Hi,
I was wondering if i could rack the brains of fellow Audio Enthusiasts for recommendation of complete Tube Amp Kits (minus case) for < $400. I'm after ease of purchase but if there's a particular kit thats value for money and has easily sourced better then stock components, i would definitely be interested.
I'm don't really mind if its a SE or PP design, but i would like the best sound i could get for a pair of bookshelf speakers i'm looking to buy.
These are the specs of the speakers from Firesprite Bookshelf Speakers - Adelaide Speakers - Ascension
Firesprite 502SV
Price: $595/pr (or $350 kit less cabinet)
Finish: Satin/gloss American Oak veneer (can be stained Jarrah, Maple, Walnut, Rosewood or charcoal black)
Cabinet: 300h x 200w x 215d bass reflex 7 litres
Power Handling: 60/120 wrms/wmax
Nominal Impedance: 8 ohms (or 4 ohms on request)
Frequency Response: 55 -- 35,000 hertz +/-2db
Sensitivity: 89.5db 1w/1m
Drivers: SB Acoustics 150mm high end bass/midrange and Vifa 25mm soft dome tweeter.(optional ribbon tweeter extra $100)
Description: Ultra smooth and fast response; this is a beautiful sounding little speaker that packs a lot of punch along with its "being there" clarity. Also ideal speaker as high end studio monitor, complete satelite home theatre system, or surround speaker. Ideal speaker for music shops etc. where wider dispersion is required. zribbon option recommended.
Thus far i'm thinking the 16LS kit from s5 seems to be a decent pick, but again trying to see if there's anything better that will still suit my budget.
Any help will be much appreciated.
Thanks,
Bismar
I was wondering if i could rack the brains of fellow Audio Enthusiasts for recommendation of complete Tube Amp Kits (minus case) for < $400. I'm after ease of purchase but if there's a particular kit thats value for money and has easily sourced better then stock components, i would definitely be interested.
I'm don't really mind if its a SE or PP design, but i would like the best sound i could get for a pair of bookshelf speakers i'm looking to buy.
These are the specs of the speakers from Firesprite Bookshelf Speakers - Adelaide Speakers - Ascension
Firesprite 502SV
Price: $595/pr (or $350 kit less cabinet)
Finish: Satin/gloss American Oak veneer (can be stained Jarrah, Maple, Walnut, Rosewood or charcoal black)
Cabinet: 300h x 200w x 215d bass reflex 7 litres
Power Handling: 60/120 wrms/wmax
Nominal Impedance: 8 ohms (or 4 ohms on request)
Frequency Response: 55 -- 35,000 hertz +/-2db
Sensitivity: 89.5db 1w/1m
Drivers: SB Acoustics 150mm high end bass/midrange and Vifa 25mm soft dome tweeter.(optional ribbon tweeter extra $100)
Description: Ultra smooth and fast response; this is a beautiful sounding little speaker that packs a lot of punch along with its "being there" clarity. Also ideal speaker as high end studio monitor, complete satelite home theatre system, or surround speaker. Ideal speaker for music shops etc. where wider dispersion is required. zribbon option recommended.
Thus far i'm thinking the 16LS kit from s5 seems to be a decent pick, but again trying to see if there's anything better that will still suit my budget.
Any help will be much appreciated.
Thanks,
Bismar
Those speakers require substantial power. Let's apply Paul Joppa's useful 102 dB. rule of thumb. An amp/speaker combo should be able to produce 102 dB. SPL peaks at a 1 M. distance, assuming a listening space of "average" volume. Looks like upwards of 30 WPC are in order.
BTW, you need to find out what the speakers' impedance curve looks like. 8 Ω nominal will have to be lowered, if significant dips in the impedance curve occur, especially in the power hungry deep bass region.
IF the impedance curve is reasonably flat, you might be able to do a 7591 based "El Cheapo Grande" and not blast the budget to bits. Edcor's model CXPP50-8-6.6K is suitable and costs $62.26 each. Magnetics chew a budget up, very quickly.
