Hey Mosquito! You're my man!
Can't believe you build it.
First of all, Joe Rosen is a clever and funny guy (mad) who used to post in Audio Asylum. Do a search with his name, it is really worth the trouble.
That amp comes from a cheap console that Joe and others audiophiles found incredible sounding. So he got interested and did a few mods- basically the current feedback scheme.
You need to use a 12ax7 or something similar to get the bias and the sound right.
I like your amp, and I'm glad posting here its not as useless as I thought it was.
Do you like the sound?
Can't believe you build it.
First of all, Joe Rosen is a clever and funny guy (mad) who used to post in Audio Asylum. Do a search with his name, it is really worth the trouble.
That amp comes from a cheap console that Joe and others audiophiles found incredible sounding. So he got interested and did a few mods- basically the current feedback scheme.
You need to use a 12ax7 or something similar to get the bias and the sound right.
I like your amp, and I'm glad posting here its not as useless as I thought it was.
Do you like the sound?
Hi Stalker, yes It sounds good to me, even if obviously not optimezed. Later today, I'll check voltages and current to see if everything's Ok in this department. I found a couple of JAN5751 for cheap on the shore. I'm ordering a 250K 2-gang pot, as well, whith the 100K one I can hardly turn the knob over a quarter of the total run.
Once the tweaking is finished, I'll paint the chassis (Hammond 1444-16) with this lovely mate grey primer. And change the volume knob for this one:
Once the tweaking is finished, I'll paint the chassis (Hammond 1444-16) with this lovely mate grey primer. And change the volume knob for this one:
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Maybe it is better to keep this one as is, original. I'm thinking to repeat the concept (single secondary, series string filaments) but using better transformers, a couple of 16GK6 japanese tubes that I own, full wave rectifier 🙂 and cathode bias input stage
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How did you create this schematic ? EAGLE uses dots where signals meet, lack of dots means the signals just cross one another. You somehow managed to create a schematic where some signals are missing dots while others have them.
Now the amp is suited with a NOS RCA 12BZ7, the most similar to the original 5751, that is on the way. The first one that I try was a faulty unit. It remains the pot problem, but now I believe that this amp deserves a 250K stepped attenuator that I saw on Ebay.
The voice of Rachel Nagy singing "As Long as I have You" is my witness 🙂
The voice of Rachel Nagy singing "As Long as I have You" is my witness 🙂
Mr. Fluke & The Rats Nest
About my wiring skills, a Cuban friend in place of "rats nest" will say: "parece un bollo e' perra!"😀
About my wiring skills, a Cuban friend in place of "rats nest" will say: "parece un bollo e' perra!"😀
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Each section in the BZ7 is essentially equivalent to two sections of 12AX7 in parallel. But, according to SY, BZ7's often exhibit a lot more distortion than the AX7.
In my limited experience, there is a lot of overlap between actual samples of AX7 and 5751. So much so that, unless you sort them according to gain, I would consider them equivalent.
Sheldon
Thanks for the info. I'm waiting for a couple of JAN5751 that are on arrival, so the amp will become exactly as referred on the original schem.
I draw the schem using this one:
Suigyodo online
And picked the tube symbols libraries from here:
.:: Bazzi Amplifiers - Software & Utilidades ::.
Suigyodo online
And picked the tube symbols libraries from here:
.:: Bazzi Amplifiers - Software & Utilidades ::.
Mosquito:
So do you think the 12AT7 seems to run the best (Considering I can't find a 5751 available).... for your amp?
Note Bazziamps.com.ar has an SE OPT at 6W & 11W....with a four and eight ohm tap! Bazzi won't respond to my E-mails...Is their prices in dollars or Pesos?
Some 12AT7s run about fifty dollars per... here!
What is the socket for the 50C5 tube..octal?, Mini?...
I can build the PS with parts I have on-hand....The Auto-transformer is not particularly safe but thats' all there is here....& cheap!
