Hi all.
I am quite new with tube amplifiers, but after i built my pre-amp i am ready to go into more advanced builds. I came across the bare PCB's at 8ball and decided to give it a go. Unfortunately i am not quite certain where to look for the transformers and chokes.
The system consist of follow two boards:
8audio was so kind to tell me which specs to look for:
So my questions are:
I hope this help also helps other people trying to build a system based on the 8audio benefit from the replies.
Thanks in advance!
I am quite new with tube amplifiers, but after i built my pre-amp i am ready to go into more advanced builds. I came across the bare PCB's at 8ball and decided to give it a go. Unfortunately i am not quite certain where to look for the transformers and chokes.
The system consist of follow two boards:
- Tube amp: EL34 Tube Amp Bare PCB - Upgraded design of Jadis JA30 - 8Audio
- PSU (Option a.): Diode rectified: EL34 Tube Amp - Diode Rectified Power Supply Bare PCB - 8Audio
- PSU (Option b.): Tube rectified: EL34 Tube Amp - Tube Rectified Power Supply Bare PCB - 8Audio
8audio was so kind to tell me which specs to look for:
So my questions are:
- Where do i find the transformers for european voltage (230VAC)?
- Should i go for a tube or diode rectified PSU?
- Should i be aware of anything when i choose capacitors and resistors (quality and type?)
- Can i use toroidal instead of traditional transformers?
I hope this help also helps other people trying to build a system based on the 8audio benefit from the replies.
Thanks in advance!
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I can't answer your questions, but I must point out that you need two of the amp PCB as each is mono.
You will need either one or two of PSU PCB, depending on whether you are building on a single chassis or as two monoblocks.
As a single chassis it is going to be very large and heavy.
You will need either one or two of PSU PCB, depending on whether you are building on a single chassis or as two monoblocks.
As a single chassis it is going to be very large and heavy.
Thank you for the comment. It's definetely going to be a heavy beast! I intended to have it as one unit knowing the fact that's going to be massive! i found it quite challenging to find the transformers which is a bit of a show stopper at the moment and will probably kill my budget, so i really need to calculate the trafo cost before I proceed any further..
I detect the odor of "snake oil". 😡 A regulated heater supply in a power amp is complete fluff. FYI, while a VERY tall mountain to climb, it is possible to build a phono preamp, whose residual hum levels are satisfactory, that employs AC heating.
Without the signal schematic, it's difficult to make good recommendations. However, I suspect a perfectly suitable PSU could be built around the highly affordable AnTek AS-3T325 toroidal power trafo. When a toroidal power transformer is employed, ferrite beads have to be mounted on the AC mains wires, to suppress the garbage that rides on the mains. Toroids are wide bandwidth and the trash can work its way into the PSU.
Whether or not a true schematic, as opposed to "connect the dots" is provided, I can't say. The PCB price is (IMO) low enough to consider taking the risk of ordering.
Without the signal schematic, it's difficult to make good recommendations. However, I suspect a perfectly suitable PSU could be built around the highly affordable AnTek AS-3T325 toroidal power trafo. When a toroidal power transformer is employed, ferrite beads have to be mounted on the AC mains wires, to suppress the garbage that rides on the mains. Toroids are wide bandwidth and the trash can work its way into the PSU.
Whether or not a true schematic, as opposed to "connect the dots" is provided, I can't say. The PCB price is (IMO) low enough to consider taking the risk of ordering.
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I have attached the schematics provided from them. Snake oil or shark fin soup is the last thing i wan't as my morning meal!
If you are unsure where to find components, why don't you just order a complete kit ( like a st70 from dynakitparts.com ) ? 220V transformers are available.
Its too early for me to give up! 8audio offers completed PCB's without the transformers, but its too early to give up on this project. Although i will benefit from some guidance before i gets too steamy.
It's not to give up, it's more like getting a working amp and have all the nitti-gritty details taken care of.
When you have a well-sounding amp you have more time to complete "the project" and not having to take shortcuts.
When both are working you can decide which one to sell, you will also have the position to actually listen to both and learn from that.
Thanks for the heads up. You would advise against such DIY project with the 8audio board? I have to admit that the PCB and cost was really tempting as i can get all the components and tubes for free (except for trafo).
No i will not advice against the 8audio. But i will advice against forced completion, that's why i recommend to get a complete fully working tube amp first, as a kit it will have all
the tasks that you need to do with the 8audio, any you can build the 8audio in a well-planned manner.
the tasks that you need to do with the 8audio, any you can build the 8audio in a well-planned manner.