BTW, you need to find out what the speakers' impedance curve looks like. 8 Ω nominal will have to be lowered, if significant dips in the impedance curve occur, especially in the power hungry deep bass region.
IF the impedance curve is reasonably flat, you might be able to do a 7591 based "El Cheapo Grande" and not blast the budget to bits. Edcor's model CXPP50-8-6.6K is suitable and costs $62.26 each. Magnetics chew a budget up, very quickly.
Hi guys thanks for your replies.
I'll enquire with the manufacturer for the impedance curves.
Regarding the WPC, during my enquiry to s5, they mentioned the 8LS or 16LS will be sufficient to power it. But their WPC is no where near 30?!. Perhaps if i chose the 4 ohms nominal impedance it will be easier to drive?
DualTriode: I'm really after a kit, can you suggest which kit on tubecad is sufficient to drive those speakers?
Eli Duttman: Any idea who does a kit for the El Cheapon Grande?
I'll enquire with the manufacturer for the impedance curves.
Regarding the WPC, during my enquiry to s5, they mentioned the 8LS or 16LS will be sufficient to power it. But their WPC is no where near 30?!. Perhaps if i chose the 4 ohms nominal impedance it will be easier to drive?
DualTriode: I'm really after a kit, can you suggest which kit on tubecad is sufficient to drive those speakers?
Eli Duttman: Any idea who does a kit for the El Cheapon Grande?
"Only" is a relative turn.
It would be lot's, if your speakers were not so power hungry. (inefficient.)
Whichever way you go it will be a learning experience, hopefully not your last project.
IMO, larger, more efficient speakers sound better anyways, you may end up upgrading speakers, which would make your life in the tube world much, much easier.
Moving up just 3db will sound twice as loud, something to consider, it's more practical to use efficient speakers than building a beefier tube amp.
In reality, 30watt is not much more power then 15watt anyways, not "twice" as loud.
You could simulate the same power level increase with speakers just 3db more efficient then you have now. (92db or higher)
It would be lot's, if your speakers were not so power hungry. (inefficient.)
Whichever way you go it will be a learning experience, hopefully not your last project.
IMO, larger, more efficient speakers sound better anyways, you may end up upgrading speakers, which would make your life in the tube world much, much easier.
Moving up just 3db will sound twice as loud, something to consider, it's more practical to use efficient speakers than building a beefier tube amp.
In reality, 30watt is not much more power then 15watt anyways, not "twice" as loud.
You could simulate the same power level increase with speakers just 3db more efficient then you have now. (92db or higher)
Bismar,
Other posters have correctly pointed out that more efficient speakers than those you are contemplating make life easier, if tubed power amplification is to be used. However, I have a sneaking suspicion that you have your heart set on those speakers. If the Firesprite 502SV purchase is "cast in concrete", you may be better of with quality SS power amplification and tubed preamplification. More than 1 good sounding rig has been set up that way.
Other posters have correctly pointed out that more efficient speakers than those you are contemplating make life easier, if tubed power amplification is to be used. However, I have a sneaking suspicion that you have your heart set on those speakers. If the Firesprite 502SV purchase is "cast in concrete", you may be better of with quality SS power amplification and tubed preamplification. More than 1 good sounding rig has been set up that way.
Tubelab George does have an EL84 PP amp (17W/CH) too with parts kit for $65 to populate the $35 circuit board. Those speakers look to be power hungry so you could probably run 7591 output tubes outboard of the board for 35W/CH with suitable output & PS transformers, but a bit over budget.
You could also bi-amp with one stereo EL84 PP amp per channel if the speakers have taps for separate amps to supply the woofer & tweeter , so so you would have a nice 35W/CH with great sounding EL84 tubes.
If you want more power another option in kit form is the ST-70 type Dynaco clone kit amps out there, for up to 50-60W/ CH. with KT-88 and bigger OPT's , but out of budget.
Randy
You could also bi-amp with one stereo EL84 PP amp per channel if the speakers have taps for separate amps to supply the woofer & tweeter , so so you would have a nice 35W/CH with great sounding EL84 tubes.
