Yes I do. A nice young fellow sent me nice little stash of CCS boards. Now I know what his DIY Moniker is.
I will go look at the El cheapo schematic now, but what is your opinion of that circuit with these TXs Boris?
Not to complicate things further gents, but I just realized that I'm not "exactly" married to these outputs. The thing is, that I was trying to use some Conn organ outputs, and already had the end bells plated. I ended up not liking those outputs due in part to stability issues and frequency response. It just so happens that the A470 take the same size end bell, so I was trying to "save" the plated ends. I haven't actually purchased them yet, but the guy I'm building the amplifier for, liked the 95 dollar price. Also, not to give anyone the wrong idea, I build amps for friends, but at no charge labor, just as a hobby. I love building amps, and was ending up with too many here, and not enough money to keep buying bits, so building for others seemed the natural remedy. I just didn't want you folks to think I would try to profit monetarily on the generous help you all give so freely. Thanks, Jay
I will go look at the El cheapo schematic now, but what is your opinion of that circuit with these TXs Boris? Not to complicate things further gents, but I just realized that I'm not "exactly" married to these outputs. The thing is, that I was trying to use some Conn organ outputs, and already had the end bells plated. I ended up not liking those outputs due in part to stability issues and frequency response. It just so happens that the A470 take the same size end bell, so I was trying to "save" the plated ends. I haven't actually purchased them yet, but the guy I'm building the amplifier for, liked the 95 dollar price. Also, not to give anyone the wrong idea, I build amps for friends, but at no charge labor, just as a hobby. I love building amps, and was ending up with too many here, and not enough money to keep buying bits, so building for others seemed the natural remedy. I just didn't want you folks to think I would try to profit monetarily on the generous help you all give so freely. Thanks, Jay
Yes, the "El Cheapo" schematic is here. The LTP splitter/driver should be made from high mu/high gm triodes. That pretty well rules the idea out, If Jay's all Octal requirement is to be satisfied.
A Mullard style circuit using a 6SJ7 voltage amplifier and a 6SN7 LTP provides a reasonable gain structure and some resistance to slew limiting. The really high gm types that provide substantial resistance to slew limiting come in 7 and 9 pin mini packages.
A Mullard style circuit using a 6SJ7 voltage amplifier and a 6SN7 LTP provides a reasonable gain structure and some resistance to slew limiting. The really high gm types that provide substantial resistance to slew limiting come in 7 and 9 pin mini packages.
WB, you should be able to use either the sand diodes or a 5AR4 and get your B+ in a reasonable range. The 380V that I show is sort of a minimum, and up to 410V or so is still cool. It will sort of depend on your sonic preference and the rest of your rig. I prefer SS rectification slightly - it's more transparent and 'fast', but vacuum rectification has a little more smoothness and ease.
Also, If your output transformers are 5K primary load, you may want to get a little less B+ voltage and turn up the current, to get a lower rp and thus more optimum load for your output circuit. You know, If I were using the Hashimoto outputs, I would be looking at the HW25-5. This circuit will deliver about 18W max, so there's no real need for a 40W output transformer, unless you just like 'em mongo.
Aloha,
Poinz
Also, If your output transformers are 5K primary load, you may want to get a little less B+ voltage and turn up the current, to get a lower rp and thus more optimum load for your output circuit. You know, If I were using the Hashimoto outputs, I would be looking at the HW25-5. This circuit will deliver about 18W max, so there's no real need for a 40W output transformer, unless you just like 'em mongo.
Aloha,
Poinz
Poindexter said:
Poinz: Thanks for the feedback. The One Electron Power transformer has 385-0-385 or 260-0-260 secondaries. I'm presently breadbording using the 260-0-260 taps and using the 100v primary tap, to hopefully yeild around 310 or so for SS rectification. I am also planning on trying a 5AR4 (or something else, if it makes more sense) with the 385-0-385 taps.
I bought the Hashimotos used from the trading post (thanks Jazzbo!), so they were cheaper than practically any new Hashimoto. If it turns out I need more than 16w for happiness, I can always rebuild the amp as a UL EL34 or KT88.
Two questions, are there any special wattage requirements for the 30 ohm R's shown going to the 5AR4 on the schematic? What is the typical current draw on the bias voltage? (-66V)
thanks
I'm using the Antek 1T-300, and using the two 6.3v windings in series as a 'boost' winding to get about 315v. PSUD tells me I'll get about 385Vdc with sand diodes. You should be able to tune in with that beautiful power trans somehow. If you use a nice mongo choke as the second element in your filter, you can use the 385v winding and adjust the voltage with the cap before the choke (the first filter element).
I prophesy that once you have heard zero NFB triode sound, UL and pentode ain't gonna send you. With your nice mongo iron, maybe a better call would be to adjust the circuit values (both signal and power) and use 6550s as outputs. That's another very linear device. The 6GK5s will drive them too.
Aloha,
Poinz
I prophesy that once you have heard zero NFB triode sound, UL and pentode ain't gonna send you. With your nice mongo iron, maybe a better call would be to adjust the circuit values (both signal and power) and use 6550s as outputs. That's another very linear device. The 6GK5s will drive them too.
Aloha,
Poinz
The very simple and good
Hi Jay ,
My suggestion is the DYNACO Mark III , that uses the inexpensive
and easy to find 6AN8 ( triode / pentode ) .
The pentode works as a voltage amplifier , direct coupled to the
triode , that works as a concertina phase inverter , driving a
pair of EL34 PP @ 4300 ohms plate to plate .
The nominal power is 35 Watts ,
A very simple design , with excellent results.
Regards ,
Carlos
Hi Jay ,
My suggestion is the DYNACO Mark III , that uses the inexpensive
and easy to find 6AN8 ( triode / pentode ) .
The pentode works as a voltage amplifier , direct coupled to the
triode , that works as a concertina phase inverter , driving a
pair of EL34 PP @ 4300 ohms plate to plate .
The nominal power is 35 Watts ,
A very simple design , with excellent results.
Regards ,
Carlos
Poindexter said:
Poinz: I am planning on a CLC and adjusting the first C to dial in the B+. I have done some PSUD modeling; the thing I find tricky is to get both the 390 and 320 voltages correct, since I'm still a newbie.
I have some 6550's and would be interested in the mods req'd to pop them in the circuit; I'm assuming that the changes would be minimal. What's the estimated power output with trioded 6550's?
thanks
I have built the Claus Byrith 2x30W EL34 amplifier, he made a very good writeup on the whole built, it is free to download from Lundahls homepage.
Lundahl Transformers - 30W Push Pull amplifier
This is the amp I use in my living room.
Lundahl Transformers - 30W Push Pull amplifier
This is the amp I use in my living room.
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