Hi,
I am in the process of building Tubelabs Simple SE amplifier. Most of the components are on hand and only few things must be cleared:
Due to layout issues, I have two seperate ECC81 tubes, one on each side of chassis. I would like to try different input possibilities:
1.SRPP
2.CCS loading as standard
3.CCS loading with other half of ECC81
How do I connect a ECC81 as CCS (10mA) and what values do I use?
Is there any problems with this compared with the standard solid state CCS?
Is it possible to change from UL to triode mode and from feedback to non-feedback during playback?
I am in the process of building Tubelabs Simple SE amplifier. Most of the components are on hand and only few things must be cleared:
Due to layout issues, I have two seperate ECC81 tubes, one on each side of chassis. I would like to try different input possibilities:
1.SRPP
2.CCS loading as standard
3.CCS loading with other half of ECC81
How do I connect a ECC81 as CCS (10mA) and what values do I use?
Is there any problems with this compared with the standard solid state CCS?
Is it possible to change from UL to triode mode and from feedback to non-feedback during playback?
I have started building the Simple SE but everything is in limbo for almost 4 weeks.
Most of the parts are ordered from Digikey (Canada). R2, C10, C20, C12, C22 and the Hammond choke from Mouser because Digikey does not have any in stock. Put the orders in on the same day, got my Digikey order 2 days after (Nov-12) but am still waiting for the Mouser order to arrive!
Talked to Mouser yesterday and the guy told me it will take up to 10 weeks because USPS is not very reliable lately! (I have no problem with USPS with other US online retailer). Anyway, I found a Candian online outfit that carries the caps but they do not have the Metal Oxide R2. This is what they have,
VISHAY BC COMPONENTS|PR03000201503JAC00|Metal Film Resistor | Newark.com
will it be fine to use this instead?
Most of the parts are ordered from Digikey (Canada). R2, C10, C20, C12, C22 and the Hammond choke from Mouser because Digikey does not have any in stock. Put the orders in on the same day, got my Digikey order 2 days after (Nov-12) but am still waiting for the Mouser order to arrive!
Talked to Mouser yesterday and the guy told me it will take up to 10 weeks because USPS is not very reliable lately! (I have no problem with USPS with other US online retailer). Anyway, I found a Candian online outfit that carries the caps but they do not have the Metal Oxide R2. This is what they have,
VISHAY BC COMPONENTS|PR03000201503JAC00|Metal Film Resistor | Newark.com
will it be fine to use this instead?
I don't have the circuit schematic here, but you should be fine as the value and rating are the same. You can always change to the original later if needed.
Gary
It will work fine. R2 is just a bleeder resistor to make sure that the power supply caps get discharged when the power is shut off. These new small size resistors get pretty hot so make sure that it is not placed in direct contact with the PC board. Leave 1/4 to 1/2 inch of space between them.
Need more help here.
I recevied the resistor and capacitors 2 days after I put the order in. That was fast services. Fellow canadian if you are looking for an alternative online supplier, try this outfit US - Electronic Components Distributor | Newark.com.
I made a mistake when ordering the 6.3V cap. Somehow I put in 15000uF instead of the 1500uf. I found out when I try to insert it into the pcb and the leads spacing don't line up properly. So I have to order them again. This is when the question came up:
The Didgikey part list in tubelab is a panasonic FC and the Mouser part is a Nichicon, the Newark carries United Chemi-Con. I got the 1500uf 63V and they have the 6.3V also.
UNITED CHEMI-CON|EKZE6R3ELL152MJ20S|Aluminum Electrolytic Capacitor | Newark.com
The spec looked the same but if I deviate away from these two brand, will it affect the quality of the sound?
I can order from Digikey but they don't have the FC series in stock. They do have the FM series (Part P-12343-ND). Is it not as good as the FC series and that is why it did not make it to the tubelab partlist?
Will the FM series better than the United Chemi-Con? Since both Digikey and Newark have the canadian arm, their delivery time is usually within 2 working days.