If you want more power another option in kit form is the ST-70 type Dynaco clone kit amps out there, for up to 50-60W/ CH. with KT-88 and bigger OPT's , but out of budget.
Randy
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Hi guys, really appreciate all your help. Sorry for being a complete and utter newb at this.
As for the speakers, no i am not particularly attached to them.
If however you could suggest me a kit and a drawing for the chassis that is considerably better for about $500, i will probably jump on that instead.
As for the speakers, no i am not particularly attached to them.
If however you could suggest me a kit and a drawing for the chassis that is considerably better for about $500, i will probably jump on that instead.
For your budget I would stick to George's tubelab.com PP EL84 PP amp for $100 (board and parts to populate the board. You can build a top plate out of aluminum, cutting holes for tubes using a wood base if your handy.
Triode Electronics Z-565 output transformers would be great for sonics as the Output Transformers are what makes a tube amp sound great. Edcor 23% UL 8K 25W ones for about $40 less.
As for a suitable PS. transformer an affordable one may be had from Antek so a total of $200 for transformers using SS diodes to save $ and bass may be better too. Tubes and other parts $100. The rest for a volume pot, shipping and base. There is fixed bias mod that can be done later for a bit more power and improved sonics @ $10 called the EFB mod. LED's could be tried too.
Randy
Triode Electronics Z-565 output transformers would be great for sonics as the Output Transformers are what makes a tube amp sound great. Edcor 23% UL 8K 25W ones for about $40 less.
As for a suitable PS. transformer an affordable one may be had from Antek so a total of $200 for transformers using SS diodes to save $ and bass may be better too. Tubes and other parts $100. The rest for a volume pot, shipping and base. There is fixed bias mod that can be done later for a bit more power and improved sonics @ $10 called the EFB mod. LED's could be tried too.
Randy
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Thanks guys, i think perhaps i should look to getting better speaker kits first before making a decision on the tube amps.
I'm however having trouble finding more efficient speaker kits (without chassis) with a maximum budget of $500.
I've saw some nice kits at Madisound website but their sensitivities seem even worse then the kit i previously had in mind. Or am i getting confused with terminology?
Btw rmyack i can't find any reference to the EL84 PP on tubelab website? I take it its the the Simple P-P amp but all the links are broken.
I'm however having trouble finding more efficient speaker kits (without chassis) with a maximum budget of $500.
I've saw some nice kits at Madisound website but their sensitivities seem even worse then the kit i previously had in mind. Or am i getting confused with terminology?
Btw rmyack i can't find any reference to the EL84 PP on tubelab website? I take it its the the Simple P-P amp but all the links are broken.
I did a home brew similar to the Millet Big Red board. Under $450 complete with case and outputs, 30watts/channel in triode mode. Pete's board can do over 120watts/channel depending on iron and output tubes chosen. I drive 4ohm Orions that dip under 3ohms without issue.
Original St70 Dynaco amps were a little weak, only had about 18watts RMS / channel. With larger power transformers and modern driver PCB's 60+ watt/s channel is possible....
I started a PCB project for KEGGER, tried a combo of tubes and iron, just need to try 4.3k hammonds to finish. With the smaller 6P3S tubes and smaller output iron, 25watts/channel. With 5881, 6550-c- and kt88 tubes pushing 50-60 watts/channel, less in triode mode. Currently playing with 40 watt 6.6k hammonds, 5881 in triode mode. Very respectable combo.
pic attached of PCB being evaluated, Svet 6550 output tubes.
Approx cost of a ST70 clone;
Cost of iron ~$320 40 to 60watt, 4.3k to 6.6k Raa
Output tubes ~$40 for 6P3S-E 5881 Russian
Driver tubes ~ $8
Components ~ $40 can be upgraded for higher $ coupling caps
Alum top plate ~ $9
Chassis wood ~ $10
PCB one sided ~ $5 optional , point to point for purists.
Alps pot ~$30 optional
Original St70 Dynaco amps were a little weak, only had about 18watts RMS / channel. With larger power transformers and modern driver PCB's 60+ watt/s channel is possible....
