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
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
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..
http://jacmusic.com/html/order/jacmusic-pricelist.pdf
i do not see huge price differences, but of course lundahl can be expensive with silver wires..
http://jacmusic.com/html/order/jacmusic-pricelist.pdf
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 aren’t 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 what’s 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 don’t 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.
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 aren’t 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 what’s 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 don’t 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.
blue_luke,
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
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
A1 parts has the lowest prices for Hammond anything.
Transformers: A-1 Electronic Parts
Enclosures: Hammond Electronic Enclosures
Transformers: A-1 Electronic Parts
Enclosures: Hammond Electronic Enclosures
Luc,
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
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
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Thanks Lordoff
I just went on their site and they have interesting stuff.
The LL1663 is listed 145 USD, so once in canada with exchange and taxes etc... and shipping i guestimate approximately 500 CND!
This is getting a bit steep!
(I am now retired... lots of time on my hands, few dollars less available now! )
Surprisingly, Mouser have quite a good number of Hammond transformers in stock. I am looking at the 1650HA (6k ct /4-8-16 ohms sec, 40 watt) at almost 3 Kg, it is a rather serious item... 188$ plus federal tax, free shipping.
While I was there I also checked if they have guitar amps replacement transformers and they do have a few in stock.
There is also Next Gen Canada's #1 Parts Source For DIY Musicians - Next Gen Musical Ltd. which I think is in Guelph, free shipping on order over 200$
I will be looking into that further more in early August. Tomorrow I am leaving until july 29th for a trip in the maritimes provinces and Gaspesie. I am accompanying a choir on a tour, recording the concerts etc...
I will keep in touch but there is no 'bricolage' to be made while on the road!
I just went on their site and they have interesting stuff.
The LL1663 is listed 145 USD, so once in canada with exchange and taxes etc... and shipping i guestimate approximately 500 CND!
This is getting a bit steep!
(I am now retired... lots of time on my hands, few dollars less available now!
)Surprisingly, Mouser have quite a good number of Hammond transformers in stock. I am looking at the 1650HA (6k ct /4-8-16 ohms sec, 40 watt) at almost 3 Kg, it is a rather serious item... 188$ plus federal tax, free shipping.
While I was there I also checked if they have guitar amps replacement transformers and they do have a few in stock.
There is also Next Gen Canada's #1 Parts Source For DIY Musicians - Next Gen Musical Ltd. which I think is in Guelph, free shipping on order over 200$
I will be looking into that further more in early August. Tomorrow I am leaving until july 29th for a trip in the maritimes provinces and Gaspesie. I am accompanying a choir on a tour, recording the concerts etc...
I will keep in touch but there is no 'bricolage' to be made while on the road!
There is also ClassicTone Transformers By Magnetic Components, Inc.
Anyone using these transformers?
Anyone using these transformers?
ClassicTone would probably be better suited for a guitar amp, but then again, I have not tried them.
I've built two amps similar to the circuit shown in Claus Byrith's "4-10" white paper, but I didn't follow his schematic at all.
Both of my amps were stereo chassis builds with approx 400V B+. One used a 6DJ8 voltage gain stage, a 6FQ7 cathode coupled inverter, and EL34 outputs that were UL connected, Hammond 1650H output transformers, with 12 dB feedback. The other used a 12AX7 voltage gain stage, 6FQ7 cathode coupled inverter, and 6L6-oid outputs that were pentode connected, Hammond 1650H outputs, with 19 dB global feedback.
The 1650H is a decent transformer, but it likes only about 14 dB of global feedback before the amp gets difficult to tune. On the second amp with the 12AX7 input tube and 6L6-oid outputs, and I had to use a much more aggressive low pass step filter which pretty much negated the positive effects of feedback above 15 KHz as evidenced by the distortion rising significantly in this region on that amp.
On the other hand, low end response on the Hammonds is exceptional. Other positives about the Hammonds is they are very consistent performers and I've never had one mis-wired from the factory (cant' say that about other manufacturers in this price category).
Regardless of those shortcomings, both amps sound pretty good overall with the EL-34 amp measuring a bit better on the bench, but neither amp is the last word on performance or resolution, being limited by those output transformers. You need to spend a fair amount more money to get better performance, in new production iron.
I'd love to try the Lundahl's. But never felt I wanted to fork out the money for the experiment.
I've built two amps similar to the circuit shown in Claus Byrith's "4-10" white paper, but I didn't follow his schematic at all.
Both of my amps were stereo chassis builds with approx 400V B+. One used a 6DJ8 voltage gain stage, a 6FQ7 cathode coupled inverter, and EL34 outputs that were UL connected, Hammond 1650H output transformers, with 12 dB feedback. The other used a 12AX7 voltage gain stage, 6FQ7 cathode coupled inverter, and 6L6-oid outputs that were pentode connected, Hammond 1650H outputs, with 19 dB global feedback.
The 1650H is a decent transformer, but it likes only about 14 dB of global feedback before the amp gets difficult to tune. On the second amp with the 12AX7 input tube and 6L6-oid outputs, and I had to use a much more aggressive low pass step filter which pretty much negated the positive effects of feedback above 15 KHz as evidenced by the distortion rising significantly in this region on that amp.
On the other hand, low end response on the Hammonds is exceptional. Other positives about the Hammonds is they are very consistent performers and I've never had one mis-wired from the factory (cant' say that about other manufacturers in this price category).
Regardless of those shortcomings, both amps sound pretty good overall with the EL-34 amp measuring a bit better on the bench, but neither amp is the last word on performance or resolution, being limited by those output transformers. You need to spend a fair amount more money to get better performance, in new production iron.
I'd love to try the Lundahl's. But never felt I wanted to fork out the money for the experiment.
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