I have experience working on and scratch building guitar amps. I would like to stay away from PCBs, I like building my own turret boards or PP wiring. If theres not a basic circuit out the that will get me to the end of the project, I will need some hand holding. Some of the stuff you guys do with HIFI amps I have never seen working on or building guitar amps.....so be gentle. As far as tubes go I've got a stash, 7591, 6550, EL34, 6L6, KT66, 6V6 and standard guit fiddle preamp tubes along with a bag of 6AU6s and 6U8As assorted assorted others.
Maybe 30w + PP using some of the iron I already have. That being:
Power:
EMO0726
300-0-300, 250mA
6.3V, 4.8A w/CT
5V,3A w/o CT
Emo0731 same as above but
320-0-320
and a
Em0725a
325-50-0-325,400mA
6.3v, 7A w/o CT
5V, 3A w/o CT
Most of the OPTs I have are for guitar amps. But I do have a:
EDCOR Electronics Corporation. CXPP100-MS-4.2K.
A couple of these;
TF110-48/UL Deluxe Style Ultra-Linear Output Transformer 4/8 ohm (Plastic Bobbin)
And a set of used Iron, PTs and OPTs, out of a Bogen HiFI running 6V6s PP, not UL though. And assorted old pulled stuff.
I am thinking the 6V6s won't realistically get me to 30W. But this is basically what I have in iron. I also don't mind sending some money to add to what I already have.
I listen to Blues, Jazz and Classic rock and will probably end up building some better speakers also.
BL
Maybe 30w + PP using some of the iron I already have. That being:
Power:
EMO0726
300-0-300, 250mA
6.3V, 4.8A w/CT
5V,3A w/o CT
Emo0731 same as above but
320-0-320
and a
Em0725a
325-50-0-325,400mA
6.3v, 7A w/o CT
5V, 3A w/o CT
Most of the OPTs I have are for guitar amps. But I do have a:
EDCOR Electronics Corporation. CXPP100-MS-4.2K.
A couple of these;
TF110-48/UL Deluxe Style Ultra-Linear Output Transformer 4/8 ohm (Plastic Bobbin)
And a set of used Iron, PTs and OPTs, out of a Bogen HiFI running 6V6s PP, not UL though. And assorted old pulled stuff.
I am thinking the 6V6s won't realistically get me to 30W. But this is basically what I have in iron. I also don't mind sending some money to add to what I already have.
I listen to Blues, Jazz and Classic rock and will probably end up building some better speakers also.
BL
I used 80W guitar transformers for 40W Hi-fi amps. Work nice. CXPP100-MS-4.2K is a nice beast, but for 6V6s I would not waste it, rather for 4xGU-50 it would be in a ballpack (something like 160-200W of peak power).
If you don't plan to dime the amp and/or don't mind losing some bottom-end at high volume, those guitar amp transformers are an option. Some feedback may get some of that back. Your power requirements put you in Dynaco ST-70 territory, for which there are a plethora of toplogies for (lots of driver board options, which your can wire PtP of course). Any of those output tubes besides the 6V6 will get you there. The primary impedance of the OPT is a bit high, but if you use a 4 ohm speaker on the 8 ohm tap, you get 3300 ohms which might work well for trioded 6550?
If you are willing to buy more iron, the options are nearly endless! 🙂
If you are willing to buy more iron, the options are nearly endless! 🙂
I am not at all opposed to buying more iron. I just wanted you all to know what I had as maybe a starting point. I would like to use the big Edcor OPT, but if not that fine. I think if I were going to use the 25W UL OPTs I would use the 6V6s or the like.
Not familiar with the GU50.
I read some of the EL34 threads with interest, sounds like you'd need a Pentode-PI-EL34 arrangement.
BL
Not familiar with the GU50.
I read some of the EL34 threads with interest, sounds like you'd need a Pentode-PI-EL34 arrangement.
BL
MS = Multiple secondaries? Could be abused to reflect a different primary impedance?
I'm just sayin 4.2K Plate to Plate might not be your only option.
I'm just sayin 4.2K Plate to Plate might not be your only option.
If you want that 6V6 similar sound, but more power, there is 6JC5, a 19 Watter, likely want more like a 6.6K P-P primary with them though.
Seems like you're almost there with the 6550's and the 325-50-0-325, 400mA power transformer......fixed bias UL PP 6550?
If I need to and I'm going to buy new 6.6 OPTs, which is not a problem, maybe I should build an El Cheapo Grande as suggested by Mr Eli, w/7591s UL. My problem is that I'm going to need a lot of help drawing up a correct schematic for the power supply with using the 325-50-0-325 400ma PT I have. And the schematic that I have has 12AQ5 power tubes, I may be able to deal with plugging in the 7591s that schematic.
