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This one is tempting!
This one is tempting!
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Old 10th July 2018, 10:17 PM   #1
blue_luke is offline blue_luke  Canada
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Default This one is tempting!

Hello all!
I am not new to audio electronics but somewhat 'inexperienced' in vacuum tube technology.
So to educate myself I bought a few good books on guitar amplifier design and construction and I got some success so far, meaning no explosion, smoke and some sounds!!

In my studio, my main monitors are a nice pair of Tannoys 12" gold monitor in a box built many years ago (mid '80's?)
I wanted, as a project to make new enclosures with the latest in T&S parameters and simulation etc... to find that they are just perfect as they are!
Just a tweek on the port and a few trims to beautify an otherwise spartiate ugly black plywood box!! (I should have said 'spartan' now you know English is not my mother tongue and yes, I am Canadian!)

So, after this long introduction, I am thinking very seriously of building a stereo or two monoblocs of about 25-30 watt tube amplifier to drive these excellent monitors.

I have read much about Williamson...ultra-linear, push-pull etc...

So I was leaning toward building a Heathkit WA4m or something along those lines (a Williamson with ultra-linear output) ...

Then I stumble on this gem! Lundahl Transformers • Old fashioned 30W Push Pull amplifier

On this link there is a complete instruction article, but more importantly, all the theory behind the design is exposed in a very easy to understand prose!
So this is very tempting to me.
There is also all the data on the tubes used, the transformers and some other goodies!

I am starting this thread then here to share this little 'discovery' of mine, and to discuss some aspect of the practicality of building an exemple.
To this end, I have a few first hurdles and questionning:
- Where can I buy Lundhal transformers in Canada, home turf of Hammond transformers!
- Can I replace the output transformer with a Hammond and what would be the consequences?
- In the paper, the UL taps are at 33% whereas most available transformers I could find, the UL taps are at 40%... what would be the incidence of this?
- after a few experimentations, I am quite fond of the KT77, and I like quite a bit less EL34's but this is not realy a condition, or design factor, I would use whatever is required!

Let's have some fun!

Sincerely, Luc
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Old 10th July 2018, 10:30 PM   #2
blue_luke is offline blue_luke  Canada
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OK when I closed my original post, this one appeared!! (search the forum) Claus Byrith 30W PP
Interesting thread, so I have a bit to read!
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Old 11th July 2018, 05:55 PM   #3
IceFyre13th is offline IceFyre13th
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Claus Byrith 30W PP

So hard to post a link.....
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Old 11th July 2018, 06:51 PM   #4
azazello is offline azazello  Bulgaria
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Lundhal is very expensive brand. Maybe their OT sound 5-10 % better than Hammond, but their price is some times higher. You maybe will not sense the difference....Hammond has very good OTs.
Projects: SE GK71, SE 12BQ6, PP KT88, OTL-OCL 6AS7 Gen. Electric, SEs 2A3 RCA, 300B JJ, 6S4S, 4P1L, EL11 Telefunken, 6AS7 RCA, 6S33S, 6S41S, 6S19P, E84L Siemens, E236L Telefunken, headphone ampl. OTL Loftin White 6AS7 RCA,...
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Old 11th July 2018, 08:28 PM   #5
hpeter is offline hpeter  Slovakia
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so you are comparing EI vs C cores..

i do not see huge price differences, but of course lundahl can be expensive with silver wires..
..BLOG.. XMOS_U8/PCM5102A > LL1544A > 6H9C+gyrator > 2A3_SOV/JJ > LL1660 > STAX SR207 _ SR L300 _ SR007 # LL2748 > 394A > LC 12H/1000Ķ // 4-125a test
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Old 11th July 2018, 08:48 PM   #6
spaceistheplace is offline spaceistheplace
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This one is tempting!
Default This one is tempting!

Lundahl is expensive (relative to others) but if you are inexperienced you may get some support from the designer if you run into snags using his suggested build.

Depends if the Lundahls are expensive *to you*

You could also try the Baby Huey which is in a group buy at the moment.

You want a nice overhead in wattage so you arenít driving the amps hard.

First determining ideal amplifier characteristics for your Tannoy drivers is the wisest suggestion I can offer; then surveying the available options and only then choosing whatís right for your budget.

Also for a tube power amp finding low cost high quality tubes is a frequently under-considered issue for many beginners. It adds up! Power tubes donít last like preamp tubes!

Poor choices there can make the cost differential between Hammonds and Lundahls seem totally minute in comparison on the long haul.

You might want to check out Tube Lab as well, he is a member here. Of course the Pass projects will also provide good results.
The real aim of music is to co-ordinate the minds of the people into an intelligent reach for a better world and an intelligent approach to the living future.
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Old 11th July 2018, 09:03 PM   #7
6A3sUMMER is offline 6A3sUMMER  United States
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It sounds as if you are building a pair of Hi Fi mono blocks, not a guitar amp.

A good design for a guitar amp may over-stress the output tubes in any or all of these:
plate voltage, plate current, plate dissipation, screen voltage and screen dissipation.
The amp produces the sound that is wanted, and the power that is wanted.
But the output tubes have short lives under these conditions.

A good design for a Hi Fi amp will not over-stress the output tubes. In that case,
You should be able to find quality output tubes that will last for years.

"All Generalizations have exceptions" - me
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Old 11th July 2018, 09:37 PM   #8
kodabmx is offline kodabmx  Canada
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A1 parts has the lowest prices for Hammond anything.
Transformers: A-1 Electronic Parts

Enclosures: Hammond Electronic Enclosures
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Old 12th July 2018, 01:52 AM   #9
blue_luke is offline blue_luke  Canada
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Originally Posted by IceFyre13th View Post
Claus Byrith 30W PP

So hard to post a link.....

So easy to search!
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Old 12th July 2018, 12:42 PM   #10
lordoff is offline lordoff  Bulgaria
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why not look at Kevin Carter from kandkaudio.com?
You will have excellent support and suggestion! Kevin are official distributor of Lundahl for USA,
have a massive experience with this type of transformers and more - some good design of power amplifiers.
I purchase from him several time (note that I'm from Europe) and will buy again definitely. 1st class of prices and support!

The other way, you can look to BabyHuey concept, also with Lundhal's.
Hope, my note helping you, not mess....
btw, Lundhals are very expensive only in their Silver and Amorphous core line. For example, look to prices of Tango or Tamura :-)

Last edited by lordoff; 12th July 2018 at 12:59 PM.
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