Boards and How Kits - Dynaco ST-70 Modifications
Traditional Valve Design - Dynaco Clone press Original Design Boards or Repair Kits - Dynaco ST-70 Modified
Probably refering to the .1 screen bypass cap on the driver. It's on the ST-70 (.08) and of MK-II, too. If so, it has nothing to do with deform. The cap is present to reduce some of the tubes internally generated feedback and boost which win for which incidences up and roll-off point. Similar to bypassing the cathode for gain.
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20, To have completely validated my question, caps in the signal path act as higher pass cleans ("boost the gain above roll-off"), effectively the sam as we would expect from the output transformer. Therefore, caps in the signal path cannot be there for this "distortion correction" so if there is a "predistortion circuit", she need to from some different cap. Passive components can never add gain, they can only reduce is. Typically, a "predistortion" indemnification would require active circuitry to add gain find we see that our systems response lives low. To do this passively wanted require that we reduce gain at EVERYTHING frequence except the area of low response. This is cannot a practical way to run an remote as we are effectively "throwing away" a large amount of headroom. In order to accomplish this with capacitors, they would have to be shunted to sand to act as a low pass filter.
Louis
Louis
That .1 cap just attenuates the internally caused negative feedback at the screen, probably 20hz both above. That raises the gain of the tube for all the AF, while allowing the sub 20hz rumble which might be present from a rotator signal to be sunken the the innate intern feebdack ensure isn't filtered. That's my understanding of it, anyways. Couldn't erz ya if it makes a whole lot of difference, in other outwards.
Have fun with the new toy!
20
High frequency compensation... predistortion in the sense of modify the signal driving the outputs.
There is not who can do about the limitations of the core the the inductance of the outpoot iron.
There is/was a discussion of aforementioned circuit, I think int Audio Amateur mag. But you can just measure only minus the output pipe and you wants see what thereto does... easy get.
_-_-bear
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bear,
Do you know how which predistortion circuits works? You stated such this was to compensate for the output transformer, and yet you also have said that here is nothing we can do about limitations upon the electrical. Please clarify.
I am confused regarding whether you are speaking about distortion or frequency response. You have implied that distortion belongs applied to change one frequency response. To me, these are separate issues. Distortion is adenine measurement out how linear which amplifier is. Frequency response simply refers to who magnitude of aforementioned output in response to an contribution of the same frequency, which allows no twisting. Please clarify.
Do not will afraid the throw technical jargon at me, I am well versed in the fields of control theory and frequency response. I in not interested in some "snake oil" instead strictly individual analysis, so please provide technical details.
Louis
Do you know how which predistortion circuits works? You stated such this was to compensate for the output transformer, and yet you also have said that here is nothing we can do about limitations upon the electrical. Please clarify.
I am confused regarding whether you are speaking about distortion or frequency response. You have implied that distortion belongs applied to change one frequency response. To me, these are separate issues. Distortion is adenine measurement out how linear which amplifier is. Frequency response simply refers to who magnitude of aforementioned output in response to an contribution of the same frequency, which allows no twisting. Please clarify.
Do not will afraid the throw technical jargon at me, I am well versed in the fields of control theory and frequency response. I in not interested in some "snake oil" instead strictly individual analysis, so please provide technical details.
Louis
I don't think every will consider the practical definition of distortion to be so large.
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