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Old 5th October 2010, 06:22 PM   #21
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Well if i was super broke and wanted a simple SE:
el34 winged "c" = $30 pair on ebay, less if you want others or used
10 watt gxse= $26.10 (output transformers make the most improvement to sound)
Solid state rectifier= save $10-20
no choke= save $20 or more
no motor run cap= save $20 or more
antek AN-2T350 700v ct 240ma = $35.00

Last edited by nightanole; 5th October 2010 at 06:31 PM.
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Old 5th October 2010, 07:06 PM   #22
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Quote:
Originally Posted by nightanole View Post
Well if i was super broke and wanted a simple SE:
el34 winged "c" = $30 pair on ebay, less if you want others or used
10 watt gxse= $26.10 (output transformers make the most improvement to sound)
Solid state rectifier= save $10-20
no choke= save $20 or more
no motor run cap= save $20 or more
antek AN-2T350 700v ct 240ma = $35.00
That pretty much sums it up........

really broke....use the XSE series transformers

kinda broke....use the GXSE and a choke
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Old 5th October 2010, 08:13 PM   #23
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My point was that even with the kt88's the larger xfmr isn't the correct one.
I wasn't suggesting to use the kt88's. Just sharing my experience that larger more $$ isn't always better.
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Old 5th October 2010, 08:40 PM   #24
Fenn is offline Fenn  United States
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Couple of questions before I decide which way to go. I'm broke but not too too broke otherwise I would be looking at building a transistor radio.
I have a co-worker who apparently is a knowledgeable older gentleman, who used to rebuild tube tv's, radios, but really loved building and rebuilding guitar amps. Great to know in case I get into some real trouble. He is the one who keeps pressuring me to use the 6V6. He is eccentric so I may do 6V6 to keep him in a good mood to help me. He also tells me to get a 4ohm output on the transformer. Any reasons to follow this or not? He says it will be a great sound.
Also, it seems like all I would have to do is swap out the transformers and tubes if I wanted to upgrade.
Now for the questions:
Do the power tubes have to be a matched set? Since they are on separate channels I didn't know if it mattered. I am trying to find a datasheet on the 6V6 to see what the mA required is to know whether the Edcor or the Allied transformer will work. The allied is only 120mA and the Edcor @550VCT is 200mA. I will look at Antek as well. But I lean towards Edcor because they seem to have a good review from Tubelab.
I will do the GSXE15-4/8-5k depending on your thoughts. What is the difference in the input impedance?
If I don't need a matched pair, the local tube store has like 15 used 6V6 tubes that are guaranteed to work. GE, JAN, Tung-Sol and others for $10 each.
This is making me exercise my brain, I like it.
Sgregory: I know you what you meant, they just thought I had said it. I understand your point.
Can this amp be used for a guitar as well? Just out of curiosity.

Edit: Antek has one for $40 for 550VCT 500mA or $29 for 500VCT 200mA. I haven't heard anything about these transformers, but I don't know enough to know what effect these values will have on 6V6.

Last edited by Fenn; 5th October 2010 at 08:56 PM.
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Old 5th October 2010, 09:24 PM   #25
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For quick 6V6 info, look here: TDSL Tube data [6V6]

In class A single ended with a plate voltage (Va) of 250V, you'd like to be drawing about 45 mA per tube (Ia). That's 90 mA for the pair, plus add another 16~20mA for both sides of the 12AT7 (roughly 8~10mA per side). That's a whopping total of 110mA.

If you intend to go with the 6V6, you might be able to get away with the Edcor GXSE5-8-5.5K. The 5.5K load impedance is a pretty good match for the triode strapped 6V6, assuming your speakers are roughly 8 ohms. The XPWR009 could probably work for the power transformer, but double check the specs carefully. I think it will give about 325 volts or so with a 5AR4 rectifier, or 345 volts if you try solid state rectification. The 5Y3 might work too, but has a lot of voltage drop - I'm guessing you'd end up somewhere around 260 VDC.

Last edited by Ty_Bower; 5th October 2010 at 09:39 PM.
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Old 5th October 2010, 09:30 PM   #26
Fenn is offline Fenn  United States
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That's the interesting part. I don't have any speakers yet.
Why would my co-worker tell me to go with 4ohm output what difference does it make?
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Old 5th October 2010, 09:52 PM   #27
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Quote:
Originally Posted by Fenn View Post
That's the interesting part. I don't have any speakers yet.
Why would my co-worker tell me to go with 4ohm output what difference does it make?
The output transformer just reflects the speaker load impedance to the output tube anodes, so for example connecting a 4 ohm speaker to 8 ohm taps with a 5K transformer makes it a 2.5K transformer. Conversely, connecting an 8 ohm speaker on a 4 ohm tap on a 5K transformer will make it a 10K load to the output tubes.

So.....long story short, it's best to connect the correct speaker impedance to the output taps, to assure that the output tubes see the correct load. If you get a transformer with 4 ohm secondaries, you'll need 4 ohm speakers for proper operation.
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Old 5th October 2010, 10:44 PM   #28
Fenn is offline Fenn  United States
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Ty-Bower: I'll try it tomorrow I will start ordering the transformers.
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Old 9th October 2010, 10:07 AM   #29
sureshm is offline sureshm  Australia
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Another newbie question:

For C1 the recommended part is 47uf 500V. With 500v caps harder to find, would 68uF 500v work here or would there be too much stress on the rectifier? I am thinking of using a 5AR4 rectifier.

Thanks
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Old 9th October 2010, 11:35 AM   #30
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Would be pushing it for the 5AR4. Max input capacitance is 60uF with 100 to 150R series resistance depending on you trany.
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