Turret boards
Bruce,
Where did you get those nice turret boards you used inside the amp for the point to point wiring? I have found some siimilar at welbornelabs.com but they are 10 turrets per section, yours appear to be about 12 per section. Also, did you see my question about using a polarized electrolytic on the cathode.
Thanks,
Jeff
Bruce,
Where did you get those nice turret boards you used inside the amp for the point to point wiring? I have found some siimilar at welbornelabs.com but they are 10 turrets per section, yours appear to be about 12 per section. Also, did you see my question about using a polarized electrolytic on the cathode.
Thanks,
Jeff
Hi, The just previous post covered the caps. The turret boards come from AES (tubesandmore.com). There are several types including ones with various combinations of tube sockets. You can get 7,9 and octal types. Very high quality and handy to use for prototyping.
A follow on to my auditioning of the 6L6WXTs in the Odd Blocks. My present thought is that they are not as good as the standard JJ 6L6GCs. For what ever reason JJ KT77s and 6L6GCs work extremely well in the circuit. The Gold Lion KT88s are as good and have more muscle, but cost 3 times as much.
A follow on to my auditioning of the 6L6WXTs in the Odd Blocks. My present thought is that they are not as good as the standard JJ 6L6GCs. For what ever reason JJ KT77s and 6L6GCs work extremely well in the circuit. The Gold Lion KT88s are as good and have more muscle, but cost 3 times as much.
25R Pot
Bruce,
Is this the 25R pot you used from Radioshack?
http://www.radioshack.com/product/index.jsp?productId=2062299
Thanks,
Jeff
Bruce,
Is this the 25R pot you used from Radioshack?
http://www.radioshack.com/product/index.jsp?productId=2062299
Thanks,
Jeff
I was just able to locate one at Digikey for $3.16 made by CTS. If you search google for "25 ohm pot" a digikey link will come up. I am not sure of CTS quality but I was going to try one of each to see if there were any sonic differences. These things are wirewound and likely inductive. I would think in this part of the circuit you would not want any inductance swing at all. I want to try to come up with an alternate way of acheiving this circuit without an inductive wirewound resistor here. I will let you know when I figure it out!
Jeff
Jeff
Hi Jeff, I am aware of the possibility of inductance, but in this case it is so small (below my ability to accurately measure it) and it is in parallel with 25 ohms it is really no issue. In an RF circuit it would matter, but at audio frequencies no problem. There is an alternative to use a 12 position switch and 1 and 2 ohm resistors. It is less accurate, but do-able.
Another thought is that the output transformer is in the same signal path and it has a huge amount of inductance and swamps out any effect of the tiny bit in the pot. Good thinking though on your part. Thanks
Another thought is that the output transformer is in the same signal path and it has a huge amount of inductance and swamps out any effect of the tiny bit in the pot. Good thinking though on your part. Thanks
Bruce,
I was looking at the underneath view of the Oddblock. I have decided to sans the idea of using 2 Rifas in series...takes up too much space. I went ahead and ordered the JJ's from AES. The bus wire you used, what guage is it? I have some square tinned 12AWG wire I was thinking of using.
Jeff
I was looking at the underneath view of the Oddblock. I have decided to sans the idea of using 2 Rifas in series...takes up too much space. I went ahead and ordered the JJ's from AES. The bus wire you used, what guage is it? I have some square tinned 12AWG wire I was thinking of using.
Jeff
Hi Jeff, the wire is 12 guage. It seems a good size for a ground buss. I'm sure you know to watch for alternate ground paths that can lead to ground loops. I like to think of a ground buss as a funnel for everything to get back to one singel point. I usually work from the perimiters of the chassis toward the center and at that point attach the most critical grounds. Generally this is the input signal ground and the main ps ground. Star grounding is great, just very difficult to implement in a large project like the amps. For small projects it is usually seems to be the best.
Variable resitors, etc
Bruce,
I found these as alternatives to the RS 25R pot:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=AVT25-25-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=490-2057-ND
This one is 50R
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=RV4NJ500C-ND
it is carbon.
Just FYI in case you ever wanted to try something different.
Jeff
Bruce,
I found these as alternatives to the RS 25R pot:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=AVT25-25-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=490-2057-ND
This one is 50R
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=RV4NJ500C-ND
it is carbon.
Just FYI in case you ever wanted to try something different.
