Before anything else let me make it clear that I know nothing about electronics DIY. I just ordered a soldering iron and multimeter. Some of the talk here bounces off my head.
I've been following simple pp builders here for a month now and since I'm hopelessly new at anything electronics I seek a lot of help.
I'm ordering parts soon for an EL84 build so I'm requesting people who have built simple pp to tell me what parts they used so I can get some idea what to order. I'm following George's list and manual for the parts ordering. Are there any major observed changes to parts/assembly list so far?
Especially,
1) Which PT you are using? Using a <600V PT mean lower WPC but does it also mean less than perfect sound quality and music details? I know some PTs including Edcor's ranked around 600V-650V are reaching over 650V mark.
2) Which OT's you used and with which C101, C201 you are using them? PN# will be helpful.
3) Any major changes in parts list/assembly? I don't want cutting edge tweaks as some of you have since I don't even understand what you all are saying there.
4) How to install a fuse? Which fuse? Will depend on PT I guess?
5) How is wiring done? How is PT, OTs, power cord and volume knob wired to PCB? I saw pics of OT wiring by George in the beta-builder thread.
6) How is grounding done?
I will appreciate PN# for connection wires, PT/OT wiring wires, power switch, power cord socket, volume knobs, fuses etc.
I've been following simple pp builders here for a month now and since I'm hopelessly new at anything electronics I seek a lot of help.
I'm ordering parts soon for an EL84 build so I'm requesting people who have built simple pp to tell me what parts they used so I can get some idea what to order. I'm following George's list and manual for the parts ordering. Are there any major observed changes to parts/assembly list so far?
Especially,
1) Which PT you are using? Using a <600V PT mean lower WPC but does it also mean less than perfect sound quality and music details? I know some PTs including Edcor's ranked around 600V-650V are reaching over 650V mark.
2) Which OT's you used and with which C101, C201 you are using them? PN# will be helpful.
3) Any major changes in parts list/assembly? I don't want cutting edge tweaks as some of you have since I don't even understand what you all are saying there.
4) How to install a fuse? Which fuse? Will depend on PT I guess?
5) How is wiring done? How is PT, OTs, power cord and volume knob wired to PCB? I saw pics of OT wiring by George in the beta-builder thread.
6) How is grounding done?
I will appreciate PN# for connection wires, PT/OT wiring wires, power switch, power cord socket, volume knobs, fuses etc.
Hi....
You should get plenty of good ideas / advice here, although I'm not sure how many have actually built the SP-P yet.
Anyway, to your questions.....
This cat used Edcor xfmrs. I like Edcor; terrific value for the money. The only problem being they are built to order, so you have to wait 4-8 weeks. I feel it's worth the wait.
The Edcor PT I used is #XPWR008 (600-0-600). This puts the circuit B+ at around 340V. You could also consider #XPWR007 (550-0-550) if you wanted lower volts at the plates. I'm getting the slightest hint of "red-plate" on E-H EL 84's with the higher B+, but the sound is so good I'm planning to get more hours on the amp to see if tube life will be a problem.
OPT's are Edcor CXPP25-MS-7.6K. Everyone will tell you OPT selection has a huge bearing on the sound. The Edcors may be eclipsed by other products, but not at their price point, or even several times what you pay for them. I chose the version that gives you 4-8-16 ohm taps in case I wanted to play around with different speakers in the future. I connected my amp in Ultra Linear mode. The images that George posted of his connections, show Pentode mode.
C101 and C201 were not installed on my build, and I gather are generally not required. I built my amp as per the current parts list. It worked the first time the switch was turned on, so that should verify the parts list is correct.
Regarding your general wiring questions. Have a look at the manual for the SSE on the Tubelab site. Most of this will apply to the SP-P as well.
Good luck!
You should get plenty of good ideas / advice here, although I'm not sure how many have actually built the SP-P yet.
Anyway, to your questions.....
This cat used Edcor xfmrs. I like Edcor; terrific value for the money. The only problem being they are built to order, so you have to wait 4-8 weeks. I feel it's worth the wait.
The Edcor PT I used is #XPWR008 (600-0-600). This puts the circuit B+ at around 340V. You could also consider #XPWR007 (550-0-550) if you wanted lower volts at the plates. I'm getting the slightest hint of "red-plate" on E-H EL 84's with the higher B+, but the sound is so good I'm planning to get more hours on the amp to see if tube life will be a problem.
OPT's are Edcor CXPP25-MS-7.6K. Everyone will tell you OPT selection has a huge bearing on the sound. The Edcors may be eclipsed by other products, but not at their price point, or even several times what you pay for them. I chose the version that gives you 4-8-16 ohm taps in case I wanted to play around with different speakers in the future. I connected my amp in Ultra Linear mode. The images that George posted of his connections, show Pentode mode.
