schematic from this amp 45/717a/5u4..
- Thread starter sonix
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Konnichiwa,
The Web Pages contain enough high rez photos of the innards to reverse engineer the schematic, so have a go.
Start with these, rotating them to be readable:
Then look at the picture of the circuit in thius PDF - zoom in:
http://www2.117.ne.jp/~y-s/A-08ura.pdf
Another hint, electrially the 717A and the C3m are not miles away.
Sayonara
sonix said:
The Web Pages contain enough high rez photos of the innards to reverse engineer the schematic, so have a go.
Start with these, rotating them to be readable:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Then look at the picture of the circuit in thius PDF - zoom in:
http://www2.117.ne.jp/~y-s/A-08ura.pdf
Another hint, electrially the 717A and the C3m are not miles away.
Sayonara
Konnichiwa,
I have decided to post the Schematic in another on-line group with pretty complete detail, so also find it here, in context. It is basically 99%, one or two values may be slightly different, but not much.
If you want to copy the Amplifier you do of course need the iron, considering fit/finish, component quality and inclusion of NOS Valves I'd think it's worth giving Yamamoto the business and buying the Kit if you want to build the Amplifier, a Set of Tamura Transformers and a nice case plus the valves will take most of the cost of the kit.... ;-)
Sayonara
I have decided to post the Schematic in another on-line group with pretty complete detail, so also find it here, in context. It is basically 99%, one or two values may be slightly different, but not much.
If you want to copy the Amplifier you do of course need the iron, considering fit/finish, component quality and inclusion of NOS Valves I'd think it's worth giving Yamamoto the business and buying the Kit if you want to build the Amplifier, a Set of Tamura Transformers and a nice case plus the valves will take most of the cost of the kit.... ;-)
Sayonara
Attachments
Lundahl LL1620 SE 30mA OPT for 45 tube
I found that even the output power of the 45 tube in SE mode is only 1.5W, it has the advantage over the 2A3 and 300B because its idle current is only 30-35mA. I built two 45 amps with LL1620 and LL1620AM which is specified to work at 30mA. According to the datasheet, the primary inductance almost 100H. Most of the SE OPT for 2A3 and 300B are with approx 24-30H primary inductance.
After listening to these two amps in about 2 months time, I noticed that its bass response is excellent.
My friend just bought the Yamamoto 45 amp. I would really like to hear it to see what are the differences between Yamamoto and mine. BTW, my 45 amps are using 6SN7 for the driver which is the design from Sun Audio's 2A3 SE amp.
Johnny
I found that even the output power of the 45 tube in SE mode is only 1.5W, it has the advantage over the 2A3 and 300B because its idle current is only 30-35mA. I built two 45 amps with LL1620 and LL1620AM which is specified to work at 30mA. According to the datasheet, the primary inductance almost 100H. Most of the SE OPT for 2A3 and 300B are with approx 24-30H primary inductance.
After listening to these two amps in about 2 months time, I noticed that its bass response is excellent.
My friend just bought the Yamamoto 45 amp. I would really like to hear it to see what are the differences between Yamamoto and mine. BTW, my 45 amps are using 6SN7 for the driver which is the design from Sun Audio's 2A3 SE amp.
Johnny
Have You compared them?
Am I the only one here that finds this schematic not compelling?
Unbypassed zener string, Pentode driving a triode, ewwwww! Ok, the transformers and the cherry wood and the finish are sexy, but it really looks like somethinh an amateur would design. (How am I going to drive the DHT, it needs a lot of voltage! Oh! I ll just stisck a Pentode it has all this nice voltage gain!!!!)
Unbypassed zener string, Pentode driving a triode, ewwwww! Ok, the transformers and the cherry wood and the finish are sexy, but it really looks like somethinh an amateur would design. (How am I going to drive the DHT, it needs a lot of voltage! Oh! I ll just stisck a Pentode it has all this nice voltage gain!!!!)
While I understand your objections and would have completely agreed not too long ago I have to mention that I have heard several similar amps that sounded surprisingly good in fact. (IMHO I think in a lot of cases a single stage driver is preferable to several cascade triode stages in terms of resolution if there is sufficient drive capability available. Here I would probably use a single 5842/417A triode myself.) Given the voltage levels on the screen of that pentode I would be surprised if you could hear a difference in noise levels bypassed or unbypassed. You might want to try it before dissing it, once having done so you have more than engineering dogma and opinion to base it on.. (I have been all too guilty of the same things, so please don't take my comment too seriously..) 😀 FWIW
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What's wrong with using pentode? Have you listened to it or an amp using pentode driving a triode? Didn't the Western Electric 91 use the same thing? If designed right, I don't see any reason to object to it.
.
Depends a whole lot on the pentode used, some of the more modern high transconductance types are quite good at it, the concern is always going to be the effect of output tube miller capacitance on the HF response.. High transconductance pentodes with modestly sized plate resistors running at high currents should slew well enough at high frequencies and shouldn't have a problem to well beyond 20kHz..
Can't really afford a $2400 amp as a student. What should I look for if I want to find similar irons?
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Channel outline
Hello there,
I'm interested in building this with my own components and chassis, so I picked up the schematics from one of the links (originally from Yamamoto's manual) and enhanced the image for clarity.
Being kind of new to this, I also outlined the channel-related components to highlight which ones I need 2x of.
Can someone confirm that my outline is correct? Thanks.
gm
Hello there,
I'm interested in building this with my own components and chassis, so I picked up the schematics from one of the links (originally from Yamamoto's manual) and enhanced the image for clarity.
Being kind of new to this, I also outlined the channel-related components to highlight which ones I need 2x of.
Can someone confirm that my outline is correct? Thanks.
gm