I don't want to gut my complete out of service Pioneer SX-650 just for a few parts....where do you find parts...specific caps & resistors?
PS: for all others...Mosquitos' avatar is a 'Yerba mate' phonetically, SHARE-VA MA-TAY.......A bitter tea served in a single adorned cup, an equally adorned "straw" usally metal...the cup is passed around (Communal)...a container of Sugar, a vessel for hot water, and a 'bag' of the Yerba is usually nearby. One person is "assigned" to serve the others..usually the 'Host', head of the household. Very common to see in Argentina.
( My wife uses too much sugar)
________________________________________________________Rick...
So do you think the 12AT7 seems to run the best (Considering I can't find a 5751 available).... for your amp?
Note Bazziamps.com.ar has an SE OPT at 6W & 11W....with a four and eight ohm tap! Bazzi won't respond to my E-mails...Is their prices in dollars or Pesos?
Some 12AT7s run about fifty dollars per... here!
What is the socket for the 50C5 tube..octal?, Mini?...
I can build the PS with parts I have on-hand....The Auto-transformer is not particularly safe but thats' all there is here....& cheap!
I don't want to gut my complete out of service Pioneer SX-650 just for a few parts....where do you find parts...specific caps & resistors?
PS: for all others...Mosquitos' avatar is a 'Yerba mate' phonetically, SHARE-VA MA-TAY.......A bitter tea served in a single adorned cup, an equally adorned "straw" usally metal...the cup is passed around (Communal)...a container of Sugar, a vessel for hot water, and a 'bag' of the Yerba is usually nearby. One person is "assigned" to serve the others..usually the 'Host', head of the household. Very common to see in Argentina.
( My wife uses too much sugar)
________________________________________________________Rick...
Ouch. I have a box of used (and maybe a few NOS)... if you find yourself in real need i could send at least a couple for cost of post.
7 pin
dave
The real mate is sugarless!!! anatema!!
The right tubes are in the family 5751/12AX7/12BZ7, and this is coherent with the original design. I was judging too fast, based in a faulty 12BZ7 , that the 12AT7 were better. Now the amp was provided with another BZ7 sample, and is singing like the angels! I ordered a couple of JAN5751 from an Ebayer in order to have the amp fully as designed to
You need a 250K pot. I'm providing for that.
Yes, as Planet 10 said, the socket is 7 pin. I used sockets that mount from the underside and solder most pieces directly to the sockets
Note that I've posted an updated schema with the measured voltages for various circuit nodes.
The right tubes are in the family 5751/12AX7/12BZ7, and this is coherent with the original design. I was judging too fast, based in a faulty 12BZ7 , that the 12AT7 were better. Now the amp was provided with another BZ7 sample, and is singing like the angels! I ordered a couple of JAN5751 from an Ebayer in order to have the amp fully as designed to
You need a 250K pot. I'm providing for that.
Yes, as Planet 10 said, the socket is 7 pin. I used sockets that mount from the underside and solder most pieces directly to the sockets
Note that I've posted an updated schema with the measured voltages for various circuit nodes.
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Sorry , Richard but I'm temporally based in Baleaes, for a contract, and I''ve got access to every vendor of our sacred goodies.
Ah, it looks incredibly like Eagle. You might want to give it a try (if anything, it appears to be consistent when drawing connections in schematic mode), it's free and tubes library is also avaliable for download on their webpage in Download section.
Thanks! I'll try it. I've get downloaded LTSpice as well, but I 've not figured yet how to make it work. By now I've learned how to use the Variac 🙂
Overkill for the 50c5. Don't ruin the philosophy of this amp: CHEAP.
Look for old tube radios or for people who fix them. They might sell you a pair of cheap transformers, remenber the original amp comes with thumbnail output transformers
I can send you a 5965, it might do the trick.
Mosquito, a full wave rectifier might be a possible mod but your B+ will be higher, maybe too much for your filter caps.
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