SET Suggestions

[nogoodboyo]

Hi all

I'm fishing for some suggestions / links to specs etc.

I want to build from scratch an SET to drive a Pair of Klipsch LA Scalas.

requirements:

-- About 5w per ch

-- No expensive power tubes

-- Tube rectified with a choke or 2


-- I already have this power transformer:

http://www.triodeelectronics.com/pa7dynst35sc.html

and wish to use it


-- Will get an extra transformer for rectifier.

-- wish to use the Hammond 125ESE output xformers or similar.


I already have a nice chassis and I am a competant/experienced Audio DIYer. (got stop electrocuting myself tho' [ouch!!]).

I intend to upgrade in the future but want something nice/simple/inexpensive to start off.

I guess there posts similar to this in the past, but a quick browse yielded little. But hope this post starts of some discussions -- I'm sure you folks like this kind of thing anyhow


Thanks in advance

 

[rcavictim]

You will not be satisfied with the poor F response of this output xfmer. It is only rated from 100 Hz to 15 KHz. The quality of the ouptut xfmmer sets the sound quality of the entire amp after you have done your best everywhere else. A poor xfmer will kill the best design. Here are much better xfmers.

http://www.hammondmfg.com/1627.htm

Check for recent posts by Tubelab or use search term "edcor". He has been testing economical new offerings from a company called Edcor that appear to be good value.

 

[SHiFTY]

I intend to upgrade in the future but want something nice/simple/inexpensive to start off.

OK, here's a tip- buy the best output transformers you can to start with, they make the biggest difference in the sound. The 125ESE are not the greatest, they have a slight harshness to them and roll off at 100Hz or so. Do yourself a favour and buy some decent ones at the start.

Apart from that, consider using triode-wired pentodes such as KT88 or EL34 instead of triodes proper; or even parallel KT66 / 6L6GC tubes. For a driver stage, you need to have something with some grunt, like 6SN7 or even an EL84. Have a read of the 2A3 driver thread.

For a tube rectifier, use a GZ34 for slow turnon and low voltage drop.

 

[Geek]

Hi Nogoodboyo,

Try the Edcor's. I'm 100% sold on their sound

If you want 5W of great sound without the cost, try trioded EL/PL36. Think of it as a 5 watt 2A3

Bias at 60mA with 260 to 300V on the plate with a 5K load. Your tranny with a tube rect. and L-C filter, will give just about that.

Yeah, we're pushing her at 18W total at 300+60, but it will take it!

 

[protos]

I would get two of those txs and use 6c33 which have the following advantages:
1.You can get them at around 15-20 usd each this is cheaper than any other power triode/tetrode .
2.They are twice as powerful as anything close i.e. 300b,kt88 etc.
3.They will work a dream with about 300-370 volts cathode biased.

Transformers should be in the 600 to 1000k range which are not extremely common but are available from most big tx manufacturers.If you really want to do it really cheap look at the 6c33 diy otx thread.I think a pair of otx cost the guy something like 50 usd in wire and laminations!

 

[rcavictim]

I would get two of those txs and use 6c33 which have the following advantages:
1.You can get them at around 15-20 usd each this is cheaper than any other power triode/tetrode .
2.They are twice as powerful as anything close i.e. 300b,kt88 etc.
3.They will work a dream with about 300-370 volts cathode biased.

Transformers should be in the 600 to 1000k range which are not extremely common but are available from most big tx manufacturers.If you really want to do it really cheap look at the 6c33 diy otx thread.I think a pair of otx cost the guy something like 50 usd in wire and laminations!

You have specified a factor of 1000 times too high a transformer load Z for the 6C33 tube.

What purpose would the two transmitters serve?

 

[Sherman]

Nogoodboyo,

Search this forum for Mikael's KT88 SE amp schematic. While not a real triode it can be connected as a triode or use it per the schematic in UL mode. I have built this amp and it sounds good (provided you use a good output transformer).

My amps (I built monoblocks rather than an integrated amp) have an output of about 7W just before clipping so an output of 5W should be reasonable. I haven't done any distortion measurements yet, my distortion meter needs work. (Maybe that should be my next project!)

I'm with the others who are advising getting the best OPT you can. If budget constraints are an issue (and really, they always are unfortunately) I would go with the Edcor transformers over the Hammonds. Recent threads indicate they perform far beyond their price and they have a UL tap (which the 125ESE doesn't).

 

[protos]

You have specified a factor of 1000 times too high a transformer load Z for the 6C33 tube.

What purpose would the two transmitters serve?

Sorry , 600 to 1000R is what I meant and I think you probably understood as well.
The original thread proposed a power trafo (not a transmitter as you mistakenly wrote)that would be a little underrated for a 6c33.
There is however a more expensive and bigger tx on the same site that would also serve.The 6c33 needs about 140-160ma at those voltages and about 6A filament each.