I have given up hope on my Mouser order, still no sight of it after six weeks. How long will it take to ship a <3lb package from TX to Canada? Is this an issue with Mouser or is it USPS ** Sigh**
I recevied the resistor and capacitors 2 days after I put the order in. That was fast services. Fellow canadian if you are looking for an alternative online supplier, try this outfit US - Electronic Components Distributor | Newark.com.
I made a mistake when ordering the 6.3V cap. Somehow I put in 15000uF instead of the 1500uf. I found out when I try to insert it into the pcb and the leads spacing don't line up properly. So I have to order them again. This is when the question came up:
The Didgikey part list in tubelab is a panasonic FC and the Mouser part is a Nichicon, the Newark carries United Chemi-Con. I got the 1500uf 63V and they have the 6.3V also.
UNITED CHEMI-CON|EKZE6R3ELL152MJ20S|Aluminum Electrolytic Capacitor | Newark.com
The spec looked the same but if I deviate away from these two brand, will it affect the quality of the sound?
I can order from Digikey but they don't have the FC series in stock. They do have the FM series (Part P-12343-ND). Is it not as good as the FC series and that is why it did not make it to the tubelab partlist?
Will the FM series better than the United Chemi-Con? Since both Digikey and Newark have the canadian arm, their delivery time is usually within 2 working days.
I have given up hope on my Mouser order, still no sight of it after six weeks. How long will it take to ship a <3lb package from TX to Canada? Is this an issue with Mouser or is it USPS ** Sigh**
Sorry, can you explain exactly what you mean by that?
I'm pretty sure you'll do damage to the amp, tubes and yourself trying that. Definitely don't go switching UL to triode while going. I wouldn't try switching feedback while it's on either.
As a general rule with tubes, if you're changing anything, turn it off, unplug it, change whatever it is then check again before powering up. When you're working with expensive tubes and several hundred volts, better safe than sorry.
Sometimes you can get away with switching 'on the fly' but it is not recommended,It may result in loud clicks and pops,possibly damaging to speakers,if not tubes,transformers,etc.
I've done it on certain amps,but there's usually a 'thump' involved.
Unplugging the amp is a bit excessive,but turning it off before switching settings is a good idea,if not standard practice.
I've done it on certain amps,but there's usually a 'thump' involved.
Unplugging the amp is a bit excessive,but turning it off before switching settings is a good idea,if not standard practice.
Instead of one common ECC81 (one half for each channel) I am using two seperate ECC81, one for each channel with one half left unused...
This is somewhat off topic, but anyway...
When you install the electrolytic capacitors, don't have them tight up against the board when you solder them in. Leave a small (1/16" ~ 1/8") gap between the bottom of the cap and the circuit board.
George makes a passing mention of this somewhere in the assembly instructions. If you keep them tight against the board, then each time they expand/contract from thermal cycles, they pull at the leads. Eventually it can cause early failure of the cap. Leaving just a tiny wiggle room here eliminates this problem.
Oh yes that makes sense, I was unsure of what you meant initially. Sounds like an interesting idea.
Actually he goes into incredible detail about it. Can caps these days have a rubber or foam foot at the bottom to prevent this problem. However it doesn't hurt other than making the amp a little less vibration resistant (which is not an issue unless you are shipping UPS
.
Do as we say and not as we do.
The UL/triode switch causes some pretty nasty transients on this SE amp it seems. I can do it on my ST-70 with only a tiny click. The Simple SE makes an angry scratchy pop, which I'm sure my speakers don't like. I generally avoid doing it with the amp powered on but nothing has burst into flames as a result of doing it. Also remember that you are switching several hundred volts with a switch that is probably rated for 250VAC at best. The contacts don't see much voltage across them, but relative to the chassis....
The feedback switch is much more benign and sounds perfectly clean when flipped on my amp. I suspect the transients are slugged-out by the cathode resistor bypass cap.
Giving second life to this old thread...
I have finally received parts for my SimpleSE amplifier. Output tubes will be EL34 and output transformator 5000/8, powersupply about 420-450VDC.