BL
BL
How many watts would the be, specs here say about 70.
http://www.mif.pg.gda.pl/homepages/frank/sheets/135/6/6550A.pdf
And the 4.2k OPT ought work?
BL
BL,
The 4.2 KOhm primary trafo is good for the EL34/6CA7/KT77 group. For the KT88/6550 group, about 3.2 KOhms is "right". Work backward from the speaker applying P = V2R and the fact the impedance ratio is the square of the turns ratio. A big voltage swing mandating a B+ rail well over 500 V. is needed in combination with a 4.2 KOhm primary.
The 4.2 KOhm primary trafo is good for the EL34/6CA7/KT77 group. For the KT88/6550 group, about 3.2 KOhms is "right". Work backward from the speaker applying P = V2R and the fact the impedance ratio is the square of the turns ratio. A big voltage swing mandating a B+ rail well over 500 V. is needed in combination with a 4.2 KOhm primary.
Eli;
Ok so going back EC Grande, the cocked bridge that you posted in the other thread, it wont work if the 5v winding isn't CTed? (for the B-)
BL
Ok so going back EC Grande, the cocked bridge that you posted in the other thread, it wont work if the 5v winding isn't CTed? (for the B-)
BL
Eli;
Is your example above for UL also........concerning what 6550s are looking for in the primary imp?
BL
Is your example above for UL also........concerning what 6550s are looking for in the primary imp?
BL
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The "cockeyed bridge" is a B+ rectifier setup. Look closely and you'll see it's actually FWCT, with an extra diode on the CT. The FAST diode on the CT keeps noise from getting to the PSU filter. Theoretically, the PIV rating of the "extra" diode doesn't matter. In practice, sh*t happens and the part should be able to take at least 1/2 of rectifier winding's voltage. You can't use a bias tap on the B+ winding, if a CB is used.
The 5 VAC winding gets voltage multiplied to obtain the B- and, possibly, the C-.
The voltage swing analysis for O/P trafo primary impedance applies to both full pentode and UL.
The 5 VAC winding gets voltage multiplied to obtain the B- and, possibly, the C-.
The voltage swing analysis for O/P trafo primary impedance applies to both full pentode and UL.
Ok I understand, about the cockeyed bridge. So if I were worried about diode switching noise, and I should, and schottkys are not available why not just use a tube rect? That way the 50v bias tap is still available. Or use a convensional FWCT with Schottkeys and still don't have to give up the bias tap.
What diodes and caps for the multipler?
BL
What diodes and caps for the multipler?
BL
I'm frugal. I'd rather spend less on parts to get "equivalent" results. UF5408s (1000 PIV)/3 A. are approx. 50 cents each. An Infineon IDT02S60C 600 PIV/3 A. Schottky costs about 2 bucks. The "cockeyed bridge" is less costly than a traditional FWCT setup using 1200 PIV Schottkys and the 5 VAC winding is needed for the B- supply, which rules the usual vacuum rectifiers out.
The voltage multiplier can be tapped for both the bias (C-) and the LTP tail (B-) supplies. A setup of 7 SB1100/68 μF. stages followed by a paralleled section 6AL5/4.7 μF. stage takes care of B-. Tap into the multiplier after 6 stages to get the bias (B-) voltage. Follow both taps with a RF choke/1000 pF. NPO ceramic LC section and a final RC reservoir section. The RF filter section kills the high order ripple harmonics associated with small conduction angles. "Hash" is not getting into your audio circuitry. 😀
BTW, watch out for the increasing WVDC requirements on the caps., with each successive multiplier stage. It may be easier to use all 100 WVDC parts and sleep soundly.
I'll see if I can't draw something up.....
I'll be good up till:
Follow both taps with a RF choke/1000 pF. NPO ceramic LC section and a final RC reservoir section. The RF filter section kills the high order ripple harmonics associated with small conduction angles. "Hash" is not getting into your audio circuitry.
BL
I'll be good up till:
Follow both taps with a RF choke/1000 pF. NPO ceramic LC section and a final RC reservoir section. The RF filter section kills the high order ripple harmonics associated with small conduction angles. "Hash" is not getting into your audio circuitry.
BL
I'll see if I can't draw something up.....
I'll be good up till:
Follow both taps with a RF choke/1000 pF. NPO ceramic LC section and a final RC reservoir section. The RF filter section kills the high order ripple harmonics associated with small conduction angles. "Hash" is not getting into your audio circuitry.
BL
BL: See attached power supply L2 & C2 for an example of one of Eli's "hash filters"
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