C101 and C201 were not installed on my build, and I gather are generally not required. I built my amp as per the current parts list. It worked the first time the switch was turned on, so that should verify the parts list is correct.
Regarding your general wiring questions. Have a look at the manual for the SSE on the Tubelab site. Most of this will apply to the SP-P as well.
Good luck!
1) Hammond 373CZ - just happen to have it on-hand.
2) Got mine from George, but I will cast a vote for Edcor. I used them on my SSE and they are awesome for the price.
3) Not really. I ran into issues with the input stage performance with some tubes. The jury is out if there is anything to worry about. If you want to cover your bases, get 2 extra resistors for R2 (150k 3W) for use in place of R106/R206. For your initial build, just follow the parts list and keep the two extras aside.
4) You need a fuse holder. It normally attaches to a hole in the chassis.
5) As neon said, you can use the SSE instructions as a reference until George posts the final wiring diagrams. The diagrams posted in the forums will help connect the dots.
6) Follow the advice in the SSE instructions.
2) Got mine from George, but I will cast a vote for Edcor. I used them on my SSE and they are awesome for the price.
3) Not really. I ran into issues with the input stage performance with some tubes. The jury is out if there is anything to worry about. If you want to cover your bases, get 2 extra resistors for R2 (150k 3W) for use in place of R106/R206. For your initial build, just follow the parts list and keep the two extras aside.
4) You need a fuse holder. It normally attaches to a hole in the chassis.
5) As neon said, you can use the SSE instructions as a reference until George posts the final wiring diagrams. The diagrams posted in the forums will help connect the dots.
6) Follow the advice in the SSE instructions.
Thanks for the recommendations, I've decided to go with Edcor too since they fit my budget and they are good. I'm curious about tube life in your circuit too.
Also, how to connect Ultra-linear mode? Is sound quality better in UL mode V/s. pentode mode? I don't care about WPC, I just care about sound quality.
Thanks for your reply. I'll follow (3).
If possible can you give me PN# for fuse and fuse holder. Also how and/or where to install them into the circuit? I apologize for sounding like a super dummy but I've never built any amp or installed any fuses.
Hello imnewbie,
I was in the same boat as you are, when I started building the Tubelab SE a month ago. I learned A LOT about electronics, and so that was a huge plus for me, in addition to getting a great amp! I do have some rough knowledge of electronics from owning a manufacturing company, and having to troubleshoot it, but not much experience with circuits, etc.
As for the wire size in the amp, wire size in my experience is dictated by the amperage (current) going through it. So, the more current (max at peak) going through a wire the bigger the wire needs to be or it will heat the wire up to the point of causing a fire. Amps are not like 50 hp electric motors pulling a lot of amps through the wire, so their size can be smaller. Long story short, wire size can be small. In my amp, which was a pcb and not point to point, there wasn't much for wires, but where I needed them I used 16 gauge copper wire, and the amp sounds great. Go to parts-express.com, and see what kind of inventory they have, you can actually learn from seeing what products are available.
Volume control is called a potentiometer or 'pot' for short. Look for one with a 'log taper', and is rated in impedence 1/10th the source impedence. Your preferences will differ with the requirements of your amp, so I can't give you a part number. But, in addition to parts express, try angela.com, and tubesandmore.com.
Remember to enjoy the process, learn from it, don't expect everything to go perfect, but take the time to ensure you do it right. Read books on electronics, tube amp building etc.
Hope this helps
Matt
I was in the same boat as you are, when I started building the Tubelab SE a month ago. I learned A LOT about electronics, and so that was a huge plus for me, in addition to getting a great amp! I do have some rough knowledge of electronics from owning a manufacturing company, and having to troubleshoot it, but not much experience with circuits, etc.
As for the wire size in the amp, wire size in my experience is dictated by the amperage (current) going through it. So, the more current (max at peak) going through a wire the bigger the wire needs to be or it will heat the wire up to the point of causing a fire. Amps are not like 50 hp electric motors pulling a lot of amps through the wire, so their size can be smaller. Long story short, wire size can be small. In my amp, which was a pcb and not point to point, there wasn't much for wires, but where I needed them I used 16 gauge copper wire, and the amp sounds great. Go to parts-express.com, and see what kind of inventory they have, you can actually learn from seeing what products are available.
Volume control is called a potentiometer or 'pot' for short. Look for one with a 'log taper', and is rated in impedence 1/10th the source impedence. Your preferences will differ with the requirements of your amp, so I can't give you a part number. But, in addition to parts express, try angela.com, and tubesandmore.com.
