Component selection for 6L6 clementine

sweet & juicy SE amp for 1626 Darlings and the 6L6 family

Component selection for 6L6 clementine

Postby SoIL4 » Sun Feb 02, 2014 3:46 pm

Hello all. I have a few questions about components especially output transformers for a 6L6 clementine. I would like to be able to integrate this into my current system and be able to swap it in and out with other amps for comparison. So here is a little bit about my system.

My main speakers alternate between two sets; ESS AMT monitors 6 ohm minimum 87db and Klipsch KG4s 4 ohm 94db. My source is a blue ray player for CDs. I am using a khozmo MKII 10K passive attenuator to control volume and a MyRef FE amplifier. I have a polk PSW505 sub that I use to supliment the shortcomings in low end for the AMTs. All of this resides in a 12' x 12' listening room that opens up to two other rooms, not ideal but it works.

Idealy I would like to be able to just be able to swap this with the MyRef and be plug and play. These things tend to never be that easy........

My first question is about the speakers. The schematic calls for 8ohm edcor output transformers but my speakers are 4-6ohm. In my previous amp builds I selected lower voltage transformers to acount for the lower impedance but this is not quite the same thing. Do I need to select a different part number to account for the lower impedance of these speakers? Can I even use one part number with both speakers, or should I pick 4 or 6 and go with it? Should I even consider using the clementine with the 87db AMTs at all or will I be surprised?

I promise I searched all morning on this site and some others and never really found the suitable answers ;)

My next question is about the passive volume control that I am using. It is a khozmo MKII 48 position stepped attenuator. It is the 10K variety. I thought tube amps typically liked to see higher impedance like 100k or more, but I could not find anything definative. Will I still be able to use the 10k khozmo or will I run into trouble with it?

Im sure I will have more questions but these are the main head scratching issues so far. Thanks in advance for any insight.

Will
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Re: Component selection for 6L6 clementine

Postby TomMcNally » Mon Feb 03, 2014 11:49 am

Speakers with 90+ db sensitivity would be better, but anything works, just not as loud.
Edcor makes 4, 6 and 8 ohm transformers ... I'd go with the 4's. GXSE15-4-5k

As far as the attenuator, lower source impedance can always feed higher input impedance,
it's high to low that doesn't work well.
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Tue Feb 04, 2014 5:13 pm

Great, thanks Tom. That should get me going in the right direction. I do have a question about the CL90 in the power supply. I am contemplating using this power switch and relay http://www.amb.org/audio/epsilon24/ as I have used it in the past and it works great. However In the schematic for the 6L6 clementine the CL90 is placed after the fuse, but before the power switch. Should it be after the switch, or in this case the relay? I am vaugely familiar with thermistors from other non tube class A schematics and they have the thermistor on the other side of the switch. (???)
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Re: Component selection for 6L6 clementine

Postby TomMcNally » Tue Feb 04, 2014 5:51 pm

In a normal, simple on/off switch system, the CL-90 can theoretically go anywhere in line ... since it has no path to ground, it can't hurt anything if it fails, shorts or opens. In your case, with an external relay driven from the on/off controller board, the CL-90 would have to go after that relay.
simply speaking, it would be in line with the power transformer for the amp. I assume you'll use a small wall-wart to power the relay board ?
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Tue Feb 04, 2014 6:23 pm

The relay is triggered by a circuit powered by a small 12V transformer. This circuit powers the relay coil and the led on the switch. The circuit has thermal shutdown options too, but I bypass them. It makes for a professional detail.

I guess I thought the CL90 had to be isolated from the mains until power up to heat up. Thanks for all the answers Tom!
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Wed Feb 05, 2014 4:44 pm

Board and iron on order!

Does really take edcor 5-6 weeks to build an order?
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Sat Feb 14, 2015 5:28 pm

The answer to the above question is yes O:) but it is worth the wait. So after all this time I have made a great deal of progress on this build! As you can see from the photos I have taken a slightly different approach to creating an enclosure. I wanted something that little hands would not be able to touch so this is my solution.

