Thatch_Ear
Addicted Member
Built like a tank!
Pics of homebrew 300B
- Thread starter Thatch_Ear
- Start date
Thatch_Ear
Addicted Member
Those pics were taken by the man that built this amp. The rectifier tube is a 5V4 which I thank him for since the rectification is done with SS diodes. A 5V4 wouldn't handle the voltage for a pair of 300s I don't think. I might stick a 5AR4 in their someday for curiosity but since it works....etc. The transformers are air gapped Sansuis. The 300Bs are the ones that came with, the one I have now are globes. The drivers are 6SL7s and the pot is Alps Black Beauty. The circuit is a SRPP and I have had to take great care in tube selection because of only one gain pot for both channels. I am sure I paid much less for the amp than it cost to make. The chassis is around 14 AWG thick steel, copper and then chrome plated. I broke my steel nibbling tool on it when putting in a different power cord setup. I made a few modifications on it but it is mostly still his work. It took me months to save the $$ but I am not dissapointed. The bleeder resister was blown and an electrolitic broke loose during shipping and I got zapped working on it even after a 5 days in a box journey from Oregon to Texas. Watch out for those caps guys!
MikE
Color Me Gone
Cool!
I mistook that YOU built the amp, no mater she is VERY nice! A 5v4, how interesting, I just won a bid on Ebay for an RCA 5v4. I'm using an RCA 5u4gya right now, which has supplanted a number of highly-touted rectifiers (Bendix 6106, Amperex metal base & Mullard fat base 5ar4). I'm trying to get me hands on a 5r4gya and a RCA or Tungsol 5u4 vt-244.
14awg! My amp is 16awg, and thats plenty heavy enough. I subbed the Alps 100k pot for a military-grade Borne 10k pot. What power and coupling caps did he use? I went with the stock power caps, instead I put my money in the $$$ Exotica teflon caps. The output trannies are Electra-Print custom. I'm thinking about asking Jack to do the secondary silver winding at some point. Yes, those caps do retain their juice for awhile! Yikes!
MikE
I mistook that YOU built the amp, no mater she is VERY nice! A 5v4, how interesting, I just won a bid on Ebay for an RCA 5v4. I'm using an RCA 5u4gya right now, which has supplanted a number of highly-touted rectifiers (Bendix 6106, Amperex metal base & Mullard fat base 5ar4). I'm trying to get me hands on a 5r4gya and a RCA or Tungsol 5u4 vt-244.
14awg! My amp is 16awg, and thats plenty heavy enough. I subbed the Alps 100k pot for a military-grade Borne 10k pot. What power and coupling caps did he use? I went with the stock power caps, instead I put my money in the $$$ Exotica teflon caps. The output trannies are Electra-Print custom. I'm thinking about asking Jack to do the secondary silver winding at some point. Yes, those caps do retain their juice for awhile! Yikes!
MikE
Thatch_Ear
Addicted Member
In this pic that I took after I shocked myself you can see part of one of four SCR 40mF / 630V that are ps filter, the choke and fil trans. The blue electrolitic sitting by itself is what broke loose and the large red resister in the center is the blown bleeder. I didn't move stuff around a whole lot but did replace the Hoviland Musicaps with Vitamin Qs. I bumped the electros in the cathode circuits up to 470 mf and parralleled a poly in there for smoother sound and better bass responce. I put in a buss line for chassis grounds and replaced the cord with a heavy duty one that has earth ground and put a 100 ohm 5W and a .1 400V between earth and chassis. No ground loops! I need to go in and replace more wire and caps but it is playing very nice right now so I am not going to screw with it for a while yet.
Thatch_Ear
Addicted Member
I have never seen a mercury diode lit up. They really that bright? I did see some amps that were if I remember correctly SS diode with the tube setup being a 6SN7 driving a 6CA4 driving an 845. You could read by the 845s! Nice sounding amps too. Kind of like what Rob is doing with those monster 805s. Hats off to you Rob!!
Duh Veeeed
Duh Veeeed