Jeff
Parts
Well I have ordered all of the parts for the Oddblocks. I found the LM317HV at Digikey for around $3.50 a piece. They have either 600 or 1300 left there. Should be plenty available for some time. I stocked up on them a little. I also went with the CTS 25R pot to be different. I may try the carbon 50R pot I found there at some point to see if it makes any difference.
I eneded up going with all very high quality resistors and caps. I used Holcos and Black Gates in the signal circuitry. I am using all silver w/ silver sheilding 20ga wire that came from NASA. The remainder of the parts are all of top quality too.
The Chassis (how do you spell plueral chassis?) are complete as well. I am just waiting on the parts to come in now. Should be another week to 10 days then I will have some real questions for you!
Jeff
Well I have ordered all of the parts for the Oddblocks. I found the LM317HV at Digikey for around $3.50 a piece. They have either 600 or 1300 left there. Should be plenty available for some time. I stocked up on them a little. I also went with the CTS 25R pot to be different. I may try the carbon 50R pot I found there at some point to see if it makes any difference.
I eneded up going with all very high quality resistors and caps. I used Holcos and Black Gates in the signal circuitry. I am using all silver w/ silver sheilding 20ga wire that came from NASA. The remainder of the parts are all of top quality too.
The Chassis (how do you spell plueral chassis?) are complete as well. I am just waiting on the parts to come in now. Should be another week to 10 days then I will have some real questions for you!
Jeff
SMPS's
I have probably 20-30 SMPS that are rated anywhere from 7.5 volts all the way up to 30+. Unfortunately I only have one 12V. I have a few 16V ones that are rather compact and would like to use them for my filament supply if possible. How would one bring the voltage down by 4 volts? Also, Bruce...What did you ever decide on calling the "Poddwatt"? When do you think the first sales orders will be taken and when will the first deliveries be shipped?
Also, for anybody reading this...if you need a SMPS let me know what voltage you need and I will see if I have it. I will sell them for reasonable offers. I acquired them at the hospital I work at. They recently upgraded a ton of computers and were literally tossing these in the garbage. For some stupid reason they couldn't just give them to me so I paid a token fee to the hospital for them. They are just taking up space now and I doubt I will ever use them. My wife would be very happy to see them go away!
Jeff
I have probably 20-30 SMPS that are rated anywhere from 7.5 volts all the way up to 30+. Unfortunately I only have one 12V. I have a few 16V ones that are rather compact and would like to use them for my filament supply if possible. How would one bring the voltage down by 4 volts? Also, Bruce...What did you ever decide on calling the "Poddwatt"? When do you think the first sales orders will be taken and when will the first deliveries be shipped?
Also, for anybody reading this...if you need a SMPS let me know what voltage you need and I will see if I have it. I will sell them for reasonable offers. I acquired them at the hospital I work at. They recently upgraded a ton of computers and were literally tossing these in the garbage. For some stupid reason they couldn't just give them to me so I paid a token fee to the hospital for them. They are just taking up space now and I doubt I will ever use them. My wife would be very happy to see them go away!
Jeff
Hi Jeff, There are a number of ways to get the right heater voltages from SMPS. You mentioned that you had 7.5 volt ones. If they have sufficient current, you could rewire the heater circuit to use 6 volts. Then I would add rectifiers in series with the outputs of the SMPS to bring it down to what is needed. A typical silicon rectifier has a drop of about 0.7 volts, so two in series would be close. It would require measuring to be sure though as PS ratings are not always accurate. Be sure to factor in the current and amount of heat the diodes will generate. Alternatively you could select one above 12 volts and use a regulator to drop it the correct output. Four volts is about the minimum drop for most such circuits. It would probably be most efficient to use a pass transistor (large NPN) and a SS regulator chip like the LM317s to meet the current demands of the heaters.
Right now the amp is being called the S2. (=stereo #2) Final development is underway and proof testing. I would expect it to show up as a product in the next 60 days. It takes time to source parts fof such things.
Right now the amp is being called the S2. (=stereo #2) Final development is underway and proof testing. I would expect it to show up as a product in the next 60 days. It takes time to source parts fof such things.
Can you refer me to a diagram of the circuit required to make the regulator with a transistor and LM317? I like the idea of a regulator. What about a zeneer voltage divider? I know most have a maximum current of around 1300mA but could 2 or three parallel zeneer dividers be put together? I am familiar with zeneers just a little, it is the topic I am studying right now in my own self directed educational series (i.e. the Art of Electronics and the internet) I know how to use a voltage regulator but I have never heard of using it in conjunction w/ a transistor. Do you or anybody know of where I can read up on this concept?