 

[protos]

Other ingredients for success
1.to save on heavy expensive chokes use a capacitor multiplier- ripple filter
2. use ccs on driver stage to maximize efficiency.The simplest ixys 10m45 or a more complex gary pimm clone.

 

[Tubelab_com]

Any time you ask a question like this you are bound to get several differing opinions. OK here is mine.

You already have a power transformer, so find a way to use it. It can be used to create a power supply in the 300 to 400 volt range. This is about right for a 5 watt SE amp.

Many advise to buy the best transformers that you can afford. This is good advice, but you must also work within your budget. If you have $100 plus per transformer, then buy some One Electron's or Electra-Prints, but since you specified "no expensive tubes". I am going to take this as "no expensive trasnformers either" This means the Hammond 125 series or the Edcors. There are those who claim that the larger Hammonds (125ESE) don't sound as good as the 125CSE. I have not tried the larger ones, so I don't know. The small Edcor XSE25-8-5K sounds as good as the Hammond 125 CSE, and it costs $18. See the following thread for further info:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=72654&highlight=

"No expensive tubes". This rules out most true triodes. What we have left is a triode connected pentode, or a UL connected pentode. If you use the Edcor transformer, then you can try it both ways.

There are lots of tubes that will work with the Edcor or the Hammond output transformers, and the power transformer that you currently have. The suggested 6L6, KT-88, EL-34 types come to mind. Another possibility is a tube made for TV sweep use. There are some of these that never caguht on with the CB linear amplifier crowd, so they are still cheap. I recently got several 6AV5's for $3 each. They work well with the Edcor transformers.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=74650


There have been several amplifier designs mentioned that use vertical output tubes. These tend to only deliver 2 to 3 watts, but are very simple and work very well. Search for 6DN7, 6EM7.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=73219&highlight=

 

[nogoodboyo]

Wow -- thanks for all the feedback -- just what I was looking for.

OK -- i am willing to go to $300 for a pair of OPT's. Anyone have opinions on Magnaquests?

Probably will go with triode strapped pents for now, what are your favourites?

-- I'd be goodboyo, but no one let me --

 

[rcavictim]

Sorry , 600 to 1000R is what I meant and I think you probably understood as well.
The original thread proposed a power trafo (not a transmitter as you mistakenly wrote)that would be a little underrated for a 6c33.
There is however a more expensive and bigger tx on the same site that would also serve.The 6c33 needs about 140-160ma at those voltages and about 6A filament each.

Well you speak a different language than the one of electronics, so that fact has not helped me understand what you are saying.
TX means transmit or transmitter, RX means receive or receiver. Always has during my 51 years. R is not the symbol for ohms. Omega is.

What the heck is a "trafo"? Is that the bottom half of a fizbin?

I cannot correct people's modern internet lax language laziness disease or ignorance but I can be cranky about it when I see it.

Electronics is an engineering science and it has a specific and universally standardized language designed to convey unambiguous understanding of it's principles. Compromise the language and you compromise the understanding., and eventually the science.

 

[Tubelab_com]

Well If you are willing to spend $300 on output transformers, then think about spending $100 more for a pair of Chinese 300B's. When I first started playing with tube amps I did not want to go along with the audio snobery that was associated with a 300B. I built a 300B amp for a customer at his request, and I was pleasantly surprised. They sounded great. They were Sovtek's, I have since had reliability issues (some live forever, some die young) with Sovtek 300B's, so I quit using them. I have used about 6 pairs of Shuguang's. They sound better, and there have been no issues.

I believe that it is possible to build a great sounding amp with many different tubes. Sometimes you have to try a few different circuits, or operating points to find the sweet spot for a given tube - transformer combination. I think that this sweet spot is pretty big on the 300B, so that it is pretty easy to hit. That is part of the reason for this tube's popularity.

I would still say that the transformer plays the greatest role in determining the sound quality of an amp. The choice of output tube is next.

I have heard good things about Magnequest transformers, but have not tried them.

 

[arnoldc]

Wow -- thanks for all the feedback -- just what I was looking for.

OK -- i am willing to go to $300 for a pair of OPT's. Anyone have opinions on Magnaquests?

Probably will go with triode strapped pents for now, what are your favourites?

-- I'd be goodboyo, but no one let me --

Hi, I use MgneQuest DS-025 on my 2A3 amplifier. They definitely have better bandwidth (obvious in specs) compared to the cheap 125ESE which I also have. I have other OPTs in use such as Tamura where the MagneQuest compares favorably (the Tamura F-475 is in fact a lot cheaper but only 45mA). I also have the older, smaller (better) Hammond 1628 that sounds very good too.