I do have a question about the tube sockets. as it sits the top of the sockets is a mm or two below the copper top panel. When installed the base of the tubes sits flush with the top panel. Is this acceptable or do the tops of the sockets need to be above the panel. I have seen examples of both ways while scouring tube amp photos on the web. If anyone can shed some light on this topic let me know. Thanks
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Sat Feb 14, 2015 5:37 pm

Another view
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Re: Component selection for 6L6 clementine

Postby Shannon Parks » Thu Feb 19, 2015 5:38 pm

SoIL4 wrote:I do have a question about the tube sockets. as it sits the top of the sockets is a mm or two below the copper top panel. When installed the base of the tubes sits flush with the top panel. Is this acceptable or do the tops of the sockets need to be above the panel. I have seen examples of both ways while scouring tube amp photos on the web. If anyone can shed some light on this topic let me know. Thanks


This can be tricky sometimes - or as Dave at the EEVblog would say, "a trap for young players". Your gap doesn't look like a problem to me. But on 3mm and thicker chassis materials, it's something to consider ahead of time, as even the old style chassis mount caps might be quite recessed (particularly the flat football shaped ones). You can always raise it an 1/8" with shorter hex standoffs, too.

Shannon
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Sun Apr 12, 2015 3:30 pm

I am finishing up the wiring and doing the resistance measurements today. While measuring all of the pins are reading perfectly according to the 6l6 chart except for pin 1 and pin 8 on the 6l6 socket (both) . I cannot get a reading at pin at all both sides. The chart tells me I should have 725 ohms. Should i be getting a reading for pin 1? I thought pin 1 for a 6l6 tube had no connection? As for pin 8 am I okay or did I make a mistake? I would like to get this up and running soon! Thanks
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Re: Component selection for 6L6 clementine

Postby TomMcNally » Sun Apr 12, 2015 7:06 pm

There is no connection to Pin 1, and it isn't needed for 6L6's ...

quoting Shannon:

The Clementine 6L6 supports all 6L6-types, so 6L6, KT66, KT88, 6550, KT90, KT120, etc. EL34s require a jumper at V2-1 to V2-8 as well as a jumper at V3-1 to V3-8 (very easy - you can use clipped resistor leads).

Fire that amp up and let us know how it sounds !

... tom
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Mon Apr 13, 2015 7:06 pm

Thank you Tom! Hopefully it will be up and running by this coming weekend.
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Sat Apr 25, 2015 4:00 pm

We have sound! Well actually I have all week. I am happy to report the amp fired up without any issue and is beginning to sound great. I moved the ess amt monitors out of the listening room and moved my kg4s back in. This combination sounds very different than the previous setup so I am still in the process of speaker setup and sub integration. I am getting close though. I have found that I am using steps much higher on my attenuator than I used with my previous amp so these steps need a little time to "burn in". All in all it sounds great. It is very relaxed though compared to my other amps but it is very detailed and has a great soundstage. I should also say it is dead quiet at idle through the 94dBm kg4s. This is a great amp, thanks Shannon!

I am curious about any different flavors of coupling caps some of you may have tried with this amp. I experimented with different caps on my MyRef amp and found that they had a great impact on the sound. Not to say that veils were lifted and all that just that they affected the resolution of the sound. I settled on the jantzen silver z as my favorite by far. I felt they sounded more like a piece of wire than all the others....which is how parts express describes them too. They do have versions with voltage ratings up to 1200vdc so I may give them a try in this amp too. I plan on listening for awhile as is, but that is one "upgrade" I may pursue. If any of you have experience "rolling" coupling caps let me know.


This amp leads me into my next audio project which will be a pair of 104dBm la scala clones. I should be able to get the most out of the Clementine with those (y)
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Sat Apr 25, 2015 4:59 pm

Here are a few pics in action!
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Re: Component selection for 6L6 clementine

Postby SoIL4 » Sat Apr 25, 2015 5:01 pm

More
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