I really understand your advice now. I am not really in a rush right now as i have a pre-amp system up and running in a "hybrid" setup with my Class-D amplifier which is working ok. This project has no rush at all. I am trying to keep the budget quite low.
Rob,
IMO, that circuit SUCKS. Asking the very wimpy 12AX7/ECC83 triode to drive ultra-linear (UL) mode EL34 "finals" is poor practice.
Also, the setup includes a volume control and you already have a preamp. Does your preamp have line stage gain?
What sort of speakers are you planning on mating to a tubed power amp? Would they work well with the 15 or so WPC an EL84/6BQ5 based PP amp yields?
IMO, that circuit SUCKS. Asking the very wimpy 12AX7/ECC83 triode to drive ultra-linear (UL) mode EL34 "finals" is poor practice.
Also, the setup includes a volume control and you already have a preamp. Does your preamp have line stage gain?
What sort of speakers are you planning on mating to a tubed power amp? Would they work well with the 15 or so WPC an EL84/6BQ5 based PP amp yields?
@Robfreak - thanks for posting the schematic,I was looking for this for a long time.Did they sent you also a BOM list for the parts?
What I do not understand is why the coupling capacitor C8 (0,47UF) is doubled by C9 (0,01uF)....😕
@Eli- it is so poor schematic?I am thinking to give it a try for that schematic,but maybe in winter time,now I have other projects to work on ....
But not with DC circuit for heathers,I don*t think is necessary.Should work OK only with 2 x 120 Ohm resistors to ground for balance.
Regards,
Post edit:Rob,in Europe you can order custom Power Trafo & Output Trafo at Roehrehtechnik.de or Asjanfirst....Google it and you will find them.The cost are around 120 Euro each.
What I do not understand is why the coupling capacitor C8 (0,47UF) is doubled by C9 (0,01uF)....😕
@Eli- it is so poor schematic?I am thinking to give it a try for that schematic,but maybe in winter time,now I have other projects to work on ....
But not with DC circuit for heathers,I don*t think is necessary.Should work OK only with 2 x 120 Ohm resistors to ground for balance.
Regards,
Post edit:Rob,in Europe you can order custom Power Trafo & Output Trafo at Roehrehtechnik.de or Asjanfirst....Google it and you will find them.The cost are around 120 Euro each.
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As an engineer i love to hear honest answers like this. The pre-amp i have right now is something i have borrowed which i have to return again, so infact i do not have any pre-stage.
The speakers i am running are a pair of open-baffle beasts with a passive cross-over. Link to build
I loved the convenience of a PCB, but i am surely up for finding an alternatively to this amp.
Unfortunately he would not sent me a BOM list so i basically made an excel overview of the tube parts.
I just reviewed the schematic and i see your point, makes no sense..
Rob,
When I get home from work, I can follow links, more or less as I please. Right now, the "Web Nazis" limit me. What is the sensitivity of your speakers? How complex is the crossover? What does the impedance curve look like? Large dips, especially in the deep bass, are highly problematic.
Paul Joppa has provided us with a useful (IMO) rule of thumb for mating amps and speakers. "Joppa's Rule" states that in a listening space of "average" volume an amp/speaker combo should be capable of 102 dB. SPL peaks, at a 1 M. distance. For instance, 8 WPC amplification combined with 94 dB. sensitive speakers rate to be satisfactory.
When I get home from work, I can follow links, more or less as I please. Right now, the "Web Nazis" limit me. What is the sensitivity of your speakers? How complex is the crossover? What does the impedance curve look like? Large dips, especially in the deep bass, are highly problematic.
Paul Joppa has provided us with a useful (IMO) rule of thumb for mating amps and speakers. "Joppa's Rule" states that in a listening space of "average" volume an amp/speaker combo should be capable of 102 dB. SPL peaks, at a 1 M. distance. For instance, 8 WPC amplification combined with 94 dB. sensitive speakers rate to be satisfactory.
I have attached the crossover in a document. There are some graphs in the build thread i have referred. A part from that the setup is quite "simple".
Is there a decent way that i could do this measurements or calculations?
Attachments
That crossover is not horribly complex. No Zobel networks are present.
Can you upload the specifications for the PAP1075 driver?
Can you upload the specifications for the PAP1075 driver?
No go. 🙁 The "Web Nazis" block me. What is the nominal impedance? What is the claimed sensitivity?