I still like the name Podwatt. Maybe you could ask permission from iPod
Yeah right!
I know this is off topic, but speaking of name/logo/brand infringement....check out the webpage www.nissan.com
This will blow you away. Read the links on the top of the page to the lawsuits. It really ticked me off at Nissan Motor Co. I just typed in Nissan.com the other day to look into possibly buying a new 370Z. I don't know if I am so upset w/ Nissan Motor that I won't buy it but it does make me have second thoughts.
Anyway, I got all of my resistors in today, I should be getting the iron this week and the tubes this week as well. My chassis are done...well almost, gotta redo the top of one now...long story.
I bought all Vampire RCA and binding posts for it. The resistors are PRP, not Holco as I mentioned earlier (brainfart), I bought JJ caps just like Bruces. I have Russian PIO's on the way over the pond as well. I also went with the CTS 25R pots, $3.69 at Digikey. They also have plenty of LM317HV's available there too.
One of my patients just gave me a box of about 500-600 tubes that I haven't had time to go through. He says there are EL34, 84, 6L6, and 6550 tubes in it. I honestly havent even opened the box yet. I am hoping I will have 4 of a kind in there to start this project with. I will likely be in the tube selling business before long too.
I can't wait to get going with the solder gun!
Thanks,
Jeff
I still like the name Podwatt. Maybe you could ask permission from iPod
Yeah right!I know this is off topic, but speaking of name/logo/brand infringement....check out the webpage www.nissan.com
This will blow you away. Read the links on the top of the page to the lawsuits. It really ticked me off at Nissan Motor Co. I just typed in Nissan.com the other day to look into possibly buying a new 370Z. I don't know if I am so upset w/ Nissan Motor that I won't buy it but it does make me have second thoughts.
Anyway, I got all of my resistors in today, I should be getting the iron this week and the tubes this week as well. My chassis are done...well almost, gotta redo the top of one now...long story.
I bought all Vampire RCA and binding posts for it. The resistors are PRP, not Holco as I mentioned earlier (brainfart), I bought JJ caps just like Bruces. I have Russian PIO's on the way over the pond as well. I also went with the CTS 25R pots, $3.69 at Digikey. They also have plenty of LM317HV's available there too.
One of my patients just gave me a box of about 500-600 tubes that I haven't had time to go through. He says there are EL34, 84, 6L6, and 6550 tubes in it. I honestly havent even opened the box yet. I am hoping I will have 4 of a kind in there to start this project with. I will likely be in the tube selling business before long too.
I can't wait to get going with the solder gun!
Thanks,
Jeff
The 6NO30 is impossible to find, but I was willing to compromise with a switch. However, DigiKey is "back ordered" on LM317HV now. Since it's an obsolete part, and with no other suppliers, this means no simple way to build this project without it. Is there a no compromise, tested, and simple substitute for the LM317HV?
One final search yielded a LM317HVT/NOPB at Avnet Express with 5800 units available. Is it okay to use the NOPB over the non NOPB version?
http://avnetexpress.avnet.com/store...gId=-1&storeId=500201&listIndex=1&yposition=0
One final search yielded a LM317HVT/NOPB at Avnet Express with 5800 units available. Is it okay to use the NOPB over the non NOPB version?
http://avnetexpress.avnet.com/store...gId=-1&storeId=500201&listIndex=1&yposition=0
Last edited:
Hi 88Man, Either LM317HV will work fine. You only need the HV version for some of the tubes. 6L6GCs, EL34s, KT77s and similar can use the standard LM317. The difference in the parts is the rated voltage. The standard ones are rated at 37 volts and the HV at 57. The typical bias on a KT88 is between 33 and 40 volts. Thus the need for the HV part. I know of builders that used the standard one with KT88s and had no problems. I don't like to take that chance.
The 6NO30 is a bit hard to find. The most recent source was tubesandmore.com
A switch will work fine. In our kits we used a transistor to do the delay and activate the relay. The newer projects use a LM555 IC timer to do the job.
Good Listening
Bruce
The 6NO30 is a bit hard to find. The most recent source was tubesandmore.com
A switch will work fine. In our kits we used a transistor to do the delay and activate the relay. The newer projects use a LM555 IC timer to do the job.
Good Listening
Bruce
Thank you, Bruce, for your good advice and leads. BTW, great price for the LM317HVT @ avnetexpress.com for $1.29. I found the 6NO30 tube as well @ tubesandmore.com. I am looking forward to building your elegant circuit.