I just want to tell you about this diminishing returns- you can spend all you want on a transformer, and most likely measure the differences. But hearing those differences is a different thing, at least for me. Having said that, at $300 range, opens up a lot of options- such as James, Electra-Print (I also heard and they're nice), etc, etc. And don't forget MagneQuest's cheaper Robin Hood series.

If you go for the Robin Hood, you can buy yourself a good pair of 300Bs and I've heard the Valve Art globes, they're ok. I my self use a "generic" China 300B "Coke" bottle I got for $60 a pair.

If you don't like a Triode, I would like to suggest the 807 Tetrode because I like its sound, but you need to use good top caps as its plate is its "unicorn"

Ok, that's my 1€

ps.

Hi rcavictim, I think the "R" is pretty much acceptable to me too, and maybe I'm not that "standardized" (sic). However, I've seen many schematics that use "R" when the value is < 1K, such as 820R, 10R or something like that. But then again, the post you mentioned said "1000R" which should have been 1K. Oh well. I totally agree with you all points, I also thought that RX is receive and TX is transmit. Educating the poster is a good thing. I myself is always guilty of posting in all lower case and I am changing that as this post suggests.

 

[Tubes4e4]

Hi,

If you don't like a Triode, I would like to suggest the 807 Tetrode because I like its sound,

While 807 is a very nice tube in tetrode mode indeed, being triode strapped it is extremely inefficient. You will have a hard time to squeeze more than, say, 2.5 Watt Po out of it without exceeding max. ratings (especially regarding screen voltage).

Tom

 

[Fuling]

On the subject of budget 2A3 OPT´s I must mention Lundahls LL1664. 3k/8 rated for 8W and available with 60mA airgap.

 

[G]

Hi all

I'm fishing for some suggestions / links to specs etc.

I want to build from scratch an SET to drive a Pair of Klipsch LA Scalas.

requirements:

-- About 5w per ch

-- No expensive power tubes

-- Tube rectified with a choke or 2


-- I already have this power transformer:

http://www.triodeelectronics.com/pa7dynst35sc.html

and wish to use it


-- Will get an extra transformer for rectifier.

-- wish to use the Hammond 125ESE output xformers or similar.


I already have a nice chassis and I am a competant/experienced Audio DIYer. (got stop electrocuting myself tho' [ouch!!]).

I intend to upgrade in the future but want something nice/simple/inexpensive to start off.

I guess there posts similar to this in the past, but a quick browse yielded little. But hope this post starts of some discussions -- I'm sure you folks like this kind of thing anyhow


Thanks in advance

I would try a SE EL34 or KT88 amplifier. THe power tubes are plentiful and inexpensive. A Tesla ECC99 would make an excellent gain tube for this amp. That and a couple of One Electron output transformers and you have the makings of a good sounding amp.

 

[knubie]

Well everybodies talking about output transformers and output tubes. How will your driver stage look, are you using balanced input or not. They have a post regarding nice CCS boards at this forum. If you want a driver as "something with a little grunt" maybe think about a 5842, E182CC or 6c45Pe. 5842 can be had pretty cheap for around 25$ I think. These tubes have high transconductance and high amplification factor and low plate resistance and can drive just about anything....

 

[protos]

R is not the symbol for ohms. Omega is.

What the heck is a "trafo"? Is that the bottom half of a fizbin?

I cannot correct people's modern internet lax language laziness disease or ignorance but I can be cranky about it when I see it.

Electronics is an engineering science and it has a specific and universally standardized language designed to convey unambiguous understanding of it's principles. Compromise the language and you compromise the understanding., and eventually the science.

Well you would be surprised if you were to pick up a recent RS or digikey catalogue in these modern lazy times.R is pretty much widely accepted as describing ohms.Even manufacturers are willing to print R on their resistors.Try typing the Omega symbol here and I will take my hat off to you.
As to trafo I think it is a pretty much accepted shorthand way of writing transformer at least in this forum.
This is an internet forum not a PH.D. E.E. seminar and the custom is to make certain allowances for these unscientific terms.It is more about enjoying a hobby and not about safeguarding scientific knowledge.
I will be careful with my tx though.
Why be cranky anyway ?

 

[G]

Well you would be surprised if you were to pick up a recent RS or digikey catalogue in these modern lazy times.R is pretty much widely accepted as describing ohms.Even manufacturers are willing to print R on their resistors.Try typing the Omega symbol here and I will take my hat off to you.
As to trafo I think it is a pretty much accepted shorthand way of writing transformer at least in this forum.
This is an internet forum not a PH.D. E.E. seminar and the custom is to make certain allowances for these unscientific terms.It is more about enjoying a hobby and not about safeguarding scientific knowledge.
I will be careful with my tx though.
Why be cranky anyway ?