members builds in progress

[LooseChange]

Sorry, jumping in late... Normster, What Schematic are you using?

[Normster]

Sorry, jumping in late... Normster, What Schematic are you using?

It's based on the hybrid-a with a few minor changes to values and switching. I'll try to get it documented this week.

[groovtubin]

Normster and Groovtubin, both are excellent looking amps, great work. I am impressed how exact Normsters amp looks inside and out. You can always tell when an AE performs the work, nothin but top notch. I used to work with a few Navy Techs years ago, and learned a lot from them. Normster do you have a website? my email is robert_walters@raytheon

Not worried about the practice, can make it pretty once the values are nailed down. I started w/turret board, all I had in my shop, but don't suggest this for protos. I am very close to the tone I want ,but would like to hear Normsters amp, since I play blues too (+30 yrs). BobW

[toneman]

A week early, thought I'd try a test pic

[Normster]

Wow, that looks killer! Is that a "Bangkok" chassis? Nice layout of relays and post-OD tone stack. What are you doing with the dual-gang pots?

[toneman]

Thanks Normster, It' a Bangkok. The pedal switch on the front panel swithes Pre/Post tone stack. Had to mod a couple of concentric pots for my needs..100K A/1m A---100K A/250K A. Wanted to see if I liked the PTS or not. I,m sure it could be switched with a relay.. Would be a nice double edge lead as you can control the volume and drive of each. I had also added two more power tubes to run a quad of JJ 6v6's with Pent/ Tri switch and a half power switch on outer tubes.

[dogears]

Nice job!!! Build looks great!

So how do you like the stack versus no stack?? Did you swap the OD1 coupling cap as well? That needs to be changed if you change the circuit impedences. Also, you would not be able to use the interesting pre OD network that the 1997 HRM ODS amp used. It optimizes things for using the boost. Do you find the bass trimmer to be really touchy when using HRM mode and not in boost mode? Do you use switchable snubbers on V2 so you can use non HRM mode?

Question.... Did you use 23uf or 40uf on the screens? I understand that some of the later amps used the Precision Power section with 40uf screen caps. What is your tonal take on this??

Thanks!!!

Thanks Normster, It' a Bangkok. The pedal switch on the front panel swithes Pre/Post tone stack. Had to mod a couple of concentric pots for my needs..100K A/1m A---100K A/250K A. Wanted to see if I liked the PTS or not. I,m sure it could be switched with a relay.. Would be a nice double edge lead as you can control the volume and drive of each. I had also added two more power tubes to run a quad of JJ 6v6's with Pent/ Tri switch and a half power switch on outer tubes.

[toneman]

WOW, Just the feed back I need.It's my first Humble build so it's a learning curve.I,m going to fire it up in a couple days. The JJ's aren't here yet, although I"v got a few sets of old stock laying around. Would have to put a zenner on the center tap to bring the voltage down a tad. Building a current limiter and dummy load box today.On the coupling cap and the switchable snubbers well I guess Ill have to work that out. This is what it's all about test and grin. 23 on the screens. Got to thank you for the sound clips. Great tone and Glasman and Funkalicous . Glasman I account for at least 90 hits on your site.

[BobW]

Bob, try a 70`s architecture w/ a Voltage divider of 180K to ground into a one meg into relay ( to master vol) AFTER V2B coupling cap( .0047) gets ya mo gain for hot nasty blues.. thats off the ac plink 77 model.. trya 820 feedback w/100 ohm tail resistor as well. Twin values w/47K and 51K plates for PI ( 60`s mixed w/twin) 100K bias feed 3.3K grids. Enjoy!
jim[/quote][/quote]

This week I'm out of town and the amps 1500 miles away, talk about the blues! Am using, as dogears put it, the funky network into OD1, and will simplify it, and try your PI suggestions. Thank you. The last change I performed eliminated the .001 across the Bass pot. This helped tame the booming bass in either CL or OD modes. Suprisingly, with all the changes to this amp, the noise level is still very quiet.
This is a great forum! Too bad I can't offer any suggestions to the guys who have been there done that, so I try to help out when I can with noise, relays, layout issues, etc. BobW

[BobW]

Bob, try a 70`s architecture w/ a Voltage divider of 180K to ground into a one meg into relay ( to master vol) AFTER V2B coupling cap( .0047) gets ya mo gain for hot nasty blues.. thats off the ac plink 77 model.. trya 820 feedback w/100 ohm tail resistor as well. Twin values w/47K and 51K plates for PI ( 60`s mixed w/twin) 100K bias feed 3.3K grids. Enjoy!
jim[/quote][/quote]

This week I'm out of town and the amps 1500 miles away, talk about the blues! Am using, as dogears put it, the funky network into OD1, and will simplify it, and try your PI suggestions. Thank you. The last change I performed eliminated the .001 across the Bass pot. This helped tame the booming bass in either CL or OD modes. Suprisingly, with all the changes to this amp, the noise level is still very quiet.
This is a great forum! Too bad I can't offer any suggestions to the guys who have been there done that, so I try to help out when I can with noise, relays, layout issues, etc. BobW

[LooseChange]

Nice.
Q: That trimpot on the PI (assuming between two 100k's), does this trimpot take any wattage? OR can a simple Radio Shack trimpot do the job??

[toneman]

Thanks LooseChange.Alot of what,s been built is based on my readings from defferent sites hopfully it's in the ballpark!I must admit the trimmer came from Rad Shack one of thoes mixed value packages. It's a Piher. I believe I had read on Gary,s site he had used a 20K( What woked for him) It should be 10K.The Piher is 25K and I know it's a bit on the high side it's what I had at the time. Since it's installment parts have come in and now have different values to test with. I like the look of the Piher:)

[LooseChange]

How about the sound of that trimmer. What should I expect when shifting the balance? Does it clean up/ Harmonics increase at a certain point. etc.?? I build my PI's with the standard 82k and 100k, is this really a better way?

[toneman]

Glasman / Dogears or Funkalicousgroove could give a better answer than I. I'm still in the testing stage.

[Funkalicousgroove]

What I did was put my amp on a scope and using a 1Khz signal I adjusted the trimmer so that the sinewave on the scope was equal on both sides of "0" as a starting point, then marked it with a sharpie. From there I played while a tech friend of mine turned the trimmer and we stopped when it sounded best. The amp seems to have a bit more lush harmonic content when it's slightly off balance, but it puts out the most wattage when fully balanced.