There is only one primary winding on the OPT (25W type) so I have no option for UL...
Seeking some answers:
1) What will be the output power in Triode and Penthode mode?
2) Will 470R be a good value for Triode connection and Penthode connection?
3) What will input sensitivity be in the two modes?
I have finally received parts for my SimpleSE amplifier. Output tubes will be EL34 and output transformator 5000/8, powersupply about 420-450VDC.
There is only one primary winding on the OPT (25W type) so I have no option for UL...
Seeking some answers:
1) What will be the output power in Triode and Penthode mode?
2) Will 470R be a good value for Triode connection and Penthode connection?
3) What will input sensitivity be in the two modes?
Output power in triode mode with 450 volts B+, EL34 tubes, 5K primary loading, and 470 ohm cathode resistance should be about 6.29 watts. See George's chart here: Tubes & Transformers
Power in UL mode would be higher, but you say you do not have the required tap on the OPT secondary for it. George's board is not inherently designed to operate the finals in a true pentode mode. You would have to rig up some kind of screen supply for that.
I think 470 ohms cathode resistance is much too low for EL34 types, especially if you expect to have B+ around 450 volts. The tubes will be significantly over their dissipation limit. I'm using 810 ohms in my Simple SE (started with 560, and added another 250 in series).
I've found my Simple SE to be fairly sensitive, but the final result depends on many factors (output transformer's effective primary impedance, use of cathode feedback, use of ultra-linear connection, etc). I need very little gain from my preamp to drive it to the levels I want. I should expect it could be driven directly from an iPod or CD player without the need for a preamp at all.
Power in UL mode would be higher, but you say you do not have the required tap on the OPT secondary for it. George's board is not inherently designed to operate the finals in a true pentode mode. You would have to rig up some kind of screen supply for that.
I think 470 ohms cathode resistance is much too low for EL34 types, especially if you expect to have B+ around 450 volts. The tubes will be significantly over their dissipation limit. I'm using 810 ohms in my Simple SE (started with 560, and added another 250 in series).
I've found my Simple SE to be fairly sensitive, but the final result depends on many factors (output transformer's effective primary impedance, use of cathode feedback, use of ultra-linear connection, etc). I need very little gain from my preamp to drive it to the levels I want. I should expect it could be driven directly from an iPod or CD player without the need for a preamp at all.
UL gives more power and noticeably higher sensitivity. As far as the quality of sound is concerned, I think I prefer triode mode - although I couldn't explain why. Overall, the differences seem subtle to me.
Not too many people run the SSE in pentode mode. I have not tried it. You'll most likely want CFB when using pentode mode to improve the output impedance and DF.
The simplest way to do it is to connect the screens to the B+ rail...probably right where the OPT gets B+ from. You just need to watch that you are not exceeding the screen's rating. This puts the screen voltage above the plate voltage, which is normally not what you want (though many designs get away with it). The "proper" way to do it would be to add another RC step after the B+ rail and connect the screens to that.
On my system, the main difference between triode and UL mode on this amp depends which speakers I am using. My less sensitive speakers (~90dB) like the extra power from UL mode, but I don't hear a huge difference otherwise. My more sensitive speakers (98dB) have horns and they seem to protest less when the amp is in triode mode, perhaps simply due to some HF roll-off from driving the finals in triode. There is also more "detail" or "sound stage" in triode mode.
The simplest way to do it is to connect the screens to the B+ rail...probably right where the OPT gets B+ from. You just need to watch that you are not exceeding the screen's rating. This puts the screen voltage above the plate voltage, which is normally not what you want (though many designs get away with it). The "proper" way to do it would be to add another RC step after the B+ rail and connect the screens to that.
On my system, the main difference between triode and UL mode on this amp depends which speakers I am using. My less sensitive speakers (~90dB) like the extra power from UL mode, but I don't hear a huge difference otherwise. My more sensitive speakers (98dB) have horns and they seem to protest less when the amp is in triode mode, perhaps simply due to some HF roll-off from driving the finals in triode. There is also more "detail" or "sound stage" in triode mode.
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