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design advise

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The point about PSU quality is spot on. When a quality PSU, with substantial current reserves is present, an extra 3 dB. of dynamic headroom is frequently observed.

The Heath W6M, with its Class "AB2" "finals" is a good place to start in obtaining the sort of power desired from a single PP KT88 pair. Don't use mediocre O/P "iron" in an amp with Williamson style circuitry.
 

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GKF

Member
2011-10-27 12:48 am
miramichi NB
thank you guys for your thoughts
i should have mentioned this in my first post
idea for tube amp is first for a visual knock your socks off view when they are first seen.
push pull design
and 4 or more tubes per chassis.
you know the effect i'm after, when you walk into a room and see tubes glowing you have to hear it.
i'm not disrespecting ss amp's here , they are powerful and great designs but just lack that room glow look.
checking out that tubes4hifi.com m 125 thank you petertub.
and Eli Duttman yes sir the best iron money can buy
 
Speaking off a quality PSU ... one that starts with a voltage doubler ??
And all the heater on one winding ? I prefere separate for the finals.
Mona

The Marantz 8B and the Harman/Kardon Citation II are among the very finest amps ever made. They use "full wave" doubler B+ PSUs. :yes: Implementation details affect the outcome, regardless of the topology chosen. Plenty of capacitance in the doubler stack and a choke to suppress ripple overtones are key elements in a well executed doubler setup. Often overlooked is the fact that copper losses are low in quality doubler setups.

There are several ways to obtain a low impedance, high current, B+ PSU. Any of them becomes the foundation stone upon which the entire amp is built. All good amps, both tube and SS, have good PSUs.
 
i should have mentioned this in my first post
idea for tube amp is first for a visual knock your socks off view when they are first seen.
push pull design
and 4 or more tubes per chassis.

We know that PP KT88s operated in Class "AB2" will produce sufficient power. You are going to need 2 or 3 small signal tubes to drive the beam power tetrodes.

We can add more glowing bottles to the cosmetics by using a pair of damper diodes in the B+ rectification setup. The 6CJ3 is a brute that is more than capable of handling a KT88 amp.
 
guys i have been looking all weekend at designs.
came along into this at some post link
Schematic - Genelex 100W Tube Amplifier @ AmpsLab.com

what i don't understand is this claims 100 watt from 2 kt88 when most others claim 35 or 40 watts from only 2.
can more kt88 tubes be added to this amp and will adding more mean more power?
 
guys i have been looking all weekend at designs.
came along into this at some post link
Schematic - Genelex 100W Tube Amplifier @ AmpsLab.com

what i don't understand is this claims 100 watt from 2 kt88 when most others claim 35 or 40 watts from only 2.
can more kt88 tubes be added to this amp and will adding more mean more power?

Oh it will do it, but the tubes will wear out very quickly. :mad: There is no escaping the reality of TANSTAAFL.

PPP can be "a can of worms". Getting quads of tubes closely matched for gm runs costs up. Reliable vendors work hard to get well matched quads that can be sold and they charge accordingly.

JMO, tweak the Heath W6M design and you'll be highly satisfied.
 
Oh it will do it, but the tubes will wear out very quickly. :mad: There is no escaping the reality of TANSTAAFL.

PPP can be "a can of worms". Getting quads of tubes closely matched for gm runs costs up. Reliable vendors work hard to get well matched quads that can be sold and they charge accordingly.

JMO, tweak the Heath W6M design and you'll be highly satisfied.
thanks
what is the power rating of the heath you mention?




100W from a pair of GU-50 is easy, and they last long. However, they require 800+ Volt B+ and 8-10K power transformer.

thank you and were can i see any design for this?
also guys i should mention this
in the past i have had a dynaco st70 cudcio mods and a cary rocket 88 with 4 kt88's but neither one could run my high impedance 3 ways to any good output.
they are just not powerful enough and run out of clean output.
i have sold both.
so that being said , and my goal of 100 watts stated, what else can i do?
maybe 60 or 80 watts if it's easier for a first time build.
i have now 2 mono esp p101 i use often but what a project.

you can direct me any where if you like please. you all have more history with tubes then me so i value very much your thoughts.
gordie

oh almost forgot , i want to do a point to point wiring as well no circuit boards.
 
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exeric

Member
2008-03-24 6:23 am
I'm coming late to this conversation. Perhaps I'm not looking at this correctly, but it seems like there might be an advantage to PPP over PP. No one ever said there was, or even could be, perfect matching of output tubes in PP. People pretty much accept that without even realizing it. You can get matched pairs but they certainly aren't perfectly matched.

However, there will be a statistical mean of tube characteristics from identical tubes from the same manufacturer. And there will a deviation from that mean of characteristics in each tube. However, the more tubes you have to select from in a PPP amp the more opportunity you have to equalize that mean on each side of the push pull by selecting tubes for more equal OVERALL characteristics on each side. I think people forget that the output tfmr is a very very good device for making a homogenous mixture of different characteristics for each side of the PPP. It just cannot equalize the opposing sides of the push pull action.
 

exeric

Member
2008-03-24 6:23 am
To add to the idea of mixing and matching on both sides of the output xfmr: It would be easiest to facilitate that idea in a non self-balancing design unlike a cathode bias with a common resistor. That self balancing would bypass the tube selection process. But discrete biasing will for each side will work just fine.

The best way to facilitate the selection process is to have 10 ohm or so resistors in the cathode circuit, one for each side of the push pull. Then all you do is measure the bias voltage to the common grids on each side of the push pull. What you aim to do then is move the tubes around so there is the most equal cathode currents on each side to the push pull for equal grid voltages on both sides.
 
Heath claimed a conservative 70 W. from the W6M. Build with a better B+ PSU whose impedance is low and whose current reserves are high and you rate to get pulses at 2X+ the continuous O/P power.

thanks guys for all your ideas
i have looked at so much over the last few days .
eli i got the heath circuit from a post you did on another site in 2013
how do find the needed output and power irons for the w-6m?
i'm such a novice that the ru-50 amps with 800v b+ has me scared.
i think the heath will be more friendly for a first build.
if any of you were to set out to build a w-6m what would you use for the best kt88?
 
thanks guys for all your ideas
i have looked at so much over the last few days .
eli i got the heath circuit from a post you did on another site in 2013
how do find the needed output and power irons for the w-6m?
i'm such a novice that the ru-50 amps with 800v b+ has me scared.
i think the heath will be more friendly for a first build.
if any of you were to set out to build a w-6m what would you use for the best kt88?

Heyboer may know how to wind the O/P "iron". If Heyboer can make the O/P transformers, they probably can make suitable power transformers too. However, if AnTek has a suitable model, their prices can't be beat.

The best current production KT88 is the "reissue" Gold Lion. Talk to Jim McShane or other reliable dealer, for your tube needs.

Send me a PM, should decide to take the plunge. Heath's Class "AB2" Williamson style topology is fine, but we can do better in small signal type selection, from both a gm perspective and a gain structure perspective. A 12AX7/ECC83 "can't fight its way out of a wet paper bag".
 
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