Remember to enjoy the process, learn from it, don't expect everything to go perfect, but take the time to ensure you do it right. Read books on electronics, tube amp building etc.
Hope this helps
Matt
Most of the wires you need will come attached to the output trannies and mains tranny. However you will need a little bit of mains wiring (cut up a piece of spare extension cord or mains cord, or steal some mains wiring from a dead household appliance - iron, beside lamp, broken alarm clock, your mate's toaster, whatever). You will need this mains rated wire to connect from the IEC mains inlet socket (if you choose to use one) to the power switch and the fuse, and also for earthing the chassis to the mains earth. The other type of wire you will need is shielded audio wire to go from the RCA input connectors to the volume pot and then to the PCB terminals. I would go with Neon's choice of Edcor transformers (XPWR008 and CXPP25-MS-7.6K), and a JJ EL84 matched quad from Jim McShane (tested tubes, no issues, will handle the B+ of 340V easy), he also sells some nice shielded audio wire very cheap. I'm sure someone can come up with part numbers for a fuse holder and a pot for you, I can but not right now. It's a great amp, extremely well worth building IMO. I think your other questions are well answered by previous posts, except maybe ultra-linear vs pentode mode, seems it sounds good in either mode. I hope you are ready for a big learning curve, if you have the enthusiasm, it will carry you through.
Ian.
Ian.
WRT the fuse holder, I suggest you head over to your local Radio Shack and start looking through their drawers. You'll find a few different chassis-mount fuse holders. The ones we typically use look something like this:
If you find one you like, just buy it there. You can get your fuses there too. Get a pack of 1.5A slo-blo fuses. They also have a few other things, like RCA jacks, binding posts, etc. But their prices are on the high side. For those types of things, Parts Express is a good choice.
That's about all Radio Shack is good for in terms of parts. They have a few odds and ends, but you'll need to get the bulk of it from Mouser, etc.
The IEC socket mentioned is the same power socket you find on the back of your computer. Using one lets you use any common computer power cord for power and makes it easy to swap the cord later for a longer/shorter/better with ease. It's not necessary, though. What is necessary is that you use a grounded power cord of some sort. The only drawback to the socket is that you have to cut a square-ish hole in your chassis. Radio Shack's "nibble tool" is handy for this.
If you find one you like, just buy it there. You can get your fuses there too. Get a pack of 1.5A slo-blo fuses. They also have a few other things, like RCA jacks, binding posts, etc. But their prices are on the high side. For those types of things, Parts Express is a good choice.
That's about all Radio Shack is good for in terms of parts. They have a few odds and ends, but you'll need to get the bulk of it from Mouser, etc.
The IEC socket mentioned is the same power socket you find on the back of your computer. Using one lets you use any common computer power cord for power and makes it easy to swap the cord later for a longer/shorter/better with ease. It's not necessary, though. What is necessary is that you use a grounded power cord of some sort. The only drawback to the socket is that you have to cut a square-ish hole in your chassis. Radio Shack's "nibble tool" is handy for this.
chokes?
I'm a newb as well, builing a el84 simple pp. I am wondering what choke to use with this amp. I' guessing I would want one that would handle 200ma to match an Edcor xprwr008, but what about inductance and resistance? optimal values for these? I was looking at these Hammond Mfg. - D.C. Filter Chokes - (153 - 159 Series)
and 1 more question, a suplimental capacitor, guidlines for this?
thank you in advance.
I'm a newb as well, builing a el84 simple pp. I am wondering what choke to use with this amp. I' guessing I would want one that would handle 200ma to match an Edcor xprwr008, but what about inductance and resistance? optimal values for these? I was looking at these Hammond Mfg. - D.C. Filter Chokes - (153 - 159 Series)
and 1 more question, a suplimental capacitor, guidlines for this?
thank you in advance.
I appreciate your help Russ, Neon, Matt and Ian. Your posts here and on other threads have cleared a lot of brainstorming.
Seems like mouser and digikey are all out of a total of 3 to 4 types of caps and 1 or 2 types of resistors with lead times like mid-July and mid-August.
moparman, chokes are optional in simple pp right?
Seems like mouser and digikey are all out of a total of 3 to 4 types of caps and 1 or 2 types of resistors with lead times like mid-July and mid-August.
moparman, chokes are optional in simple pp right?
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OK...
Although it's handy to "one stop shop", you may end up ordering from several sources. So also try: Allied Electronics, AES, Angela, Parts Express and Parts Connection just to name a few more. Don't get too hung up on brands of resistors or caps. Just make sure to use the correct type as called for in the parts list (ie: metal-film resistor; electrolytic capacitor; etc.)
And don't bother with a choke. Built properly, the SP-P is dead quiet without a choke or fancy caps.
