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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 22 Aug 2020, 09:32 
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soundoutlad wrote:
Do I need to toss the chokes? Or is it possible to supplement them using caps and resistors?
No.

I'd say build the signal schematic found here. And build the original power supply. It should work out fine.

The real reasons I went with the Edcor power transformer were it runs cooler (because of my case design), I wanted to run a jewel indicator off the filament winding and the Hammond transformer filament winding is maxed out with just the tubes, and I wanted an all Edcor blue design above the plate.

Hope this helps.

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 22 Aug 2020, 12:53 
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Joined: 03 Jul 2019, 10:36
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Thanks Suncalc, that's good to know, I've emailed the supplier to see if I can return
the originals and I prefer keeping things simple. I assume the increase in fuse size
is to cope with the inrush in a higher rated transformer. Now I'd better get on with this
build and finish in case there's a MK.3 on the way,
thanks again.


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 22 Aug 2020, 13:36 
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soundoutlad wrote:
Now I'd better get on with this build and finish in case there's a MK.3 on the way
No V3 coming for this amp. Next project is a big one, optimized 6L6GCs in UL with an integrated tone control preamp and input selector. Just need to get the time to finish it.

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 31 Aug 2020, 19:35 
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Finally got the full scale testing done on the V2 version of this amp.
Attachment:
6CY7 V2 Bandpass.png
Looks like my changes really paid off. The improvements are 0.91dB @ 50Hz, 1.46dB @ 40Hz, 2.66dB @ 30Hz, and a full 5.0dB @ 20Hz. I just A/B tested the amps and you can really feel the improvement in the low end. It's well worth the effort.

Look for the full writeup on all the design improvements and how it sounds in a week or so.


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 31 Aug 2020, 19:41 
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Looks like the Edcor performs close to or better than their specifications.

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 31 Aug 2020, 21:58 
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Woodo wrote:
Looks like the Edcor performs close to or better than their specifications.
Yes. The GXSE is rated from 40Hz to 18KHz for <1dBu which is -3.2dB power into load. In this amp the response is only off 1/2dB at 40Hz. Even at 20Hz it's only down about 1.7dB.
Attachment:
6CY7 V2 Low Band Data.png
However you listen to it, the Edcor GXSE transformers are doing a fine job.


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 05 Sep 2020, 17:27 
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Attachment:
6CY7 Zebrawood.jpg
A complete write up on the 6CY7 V.2 amplifier is now available on my website at https://www.cascadetubes.com/the-6cy7-v2-0-zebrawood-amp/. This amp meets it promise of improved low end performance and excellent sound. Feel free to take a look.

As always, question and comments are more than welcome.


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 05 Mar 2021, 10:21 
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Hi Matt,

Just discovered this support thread and as an intermediate builder, I'm currently studying your plans with the goal of building the 6CY7 ver2.0 stereo amp. I understand low wattage SET amplifiers need high efficient speakers to reproduce an acceptable volume level.

Can you recommend high-sensitivity speaker drivers (north of 90dB) to be utilized in an efficient speaker system for use with the 6CY7 ver. 2.0 stereo amplifier? I will eventually build my own speaker cabinets to match the 1+ watt output of this amp. My listening room is roughly 17' x 17'.

Haven't decided yet on a 2 way or 3 way speaker cabinet system.

Thank you


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 06 Mar 2021, 15:11 
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Since no one has responded, I'll throw in my 2¢ worth.

For truly great performance, in a first speaker build I recommend some nice high efficiency full range Fostex drivers in a back loaded horn enclosure. Something like the FE166NV in a custom enclosure. If the back loaded horn enclosure is too much, the base reflex enclosure for this driver is not bad. These are a good match for both low power SETs and SE-UL amplifiers.

If you aren't looking to build at first, your best bet without breaking the bank is probably a pair of BIC DV62si speakers. They are currently about $120/pair and they'll do well with SETs that have a fairly low output impedance. The bass might get a little out of control (slight booming and overhang) with SE-UL amps but it is generally acceptable at lower listening levels.

The Fostex drivers are 94dB efficient. The DV62si speakers are about 90dB.

There are lots of other options, obviously. But this should get you started.

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 08 Mar 2021, 16:35 
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My amp is about 6w I think ( not measured) but it seems to match well with my full range Dayton audio ps180 full range speakers in a small TL of about 15 litres. I found I liked it better with a baffle step correction but could easily live without it. In this type of enclosure I should have increased the volume for better bass but wanted to keep it small. I have similar sized commercial B&W bass reflex speakers that the amp handles well too, loads of bass and on paper less efficient but it’s not evident.

I opted for the Dayton audio as it was easier to obtain for me but depending on where you are you might be spoilt for options. These took months of listening to break in. I note Mark Audio has become popular among diyers for 4-8 inch full range drivers and also have recommended enclosure designs.

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