I started a PCB project for KEGGER, tried a combo of tubes and iron, just need to try 4.3k hammonds to finish. With the smaller 6P3S tubes and smaller output iron, 25watts/channel. With 5881, 6550-c- and kt88 tubes pushing 50-60 watts/channel, less in triode mode. Currently playing with 40 watt 6.6k hammonds, 5881 in triode mode. Very respectable combo.
pic attached of PCB being evaluated, Svet 6550 output tubes.
Approx cost of a ST70 clone;
Cost of iron ~$320 40 to 60watt, 4.3k to 6.6k Raa
Output tubes ~$40 for 6P3S-E 5881 Russian
Driver tubes ~ $8
Components ~ $40 can be upgraded for higher $ coupling caps
Alum top plate ~ $9
Chassis wood ~ $10
PCB one sided ~ $5 optional , point to point for purists.
Alps pot ~$30 optional
Attachments
Once you start talking "12" W. tubes, like the EL84/6BQ5, an "El Cheapo" fits easily into the budget. The Triad N-77U (main B+) and Triad VPS24-1800 ("12" V. heater power and B+ boost) work in both "120" and "240" V. zones, thanks to dual primaries. 
Something will have to be scrounged up to replace the "120" V. only Allied 6K27VF (B- and 12AT7 heater power). Perhaps a Triad VPS24-3300, for all the heaters plus B+ boost and figure out something low cost for B-. The currently recommended filter choke is the Triad C-24X.
Z565 O/P trafos are "Gold Standard" for "12" W. tubes, but Edcor is respectable. Also, "iron" winders are to be found in "Oz".
Any tube in the 6V6 "clan" will work without parts value changes. A low cost option for the O/P tubes is the Russian 6П1П (6p1p), which is electrically equivalent to the 6AQ5/EL90, but is 9 pin mini, instead of 7 pin mini.
Something will have to be scrounged up to replace the "120" V. only Allied 6K27VF (B- and 12AT7 heater power). Perhaps a Triad VPS24-3300, for all the heaters plus B+ boost and figure out something low cost for B-. The currently recommended filter choke is the Triad C-24X. Z565 O/P trafos are "Gold Standard" for "12" W. tubes, but Edcor is respectable. Also, "iron" winders are to be found in "Oz".
Any tube in the 6V6 "clan" will work without parts value changes. A low cost option for the O/P tubes is the Russian 6П1П (6p1p), which is electrically equivalent to the 6AQ5/EL90, but is 9 pin mini, instead of 7 pin mini.
Attachments
Eli Duttman, i take it theres no kits for the El Cheapo?
Also found the speaker impedance curve for the original firesprite i linked.
SB Acoustics :: 6" SB17NRXC35-8
Seems pretty flat.
Also found the speaker impedance curve for the original firesprite i linked.
SB Acoustics :: 6" SB17NRXC35-8
Seems pretty flat.
I would suggest Fostex Fe206 or line array.
Tube sound is all about quality passive components (audio-grade foil capacitors, chokes, OTs). Do not waist your time on tubes in case you are limited in funds. Use LM3886 instead you will get a better sounding result in case you are on a budget.
Start with back loaded horn speakers and LM3886. Later on upgrade your signal path with tubes first audio source (TriVista Musical Fidelity for example or google Lampizator) then made yourself a tube preamp-amp.
Otherwise you gonna amplify AB OPAMP output with a pricey inefficient class A tube power amp.
Tube sound is all about quality passive components (audio-grade foil capacitors, chokes, OTs). Do not waist your time on tubes in case you are limited in funds. Use LM3886 instead you will get a better sounding result in case you are on a budget.
Start with back loaded horn speakers and LM3886. Later on upgrade your signal path with tubes first audio source (TriVista Musical Fidelity for example or google Lampizator) then made yourself a tube preamp-amp.
Otherwise you gonna amplify AB OPAMP output with a pricey inefficient class A tube power amp.
Hi thanks for your advice, but i believe the speakers your recommending are large floor standing speakers.
I am looking for small bookshelf speakers instead.
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