The SPP really doesn't benefit much from a choke. Being push-pull, the ripple on B+ is common-mode in the output stage (which means it cancels itself out because it "ripples" both sides at the same time in opposite directions). The input and phase splitter stages are isolated by an additional RC circuit, so their plates are fairly ripple-free. On my sensitive speakers (98dB), I can hear some 120Hz buzz when I put my ear up to the speaker. But in my shop (89dB speaker, IIRC), it is dead quiet.
The SSE and TSE benefit from the extra filtering the choke provides because they are both single ended and therefore don't have very good CMRR (common mode rejection ratio).
The SSE and TSE benefit from the extra filtering the choke provides because they are both single ended and therefore don't have very good CMRR (common mode rejection ratio).
I got curious about a choke too, and started doing scenario's with Duncan Amps' PSUD and a C354 choke. It looked good so I bought a C354 choke from Triode Electronics, 1.5H, 200mA and 55 ohms and ran it in series with a 100 ohm resistor to keep the B+ the same as with just the 150 ohm resistor. Surprisingly (to me, a newb) the sound quality suffered, there were slightly less details. I have no idea why, and I took the choke out.
Now, Russ, or anyone, I have one question which has been puzzling me for some time, that is, the 150 ohm resistor between the two power supply caps, R1, is rated at 5W, and drops around 28V or so, so it is running right near its 5W rating. Normally I allow 3 to 5 times the resistor rating to keep a resistor comfortable heat-wise. But R1 in my amp does not appear to be stressed, so where is the faulty bit in my thinking?
Moparman, I am thinking if you want to spend a bit more money maybe put it into output transformers. From the sound I hear from this amp, I think George "fine tuned" this design a lot more than he lets on about (or wrote about), so I think it's safe to build it just as it is.
Ian.
Now, Russ, or anyone, I have one question which has been puzzling me for some time, that is, the 150 ohm resistor between the two power supply caps, R1, is rated at 5W, and drops around 28V or so, so it is running right near its 5W rating. Normally I allow 3 to 5 times the resistor rating to keep a resistor comfortable heat-wise. But R1 in my amp does not appear to be stressed, so where is the faulty bit in my thinking?
Moparman, I am thinking if you want to spend a bit more money maybe put it into output transformers. From the sound I hear from this amp, I think George "fine tuned" this design a lot more than he lets on about (or wrote about), so I think it's safe to build it just as it is.
Ian.
Well the output tubes draw something like 100mA total at idle for all four. Add say 20 more for everything else.
P=I^2 * R
So that's a little over 2W. The voltage across that resistor is not DC, so if you were trying to measure it with a meter it is not going to give you a useful result. It was more like a peak voltage than the average voltage.
P=I^2 * R
So that's a little over 2W. The voltage across that resistor is not DC, so if you were trying to measure it with a meter it is not going to give you a useful result. It was more like a peak voltage than the average voltage.
This is how I will ground. In UL with cathode feedback.
So this ONE wire(green) coming out of ONE input jack and the grounding is DONE? George explained that PT and OPT are grounded on pcb and pcb is grounded via this one green wire. But then he said the green wirings are actually included in the PCB. So no need to run a separate wire from that input jack to IEC? Then, at which physical place of the PCB is wired to IEC ground?
I just want to be sure since the day I hook it up I should be playing it, not playing a harp with a halo on head. I'm almost chickening out now.
So this ONE wire(green) coming out of ONE input jack and the grounding is DONE? George explained that PT and OPT are grounded on pcb and pcb is grounded via this one green wire. But then he said the green wirings are actually included in the PCB. So no need to run a separate wire from that input jack to IEC? Then, at which physical place of the PCB is wired to IEC ground?
I just want to be sure since the day I hook it up I should be playing it, not playing a harp with a halo on head. I'm almost chickening out now.
An externally hosted image should be here but it was not working when we last tested it.
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The grounds of the OPT secondaries (and therefore the speaker jacks) and the input jacks are all connected together. If you isolate you input RCAs from the chassis, then all of those grounds are floating relative to the earth ground. They key point he is trying to make is that the PCB should only be grounded to earth from ONE location and that location should be the same location that earth ground attaches to the chassis. This is called a "star" grounding scheme, though it's not much of a star because the PCB collects a lot of the grounds for you.
Here he suggests using one of the RCA jack grounds. This is convenient especially if your RCA jack are NOT isolated from the chassis. In that case, that RCA jack is also the chassis ground location. By attaching the earth ground there as well, the RCA becomes the star ground location.
Here he suggests using one of the RCA jack grounds. This is convenient especially if your RCA jack are NOT isolated from the chassis. In that case, that RCA jack is also the chassis ground location. By attaching the earth ground there as well, the RCA becomes the star ground location.
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