I wish I could use my NOS matched pair of Sylvania 6SN7GTB tubes for this amp, but I am not sure how to rework the circuit, and besides I am not sure if it would provide enough gain to drive the KT88s. This way, at least it will give me a chance to explore a new tube, the 12SL7.
Good suggestion too, Arne!
Thanks again, Bruce and Arne!
I wish I could use my NOS matched pair of Sylvania 6SN7GTB tubes for this amp, but I am not sure how to rework the circuit, and besides I am not sure if it would provide enough gain to drive the KT88s. This way, at least it will give me a chance to explore a new tube, the 12SL7.
Good suggestion too, Arne!
Thanks again, Bruce and Arne!
Relay option
88man,
Hi, I built these monoblocks and they work beautifully. I think I was able to find some of the LM317HV's at Farnell.com too. Haven't checked in a while.
Bruce uses the tube relay to activate another higher rated relay. Because I didn't have these extra higher rated relays when I was completing the project and I didn't want to wait for them to come in to listen to my amp, I opted to use the tube relay alone to directly switch and pass the voltage/current straight through it. It has a weird rating that is supposedly higher when "new", whatever that means. To date I have switched mine on and off probably over 100 times without any problems with failure. It gives an interesting fireworks display too when the contacts come together at the HV. My rationale was that the wost that could happen would be to have to replace a tube relay and they are cheap. I thought I would rewire the relay at a later date but since I have had no problems I am going to leave it as it is. Bruce may have some negative things to add about this idea but I just wanted you to know my experience so far has been fine using it to directly switch the HV. It is simpler to implement this way too.
Be sure to put some pics up once you are finished, would love to see how yours turn out.
I am using Svetlana 6L6's and some made for McIntosh KT88's. Both sound great but I definitely like the sound of the 6L6's the best.
If you haven't yet decided on a chassis, I built an extra set of wooden 8x12" monoblock chassis I was going to use to build a second pair. I have decided to do something different for my next project so if you are interested I will part with them for a very reasonable price. They are very nice exotic woods with an aluminum top plate. That goes for anybody who needs a set.
Good luck with your build.
Jeff Miller
Lawton, OK
88man,
Hi, I built these monoblocks and they work beautifully. I think I was able to find some of the LM317HV's at Farnell.com too. Haven't checked in a while.
Bruce uses the tube relay to activate another higher rated relay. Because I didn't have these extra higher rated relays when I was completing the project and I didn't want to wait for them to come in to listen to my amp, I opted to use the tube relay alone to directly switch and pass the voltage/current straight through it. It has a weird rating that is supposedly higher when "new", whatever that means. To date I have switched mine on and off probably over 100 times without any problems with failure. It gives an interesting fireworks display too when the contacts come together at the HV. My rationale was that the wost that could happen would be to have to replace a tube relay and they are cheap. I thought I would rewire the relay at a later date but since I have had no problems I am going to leave it as it is. Bruce may have some negative things to add about this idea but I just wanted you to know my experience so far has been fine using it to directly switch the HV. It is simpler to implement this way too.
Be sure to put some pics up once you are finished, would love to see how yours turn out.
I am using Svetlana 6L6's and some made for McIntosh KT88's. Both sound great but I definitely like the sound of the 6L6's the best.
If you haven't yet decided on a chassis, I built an extra set of wooden 8x12" monoblock chassis I was going to use to build a second pair. I have decided to do something different for my next project so if you are interested I will part with them for a very reasonable price. They are very nice exotic woods with an aluminum top plate. That goes for anybody who needs a set.
Good luck with your build.
Jeff Miller
Lawton, OK
Odd Block Class A 12SL7/KT88 Amp
I am in the process of getting parts for the Odd Block KT88 PP amp. I have a few questions:
1. I can't find an SMPS - Where can I buy 12VDC 3A or 5A SMPS?...
2. Which values should change if I use a EH 5751 in place of 12SL7?...
3. Where can I buy a series AC line filter similar to the one in the circuit?...
4. Which sounds better to your ears, a 5751 or 12SL7 in this circuit?...
Thanks!
I am in the process of getting parts for the Odd Block KT88 PP amp. I have a few questions:
1. I can't find an SMPS - Where can I buy 12VDC 3A or 5A SMPS?...
2. Which values should change if I use a EH 5751 in place of 12SL7?...
3. Where can I buy a series AC line filter similar to the one in the circuit?...
4. Which sounds better to your ears, a 5751 or 12SL7 in this circuit?...
Thanks!
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